U.S. patent application number 13/536309 was filed with the patent office on 2013-01-03 for image decoding method, image coding method, image decoding apparatus, image coding apparatus, and image coding and decoding apparatus.
Invention is credited to Toru Matsunobu, Takahiro Nishi, Hisao Sasai, Youji Shibahara, Toshiyasu SUGIO, Kyoko Tanikawa.
Application Number | 20130003850 13/536309 |
Document ID | / |
Family ID | 47390674 |
Filed Date | 2013-01-03 |
United States Patent
Application |
20130003850 |
Kind Code |
A1 |
SUGIO; Toshiyasu ; et
al. |
January 3, 2013 |
IMAGE DECODING METHOD, IMAGE CODING METHOD, IMAGE DECODING
APPARATUS, IMAGE CODING APPARATUS, AND IMAGE CODING AND DECODING
APPARATUS
Abstract
An image decoding method for decoding, on a block-by-block
basis, image data included in a coded bitstream includes: obtaining
a fixed number of merging candidates each of which is a candidate
set of a prediction direction, a motion vector, and a reference
picture index which are to be referenced in decoding of a current
block (S303); and obtaining, from the coded bitstream, an index for
identifying a merging candidate for the current block (S304),
wherein the fixed number of merging candidates include: one or more
first candidates each derived based on a prediction direction, a
motion vector, and a reference picture index which have been used
for decoding a neighboring block spatially or temporally
neighboring the current block; and one or more second candidates
having a predetermined fixed. The fixed number is greater than or
equal to two.
Inventors: |
SUGIO; Toshiyasu; (Osaka,
JP) ; Nishi; Takahiro; (Nara, JP) ; Shibahara;
Youji; (Osaka, JP) ; Tanikawa; Kyoko; (Osaka,
JP) ; Sasai; Hisao; (Osaka, JP) ; Matsunobu;
Toru; (Osaka, JP) |
Family ID: |
47390674 |
Appl. No.: |
13/536309 |
Filed: |
June 28, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61503074 |
Jun 30, 2011 |
|
|
|
Current U.S.
Class: |
375/240.16 ;
375/E7.125; 375/E7.256 |
Current CPC
Class: |
H04N 19/176 20141101;
H04N 19/573 20141101; H04N 19/96 20141101; H04N 19/52 20141101;
H04N 19/70 20141101; H04N 19/147 20141101; H04N 19/105
20141101 |
Class at
Publication: |
375/240.16 ;
375/E07.125; 375/E07.256 |
International
Class: |
H04N 7/32 20060101
H04N007/32; H04N 7/36 20060101 H04N007/36; H04N 7/34 20060101
H04N007/34 |
Claims
1. An image decoding method for decoding, on a block-by-block
basis, image data included in a coded bitstream, the method
comprising: obtaining a fixed number of merging candidates each of
which is a candidate set of a prediction direction, a motion
vector, and a reference picture index which are to be referenced in
decoding of a current block, the fixed number being greater than or
equal to two; obtaining, from the coded bitstream, an index for
identifying a merging candidate among the fixed number of merging
candidates, the identified merging candidate being a merging
candidate to be referenced in the decoding of the current block;
and identifying the merging candidate using the obtained index, and
decoding the current block using the identified merging candidate,
wherein the fixed number of merging candidates include: one or more
first candidates each derived based on a prediction direction, a
motion vector, and a reference picture index which have been used
for decoding a neighboring block spatially or temporally
neighboring the current block; and one or more second candidates
having a predetermined fixed value.
2. The image decoding method according to claim 1, wherein the
obtaining of a fixed number of merging candidates includes:
deriving the one or more first candidates and including the one or
more first candidates in the fixed number of merging candidates;
deriving one or more third candidates and including the one or more
third candidates in the fixed number of merging candidates, when a
total number of the first candidates is smaller than the fixed
number, the third candidates each having a picture index for a
picture referable in the decoding of the current block; and
deriving the one or more second candidates and including the one or
more second candidates in the fixed number of merging candidates so
that a total number of the first candidates, the second candidates,
and the third candidates equals the fixed number, when a total
number of the first candidates and the third candidates is smaller
than the fixed number.
3. The image decoding method according to claim 2, wherein in the
deriving of one or more third candidates, the one or more third
candidates are derived by selecting, according to a predetermined
priority order, one or more candidates from among a plurality of
prepared candidates different from each other.
4. The image decoding method according to claim 1, wherein the
obtaining of a fixed number of merging candidates includes:
initializing the fixed number of merging candidates by setting all
the fixed number of merging candidates to the second candidates;
deriving the one or more first candidates and updating part of the
fixed number of merging candidates so as to include the one or more
first candidates in the fixed number of merging candidates; and
deriving one or more third candidates and updating part of the
fixed number of merging candidates so as to include the one or more
third candidates in the fixed number of merging candidates, when a
total number of the first candidates is smaller than the fixed
number, the third candidates each having a picture index for a
picture referable in the decoding of the current block.
5. An image coding method for coding an image on a block-by-block
basis to generate a coded bitstream, the method comprising:
obtaining a fixed number of merging candidates each of which is a
candidate set of a prediction direction, a motion vector, and a
reference picture index which are to be referenced in coding of a
current block, the fixed number being greater than or equal to two;
and attaching, to the coded bitstream, an index for identifying a
merging candidate among the fixed number of merging candidates, the
identified merging candidate being a merging candidate to be
referenced in the coding of the current block, wherein the fixed
number of merging candidates include: one or more first candidates
each derived based on a prediction direction, a motion vector, and
a reference picture index which have been used for coding a
neighboring block spatially or temporally neighboring the current
block; and one or more second candidates having a predetermined
fixed value.
6. The image coding method according to claim 5, wherein the
obtaining of a fixed number of merging candidates includes:
deriving the one or more first candidates and including the one or
more first candidates in the fixed number of merging candidates;
deriving one or more third candidates and including the one or more
third candidates in the fixed number of merging candidates, when a
total number of the first candidates is smaller than the fixed
number, the third candidates each having a picture index for a
picture referable in the decoding of the current block; and
deriving the one or more second candidates and including the one or
more second candidates in the fixed number of merging candidates so
that a total number of the first candidates, the second candidates,
and the third candidates equals the fixed number, when a total
number of the first candidates and the third candidates is smaller
than the fixed number.
7. The image coding method according to claim 6, wherein in the
deriving of one or more third candidates, the one or more third
candidates are derived by selecting, according to a predetermined
priority order, one or more candidates from among a plurality of
prepared candidates different from each other.
8. The image coding method according to claim 5, wherein the
obtaining of a fixed number of merging candidates includes:
initializing the fixed number of merging candidates by setting all
the fixed number of merging candidates to the second candidates;
deriving the one or more first candidates and updating part of the
fixed number of merging candidates so as to include the one or more
first candidates in the fixed number of merging candidates; and
deriving one or more third candidates and updating part of the
fixed number of merging candidates so as to include the one or more
third candidates in the fixed number of merging candidates, when a
total number of the first candidates is smaller than the fixed
number, the third candidates each having a picture index for a
picture referable in the decoding of the current block.
9. An image decoding apparatus which decodes, on a block-by-block
basis, image data included in a coded bitstream, the apparatus
comprising: an merging candidate obtaining unit configured to
obtain a fixed number of merging candidates each of which is a
candidate set of a prediction direction, a motion vector, and a
reference picture index which are to be referenced in decoding of a
current block, the fixed number being greater than or equal to two;
an index obtaining unit configured to obtain, from the coded
bitstream, an index for identifying a merging candidate among the
fixed number of merging candidates, the identified merging
candidate being a merging candidate to be referenced in the
decoding of the current block; and a decoding unit configured to
identify the merging candidate using the obtained index and decode
the current block using the identified merging candidate, wherein
the fixed number of merging candidates include: one or more first
candidates each derived based on a prediction direction, a motion
vector, and a reference picture index which have been used for
decoding a neighboring block spatially or temporally neighboring
the current block; and one or more second candidates having a
predetermined fixed value.
10. An image coding apparatus which codes an image on a
block-by-block basis to generate a coded bitstream, the apparatus
comprising: an merging candidate obtaining unit configured to
obtain a fixed number of merging candidates each of which is a
candidate set of a prediction direction, a motion vector, and a
reference picture index to be referenced in decoding of a current
block, the fixed number being greater than or equal to two; and a
coding unit configured to attach, to the coded bitstream, an index
for identifying a merging candidate among the fixed number of
merging candidates, the identified merging candidate being a
merging candidate to be referenced in the coding of the current
block, wherein the fixed number of merging candidates include: one
or more first candidates each derived based on a prediction
direction, a motion vector, and a reference picture index which
have been used for coding a neighboring block spatially or
temporally neighboring the current block; and one or more second
candidates having a predetermined fixed value.
11. An image coding and decoding apparatus comprising: the image
decoding apparatus according to claim 9; and the image coding
apparatus according to claim 10.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] The present application claims the benefit of U.S.
Provisional Patent Application No. 61/503,074 filed Jun. 30, 2011.
The entire disclosures of the above-identified applications,
including the specifications, drawings and claims are incorporated
herein by reference in their entirety.
TECHNICAL FIELD
[0002] The present disclosure relates to a moving picture coding
method and a moving picture decoding method.
BACKGROUND ART
[0003] Generally, in coding processing of a moving picture, the
amount of information is reduced by compression for which
redundancy of a moving picture in spatial direction and temporal
direction is made use of. Generally, conversion to a frequency
domain is performed as a method in which redundancy in spatial
direction is made use of, and coding using prediction between
pictures (the prediction is hereinafter referred to as inter
prediction) is performed as a method of compression for which
redundancy in temporal direction is made use of. In the inter
prediction coding, a current picture is coded using, as a reference
picture, a coded picture which precedes or follows the current
picture in order of display time. Subsequently, a motion vector is
derived by performing motion estimation on the current picture with
reference to the reference picture. Then, redundancy in temporal
direction is removed using a calculated difference between picture
data of the current picture and prediction picture data which is
obtained by motion compensation based on the derived motion vector
(see Non-patent Literature 1, for example). Here, in the motion
estimation, difference values between current blocks in the current
picture and blocks in the reference picture are calculated, and a
block having the smallest difference value in the reference picture
is determined as a reference block. Then, a motion vector is
estimated from the current block and the reference block.
CITATION LIST
Non Patent Literature
[0004] [Non-patent Literature 1] ITU-T Recommendation H.264
"Advanced video coding for generic audiovisual services", March
2010 [0005] [Non-patent Literature 2] JCT-VC, "WD3: Working Draft 3
of High-Efficiency Video Coding", JCTVC-E603, March 2011
SUMMARY OF INVENTION
Technical Problem
[0006] It is still desirable to enhance error resistance of image
coding and decoding in which inter prediction is used, beyond the
above-described conventional technique.
[0007] In view of this, the object of the present disclosure is to
provide an image coding method and an image decoding method with
which error resistance of image coding and image decoding using
inter prediction is enhanced.
Solution to Problem
[0008] An image decoding method according to an aspect of the
present disclosure is a method for decoding, on a block-by-block
basis, a coded image included in a bitstream, and includes:
obtaining a fixed number of merging candidates each of which is a
candidate set of a prediction direction, a motion vector, and a
reference picture index which are to be referenced in decoding of a
current block, the fixed number being greater than or equal to two;
obtaining, from the coded bitstream, an index for identifying a
merging candidate among the fixed number of merging candidates, the
identified merging candidate being a merging candidate to be
referenced in the decoding of the current block; and identifying
the merging candidate using the obtained index, and decoding the
current block using the identified merging candidate, wherein the
fixed number of merging candidates include: one or more first
candidates each derived based on a prediction direction, a motion
vector, and a reference picture index which have been used for
decoding a neighboring block spatially or temporally neighboring
the current block; and one or more second candidates having a
predetermined fixed value.
[0009] It should be noted that these general or specific aspects
can be implemented as a system, a method, an integrated circuit, a
computer program, a computer-readable recording medium such as a
compact disc read-only memory (CD-ROM), or as any combination of a
system, a method, an integrated circuit, a computer program, and a
computer-readable recording medium.
Advantageous Effects of Invention
[0010] According to an aspect of the present disclosure, error
resistance of image coding and decoding using inter prediction can
be enhanced.
BRIEF DESCRIPTION OF DRAWINGS
[0011] These and other objects, advantages and features of the
invention will become apparent from the following description
thereof taken in conjunction with the accompanying drawings that
illustrate a specific embodiment of the present invention. In the
Drawings:
[0012] FIG. 1A is a diagram for illustrating an exemplary reference
picture list for a B-picture;
[0013] FIG. 1B is a diagram for illustrating an exemplary reference
picture list of a prediction direction 0 for a B-picture;
[0014] FIG. 1C is a diagram for illustrating an exemplary reference
picture list of a prediction direction 1 for a B-picture;
[0015] FIG. 2 is a diagram for illustrating motion vectors for use
in the temporal motion vector prediction mode;
[0016] FIG. 3 shows an exemplary motion vector of a neighboring
block for use in the merging mode;
[0017] FIG. 4 is a diagram for illustrating an exemplary merging
block candidate list;
[0018] FIG. 5 shows a relationship between the size of a merging
block candidate list and bit sequences assigned to merging block
candidate indexes;
[0019] FIG. 6 is a flowchart showing an example of a process for
coding when the merging mode is used;
[0020] FIG. 7 is a block diagram showing a configuration of an
image coding apparatus;
[0021] FIG. 8 is a flowchart showing a process for decoding using
the merging mode;
[0022] FIG. 9 is a block diagram showing a configuration of an
image decoding apparatus;
[0023] FIG. 10 shows syntax for attachment of a merging block
candidate index to a coded bitstream;
[0024] FIG. 11 is a block diagram showing a configuration of an
image coding apparatus according to Embodiment 1;
[0025] FIG. 12 is a flowchart showing processing operations of the
image coding apparatus according to Embodiment 1;
[0026] FIG. 13A shows an exemplary merging block candidate list
according to Embodiment 1;
[0027] FIG. 13B shows an exemplary merging block candidate list
according to Embodiment 1;
[0028] FIG. 13C shows an exemplary merging block candidate list
according to Embodiment 1;
[0029] FIG. 14A is a flowchart illustrating a process for
calculating merging block candidates and the size of a merging
block candidate list according to Embodiment 1;
[0030] FIG. 14B is a flowchart illustrating a process for
calculating merging block candidates and the size of a merging
block candidate list according to a modification of an
embodiment;
[0031] FIG. 14C is a flowchart illustrating a process for
calculating merging block candidates and the size of a merging
block candidate list according to a modification of an
embodiment;
[0032] FIG. 15A is a flowchart illustrating a process for
determining whether or not a merging block candidate is a
usable-for-merging candidate and updating the total number of
usable-for-merging candidates according to Embodiment 1;
[0033] FIG. 15B is a flowchart illustrating a process for
determining whether or not a merging block candidate is a
usable-for-merging candidate and updating the total number of
usable-for-merging candidates according to a modification of an
embodiment;
[0034] FIG. 16 is a flowchart illustrating a process for adding a
new candidate according to Embodiment 1;
[0035] FIG. 17 is a flowchart illustrating a process for adding a
second candidate according to a modification of an embodiment;
[0036] FIG. 18 is a flowchart illustrating a process for selecting
a merging block candidate according to Embodiment 1;
[0037] FIG. 19 is a block diagram showing a configuration of an
image decoding apparatus according to Embodiment 2;
[0038] FIG. 20 is a flowchart showing processing operations of the
image decoding apparatus according to Embodiment 2;
[0039] FIG. 21 is a flowchart illustrating a process for
determining whether or not a merging block candidate is a
usable-for-merging candidate and updating the total number of
usable-for-merging candidates according to Embodiment 2;
[0040] FIG. 22 is a flowchart illustrating a process for generating
a merging block candidate list according to Embodiment 2;
[0041] FIG. 23 shows exemplary syntax for attachment of a merging
block candidate index to a coded bitstream;
[0042] FIG. 24 shows exemplary syntax in the case where the size of
a merging block candidate list is fixed at the maximum value of the
total number of merging block candidates;
[0043] FIG. 25 shows an overall configuration of a content
providing system for implementing content distribution
services;
[0044] FIG. 26 shows an overall configuration of a digital
broadcasting system;
[0045] FIG. 27 shows a block diagram illustrating an example of a
configuration of a television;
[0046] FIG. 28 is a block diagram illustrating an example of a
configuration of an information reproducing/recording unit that
reads and writes information from and on a recording medium that is
an optical disk;
[0047] FIG. 29 shows an example of a configuration of a recording
medium that is an optical disk;
[0048] FIG. 30A shows an example of a cellular phone;
[0049] FIG. 30B is a block diagram showing an example of a
configuration of a cellular phone;
[0050] FIG. 31 illustrates a structure of multiplexed data;
[0051] FIG. 32 schematically shows how each stream is multiplexed
in multiplexed data;
[0052] FIG. 33 shows how a video stream is stored in a stream of
PES packets in more detail;
[0053] FIG. 34 shows a structure of TS packets and source packets
in the multiplexed data;
[0054] FIG. 35 shows a data structure of a PMT;
[0055] FIG. 36 shows an internal structure of multiplexed data
information;
[0056] FIG. 37 shows an internal structure of stream attribute
information;
[0057] FIG. 38 shows steps for identifying video data;
[0058] FIG. 39 is a block diagram showing an example of a
configuration of an integrated circuit for implementing the moving
picture coding method and the moving picture decoding method
according to each of embodiments;
[0059] FIG. 40 shows a configuration for switching between driving
frequencies;
[0060] FIG. 41 shows steps for identifying video data and switching
between driving frequencies;
[0061] FIG. 42 shows an example of a look-up table in which video
data standards are associated with driving frequencies;
[0062] FIG. 43A is a diagram showing an example of a configuration
for sharing a module of a signal processing unit; and
[0063] FIG. 43B is a diagram showing another example of a
configuration for sharing a module of the signal processing
unit.
DESCRIPTION OF EMBODIMENTS
Underlying Knowledge Forming Basis of the Present Disclosure
[0064] In a moving picture coding scheme already standardized,
which is referred to as H.264, three picture types of I-picture,
P-picture, and B-picture are used for reduction of the amount of
information by compression.
[0065] The I-picture is not coded by inter prediction coding.
Specifically, the I-picture is coded by prediction within the
picture (the prediction is hereinafter referred to as intra
prediction). The P-picture is coded by inter prediction coding with
reference to one coded picture preceding or following the current
picture in order of display time. The B-picture is coded by inter
prediction coding with reference to two coded pictures preceding
and following the current picture in order of display time.
[0066] In inter prediction coding, a reference picture list for
identifying a reference picture is generated. In a reference
picture list, reference picture indexes are assigned to coded
reference pictures to be referenced in inter prediction. For
example, two reference picture lists (L0, L1) are generated for a
B-picture because it can be coded with reference to two
pictures.
[0067] FIG. 1A is a diagram for illustrating an exemplary reference
picture list for a B-picture. FIG. 1B shows an exemplary reference
picture list 0 (L0) for a prediction direction 0 in bi-prediction.
In the reference picture list 0, the reference picture index 0
having a value of 0 is assigned to a reference picture 0 with a
display order number 2. The reference picture index 0 having a
value of 1 is assigned to a reference picture 1 with a display
order number 1. The reference picture index 0 having a value of 2
is assigned to a reference picture 2 with a display order number 0.
In other words, the shorter the temporal distance of a reference
picture from the current picture, the smaller the reference picture
index assigned to the reference picture.
[0068] On the other hand, FIG. 1C shows an exemplary reference
picture list 1 (L1) for a prediction direction 1 in bi-prediction.
In the reference picture list 1, the reference picture index 1
having a value of 0 is assigned to a reference picture 1 with a
display order number 1. The reference picture index 1 having a
value of 1 is assigned to a reference picture 0 with a display
order number 2. The reference picture index 1 having a value of 2
is assigned to a reference picture 2 with a display order number
0.
[0069] In this manner, it is possible to assign reference picture
indexes having values different between prediction directions to a
reference picture (the reference pictures 0 and 1 in FIG. 1A) or to
assign the reference picture index having the same value for both
directions to a reference picture (the reference picture 2 in FIG.
1A).
[0070] In a moving picture coding method referred to as H.264 (see
Non-patent Literature 1), a motion vector estimation mode is
available as a coding mode for inter prediction of each current
block in a B-picture. In the motion vector estimation mode, a
difference value between picture data of a current block and
prediction picture data and a motion vector used for generating the
prediction picture data are coded. In addition, in the motion
vector estimation mode, bi-prediction and uni-prediction can be
selectively performed. In bi-prediction, a prediction picture is
generated with reference to two coded pictures one of which
precedes a current picture to be coded and the other of which
follows the current picture. In uni-prediction, a prediction
picture is generated with reference to one coded picture preceding
or following a current picture to be coded.
[0071] Furthermore, in the moving picture coding method referred to
as H.264, a coding mode referred to as a temporal motion vector
prediction mode can be selected for derivation of a motion vector
in coding of a B-picture. The inter prediction coding method
performed in the temporal motion vector prediction mode will be
described below using FIG. 2. FIG. 2 is a diagram for illustrating
motion vectors for use in the temporal motion vector prediction
mode. Specifically, FIG. 2 shows a case where a block a in a
picture B2 is coded in temporal motion vector prediction mode.
[0072] In the coding, a motion vector vb is used which has been
used in coding of a block b located in the same position in a
picture P3, which is a reference picture following the picture B2,
as the position of the block a in the picture B2 (the block b is
hereinafter referred to as a "co-located block" of the block a).
The motion vector vb is a motion vector used in coding the block b
with reference to the picture P1.
[0073] Motion vectors parallel to the motion vector vb are used for
obtaining two reference blocks for the block a are obtained from a
forward reference picture and a backward reference picture, that
is, a picture P1 and a picture P3. Then, the block a is coded using
bi-prediction based on the two obtained reference blocks.
Specifically, in the coding of the block a, a motion vector va1 is
used to reference the picture P1, and a motion vector va2 is used
to reference the picture P3.
[0074] In addition, a merging mode has been discussed which is an
inter prediction mode for coding of each current block in a
B-picture or a P-picture (see Non-patent Literature 2). In the
merging mode, a current block is coded using a prediction
direction, a motion vector, and a reference picture index which are
copies of those used in coding a neighboring block of the current
block. At this time, the copies of the index and others of the
neighboring block are attached to a coded bitstream (hereinafter
simply referred to as a "bitstream" as appropriate) so that the
motion direction, motion vector, and reference picture index used
for the coding can be selected in decoding.
[0075] FIG. 3 shows an exemplary motion vector of a neighboring
block for use in the merging mode. In FIG. 3, a neighboring block A
is a coded block located on the immediate left of a current block.
A neighboring block B is a coded block located immediately above
the current block. A neighboring block C is a coded block located
on the immediate above right of the current block. A neighboring
block D is a coded block located on the immediate below left of the
current block.
[0076] The neighboring block A is a block coded using
uni-prediction in the prediction direction 0. The neighboring block
A has a motion vector MvL0_A having the prediction direction 0 as a
motion vector to a reference picture indicated by a reference
picture index RefL0_A of the prediction direction 0. Here, MvL0
represents a motion vector which references a reference picture
specified in a reference picture list 0 (L0). MvL1 represents a
motion vector which references a reference picture specified in a
reference picture list 1 (L1).
[0077] The neighboring block B is a block coded using
uni-prediction in the prediction direction 1. The neighboring block
B has a motion vector MvL1_B having the prediction direction 1 as a
motion vector to a reference picture indicated by a reference
picture index RefL1_B of the prediction direction 1.
[0078] The neighboring block C is a block coded using intra
prediction.
[0079] The neighboring block D is a block coded using
uni-prediction in the prediction direction 0. The neighboring block
D has a motion vector MvL0_D having the prediction direction 0 as a
motion vector to a reference picture indicated by a reference
picture index RefL0_D of the prediction direction 0.
[0080] In this case, for example, a set of a prediction direction,
a motion vector, and a reference picture index with which the
current block can be coded with the highest coding efficiency is
selected as a set of a prediction direction, a motion vector, and a
reference picture index of the current block from among the sets of
prediction directions, motion vectors, and reference picture
indexes of the neighboring blocks A to D and the set of a
prediction direction, a motion vector, and a reference picture
index which are calculated using a co-located block in temporal
motion vector prediction mode. Then, a merging block candidate
index indicating a block having the selected set of a prediction
direction, a motion vector, and a reference picture index is
attached to a bitstream.
[0081] For example, when the neighboring block A is selected, the
current block is coded using the motion vector MvL0_A having the
prediction direction 0 and the reference picture index RefL0_A.
Then, only the merging block candidate index having a value of 0
which indicates use of the neighboring block A as shown in FIG. 4
is attached to a bitstream. The amount of information on a
prediction direction, a motion vector, and a reference picture
index is thereby reduced.
[0082] Furthermore, in the merging mode, a candidate which cannot
be used for coding (hereinafter referred to as an
"unusable-for-merging candidate"), and a candidate having a set of
a prediction direction, a motion vector, and a reference picture
index identical to a set of a prediction direction, a motion
vector, and a reference picture index of any other merging block
(hereinafter referred to as an "identical candidate") are removed
from merging block candidates as shown in FIG. 4.
[0083] In this manner, the total number of merging block candidates
is reduced so that the amount of code assigned to merging block
candidate indexes can be reduced. Here, "unusable for merging"
means (1) that the merging block candidate has been coded using
intra prediction, (2) that the merging block candidate is outside
the boundary of a slice including the current block or the boundary
of a picture including the current block, or (3) that the merging
block candidate is yet to be coded.
[0084] In the example shown in FIG. 4, the neighboring block C is a
block coded using intra prediction. The merging block candidate
having the merging block candidate index 3 is therefore an
unusable-for-merging candidate and removed from the merging block
candidate list. The neighboring block D is identical in prediction
direction, motion vector, and reference picture index to the
neighboring block A. The merging block candidate having the merging
block candidate index 4 is therefore removed from the merging block
candidate list. As a result, the total number of the merging block
candidates is finally three, and the size of the merging block
candidate list is set at three.
[0085] Merging block candidate indexes are coded by variable-length
coding by assigning bit sequences according to the size of each
merging block candidate list as shown in FIG. 5. Thus, in the
merging mode, bit sequences assigned to merging mode indexes are
changed according to the size of each merging block candidate list
so that the amount of code can be reduced.
[0086] FIG. 6 is a flowchart showing an example of a process for
coding when the merging mode is used. In Step S1001, sets of a
motion vector, a reference picture index, and a prediction
direction of merging block candidates are obtained from neighboring
blocks and a co-located block. In Step S1002, identical candidates
and unusable-for-merging candidates are removed from the merging
block candidates. In Step S1003, the total number of the merging
block candidates after the removing is set as the size of the
merging block candidate list. In Step S1004, the merging block
candidate index to be used in coding of the current block is
determined. In Step S1005, the determined merging block candidate
index is coded by performing variable-length coding in bit sequence
according to the size of the merging block candidate list.
[0087] FIG. 7 is a block diagram illustrating an exemplary
configuration of an image coding apparatus in which the merging
mode is used. In FIG. 7, the merging block candidate calculation
unit derives a merging block candidate list (Steps S1001 and S1002)
and transmits the total number of merging block candidates to the
variable-length-coding unit. The variable-length-coding unit 116
sets the total number of merging block candidates as the size of
the merging block candidate list (Step 1003). Furthermore, the
variable-length-coding unit determines a merging block candidate
index to be used in coding of a current block (Step 1004).
Furthermore, the variable-length-coding unit performs
variable-length coding on the determined merging block candidate
index using a bit sequence according to the size of the merging
block candidate list (Step S1005).
[0088] FIG. 8 is a flowchart showing an example of a process for
decoding using the merging mode. In Step S2001, sets of a motion
vector, a reference picture index, and a prediction direction of
merging block candidate are obtained from neighboring blocks and a
co-located block. In Step S2002, identical candidates and
unusable-for-merging candidates are removed from the merging block
candidates. In Step S2003, the total number of the merging block
candidates after the removing is set as the size of the merging
block candidate list. In Step S2004, the merging block candidate
index to be used in decoding of a current block is decoded from a
bitstream using the size of the merging block candidate list. In
Step S2005, the current block is decoded by generating a prediction
picture using the merging block candidate indicated by the decoded
merging block candidate index.
[0089] FIG. 9 is a block diagram illustrating an exemplary
configuration of an image decoding apparatus in which the merging
mode is used. In FIG. 9, the merging block candidate calculation
unit derives a merging block candidate list (Steps S2001 and S2002)
and transmits the total number of merging block candidates to the
variable-length-decoding unit. The variable-length-decoding unit
sets the total number of merging block candidates as the size of
the merging block candidate list (Step S2003). Furthermore, using
the size of the merging block candidate list, the
variable-length-decoding unit decodes, from a bitstream, a merging
block candidate index to be used in decoding of a current block
(Step S2004).
[0090] FIG. 10 shows syntax for attachment of a merging block
candidate index to a bitstream. In FIG. 10, merge_idx represents a
merging block candidate index, and merge_flag represents a merging
flag. NumMergeCand represents the size of a merging block candidate
list. NumMergeCand is set at the total number of merging block
candidates after unusable-for-merging candidates and identical
candidates are removed from the merging block candidates.
[0091] Coding or decoding of an image is performed using the
merging mode in the above-described manner.
[0092] As described above, in the conventional merging mode, a
merging block candidate list is derived by removing
unusable-for-merging candidates and identical candidates based on
information on reference pictures including a co-located block.
Then, the total number of merging block candidates in the merging
block candidate list after the removing is set as the size of the
merging block candidate list. In the case where there is a
difference in the total number of merging block candidates between
an image coding apparatus and an image decoding apparatus, a
discrepancy arises in bit sequence assigned to a merging block
candidate index between the image coding apparatus and the image
decoding apparatus, which causes a problem that a bitstream cannot
be normally decoded.
[0093] For example, when information on a reference picture
referenced as a co-located block is lost due to packet loss in a
transmission path, the motion vector or reference picture index of
the co-located block becomes unknown so that information on a
merging block candidate to be generated from the co-located block
is no longer unavailable. Then, it is impossible to correctly
remove unusable-for-merging candidates and identical candidates
from merging block candidates in decoding, and a correct size of a
merging block candidate list is therefore no longer obtainable. As
a result, it is impossible to normally decode a merging block
candidate index.
[0094] This problem can be solved by using merging block candidate
lists having a fixed size. When merging block candidate lists have
a fixed size, it is no longer necessary to calculate the size of
merging block candidate lists.
[0095] However, such a merging block candidate list having a fixed
size includes an empty entry when the size of the merging block
candidate list is larger than the total number of candidates
derived from spatially neighboring blocks (usable-for-merging
candidates except identical candidates) and a candidate which is
derived from a co-located block, that is, a temporally neighboring
block (first candidate). In this case, there is a problem that an
unexpected operation may be performed when the empty entry is
referenced in the image decoding apparatus due to an error.
[0096] Here, an image decoding method according to an aspect of the
present disclosure is a method for decoding, on a block-by-block
basis, image data included in a coded bitstream, and includes:
obtaining a fixed number of merging candidates each of which is a
candidate set of a prediction direction, a motion vector, and a
reference picture index which are to be referenced in decoding of a
current block, the fixed number being greater than or equal to two;
obtaining, from the coded bitstream, an index for identifying a
merging candidate among the fixed number of merging candidates, the
identified merging candidate being a merging candidate to be
referenced in the decoding of the current block; and identifying
the merging candidate using the obtained index, and decoding the
current block using the identified merging candidate, wherein the
fixed number of merging candidates include: one or more first
candidates each derived based on a prediction direction, a motion
vector, and a reference picture index which have been used for
decoding a neighboring block spatially or temporally neighboring
the current block; and one or more second candidates having a
predetermined fixed value.
[0097] In the image decoding method, a fixed number (greater than
or equal to two) of merging candidates are obtained, that is, a
merging block candidate list has a fixed size (hereinafter simply
referred to as "candidate list size" as appropriate), and any empty
entry after deriving the first candidates is filled with a second
candidate. This prevents an unexpected operation which may be
performed when such an empty entry is referenced, so that error
resistance can be enhanced.
[0098] It should be noted that the phrase "having a predetermined
fixed value" means that second candidates in a merging block
candidate list are identical in prediction direction, motion
vector, and reference picture index. In other words, second
candidates in different merging block candidate lists may be
different in prediction direction, motion vector, or reference
picture index.
[0099] It should be noted that a third candidate may be further
added to increase coding efficiency in the image decoding method.
Also in this case, when a merging block candidate list (hereinafter
simply referred to as a "candidate list" as appropriate) has any
empty entry after first candidates and third candidates are
derived, the empty entry is filled with a second candidate so that
error resistance can be enhanced. It should be noted that unlike
the second candidates, the third candidates added in a single
merging block candidate list are different in at least one of
prediction direction, motion vector, and reference picture index
from each other because the third candidates are added for the
purpose of increasing coding efficiency (however, the third
candidates may be identical to any of a first candidate and a
second candidate as a result).
[0100] Furthermore, for example, the obtaining of a fixed number of
merging candidates may include: deriving the one or more first
candidates and including the one or more first candidates in the
fixed number of merging candidates; deriving one or more third
candidates and including the one or more third candidates in the
fixed number of merging candidates, when a total number of the
first candidates is smaller than the fixed number, the third
candidates each having a picture index for a picture referable in
the decoding of the current block; and deriving the one or more
second candidates and including the one or more second candidates
in the fixed number of merging candidates so that a total number of
the first candidates, the second candidates, and the third
candidates equals the fixed number, when a total number of the
first candidates and the third candidates is smaller than the fixed
number.
[0101] Furthermore, for example, in the deriving of one or more
third candidates, the one or more third candidates may be derived
by selecting, according to a predetermined priority order, one or
more candidates from among a plurality of prepared candidates
different from each other.
[0102] Furthermore, for example, the obtaining of a fixed number of
merging candidates may include: initializing the fixed number of
merging candidates by setting all the fixed number of merging
candidates to the second candidates; deriving the one or more first
candidates and updating part of the fixed number of merging
candidates so as to include the one or more first candidates in the
fixed number of merging candidates; and deriving one or more third
candidates and updating part of the fixed number of merging
candidates so as to include the one or more third candidates in the
fixed number of merging candidates, when a total number of the
first candidates is smaller than the fixed number, the third
candidates each having a picture index for a picture referable in
the decoding of the current block.
[0103] An image coding method according to an aspect of the present
disclosure is a method for coding an image on a block-by-block
basis to generate a coded bitstream, and includes: obtaining a
fixed number of merging candidates each of which is a candidate set
of a prediction direction, a motion vector, and a reference picture
index which are to be referenced in coding of a current block, the
fixed number being greater than or equal to two; and attaching, to
the coded bitstream, an index for identifying a merging candidate
among the fixed number of merging candidates, the identified
merging candidate being a merging candidate to be referenced in the
coding of the current block, wherein the fixed number of merging
candidates include: one or more first candidates each derived based
on a prediction direction, a motion vector, and a reference picture
index which have been used for coding a neighboring block spatially
or temporally neighboring the current block; and one or more second
candidates having a predetermined fixed value.
[0104] Furthermore, for example, the obtaining of a fixed number of
merging candidates may include: deriving the one or more first
candidates and including the one or more first candidates in the
fixed number of merging candidates; deriving one or more third
candidates and including the one or more third candidates in the
fixed number of merging candidates, when a total number of the
first candidates is smaller than the fixed number, the third
candidates each having a picture index for a picture referable in
the decoding of the current block; and deriving the one or more
second candidates and including the one or more second candidates
in the fixed number of merging candidates so that a total number of
the first candidates, the second candidates, and the third
candidates equals the fixed number, when a total number of the
first candidates and the third candidates is smaller than the fixed
number.
[0105] Furthermore, for example, in the deriving of one or more
third candidates, the one or more third candidates may be derived
by selecting, according to a predetermined priority order, one or
more candidates from among a plurality of prepared candidates
different from each other.
[0106] Furthermore, for example, the obtaining of a fixed number of
merging candidates may include: initializing the fixed number of
merging candidates by setting all the fixed number of merging
candidates to the second candidates; deriving the one or more first
candidates and updating part of the fixed number of merging
candidates so as to include the one or more first candidates in the
fixed number of merging candidates; and deriving one or more third
candidates and updating part of the fixed number of merging
candidates so as to include the one or more third candidates in the
fixed number of merging candidates, when a total number of the
first candidates is smaller than the fixed number, the third
candidates each having a picture index for a picture referable in
the decoding of the current block.
[0107] An image decoding apparatus according to an aspect of the
present disclosure is an image decoding apparatus which decodes, on
a block-by-block basis, image data included in a coded bitstream,
and includes: an merging candidate obtaining unit configured to
obtain a fixed number of merging candidates each of which is a
candidate set of a prediction direction, a motion vector, and a
reference picture index which are to be referenced in decoding of a
current block, the fixed number being greater than or equal to two;
an index obtaining unit configured to obtain, from the coded
bitstream, an index for identifying a merging candidate among the
fixed number of merging candidates, the identified merging
candidate being a merging candidate to be referenced in the
decoding of the current block; and a decoding unit configured to
identify the merging candidate using the obtained index and decode
the current block using the identified merging candidate, wherein
the fixed number of merging candidates include: one or more first
candidates each derived based on a prediction direction, a motion
vector, and a reference picture index which have been used for
decoding a neighboring block spatially or temporally neighboring
the current block; and one or more second candidates having a
predetermined fixed value.
[0108] An image coding apparatus according to an aspect of the
present disclosure is an image coding apparatus which codes an
image on a block-by-block basis to generate a coded bitstream, and
includes: an merging candidate obtaining unit configured to obtain
a fixed number of merging candidates each of which is a candidate
set of a prediction direction, a motion vector, and a reference
picture index to be referenced in decoding of a current block, the
fixed number being greater than or equal to two; and a coding unit
configured to attach, to the coded bitstream, an index for
identifying a merging candidate among the fixed number of merging
candidates, the identified merging candidate being a merging
candidate to be referenced in the coding of the current block,
wherein the fixed number of merging candidates include: one or more
first candidates each derived based on a prediction direction, a
motion vector, and a reference picture index which have been used
for coding a neighboring block spatially or temporally neighboring
the current block; and one or more second candidates having a
predetermined fixed value.
[0109] An image coding and decoding apparatus according to an
aspect of the present disclosure includes: the image decoding
apparatus; and the image coding apparatus.
[0110] It should be noted that these general or specific aspects
can be implemented as a system, a method, an integrated circuit, a
computer program, a computer-readable recording medium such as a
compact disc read-only memory (CD-ROM), or as any combination of a
system, a method, an integrated circuit, a computer program, and a
computer-readable recording medium.
[0111] An image coding apparatus and an image decoding apparatus
according to an aspect of the present disclosure will be described
specifically below with reference to the drawings.
[0112] Each of the exemplary embodiments described below shows a
specific example for the present disclosure. The numerical values,
shapes, materials, constituent elements, the arrangement and
connection of the constituent elements, steps, the processing order
of the steps etc. shown in the following exemplary embodiments are
mere examples, and therefore do not limit the inventive concept in
the present disclosure. Furthermore, among the constituent elements
in the following exemplary embodiments, constituent elements not
recited in any one of the independent claims defining the most
generic part of the inventive concept are not necessarily required
in order to overcome the disadvantages.
Embodiment 1
[0113] An image coding apparatus using an image coding method
according to Embodiment 1 will be described with reference to FIG.
11 to FIG. 18. FIG. 11 is a block diagram showing a configuration
of an image coding apparatus according to Embodiment 1. An image
coding apparatus 100 codes an image on a block-by-block basis to
generate a bitstream.
[0114] As shown in FIG. 11, the image coding apparatus 100 includes
a subtractor 101, an orthogonal transformation unit 102, a
quantization unit 103, an inverse-quantization unit 104, an
inverse-orthogonal-transformation unit 105, an adder 106, block
memory 107, frame memory 108, an intra prediction unit 109, an
inter prediction unit 110, an inter prediction control unit 111, a
picture-type determination unit 112, a switch 113, a merging block
candidate calculation unit 114, colPic memory 115, and a
variable-length-coding unit 116.
[0115] The subtractor 101 subtracts, on a block-by-block basis,
prediction picture data from input image data included in an input
image sequence to generate prediction error data.
[0116] The orthogonal transformation unit 102 transforms the
generated prediction error data from a picture domain into a
frequency domain.
[0117] The quantization unit 103 quantizes the prediction error
data transformed into a frequency domain.
[0118] The inverse-quantization unit 104 inverse-quantizes the
prediction error data quantized by the quantization unit 103. The
inverse-orthogonal-transformation unit 105 transforms the
inverse-quantized prediction error data from a frequency domain
into a picture domain.
[0119] The adder 106 adds, on a block-by-block basis, prediction
picture data and the prediction error data inverse-quantized by the
inverse-orthogonal-transformation unit 105 to generate
reconstructed image data.
[0120] The block memory 107 stores the reconstructed image data in
units of a block.
[0121] The frame memory 108 stores the reconstructed image data in
units of a frame.
[0122] The picture-type determination unit 112 determines in which
of the picture types of I-picture, B-picture, and P-picture the
input image data is to be coded. Then, the picture-type
determination unit 112 generates picture-type information
indicating the determined picture type.
[0123] The intra prediction unit 109 generates intra prediction
picture data of a current block by performing intra prediction
using reconstructed image data stored in the block memory 107 in
units of a block.
[0124] The inter prediction unit 110 generates inter prediction
picture data of a current block by performing inter prediction
using reconstructed image data stored in the frame memory 108 in
units of a frame and a motion vector derived by a process including
motion estimation.
[0125] When a current block is coded by intra prediction coding,
the switch 113 outputs intra prediction picture data generated by
the intra prediction unit 109 as prediction picture data of the
current block to the subtractor 101 and the adder 106. On the other
hand, when a current block is coded by inter prediction coding, the
switch 113 outputs inter prediction picture data generated by the
inter prediction unit 110 as prediction picture data of the current
block to the subtractor 101 and the adder 106.
[0126] The merging block candidate calculation unit 114 according
to Embodiment 1 generates a merging block candidate list to include
a fixed number of merging block candidates.
[0127] Specifically, the merging block candidate calculation unit
114 derives first candidates which are merging block candidates for
merging mode using motion vectors and others of neighboring blocks
of the current block and a motion vector and others of the
co-located block (colPic information) stored in the colPic memory
115. Furthermore, the merging block candidate calculation unit 114
adds the derived merging block candidates to the merging block
candidate list.
[0128] Furthermore, when the merging block candidate list has any
empty entry, the merging block candidate calculation unit 114
selects a third candidate, which is a new candidate, from among
predetermined merging block candidates to increase coding
efficiency. Then, the merging block candidate calculation unit 114
adds the derived new candidate as a new merging block candidate to
the merging block candidate list. Furthermore, the merging block
candidate calculation unit 114 calculates the total number of the
merging block candidates.
[0129] Furthermore, the merging block candidate calculation unit
114 assigns merging block candidate indexes each having a different
value to the derived merging block candidates. Then, the merging
block candidate calculation unit 114 transmits the merging block
candidates and merging block candidate indexes to the inter
prediction control unit 111. Furthermore, the merging block
candidate calculation unit 114 transmits the calculated total
number of the merging block candidates to the
variable-length-coding unit 116.
[0130] The inter prediction control unit 111 selects a prediction
mode using which prediction error is the smaller from a prediction
mode in which a motion vector derived by motion estimation is used
(motion estimation mode) and a prediction mode in which a motion
vector derived from a merging block candidate is used (merging
mode). The inter prediction control unit 111 also transmits a
merging flag indicating whether or not the selected prediction mode
is the merging mode to the variable-length-coding unit 116.
Furthermore, the inter prediction control unit 111 transmits a
merging block candidate index corresponding to the determined
merging block candidates to the variable-length-coding unit 116
when the selected prediction mode is the merging mode. Furthermore,
the inter prediction control unit 111 transfers the colPic
information including the motion vector and others of the current
block to the colPic memory 115.
[0131] The variable-length-coding unit 116 generates a bitstream by
performing variable-length coding on the quantized prediction error
data, the merging flag, and the picture-type information. The
variable-length-coding unit 116 also sets the total number of
merging block candidates as the size of the merging block candidate
list. Furthermore, the variable-length-coding unit 116 performs
variable-length coding on a merging block candidate index to be
used in coding, by assigning, according to the size of the merging
block candidate list, a bit sequence to the merging block candidate
index.
[0132] FIG. 12 is a flowchart showing processing operations of the
image coding apparatus 100 according to Embodiment 1.
[0133] In Step S101, the merging block candidate calculation unit
114 derives merging block candidates from neighboring blocks and a
co-located block of a current block. Furthermore, the merging block
candidate calculation unit 114 calculates the size of a merging
block candidate list using a method described later when the size
of the merging block candidate list is set variable.
[0134] For example, in the case shown in FIG. 3, the merging block
candidate calculation unit 114 selects the neighboring blocks A to
D as merging block candidates. Furthermore, the merging block
candidate calculation unit 114 calculates, as a merging block
candidate, a co-located merging block having a motion vector, a
reference picture index, and a prediction direction which are
calculated from the motion vector of a co-located block using the
time prediction mode.
[0135] The merging block candidate calculation unit 114 assigns
merging block candidate indexes to the respective merging block
candidates. (a) in FIG. 13A is a table of a merging block candidate
list in which merging block candidate indexes are assigned to
neighboring blocks. The left column of the merging block candidate
list in (a) in FIG. 13A lists merging block candidate indexes. The
right column lists sets of a prediction directions, reference
picture indexes, and motion vectors. Furthermore, using a method
described later, the merging block candidate calculation unit 114
removes unusable-for-merging candidates and identical candidates
and adds new candidates to update the merging block candidate list,
and calculates the size of the merging block candidate list. (b) in
FIG. 13A is a merging block candidate list after removing an
unusable-for-merging candidate and an identical candidate and
adding a new candidate. The neighboring block A and the neighboring
block D are identical and the neighboring block D is removed in
Embodiment 1, but the neighboring block A may be removed
instead.
[0136] Shorter codes are assigned to merging block candidate
indexes of smaller values. In other words, the smaller the value of
a merging block candidate index, the smaller the amount of
information necessary for indicating the merging block candidate
index.
[0137] On the other hand, the larger the value of a merging block
candidate index, the larger the amount of information necessary for
the merging block candidate index. Therefore, coding efficiency
will be increased when merging block candidate indexes of smaller
values are assigned to merging block candidates which are more
likely to have motion vectors of higher accuracy and reference
picture indexes of higher accuracy.
[0138] Therefore, there may be case in which the merging block
candidate calculation unit 114 counts the total number of times of
selection of each merging block candidates as a merging block, and
assigns merging block candidate indexes of smaller values to blocks
with a larger total number of the times. Specifically, this can be
achieved by specifying a merging block selected from neighboring
blocks and assigning a merging block candidate index of a smaller
value to the specified merging block when a current block is
coded.
[0139] When a merging block candidate does not have information
such as a motion vector (for example, when the merging block has
been a block coded by intra prediction, it is located outside the
boundary of a picture or the boundary of a slice, or it is yet to
be coded), the merging block candidate is unusable for coding.
[0140] In Embodiment 1, such a merging block candidate unusable for
coding is referred to as an unusable-for-merging candidate, and a
merging block candidate usable for coding is referred to as a
usable-for-merging candidate. In addition, among a plurality of
merging block candidates, a merging block candidate identical in
motion vector, reference picture index, and prediction direction to
any other merging block is referred to as an identical
candidate.
[0141] In the case shown in FIG. 3, the neighboring block C is an
unusable-for-merging candidate because it is a block coded by intra
prediction. The neighboring block D is an identical candidate
because it is identical in motion vector, reference picture index,
and prediction direction to the neighboring block A.
[0142] In Step S102, the inter prediction control unit 111 selects
a prediction mode based on comparison, using a method described
later, between prediction error of a prediction picture generated
using a motion vector derived by motion estimation and prediction
error of a prediction picture generated using a motion vector
obtained from a merging block candidate. When the selected
prediction mode is the merging mode, the inter prediction control
unit 111 sets the merging flag to 1, and when not, the inter
prediction control unit 111 sets the merging flag to 0.
[0143] In Step S103, whether or not the merging flag is 1 (that is,
whether or not the selected prediction mode is the merging mode) is
determined.
[0144] When the result of the determination in Step S103 is true
(Yes, S103), the variable-length-coding unit 116 attaches the
merging flag to a bitstream in Step S104. Subsequently, in Step
S105, the variable-length-coding unit 116 assigns bit sequences
according to the size of the merging block candidate list as shown
in FIG. 5 to the merging block candidate indexes of merging block
candidates to be used for coding. Then, the variable-length-coding
unit 116 performs variable-length coding on the assigned bit
sequence.
[0145] On the other hand, when the result of the determination in
Step S103 is false (S103, No), the variable-length-coding unit 116
attaches information on a merging flag and a motion estimation
vector mode to a bitstream in Step S106.
[0146] In Embodiment 1, a merging block candidate index having a
value of "0" is assigned to the neighboring block A as shown in (a)
in FIG. 13A. A merging block candidate index having a value of "1"
is assigned to the neighboring block B. A merging block candidate
index having a value of "2" is assigned to the co-located merging
block. A merging block candidate index having a value of "3" is
assigned to the neighboring block C. A merging block candidate
index having a value of "4" is assigned to the neighboring block
D.
[0147] It should be noted that the merging block candidate indexes
having such a value may be assigned otherwise. For example, when a
new candidate is added using a method described later, the
variable-length-coding unit 116 may assign smaller values to
preexistent merging block candidates and a larger value to the new
candidate. In other words, the variable-length-coding unit 116 may
assign a merging block candidate index of a smaller value to a
preexistent merging block candidate in priority to a new
candidate.
[0148] Furthermore, merging block candidates are, not limited to
the blocks at the positions of the neighboring blocks A, B, C, and
D. For example, a neighboring block located above the lower left
neighboring block D can be used as a merging block candidate.
Furthermore, it is not necessary to use all the neighboring blocks
as merging block candidates. For example, it is also possible to
use only the neighboring blocks A and B as merging block
candidates.
[0149] Furthermore, although the variable-length-coding unit 116
attaches a merging block candidate index to a bitstream in Step
S105 in FIG. 12 in Embodiment 1, attaching such a merging block
candidate index to a bitstream is not always necessary. For
example, the variable-length-coding unit 116 need not attach a
merging block candidate index to a bitstream when the size of the
merging block candidate list is "1". The amount of information on
the merging block candidate index is thereby reduced.
[0150] FIG. 14A is a flowchart showing details of the process in
Step S101 in FIG. 12. Specifically, FIG. 14A illustrates a method
of calculating merging block candidates and the size of a merging
block candidate list. FIG. 14A will be described below.
[0151] Before the process shown in FIG. 14A, the merging block
candidate calculation unit 114 assigns index values to the
neighboring blocks (the neighboring blocks A to D and the
co-located merging block) as shown in (a) in FIG. 13A.
[0152] Here, N denotes an index value for identifying a merging
block candidate. In Embodiment 1, N takes values from 0 to 4.
Specifically, the neighboring block A in FIG. 3 is assigned to a
merging block candidate [0]. The neighboring block B in FIG. 3 is
assigned to a merging block candidate [1]. The co-located merging
block is assigned to a merging block candidate [2]. The neighboring
block C in FIG. 3 is assigned to a merging block candidate [3]. The
neighboring block D in FIG. 3 is assigned to a merging block
candidate [4].
[0153] After assigning the index values to the neighboring blocks,
the merging block candidate calculation unit 114 determines whether
or not each of the merging block candidates [0] to [4] is usable
for merging (Step S111), and obtains information on the merging
block candidates [0] to [4] to enter in the right column of the
merging block candidate list shown in FIG. 13A (Step S112).
[0154] In Step S111, the merging block candidate calculation unit
114 determines whether or not the merging block candidate [N] is a
usable-for-merging candidate using a method described later, and
derives the total number of merging block candidates.
[0155] In Step S112, the merging block candidate calculation unit
114 obtains a set of a motion vector, a reference picture index,
and a prediction direction of the merging block candidate [N], and
adds them to a merging block candidate list (the right column).
[0156] In Step S113, the merging block candidate calculation unit
114 searches the merging block candidate list for any
unusable-for-merging candidate and identical candidate, and removes
the unusable-for-merging candidate and identical candidate from the
merging block candidate list as shown in (b) in FIG. 13A.
Furthermore, the merging block candidate calculation unit 114
subtracts the total number of the removed identical candidates from
the total number of the merging block candidates.
[0157] In Step S114, the merging block candidate calculation unit
114 adds a new candidate (third candidate) to the merging block
candidate list using a method described later. Here, when the new
candidate is added, merging block candidate indexes may be
reassigned so that the merging block candidate indexes of smaller
values are assigned to preexistent merging block candidates in
priority to the new candidate. In other words, the merging block
candidate calculation unit 114 may reassign the merging block
candidate indexes so that a merging block candidate index of a
larger value is assigned to the new candidate. The amount of code
of merging block candidate indexes is thereby reduced.
[0158] In Step S115, the merging block candidate calculation unit
114 sets the total number of merging block candidates after the
adding of the new candidate as the size of the merging block
candidate list. In the example shown in (b) in FIG. 13A, the total
number of merging block candidates is calculated to be "5", and the
size of the merging block candidate list is set at "5". It should
be noted that when the size of the merging block candidate list is
set not variable but at a fixed number, for example, a number
greater than or equal to two, the fixed number greater than or
equal to two is set as the size of the merging block candidate
list.
[0159] The new candidate in Step S114 is a candidate newly added to
merging block candidates using a method described later when the
total number of merging block candidates is smaller than a maximum
number of merging block candidates. Examples of such a new
candidate include a neighboring block located above the lower-left
neighboring block D in FIG. 3, a block which is included in a
reference picture including a co-located block and corresponds to
one of the neighboring blocks A, B, C, and D, and a block having
values statistically obtained from motion vectors, reference
picture indexes, and prediction directions of the whole or a
certain region of a reference picture. Examples of such a new
candidate further include a zero candidate which has a motion
vector having a value of zero for each referable reference picture.
Examples of such a new candidate further include a bi-predictive
merging block candidate which is a combination of a set of a motion
vector and a reference picture index for a prediction direction 0
of one of derived merging block candidates and a set of a motion
vector and a reference picture index for a prediction direction 1
of a different one of the derived merging block candidates. Such a
bi-predictive merging block candidate is hereinafter referred to as
a combined merging block. In this manner, when the total number of
merging block candidates is smaller than a maximum number of
merging block candidates, the image coding apparatus 100 adds a new
candidate so that coding efficiency can be increased.
[0160] FIG. 15A is a flowchart showing details of the process in
Step S111 in FIG. 14A. Specifically, FIG. 15A illustrates a method
of determining whether or not a merging block candidate [N] is a
usable-for-merging candidate and updating the total number of
usable-for-merging candidates. FIG. 15A will be described
below.
[0161] In Step S121, the merging block candidate calculation unit
114 determines whether it is true or false that (1) a merging block
candidate [N] has been coded by intra prediction, (2) the merging
block candidate [N] is a block outside the boundary of a slice
including the current block or the boundary of a picture including
the current block, or (3) the merging block candidate [N] is yet to
be coded.
[0162] When the result of the determination in Step 121 is true
(Step S121, Yes), the merging block candidate calculation unit 114
sets the merging block candidate [N] as an unusable-for-merging
candidate in Step S122. On the other hand, when the result of the
determination in Step S121 is false (Step S121, No), the merging
block candidate calculation unit 114 sets the merging block
candidate [N] as a usable-for-merging candidate in Step S123.
[0163] In Step S124, the merging block candidate calculation unit
114 determines whether it is true or false that the merging block
candidate [N] is either a usable-for-merging candidate or a
co-located merging block candidate.
[0164] Here, when the result of the determination in Step S124 is
true (Step S124, Yes), the merging block candidate calculation unit
114 updates the total number of merging block candidates by
incrementing it by one in Step S125. When the result of the
determination in Step S124 is false (Step S124, No), the merging
block candidate calculation unit 114 does not update the total
number of merging block candidates.
[0165] In this manner, when a co-located merging block is
calculated as a merging block candidate, the merging block
candidate calculation unit 114 according to Embodiment 1 increments
the total number of merging block candidates by one regardless of
whether the co-located block is a usable-for-merging candidate or
an unusable-for-merging candidate. This prevents discrepancy in the
total number of merging block candidates between the image coding
apparatus and the image decoding apparatus even when information on
a co-located merging block is lost due to an incident such as
packet loss. In Step S115 in FIG. 14A, the merging block candidate
calculation unit 114 sets the total number of merging block
candidates as the size of the merging block candidate list.
Furthermore, in Step S105 in FIG. 12, the merging block candidate
calculation unit 114 performs variable-length coding on a merging
block candidate index by assigning a bit sequence according to the
size of the merging block candidate list. This makes it possible to
generate a bitstream which can be normally decoded so that a
merging block candidate index can be obtained even when information
on reference picture including a co-located block is lost.
[0166] FIG. 16 is a flowchart showing details of the process in
Step S114 in FIG. 14A. Specifically, FIG. 16 illustrates a method
of adding a new candidate (third candidate) to increase coding
efficiency. FIG. 16 will be described below.
[0167] In Step S131, the merging block candidate calculation unit
114 determines whether or not the total number of merging block
candidates is smaller than the size of the merging block candidate
list. More specifically, when the size of the merging block
candidate list is variable, the merging block candidate calculation
unit 114 determines whether or not the total number of merging
block candidates is smaller than a maximum value of the candidate
list size (a maximum number of merging block candidates). On the
other hand, when the size of the merging block candidate list is
invariable (the size of the merging block candidate list is a fixed
number greater than or equal to two), the merging block candidate
calculation unit 114 determines whether or not the total number of
merging block candidates is smaller than the fixed number greater
than or equal to two.
[0168] Here, when the result of the determination in Step S131 is
true (Step S131, Yes), in Step S132, the merging block candidate
calculation unit 114 determines whether or not there is a new
candidate which can be added as a merging block candidate to the
merging block candidate list.
[0169] The new candidate is a prepared candidate, such as a zero
candidate which has a motion vector having a value of zero for each
referable reference picture. In this case, the total number of
referable reference pictures is the total number of candidates
which can be added as new candidates. The new candidate may be a
candidate other than such a zero candidate, such as a combined
candidate as described above.
[0170] When the result of the determination in Step S132 is true
(Step S132, Yes), the merging block candidate calculation unit 114
assigns a merging block candidate index having a value to the new
candidate and adds the new candidate to the merging block candidate
list in Step S133.
[0171] Furthermore, in Step S134, the merging block candidate
calculation unit 114 increments the total number of merging block
candidates by one.
[0172] On the other hand, when the result of the determination in
Step S131 or in Step S132 is false (Step S131 or Step S132, No),
the process for adding a new candidate ends. In other words, when
the total number of merging block candidates reaches the maximum
number of merging block candidates or when there is no more new
candidate (that is, all new candidates have been added as merging
block candidates to the candidate list), the process for adding a
new candidate ends.
[0173] FIG. 18 is a flowchart showing details of the process in
Step S102 in FIG. 12. Specifically, FIG. 18 illustrates a process
for selecting a merging block candidate. FIG. 18 will be described
below.
[0174] In Step S151, the inter prediction control unit 111 sets a
merging block candidate index at 0, the minimum prediction error at
the prediction error (cost) in the motion vector estimation mode,
and a merging flag at 0. Here, the cost is calculated using the
following equation for an R-D optimization model, for example.
Cost=D+.lamda.R (Equation 1)
[0175] In Equation 1, D denotes coding distortion. For example, D
is the sum of absolute differences between original pixel values of
a current block to be coded and pixel values obtained by coding and
decoding of the current block using a prediction picture generated
using a motion vector. R denotes the amount of generated codes. For
example, R is the amount of code necessary for coding a motion
vector used for generation of a prediction picture. .lamda. denotes
an undetermined Lagrange multiplier.
[0176] In Step S152, the inter prediction control unit 111
determines whether or not the value of a merging block candidate
index is smaller than the total number of merging block candidates
of a current block. In other words, the inter prediction control
unit 111 determines whether or not there is still a merging block
candidate on which the process from Step S153 to Step S155 has not
been performed yet.
[0177] When the result of the determination in Step S152 is true
(S152, Yes), in Step S153, the inter prediction control unit 111
calculates the cost for a merging block candidate to which a
merging block candidate index is assigned. Then, in Step S154, the
inter prediction control unit 111 determines whether or not the
calculated cost for a merging block candidate is smaller than the
minimum prediction error.
[0178] Here, when the result of the determination in Step S154 is
true, (S154, Yes), the inter prediction control unit 111 updates
the minimum prediction error, the merging block candidate index,
and the value of the merging flag in Step S155. On the other hand,
when the result of the determination in Step S154 is false (S154,
No), the inter prediction control unit 111 does not update the
minimum prediction error, the merging block candidate index, or the
value of the merging flag.
[0179] In Step S156, the inter prediction control unit 111
increments the merging block candidate index by one, and repeats
from Step S152 to Step S156.
[0180] On the other hand, when the result of the determination in
Step S152 is false (S152, No), that is, there is no more
unprocessed merging block candidate, the inter prediction control
unit 111 fixes the final values of the merging flag and merging
block candidate index in Step S157.
[0181] Thus, the image coding apparatus 100 according to Embodiment
1 calculates the size of a merging block candidate list for use in
coding or decoding of a merging block candidate index, using a
method independent of information on reference pictures including a
co-located block so that error resistance can be enhanced. More
specifically, in the image coding apparatus 100 according to
Embodiment 1, the total number of merging block candidates is
incremented by one for each co-located merging block regardless of
whether the co-located merging block is a usable-for-merging
candidate or an unusable-for-merging candidate. Then, bit sequences
to be assigned to merging block candidate indexes are determined
according to the total number of merging block candidates. This
allows the image coding apparatus 100 and the image decoding
apparatus 300 to have the same total number of merging block
candidates so that a bitstream can be normally decoded to obtain a
merging block candidate index even when information on reference
picture including a co-located block is lost. Thus, when the total
number of merging block candidates is smaller than the total number
of usable-for-merging candidates, a new candidate having a new set
of a motion vector, a reference picture index, and a prediction
direction is added so that coding efficiency can be increased.
[0182] It should be noted that Embodiment 1 in which the total
number of merging block candidates is incremented by one only for
each co-located merging block regardless of whether the co-located
merging block is a usable-for-merging candidate or an
unusable-for-merging candidate as shown in Step S125 and Step S126
in FIG. 15A, is not limiting. The total number of merging block
candidates may be incremented by one for any other block regardless
of whether the block is a usable-for-merging candidate or an
unusable-for-merging candidate.
[0183] Optionally, in Embodiment 1, when the size of a merging
block candidate list is a fixed number greater than or equal to
two, the fixed number greater than or equal to two may be set as a
maximum value Max of the total number of merging block candidates.
In other words, merging block candidate indexes may be coded using
the size of a merging block candidate list fixed at a maximum value
Max of the total number of merging block candidates on the
assumption that the merging block candidates which are neighboring
blocks are all usable-for-merging candidates. For example, in
Embodiment 1, the maximum value Max of the total number of merging
block candidates is 5 (neighboring block A, neighboring block B,
co-located merging block, neighboring block C, and neighboring
block D). In this case, merging block candidate indexes may be
coded using the size of a merging block candidate list fixedly set
at "5".
[0184] Optionally, for example, when the maximum value Max of the
total number of merging block candidates is set at 4 (neighboring
block A, neighboring block B, neighboring block C, and neighboring
block D) for a current picture which is to be coded without
referencing a co-located merging block (a B-picture or a P-picture
to be coded with reference to an I-picture), merging block
candidate indexes may be coded using the size of a merging block
candidate list fixedly set at "4".
[0185] In this manner, when the size of a merging block candidate
list is a fixed number greater than or equal to two, a maximum
value Max of the total number of merging block candidates may be
set at the fixed number greater than or equal to two to determine
the size of the merging block candidate list according to the fixed
number greater than or equal to two. In this case, the image coding
apparatus 100 performs variable-length coding using the fixed
number greater than or equal to two in Step S105 in FIG. 12.
[0186] It is therefore possible to generate a bitstream from which
a variable-length-decoding unit of an image decoding apparatus can
decode a merging block candidate index without referencing
information on a neighboring block or on a co-located block, so
that computational complexity for the variable-length-decoding unit
can be reduced. Furthermore, for example, a fixed number greater
than or equal to two (for example, a maximum value Max of the total
number of merging block candidates) may be embedded in a sequence
parameter set (SPS), a picture parameter set (PPS), a slice header,
or the like. This makes it possible to switch between fixed numbers
greater than or equal to two for each current picture so that
computational complexity can be reduced and coding efficiency can
be increased.
[0187] It should be noted that the example described in Embodiment
1 in which merging flag is always attached to a bitstream in
merging mode is not limiting. For example, the merging mode may be
forcibly selected based on the shape of a reference block for use
in inter prediction of a current block. In this case, the amount of
information can be reduced by attaching no merging flag to a
bitstream.
[0188] It should be noted that the example described in Embodiment
1 where the merging mode is used in which a current block is coded
using a prediction direction, a motion vector, and a reference
picture index copied from a neighboring block of the current block
is not limiting. For example, a skip merging mode may be used. In
the skip merging mode, a current block is coded with reference to a
merging block candidate list created as shown in (b) in FIG. 13A,
using a prediction direction, a motion vector, and a reference
picture index copied from a neighboring block of the current block
in the same manner as in the merging mode. When all resultant
prediction errors are zero for the current block, a skip flag set
at 1 and the skip flag and a merging block candidate index are
attached to a bitstream. When any of the resultant prediction
errors is non-zero, a skip flag is set at 0 and the skip flag, a
merging flag, a merging block candidate index, and data of the
prediction errors are attached to a bitstream.
[0189] It should be noted that the example described in Embodiment
1 where the merging mode is used in which a current block is coded
using a prediction direction, a motion vector, and a reference
picture index copied from a neighboring block of the current block
is not limiting. For example, a motion vector in the motion vector
estimation mode may be coded using a merging block candidate list
created as shown in (b) in FIG. 13A. Specifically, a difference is
calculated by subtracting a motion vector of a merging block
candidate indicated by a merging block candidate index from a
motion vector in the motion vector estimation mode. Furthermore,
the calculated difference and the merging block candidate index may
be attached to a bitstream.
[0190] Optionally, a difference may be calculated by scaling a
motion vector MV_Merge of a merging block candidate using a
reference picture index RefIdx_ME in the motion estimation mode and
a reference picture index RefIdx_Merge of the merging block
candidate and subtracting a motion vector scaledMV_Merge of the
merging block candidate after the scaling from the motion vector in
the motion estimation mode. Furthermore, the calculated difference
and the merging block candidate index may be attached to a
bitstream. The following is an exemplary formula for the
scaling.
(Equation 2)
scaledMV_Merge=MV_Merge.times.(POC(RefIdx_ME)-curPOC)/(POC(RefIdx_Merge)-
-curPOC) (2)
[0191] Here, POC (RefIdx_ME) denotes the display order of a
reference picture indicated by a reference picture index RefIdx_ME.
POC (RefIdx_Merge) denotes the display order of a reference picture
indicated by a reference picture index RefIdx_Merge. curPOC denotes
the display order of a current picture to be coded.
[0192] It should be noted that the variable-length coding (see FIG.
5) which is performed in Embodiment 1 according to the size of a
merging block candidate list in Step S105 in FIG. 12 may be
performed optionally according to another parameter such as the
total number of merging block candidates calculated as the total
number of usable-for-merging candidates which is the sum of the
total number of first candidates and the total number of identical
candidates calculated in Step S111 (detailed in FIG. 15A) in FIG.
14A.
Embodiment 2
[0193] An image decoding apparatus using an image decoding method
according to Embodiment 2 will be described with reference to FIG.
19 to FIG. 22. FIG. 19 is a block diagram showing a configuration
of an image decoding apparatus 300 according to Embodiment 2. The
image decoding apparatus 300 is an apparatus corresponding to the
image coding apparatus 100 according to Embodiment 1. Specifically,
for example, the image decoding apparatus 300 decodes, on a
block-by-block basis, coded images included in a bitstream
generated by the image coding apparatus 100 according to Embodiment
1.
[0194] As shown in FIG. 19, the image decoding apparatus 300
includes a variable-length-decoding unit 301, an
inverse-quantization unit 302, an inverse-orthogonal-transformation
unit 303, an adder 304, block memory 305, frame memory 306, an
intra prediction unit 307, an inter prediction unit 308, an inter
prediction control unit 309, a switch 310, a merging block
candidate calculation unit 311, and colPic memory 312.
[0195] The variable-length-decoding unit 301 generates picture-type
information, a merging flag, and a quantized coefficient by
performing variable-length decoding on an input bitstream.
Furthermore, the variable-length-decoding unit 301 performs
variable-length decoding on a merging block candidate index using
the total number of merging block candidates calculated by the
merging block candidate calculation unit 311.
[0196] The inverse-quantization unit 302 inverse-quantizes the
quantized coefficient obtained by the variable-length decoding.
[0197] The inverse-orthogonal-transformation unit 303 generates
prediction error data by transforming an orthogonal transformation
coefficient obtained by the inverse quantization from a frequency
domain to a picture domain.
[0198] The block memory 305 stores, in units of a block, decoded
image data generated by adding the prediction error data and
prediction picture data.
[0199] The frame memory 306 stores decoded image data in units of a
frame.
[0200] The intra prediction unit 307 generates prediction picture
data of a current block to be decoded, by performing intra
prediction using the decoded image data stored in the block memory
305 in units of a block.
[0201] The inter prediction unit 308 generates prediction picture
data of a current block to be decoded, by performing inter
prediction using the decoded image data stored in the frame memory
306 in units of a frame.
[0202] When a current block is decoded by intra prediction
decoding, the switch 310 outputs intra prediction picture data
generated by the intra prediction unit 307 as prediction picture
data of the current block to the adder 304. On the other hand, when
a current block is decoded by inter prediction decoding, the switch
310 outputs inter prediction picture data generated by the inter
prediction unit 308 as prediction picture data of the current block
to the adder 304.
[0203] The merging block candidate calculation unit 311 derives
merging block candidates from motion vectors and others of
neighboring blocks of the current block and a motion vector and
others of a co-located block (colPic information) stored in the
colPic memory 312. Furthermore, the merging block candidate
calculation unit 311 adds the derived merging block candidate to a
merging block candidate list.
[0204] Furthermore, using a method described later, the merging
block candidate calculation unit 311 derives, for example, a
merging block candidate having a prediction direction, a motion
vector, and a reference picture index for a stationary region as a
new candidate (third candidate) for increasing coding efficiency.
Then, the merging block candidate calculation unit 311 adds the
derived new candidate as a new merging block candidate to the
merging block candidate list. Furthermore, the merging block
candidate calculation unit 311 calculates the total number of
merging block candidates when the size of the merging block
candidate list is variable.
[0205] Furthermore, the merging block candidate calculation unit
311 assigns merging block candidate indexes each having a different
value to the derived merging block candidates. Then, the merging
block candidate calculation unit 311 transmits the merging block
candidates to which the merging block candidate indexes have been
assigned to the inter prediction control unit 309. Furthermore, the
merging block candidate calculation unit 311 transmits the
calculated total number of merging block candidates to the
variable-length-decoding unit 301 when the size of the merging
block candidate list is variable.
[0206] The inter prediction control unit 309 causes the inter
prediction unit 308 to generate an inter prediction picture using
information on motion vector estimation mode when the merging flag
decoded is "0". On the other hand, when the merging flag is "1",
the inter prediction control unit 309 determines, based on a
decoded merging block candidate index, a motion vector, a reference
picture index, and a prediction direction for use in inter
prediction from a plurality of merging block candidates. Then, the
inter prediction control unit 309 causes the inter prediction unit
308 to generate an inter prediction picture using the determined
motion vector, reference picture index, and prediction direction.
Furthermore, the inter prediction control unit 309 transfers colPic
information including the motion vector of the current block to the
colPic memory 312.
[0207] Finally, the adder 304 generates decoded image data by
adding the prediction picture data and the prediction error
data.
[0208] FIG. 20 is a flowchart showing processing operations of the
image decoding apparatus 300 according to Embodiment 2.
[0209] In Step S301, the variable-length-decoding unit 301 decodes
a merging flag.
[0210] When the merging flag is "1" in Step S302 (Step S302, Yes),
in Step S303, the merging block candidate calculation unit 311
calculates the total number of merging block candidates as the size
of a merging block candidate list.
[0211] In Step S304, the variable-length-decoding unit 301 performs
variable-length decoding on a merging block candidate index from a
bitstream using the calculated size of a merging block candidate
list.
[0212] In Step S305, the merging block candidate calculation unit
311 generates merging block candidates (and a merging block
candidate list) in the same manner as in Step S101 in FIG. 12.
Furthermore, the inter prediction control unit 309 identifies,
based on a decoded merging block candidate index, a merging block
candidate to be used for decoding a current block listed in the
merging block candidate list generated by the merging block
candidate calculation unit 311.
[0213] In Step S306, the inter prediction control unit 309 causes
the inter prediction unit 308 to generate an inter prediction
picture using the motion vector, reference picture index, and
prediction direction of the merging block candidate identified in
Step S305.
[0214] When the merging flag is "0" in Step S302 (Step S302, No),
in Step S307, the inter prediction unit 308 generates an inter
prediction picture using information on motion vector estimation
mode decoded by the variable-length-decoding unit 301.
[0215] Optionally, when the size of a merging block candidate list
calculated in Step S303 is "1", a merging block candidate index may
be estimated to be "0" without being decoded.
[0216] FIG. 21 and FIG. 22 are flowcharts showing details of the
process in Step S303 shown in FIG. 20. The process shown in FIG. 21
is followed by the process shown in FIG. 22.
[0217] Specifically, FIG. 21 illustrates a method of calculating
merging block candidates [N] and the size of a merging block
candidate list. FIG. 21 will be described below.
[0218] At the beginning of the process, the merging block candidate
calculation unit 311 initializes N to zero. Furthermore, the
merging block candidate calculation unit 311 assigns index values
to the neighboring blocks (the neighboring blocks A to D and the
co-located merging block).
[0219] In Step S311, the merging block candidate calculation unit
311 determines whether it is true or false that (1) a merging block
candidate [N] has been decoded by intra prediction, (2) the merging
block candidate [N] is a block outside the boundary of a slice
including the current block or the boundary of a picture including
the current block, or (3) the merging block candidate [N] is yet to
be decoded.
[0220] When the result of the determination in Step S311 is true
(Step S311, Yes), the merging block candidate calculation unit 311
sets the merging block candidate [N] as an unusable-for-merging
candidate in Step S312. On the other hand, when the result of the
determination in Step S311 is false (Step S311, No), the merging
block candidate calculation unit 311 sets the merging block
candidate [N] as a usable-for-merging candidate in Step S313.
[0221] In Step S314, the merging block candidate calculation unit
311 determines whether it is true or false that the merging block
candidate [N] is either a usable-for-merging candidate or a
co-located merging block candidate.
[0222] Here, when the result of the determination in Step S314 is
true (Step S314, Yes), the merging block candidate calculation unit
311 updates the total number of merging block candidates by
incrementing it by one in Step S315. When the result of the
determination in Step S314 is false (Step S314, No), the merging
block candidate calculation unit 311 does not update the total
number of merging block candidates.
[0223] In this manner, when a co-located merging block is
calculated as a merging block candidate, the merging block
candidate calculation unit 311 according to Embodiment 2 increments
the total number of merging block candidates by one regardless of
whether the co-located block is a usable-for-merging candidate or
an unusable-for-merging candidate. This prevents discrepancy in the
total number of merging block candidates between the image coding
apparatus and the image decoding apparatus even when information on
a co-located merging block is lost due to an incident such as
packet loss.
[0224] Subsequently, the process shown in FIG. 22 is performed.
FIG. 22 illustrates a method of calculating a merging block
candidate. FIG. 22 will be described below.
[0225] In Step S321, the merging block candidate calculation unit
311 obtains a set of a motion vector, a reference picture index,
and a prediction direction of a merging block candidate [N], and
adds it to a merging block candidate list.
[0226] In Step S322, the merging block candidate calculation unit
311 searches the merging block candidate list for any
unusable-for-merging candidate and identical candidate, and removes
the unusable-for-merging candidate and identical candidate from the
merging block candidate list as shown in (a) and (b) in FIG. 13A.
Furthermore, the merging block candidate calculation unit 311
subtracts the total number of the identical candidates from the
total number of merging block candidates.
[0227] In Step S323, the merging block candidate calculation unit
311 adds a new candidate to the merging block candidate list using
the method used in the image coding apparatus 100 as illustrated in
FIG. 16. As a result, the total number of merging block candidates
is the sum of the total number of the first candidates and the
total number of the new candidates.
[0228] When the size of the merging block candidate list is
variable, the merging block candidate calculation unit 311 sets the
total number of merging block candidates as the size of the merging
block candidate list in Step S303 in FIG. 20. Furthermore, when the
size of the merging block candidate list is a fixed number greater
than or equal to two, the merging block candidate calculation unit
311 sets the fixed number greater than or equal to two as the size
of the merging block candidate list in Step S303 in FIG. 20.
[0229] Furthermore, the merging block candidate calculation unit
311 performs variable-length decoding on a merging block candidate
index using the size of the merging block candidate list in Step
S304 in FIG. 20. This makes it possible for the image decoding
apparatus 300 according to Embodiment 2 to decode merging block
candidate indexes normally even when information on reference
picture including a co-located block is lost.
[0230] FIG. 23 shows exemplary syntax for attachment of a merging
block candidate index to a bitstream. In FIG. 23, merge_idx
represents a merging block candidate index, and merge_flag
represents a merging flag. NumMergeCand represents the size of a
merging block candidate list. In Embodiment 2, the size of a
merging block candidate list is set at the total number of merging
block candidates calculated in the process shown in FIG. 21.
[0231] Thus, the image decoding apparatus 300 according to
Embodiment 2 calculates the size of a merging block candidate list
for use in coding or decoding of a merging block candidate index,
using a method independent of information on reference pictures
including a co-located block. The image decoding apparatus 300
therefore can appropriately decode a bitstream having enhanced
error resistance. More specifically, the total number of merging
block candidates is incremented by one for any co-located merging
block regardless of whether or not the co-located merging block is
a usable-for-merging candidate. Bit sequences to be applied to
merging block candidate indexes is determined using the total
number of merging block candidates calculated in this manner. This
makes it possible for the image decoding apparatus 300 to decode
merging block candidate indexes normally even when information on
reference picture including a co-located block is lost.
Furthermore, when the total number of the merging block candidates
is smaller than the total number of usable-for-merging candidates,
the image decoding apparatus 300 according to Embodiment 2 adds a
new candidate having a new set of a motion vector, a reference
picture index, and a prediction direction so that a bitstream coded
with increased efficiency can be appropriately decoded.
[0232] It should be noted that Embodiment 2 in which the total
number of merging block candidates is incremented by one for any
other block regardless of whether the block is a usable-for-merging
candidate or an unusable-for-merging candidate is not limiting. For
example, the total number of merging block candidates may be
incremented by one for any merging block candidate that is not a
co-located merging block in Step S314 in FIG. 21.
[0233] Optionally, in Embodiment 2, when the size of a merging
block candidate list is a fixed number greater than or equal to
two, the fixed number greater than or equal to two may be a maximum
number Max of the total number of merging block candidates. In
other words, the size of a merging block candidate list may be
fixed at a maximum value N of the total number of merging block
candidates on the assumption that the merging block candidates are
all usable-for-merging candidates. For example, in Embodiment 2,
the maximum value Max of the total number of merging block
candidates is 5 (neighboring block A, neighboring block B,
co-located merging block, neighboring block C, and neighboring
block D). In this case, merging block candidate indexes may be
decoded using the size of a merging block candidate list fixedly
set at "5".
[0234] Optionally, for example, when the maximum value Max of the
total number of merging block candidates is set at 4 (neighboring
block A, neighboring block B, neighboring block C, and neighboring
block D) for a current picture which is a picture to be decoded
without referencing a co-located merging block (a B-picture or a
P-picture to be decoded with reference to an I-picture), merging
block candidate indexes may be decoded using the size of a merging
block candidate list fixedly set at "4".
[0235] It is therefore possible for the variable-length-decoding
unit 301 of the image decoding apparatus 300 to decode a merging
block candidate index from a bitstream without referencing
information on a neighboring block or on a co-located block. In
this case, for example, Step S314 and Step S315 shown in FIG. 21
can be skipped so that the computational complexity for the
variable-length-decoding unit 301 can be reduced.
[0236] FIG. 24 shows exemplary syntax in the case where the size of
a merging block candidate list is fixed at the maximum value Max of
the total number of merging block candidates. As can be seen in
FIG. 24, NumMergeCand can be omitted from the syntax when the size
of a merging block candidate list is fixed at a fixed number
greater than or equal to two (for example, a maximum value Max of
the total number of merging block candidates). In other words, the
process can be performed without using NumMergeCand. Optionally,
for example, the decoding may be performed using a fixed number
greater than or equal to two (for example, a maximum value Max of
the total number of merging block candidates) embedded in a
sequence parameter set (SPS), a picture parameter set (PPS), a
slice header, or the like. This makes it possible to switch between
fixed numbers greater than or equal to two for each current picture
so that the bitstream from the image coding apparatus 100 can be
correctly decoded. In this case, merging block indexes may be
decoded using values which are the fixed numbers greater than or
equal to two decoded from the SPS, PPS, or slice header.
[0237] It should be noted that the variable-length decoding (see
FIG. 5) which is performed in Embodiment 2 according to the size of
a merging block candidate list in Step S304 in FIG. 20 may be
performed optionally according to another parameter. For example,
when the total number of merging block candidates calculated as the
total number of usable-for-merging candidates by adding the total
number of first candidates and the total number of identical
candidates in Step S111 (detailed in FIG. 15A) in FIG. 14A in the
image coding apparatus 100 according to Embodiment 1, the
variable-length decoding may be performed using the total number of
merging block candidates calculated by the process shown in FIG.
21. In this case, the process shown in FIG. 22 may be performed in
Step S305.
[0238] Furthermore, a determination in the process shown in FIG. 21
is made based on whether it is true or false that (1) a merging
block candidate [N] has been decoded by intra prediction, (2) the
merging block candidate [N] is a block outside the boundary of a
slice including the current block or the boundary of a picture
including the current block, or (3) the merging block candidate [N]
is yet to be decoded. In other words, the total number of the
merging block candidates for use in variable-length decoding can be
obtained without using information on a prediction direction, a
motion vector, and a reference picture index. Accordingly,
calculation of a prediction direction, a motion vector, and a
reference picture index and obtainment of a merging block candidate
index are performed independently of each other, and therefore the
merging block candidate index is obtained without waiting for the
result of the calculation of a prediction direction, a motion
vector, and a reference picture index so that processing speed can
be increased.
Modification of Embodiment 1 and Embodiment 2
[0239] When the size of a merging block candidate list is a fixed
number greater than or equal to two in above-described Embodiment 1
and Embodiment 2 and the merging block candidate list has an empty
entry, the empty entry of the merging block candidate list may be
filled with a predetermined merging block candidate for enhancement
of error resistance (second candidate) so that error resistance can
be enhanced.
[0240] For example, when a current picture (to be coded or to be
decoded) is a B-picture, the second candidate to be added may be a
bi-predictive merging block candidate including a set of a
reference picture index 0 for a prediction direction 0 and a motion
vector (0, 0) and a set of a reference picture index 0 for a
prediction direction 1 and a motion vector (0, 0). For example,
when a current picture to be coded is a P-picture, the second
candidate to be added may be a uni-predictive merging block
candidate including a reference picture index 0 for a prediction
direction 0 and a motion vector (0, 0). Since second candidates are
added for the purpose of enhancement of error resistance, the
second candidates may be set to have identical values. On the other
hand, third candidates are different from each other because third
candidates are added for the purpose of increasing coding
efficiency. It should be noted that a third candidate may be
identical to a first candidate or a second candidate as a
result.
[0241] A second candidate may be added either (1) by entering a
second candidate in an empty entry after adding a new candidate
(third candidate) or (2) by entering second candidates in all
entries in a merging block candidate list to initialize the merging
block candidate list.
[0242] The following describes a case with the image coding
apparatus 100 in which (1) a second candidate is entered in an
empty entry after a new candidate (third candidate) is added.
[0243] FIG. 13B shows a table of a merging block candidate list
when a second candidate is entered in an empty entry after a new
candidate (third candidate) is added. In the case shown in FIG.
13B, the maximum value Max of the total number of merging block
candidates is 6 as an example.
[0244] FIG. 14B is a flowchart showing details of the process in
Step S101 in FIG. 12. The process from Step S111 to Step S114 in
FIG. 14B is the same as the process from Step S111 to Step S114 of
the image coding apparatus 100 according to Embodiment 1 shown in
FIG. 14A, and thus the description thereof is omitted.
[0245] In Step S111 to Step S114, the merging block candidate
calculation unit 114 of the image coding apparatus 100 calculates
first candidates from neighboring blocks, removes an
unusable-for-merging candidate and an identical candidate, and then
adds new candidates. Since the total number of merging block
candidates is 6, the merging block candidate [5] is not assigned to
a merging block candidate even after the adding of new candidates
as shown in (b) in FIG. 13B.
[0246] In Step S116, the merging block candidate calculation unit
114 enters a second candidate in the empty entry. FIG. 17 is a
flowchart showing details of the process in Step S116 shown in FIG.
14B.
[0247] In Step S141, the merging block candidate calculation unit
114 determines whether or not the total number of merging block
candidates (simply referred to as candidate list size in FIG. 17)
is smaller than the size of the merging block candidate list. In
other words, the merging block candidate calculation unit 114
determines whether or not there is any empty entry.
[0248] When the result of the determination in Step S141 is true
(Step S141, Yes), the merging block candidate calculation unit 114
enters a second candidate in the empty entry in Step S142. As
described above, the merging block candidate [5] is not assigned to
a merging block candidate immediately after the adding of new
candidates. Then, the merging block candidate calculation unit 114
adds a second candidate as the merging block candidate [5]. For
example, the added second candidate may be a bi-predictive merging
block candidate including a set of a reference picture index 0 for
a prediction direction 0 and a motion vector (0, 0) and a set of a
reference picture index 0 for a prediction direction 1 and a motion
vector (0, 0) as mentioned above. Furthermore, in Step S143, the
merging block candidate calculation unit 114 increments the total
number of merging block candidates by one.
[0249] When the result of the determination in Step S141 is false
(Step S141, No), the process ends.
[0250] (c) in FIG. 13B illustrates a table of a merging block
candidate list after a second candidate is added.
[0251] The following describes a case with the image coding
apparatus 100 in which (2) a merging block candidate list is
initialized by entering second candidates in all the entries in a
merging block candidate list.
[0252] FIG. 13C shows a table of a merging block candidate list
when a second candidate is initialized by using second candidates.
In the case shown in FIG. 13C, the maximum value Max of the total
number of merging block candidates is 6 as an example.
[0253] FIG. 14C is a flowchart showing details of the process in
Step S101 in FIG. 12.
[0254] In Step 117, the merging block candidate calculation unit
114 initializes the merging block candidate list (candidate list).
(a) in FIG. 13C illustrates a candidate list after the
initialization. In (a) in FIG. 13C, all the merging block
candidates [0] to [5] are second candidates. The second candidates
are all identical, which is not indicated in (a) in FIG. 13C.
[0255] In Step 118, the merging block candidate calculation unit
114 derives first candidates and updates the total number of the
merging block candidates with the total number of the first
candidates. Ni is a value for identifying each neighboring block.
In this case, Ni takes values from 0 to 5 to identify six of
neighboring blocks which are neighboring blocks A to D and a
co-located merging block. Furthermore, the first candidates include
no unusable-for-merging candidate and no identical candidate.
Furthermore, the merging block candidate calculation unit 114 adds
the first candidates to the candidate list and obtains sets of
motion vectors, reference picture indexes, and prediction
directions of the first candidates. (b) in FIG. 13C illustrates a
table of a merging block candidate list after first candidates are
added.
[0256] In Step S114, the merging block candidate calculation unit
114 adds new candidates to the merging block candidate list using
the method described in Embodiment 1. (c) in FIG. 13C illustrates
the table of the merging block candidate list after new candidates
are added.
[0257] FIG. 15B is a flowchart showing details of the process in
Step S118 shown in FIG. 14C.
[0258] In Step S126, the merging block candidate calculation unit
114 determines whether it is true or false that (1) a neighboring
block has been coded by intra prediction, (2) the neighboring block
is a block outside the boundary of a slice including the current
block or the boundary of a picture including the current block, (3)
the neighboring block is yet to be coded, or (4) the neighboring
block is an identical candidate, that is, identical in prediction
direction, motion vector, and reference picture index to any of the
merging block candidates added to the candidate list.
[0259] When the result of the determination in Step S126 is true
(Step S126, Yes), the merging block candidate calculation unit 114
determines that the neighboring block is an unusable-for-merging
candidate. On the other hand, when the result of the determination
in Step S126 is false (Step S126, No), the merging block candidate
calculation unit 114 determines that the neighboring block is a
usable-for-merging candidate.
[0260] When the result of the determination in Step S126 is that
the neighboring block is either a usable-for-merging candidate or a
co-located block, the merging block candidate calculation unit 114
adds a merging block candidate to the merging block candidate list
and increments the total number of merging block candidates by one
in Step S124.
[0261] (c) in FIG. 13C is identical to (c) in FIG. 13B, which
therefore shows that a merging block candidate list obtained by
adding new candidates first and then second candidates and a
merging block candidate list obtained by initializing the merging
block using second candidates first are the same.
[0262] When the image decoding apparatus 300 creates a merging
block candidate list using this method, it is possible for the
image decoding apparatus 300 to decode merging block candidate
indexes normally.
[0263] When a merging block candidate list has an empty entry, the
image decoding apparatus 300 may have an error in removing an
identical candidate from merging block candidates and fail to
remove the identical candidate. In this case, when the size of the
merging block candidate list is a fixed number greater than or
equal to two, there is a possibility that the merging block
candidate list has an empty candidate entry in which no merging
block candidate is entered.
[0264] According to the present modification of Embodiments 1 and
2, second candidates are entered in all the empty entries in the
candidate list so that the image decoding apparatus 300 can avoid
having an empty candidate entry in which no merging block candidate
is entered.
[0265] It should be noted that the present modification in which a
merging block candidate having a reference picture 0 and a motion
vector (0, 0) is assigned as a second candidate to a merging block
candidate index to which no merging block candidate is applied is
not limiting. Examples of such a second candidate include a merging
block candidate having a reference picture index, a motion vector,
and a prediction direction copied from another neighboring block,
and a neighboring block generated using a candidate obtained from
other neighboring blocks such as a merging block candidate
generated by averaging candidates obtained from other neighboring
blocks.
[0266] It should be noted that the modification in which a second
candidate is added by (1) entering a second candidate in an empty
entry after adding a new candidate (third candidate) or (2)
initializing a merging block candidate list by entering second
candidates in all entries of the merging block candidate list, is
not limiting.
[0267] For example, the image decoding apparatus 300 may determine
in Step S306 in FIG. 20 whether or not a merging block candidate is
assigned to a decoded merging block candidate index, and add a
second candidate when the result of the determination is true. In
other words, Step S305 may be performed not to generate a merging
block candidate list with no empty entry but to add a second
candidate to an empty entry only when an entry indicated by a
decoded merging block candidate index is such an empty entry. This
will reduce computational complexity.
[0268] Examples of such a second candidate include a merging block
candidate having a reference picture 0 and a motion vector (0, 0),
a merging block candidate assigned to another merging block
candidate index, and a merging block candidate generated from other
neighboring blocks assigned to other merging block candidate
indexes.
[0269] For example, the image decoding apparatus 300 may determine
in Step S306 in FIG. 20 whether or not the total number of decoded
merging block candidate indexes is larger than or equal to the
total number of merging block candidates calculated in Step S303,
and add a second candidate when the result of the determination is
true. In other words, the process for adding a second candidate can
be skipped when the total number of the decoded merging block
candidate indexes is smaller than or equal to the total number of
merging block candidates calculated in Step S303. This will reduce
computational complexity.
[0270] Examples of such a second candidate include a merging block
candidate having a reference picture 0 and a motion vector (0, 0),
a merging block candidate assigned to another merging block
candidate index, and a merging block candidate generated from other
neighboring blocks assigned to other merging block candidate
indexes.
[0271] Furthermore, for example, the image decoding apparatus 300
may determine in Step S306 in FIG. 20 whether or not the total
number of decoded merging block candidate indexes is larger than or
equal to the total number of merging block candidates calculated in
Step S303, and, when the result of the determination is true, the
values of the merging block candidate indexes may be clipped so
that the total number of decoded merging block candidate indexes is
smaller than the total number of merging block candidates.
[0272] By performing the above-described process, the image coding
apparatus 100 and the image decoding apparatus 300 according to the
present modification of Embodiments 1 and 2 can avoid having a
decoded merging block candidate index to which no merging block
candidate is assigned, even when, for example, merging block
candidate indexes are normally decoded but an error occurs in
removing of an identical candidate from merging block candidates.
Error resistance is thus enhanced.
Embodiment 3
[0273] The processing described in each of embodiments can be
simply implemented in an independent computer system, by recording,
in a recording medium, a program for implementing the
configurations of the moving picture coding method (image coding
method) and the moving picture decoding method (image decoding
method) described in each of embodiments. The recording media may
be any recording media as long as the program can be recorded, such
as a magnetic disk, an optical disk, a magnetic optical disk, an IC
card, and a semiconductor memory.
[0274] Hereinafter, the applications to the moving picture coding
method (image coding method) and the moving picture decoding method
(image decoding method) described in each of embodiments and
systems using thereof will be described. The system has a feature
of having an image coding and decoding apparatus that includes an
image coding apparatus using the image coding method and an image
decoding apparatus using the image decoding method. Other
configurations in the system can be changed as appropriate
depending on the cases.
[0275] FIG. 25 illustrates an overall configuration of a content
providing system ex100 for implementing content distribution
services. The area for providing communication services is divided
into cells of desired size, and base stations ex106, ex107, ex108,
ex109, and ex110 which are fixed wireless stations are placed in
each of the cells.
[0276] The content providing system ex100 is connected to devices,
such as a computer ex111, a personal digital assistant (PDA) ex112,
a camera ex113, a cellular phone ex114 and a game machine ex115,
via the Internet ex101, an Internet service provider ex102, a
telephone network ex104, as well as the base stations ex106 to
ex110, respectively.
[0277] However, the configuration of the content providing system
ex100 is not limited to the configuration shown in FIG. 25, and a
combination in which any of the elements are connected is
acceptable. In addition, each device may be directly connected to
the telephone network ex104, rather than via the base stations
ex106 to ex110 which are the fixed wireless stations. Furthermore,
the devices may be interconnected to each other via a short
distance wireless communication and others.
[0278] The camera ex113, such as a digital video camera, is capable
of capturing video. A camera ex116, such as a digital camera, is
capable of capturing both still images and video. Furthermore, the
cellular phone ex114 may be the one that meets any of the standards
such as Global System for Mobile Communications (GSM) (registered
trademark), Code Division Multiple Access (CDMA), Wideband-Code
Division Multiple Access (W-CDMA), Long Term Evolution (LTE), and
High Speed Packet Access (HSPA). Alternatively, the cellular phone
ex114 may be a Personal Handyphone System (PHS).
[0279] In the content providing system ex100, a streaming server
ex103 is connected to the camera ex113 and others via the telephone
network ex104 and the base station ex109, which enables
distribution of images of a live show and others. In such a
distribution, a content (for example, video of a music live show)
captured by the user using the camera ex113 is coded as described
above in each of embodiments (i.e., the camera functions as the
image coding apparatus according to an aspect of the present
disclosure), and the coded content is transmitted to the streaming
server ex103. On the other hand, the streaming server ex103 carries
out stream distribution of the transmitted content data to the
clients upon their requests. The clients include the computer
ex111, the PDA ex112, the camera ex113, the cellular phone ex114,
and the game machine ex115 that are capable of decoding the
above-mentioned coded data. Each of the devices that have received
the distributed data decodes and reproduces the coded data (i.e.,
functions as the image decoding apparatus according to an aspect of
the present disclosure).
[0280] The captured data may be coded by the camera ex113 or the
streaming server ex103 that transmits the data, or the coding
processes may be shared between the camera ex113 and the streaming
server ex103. Similarly, the distributed data may be decoded by the
clients or the streaming server ex103, or the decoding processes
may be shared between the clients and the streaming server ex103.
Furthermore, the data of the still images and video captured by not
only the camera ex113 but also the camera ex116 may be transmitted
to the streaming server ex103 through the computer ex111. The
coding processes may be performed by the camera ex116, the computer
ex111, or the streaming server ex103, or shared among them.
[0281] Furthermore, the coding and decoding processes may be
performed by an LSI ex500 generally included in each of the
computer ex111 and the devices. The LSI ex500 may be configured of
a single chip or a plurality of chips. Software for coding and
decoding video may be integrated into some type of a recording
medium (such as a CD-ROM, a flexible disk, and a hard disk) that is
readable by the computer ex111 and others, and the coding and
decoding processes may be performed using the software.
Furthermore, when the cellular phone ex114 is equipped with a
camera, the video data obtained by the camera may be transmitted.
The video data is data coded by the LSI ex500 included in the
cellular phone ex114.
[0282] Furthermore, the streaming server ex103 may be composed of
servers and computers, and may decentralize data and process the
decentralized data, record, or distribute data.
[0283] As described above, the clients may receive and reproduce
the coded data in the content providing system ex100. In other
words, the clients can receive and decode information transmitted
by the user, and reproduce the decoded data in real time in the
content providing system ex100, so that the user who does not have
any particular right and equipment can implement personal
broadcasting.
[0284] Aside from the example of the content providing system
ex100, at least one of the moving picture coding apparatus (image
coding apparatus) and the moving picture decoding apparatus (image
decoding apparatus) described in each of embodiments may be
implemented in a digital broadcasting system ex200 illustrated in
FIG. 26. More specifically, a broadcast station ex201 communicates
or transmits, via radio waves to a broadcast satellite ex202,
multiplexed data obtained by multiplexing audio data and others
onto video data. The video data is data coded by the moving picture
coding method described in each of embodiments (i.e., data coded by
the image coding apparatus according to an aspect of the present
disclosure). Upon receipt of the multiplexed data, the broadcast
satellite ex202 transmits radio waves for broadcasting. Then, a
home-use antenna ex204 with a satellite broadcast reception
function receives the radio waves. Next, a device such as a
television (receiver) ex300 and a set top box (STB) ex217 decodes
the received multiplexed data, and reproduces the decoded data
(i.e., functions as the image decoding apparatus according to an
aspect of the present disclosure).
[0285] Furthermore, a reader/recorder ex218 (i) reads and decodes
the multiplexed data recorded on a recording medium ex215, such as
a DVD and a BD, or (i) codes video signals in the recording medium
ex215, and in some cases, writes data obtained by multiplexing an
audio signal on the coded data. The reader/recorder ex218 can
include the moving picture decoding apparatus or the moving picture
coding apparatus as shown in each of embodiments. In this case, the
reproduced video signals are displayed on the monitor ex219, and
can be reproduced by another device or system using the recording
medium ex215 on which the multiplexed data is recorded. It is also
possible to implement the moving picture decoding apparatus in the
set top box ex217 connected to the cable ex203 for a cable
television or to the antenna ex204 for satellite and/or terrestrial
broadcasting, so as to display the video signals on the monitor
ex219 of the television ex300. The moving picture decoding
apparatus may be implemented not in the set top box but in the
television ex300.
[0286] FIG. 27 illustrates the television (receiver) ex300 that
uses the moving picture coding method and the moving picture
decoding method described in each of embodiments. The television
ex300 includes: a tuner ex301 that obtains or provides multiplexed
data obtained by multiplexing audio data onto video data, through
the antenna ex204 or the cable ex203, etc. that receives a
broadcast; a modulation/demodulation unit ex302 that demodulates
the received multiplexed data or modulates data into multiplexed
data to be supplied outside; and a multiplexing/demultiplexing unit
ex303 that demultiplexes the modulated multiplexed data into video
data and audio data, or multiplexes video data and audio data coded
by a signal processing unit ex306 into data.
[0287] The television ex300 further includes: a signal processing
unit ex306 including an audio signal processing unit ex304 and a
video signal processing unit ex305 that decode audio data and video
data and code audio data and video data, respectively (which
function as the image coding apparatus and the image decoding
apparatus according to the aspects of the present disclosure); and
an output unit ex309 including a speaker ex307 that provides the
decoded audio signal, and a display unit ex308 that displays the
decoded video signal, such as a display. Furthermore, the
television ex300 includes an interface unit ex317 including an
operation input unit ex312 that receives an input of a user
operation. Furthermore, the television ex300 includes a control
unit ex310 that controls overall each constituent element of the
television ex300, and a power supply circuit unit ex311 that
supplies power to each of the elements. Other than the operation
input unit ex312, the interface unit ex317 may include: a bridge
ex313 that is connected to an external device, such as the
reader/recorder ex218; a slot unit ex314 for enabling attachment of
the recording medium ex216, such as an SD card; a driver ex315 to
be connected to an external recording medium, such as a hard disk;
and a modem ex316 to be connected to a telephone network. Here, the
recording medium ex216 can electrically record information using a
non-volatile/volatile semiconductor memory element for storage. The
constituent elements of the television ex300 are connected to each
other through a synchronous bus.
[0288] First, the configuration in which the television ex300
decodes multiplexed data obtained from outside through the antenna
ex204 and others and reproduces the decoded data will be described.
In the television ex300, upon a user operation through a remote
controller ex220 and others, the multiplexing/demultiplexing unit
ex303 demultiplexes the multiplexed data demodulated by the
modulation/demodulation unit ex302, under control of the control
unit ex310 including a CPU. Furthermore, the audio signal
processing unit ex304 decodes the demultiplexed audio data, and the
video signal processing unit ex305 decodes the demultiplexed video
data, using the decoding method described in each of embodiments,
in the television ex300. The output unit ex309 provides the decoded
video signal and audio signal outside, respectively. When the
output unit ex309 provides the video signal and the audio signal,
the signals may be temporarily stored in buffers ex318 and ex319,
and others so that the signals are reproduced in synchronization
with each other. Furthermore, the television ex300 may read
multiplexed data not through a broadcast and others but from the
recording media ex215 and ex216, such as a magnetic disk, an
optical disk, and a SD card. Next, a configuration in which the
television ex300 codes an audio signal and a video signal, and
transmits the data outside or writes the data on a recording medium
will be described. In the television ex300, upon a user operation
through the remote controller ex220 and others, the audio signal
processing unit ex304 codes an audio signal, and the video signal
processing unit ex305 codes a video signal, under control of the
control unit ex310 using the coding method described in each of
embodiments. The multiplexing/demultiplexing unit ex303 multiplexes
the coded video signal and audio signal, and provides the resulting
signal outside. When the multiplexing/demultiplexing unit ex303
multiplexes the video signal and the audio signal, the signals may
be temporarily stored in the buffers ex320 and ex321, and others so
that the signals are reproduced in synchronization with each other.
Here, the buffers ex318, ex319, ex320, and ex321 may be plural as
illustrated, or at least one buffer may be shared in the television
ex300. Furthermore, data may be stored in a buffer so that the
system overflow and underflow may be avoided between the
modulation/demodulation unit ex302 and the
multiplexing/demultiplexing unit ex303, for example.
[0289] Furthermore, the television ex300 may include a
configuration for receiving an AV input from a microphone or a
camera other than the configuration for obtaining audio and video
data from a broadcast or a recording medium, and may code the
obtained data. Although the television ex300 can code, multiplex,
and provide outside data in the description, it may be capable of
only receiving, decoding, and providing outside data but not the
coding, multiplexing, and providing outside data.
[0290] Furthermore, when the reader/recorder ex218 reads or writes
multiplexed data from or on a recording medium, one of the
television ex300 and the reader/recorder ex218 may decode or code
the multiplexed data, and the television ex300 and the
reader/recorder ex218 may share the decoding or coding.
[0291] As an example, FIG. 28 illustrates a configuration of an
information reproducing/recording unit ex400 when data is read or
written from or on an optical disk. The information
reproducing/recording unit ex400 includes constituent elements
ex401, ex402, ex403, ex404, ex405, ex406, and ex407 to be described
hereinafter. The optical head ex401 irradiates a laser spot in a
recording surface of the recording medium ex215 that is an optical
disk to write information, and detects reflected light from the
recording surface of the recording medium ex215 to read the
information. The modulation recording unit ex402 electrically
drives a semiconductor laser included in the optical head ex401,
and modulates the laser light according to recorded data. The
reproduction demodulating unit ex403 amplifies a reproduction
signal obtained by electrically detecting the reflected light from
the recording surface using a photo detector included in the
optical head ex401, and demodulates the reproduction signal by
separating a signal component recorded on the recording medium
ex215 to reproduce the necessary information. The buffer ex404
temporarily holds the information to be recorded on the recording
medium ex215 and the information reproduced from the recording
medium ex215. The disk motor ex405 rotates the recording medium
ex215. The servo control unit ex406 moves the optical head ex401 to
a predetermined information track while controlling the rotation
drive of the disk motor ex405 so as to follow the laser spot. The
system control unit ex407 controls overall the information
reproducing/recording unit ex400. The reading and writing processes
can be implemented by the system control unit ex407 using various
information stored in the buffer ex404 and generating and adding
new information as necessary, and by the modulation recording unit
ex402, the reproduction demodulating unit ex403, and the servo
control unit ex406 that record and reproduce information through
the optical head ex401 while being operated in a coordinated
manner. The system control unit ex407 includes, for example, a
microprocessor, and executes processing by causing a computer to
execute a program for read and write.
[0292] Although the optical head ex401 irradiates a laser spot in
the description, it may perform high-density recording using near
field light.
[0293] FIG. 29 illustrates the recording medium ex215 that is the
optical disk. On the recording surface of the recording medium
ex215, guide grooves are spirally formed, and an information track
ex230 records, in advance, address information indicating an
absolute position on the disk according to change in a shape of the
guide grooves. The address information includes information for
determining positions of recording blocks ex231 that are a unit for
recording data. Reproducing the information track ex230 and reading
the address information in an apparatus that records and reproduces
data can lead to determination of the positions of the recording
blocks. Furthermore, the recording medium ex215 includes a data
recording area ex233, an inner circumference area ex232, and an
outer circumference area ex234. The data recording area ex233 is an
area for use in recording the user data. The inner circumference
area ex232 and the outer circumference area ex234 that are inside
and outside of the data recording area ex233, respectively are for
specific use except for recording the user data. The information
reproducing/recording unit 400 reads and writes coded audio, coded
video data, or multiplexed data obtained by multiplexing the coded
audio and video data, from and on the data recording area ex233 of
the recording medium ex215.
[0294] Although an optical disk having a layer, such as a DVD and a
BD is described as an example in the description, the optical disk
is not limited to such, and may be an optical disk having a
multilayer structure and capable of being recorded on a part other
than the surface. Furthermore, the optical disk may have a
structure for multidimensional recording/reproduction, such as
recording of information using light of colors with different
wavelengths in the same portion of the optical disk and for
recording information having different layers from various
angles.
[0295] Furthermore, a car ex210 having an antenna ex205 can receive
data from the satellite ex202 and others, and reproduce video on a
display device such as a car navigation system ex211 set in the car
ex210, in the digital broadcasting system ex200. Here, a
configuration of the car navigation system ex211 will be a
configuration, for example, including a GPS receiving unit from the
configuration illustrated in FIG. 27. The same will be true for the
configuration of the computer exill, the cellular phone ex114, and
others.
[0296] FIG. 30A illustrates the cellular phone ex114 that uses the
moving picture coding method and the moving picture decoding method
described in embodiments. The cellular phone ex114 includes: an
antenna ex350 for transmitting and receiving radio waves through
the base station ex110; a camera unit ex365 capable of capturing
moving and still images; and a display unit ex358 such as a liquid
crystal display for displaying the data such as decoded video
captured by the camera unit ex365 or received by the antenna ex350.
The cellular phone ex114 further includes: a main body unit
including an operation key unit ex366; an audio output unit ex357
such as a speaker for output of audio; an audio input unit ex356
such as a microphone for input of audio; a memory unit ex367 for
storing captured video or still pictures, recorded audio, coded or
decoded data of the received video, the still pictures, e-mails, or
others; and a slot unit ex364 that is an interface unit for a
recording medium that stores data in the same manner as the memory
unit ex367.
[0297] Next, an example of a configuration of the cellular phone
ex114 will be described with reference to FIG. 30B. In the cellular
phone ex114, a main control unit ex360 designed to control overall
each unit of the main body including the display unit ex358 as well
as the operation key unit ex366 is connected mutually, via a
synchronous bus ex370, to a power supply circuit unit ex361, an
operation input control unit ex362, a video signal processing unit
ex355, a camera interface unit ex363, a liquid crystal display
(LCD) control unit ex359, a modulation/demodulation unit ex352, a
multiplexing/demultiplexing unit ex353, an audio signal processing
unit ex354, the slot unit ex364, and the memory unit ex367.
[0298] When a call-end key or a power key is turned ON by a user's
operation, the power supply circuit unit ex361 supplies the
respective units with power from a battery pack so as to activate
the cell phone ex114.
[0299] In the cellular phone ex114, the audio signal processing
unit ex354 converts the audio signals collected by the audio input
unit ex356 in voice conversation mode into digital audio signals
under the control of the main control unit ex360 including a CPU,
ROM, and RAM. Then, the modulation/demodulation unit ex352 performs
spread spectrum processing on the digital audio signals, and the
transmitting and receiving unit ex351 performs digital-to-analog
conversion and frequency conversion on the data, so as to transmit
the resulting data via the antenna ex350. Also, in the cellular
phone ex114, the transmitting and receiving unit ex351 amplifies
the data received by the antenna ex350 in voice conversation mode
and performs frequency conversion and the analog-to-digital
conversion on the data. Then, the modulation/demodulation unit
ex352 performs inverse spread spectrum processing on the data, and
the audio signal processing unit ex354 converts it into analog
audio signals, so as to output them via the audio output unit
ex357.
[0300] Furthermore, when an e-mail in data communication mode is
transmitted, text data of the e-mail inputted by operating the
operation key unit ex366 and others of the main body is sent out to
the main control unit ex360 via the operation input control unit
ex362. The main control unit ex360 causes the
modulation/demodulation unit ex352 to perform spread spectrum
processing on the text data, and the transmitting and receiving
unit ex351 performs the digital-to-analog conversion and the
frequency conversion on the resulting data to transmit the data to
the base station ex110 via the antenna ex350. When an e-mail is
received, processing that is approximately inverse to the
processing for transmitting an e-mail is performed on the received
data, and the resulting data is provided to the display unit
ex358.
[0301] When video, still images, or video and audio in data
communication mode is or are transmitted, the video signal
processing unit ex355 compresses and codes video signals supplied
from the camera unit ex365 using the moving picture coding method
shown in each of embodiments (i.e., functions as the image coding
apparatus according to the aspect of the present disclosure), and
transmits the coded video data to the multiplexing/demultiplexing
unit ex353. In contrast, during when the camera unit ex365 captures
video, still images, and others, the audio signal processing unit
ex354 codes audio signals collected by the audio input unit ex356,
and transmits the coded audio data to the
multiplexing/demultiplexing unit ex353.
[0302] The multiplexing/demultiplexing unit ex353 multiplexes the
coded video data supplied from the video signal processing unit
ex355 and the coded audio data supplied from the audio signal
processing unit ex354, using a predetermined method. Then, the
modulation/demodulation unit (modulation/demodulation circuit unit)
ex352 performs spread spectrum processing on the multiplexed data,
and the transmitting and receiving unit ex351 performs
digital-to-analog conversion and frequency conversion on the data
so as to transmit the resulting data via the antenna ex350.
[0303] When receiving data of a video file which is linked to a Web
page and others in data communication mode or when receiving an
e-mail with video and/or audio attached, in order to decode the
multiplexed data received via the antenna ex350, the
multiplexing/demultiplexing unit ex353 demultiplexes the
multiplexed data into a video data bitstream and an audio data
bitstream, and supplies the video signal processing unit ex355 with
the coded video data and the audio signal processing unit ex354
with the coded audio data, through the synchronous bus ex370. The
video signal processing unit ex355 decodes the video signal using a
moving picture decoding method corresponding to the moving picture
coding method shown in each of embodiments (i.e., functions as the
image decoding apparatus according to the aspect of the present
disclosure), and then the display unit ex358 displays, for
instance, the video and still images included in the video file
linked to the Web page via the LCD control unit ex359. Furthermore,
the audio signal processing unit ex354 decodes the audio signal,
and the audio output unit ex357 provides the audio.
[0304] Furthermore, similarly to the television ex300, a terminal
such as the cellular phone ex114 probably have 3 types of
implementation configurations including not only (i) a transmitting
and receiving terminal including both a coding apparatus and a
decoding apparatus, but also (ii) a transmitting terminal including
only a coding apparatus and (iii) a receiving terminal including
only a decoding apparatus. Although the digital broadcasting system
ex200 receives and transmits the multiplexed data obtained by
multiplexing audio data onto video data in the description, the
multiplexed data may be data obtained by multiplexing not audio
data but character data related to video onto video data, and may
be not multiplexed data but video data itself.
[0305] As such, the moving picture coding method and the moving
picture decoding method in each of embodiments can be used in any
of the devices and systems described. Thus, the advantages
described in each of embodiments can be obtained.
[0306] Furthermore, various modifications and revisions can be made
in any of the embodiments in the present disclosure.
Embodiment 4
[0307] Video data can be generated by switching, as necessary,
between (i) the moving picture coding method or the moving picture
coding apparatus shown in each of embodiments and (ii) a moving
picture coding method or a moving picture coding apparatus in
conformity with a different standard, such as MPEG-2, MPEG-4 AVC,
and VC-1.
[0308] Here, when a plurality of video data that conforms to the
different standards is generated and is then decoded, the decoding
methods need to be selected to conform to the different standards.
However, since to which standard each of the plurality of the video
data to be decoded conforms cannot be detected, there is a problem
that an appropriate decoding method cannot be selected.
[0309] In order to solve the problem, multiplexed data obtained by
multiplexing audio data and others onto video data has a structure
including identification information indicating to which standard
the video data conforms. The specific structure of the multiplexed
data including the video data generated in the moving picture
coding method and by the moving picture coding apparatus shown in
each of embodiments will be hereinafter described. The multiplexed
data is a digital stream in the MPEG-2 Transport Stream format.
[0310] FIG. 31 illustrates a structure of the multiplexed data. As
illustrated in FIG. 31, the multiplexed data can be obtained by
multiplexing at least one of a video stream, an audio stream, a
presentation graphics stream (PG), and an interactive graphics
stream. The video stream represents primary video and secondary
video of a movie, the audio stream (IG) represents a primary audio
part and a secondary audio part to be mixed with the primary audio
part, and the presentation graphics stream represents subtitles of
the movie. Here, the primary video is normal video to be displayed
on a screen, and the secondary video is video to be displayed on a
smaller window in the primary video. Furthermore, the interactive
graphics stream represents an interactive screen to be generated by
arranging the GUI components on a screen. The video stream is coded
in the moving picture coding method or by the moving picture coding
apparatus shown in each of embodiments, or in a moving picture
coding method or by a moving picture coding apparatus in conformity
with a conventional standard, such as MPEG-2, MPEG-4 AVC, and VC-1.
The audio stream is coded in accordance with a standard, such as
Dolby-AC-3, Dolby Each stream included in the multiplexed data is
identified by PID. For example, 0x1011 is allocated to the video
stream to be used for video of a movie, 0x1100 to 0x111F are
allocated to the audio streams, 0x1200 to 0x121F are allocated to
the presentation graphics streams, 0x1400 to 0x141F are allocated
to the interactive graphics streams, 0x1B00 to 0x1B1F are allocated
to the video streams to be used for secondary video of the movie,
and 0x1A00 to 0x1A1F are allocated to the audio streams to be used
for the secondary audio to be mixed with the primary audio.
[0311] FIG. 32 schematically illustrates how data is multiplexed.
First, a video stream ex235 composed of video frames and an audio
stream ex238 composed of audio frames are transformed into a stream
of PES packets ex236 and a stream of PES packets ex239, and further
into TS packets ex237 and TS packets ex240, respectively.
Similarly, data of a presentation graphics stream ex241 and data of
an interactive graphics stream ex244 are transformed into a stream
of PES packets ex242 and a stream of PES packets ex245, and further
into TS packets ex243 and TS packets ex246, respectively. These TS
packets are multiplexed into a stream to obtain multiplexed data
ex247.
[0312] FIG. 33 illustrates how a video stream is stored in a stream
of PES packets in more detail. The first bar in FIG. 33 shows a
video frame stream in a video stream. The second bar shows the
stream of PES packets. As indicated by arrows denoted as yy1, yy2,
yy3, and yy4 in FIG. 33, the video stream is divided into pictures
as I-pictures, B-pictures, and P-pictures each of which is a video
presentation unit, and the pictures are stored in a payload of each
of the PES packets. Each of the PES packets has a PES header, and
the PES header stores a Presentation Time-Stamp (PTS) indicating a
display time of the picture, and a Decoding Time-Stamp (DTS)
indicating a decoding time of the picture.
[0313] FIG. 34 illustrates a format of TS packets to be finally
written on the multiplexed data. Each of the TS packets is a
188-byte fixed length packet including a 4-byte TS header having
information, such as a PID for identifying a stream and a 184-byte
TS payload for storing data. The PES packets are divided, and
stored in the TS payloads, respectively. When a BD ROM is used,
each of the TS packets is given a 4-byte TP_Extra_Header, thus
resulting in 192-byte source packets. The source packets are
written on the multiplexed data. The TP_Extra_Header stores
information such as an Arrival_Time_Stamp (ATS). The ATS shows a
transfer start time at which each of the TS packets is to be
transferred to a PID filter. The source packets are arranged in the
multiplexed data as shown at the bottom of FIG. 34. The numbers
incrementing from the head of the multiplexed data are called
source packet numbers (SPNs).
[0314] Each of the TS packets included in the multiplexed data
includes not only streams of audio, video, subtitles and others,
but also a Program Association Table (PAT), a Program Map Table
(PMT), and a Program Clock Reference (PCR). The PAT shows what a
PID in a PMT used in the multiplexed data indicates, and a PID of
the PAT itself is registered as zero. The PMT stores PIDs of the
streams of video, audio, subtitles and others included in the
multiplexed data, and attribute information of the streams
corresponding to the PIDs. The PMT also has various descriptors
relating to the multiplexed data. The descriptors have information
such as copy control information showing whether copying of the
multiplexed data is permitted or not. The PCR stores STC time
information corresponding to an ATS showing when the PCR packet is
transferred to a decoder, in order to achieve synchronization
between an Arrival Time Clock (ATC) that is a time axis of ATSs,
and an System Time Clock (STC) that is a time axis of PTSs and
DTSs.
[0315] FIG. 35 illustrates the data structure of the PMT in detail.
A PMT header is disposed at the top of the PMT. The PMT header
describes the length of data included in the PMT and others. A
plurality of descriptors relating to the multiplexed data is
disposed after the PMT header. Information such as the copy control
information is described in the descriptors. After the descriptors,
a plurality of pieces of stream information relating to the streams
included in the multiplexed data is disposed. Each piece of stream
information includes stream descriptors each describing
information, such as a stream type for identifying a compression
codec of a stream, a stream PID, and stream attribute information
(such as a frame rate or an aspect ratio). The stream descriptors
are equal in number to the number of streams in the multiplexed
data.
[0316] When the multiplexed data is recorded on a recording medium
and others, it is recorded together with multiplexed data
information files.
[0317] Each of the multiplexed data information files is management
information of the multiplexed data as shown in FIG. 36. The
multiplexed data information files are in one to one correspondence
with the multiplexed data, and each of the files includes
multiplexed data information, stream attribute information, and an
entry map.
[0318] As illustrated in FIG. 36, the multiplexed data information
includes a system rate, a reproduction start time, and a
reproduction end time. The system rate indicates the maximum
transfer rate at which a system target decoder to be described
later transfers the multiplexed data to a PID filter. The intervals
of the ATSs included in the multiplexed data are set to not higher
than a system rate. The reproduction start time indicates a PTS in
a video frame at the head of the multiplexed data. An interval of
one frame is added to a PTS in a video frame at the end of the
multiplexed data, and the PTS is set to the reproduction end
time.
[0319] As shown in FIG. 37, a piece of attribute information is
registered in the stream attribute information, for each PID of
each stream included in the multiplexed data. Each piece of
attribute information has different information depending on
whether the corresponding stream is a video stream, an audio
stream, a presentation graphics stream, or an interactive graphics
stream. Each piece of video stream attribute information carries
information including what kind of compression codec is used for
compressing the video stream, and the resolution, aspect ratio and
frame rate of the pieces of picture data that is included in the
video stream. Each piece of audio stream attribute information
carries information including what kind of compression codec is
used for compressing the audio stream, how many channels are
included in the audio stream, which language the audio stream
supports, and how high the sampling frequency is. The video stream
attribute information and the audio stream attribute information
are used for initialization of a decoder before the player plays
back the information. In the present embodiment, the multiplexed
data to be used is of a stream type included in the PMT.
Furthermore, when the multiplexed data is recorded on a recording
medium, the video stream attribute information included in the
multiplexed data information is used. More specifically, the moving
picture coding method or the moving picture coding apparatus
described in each of embodiments includes a step or a unit for
allocating unique information indicating video data generated by
the moving picture coding method or the moving picture coding
apparatus in each of embodiments, to the stream type included in
the PMT or the video stream attribute information. With the
configuration, the video data generated by the moving picture
coding method or the moving picture coding apparatus described in
each of embodiments can be distinguished from video data that
conforms to another standard.
[0320] Furthermore, FIG. 38 illustrates steps of the moving picture
decoding method according to the present embodiment. In Step
exS100, the stream type included in the PMT or the video stream
attribute information included in the multiplexed data information
is obtained from the multiplexed data. Next, in Step exS101, it is
determined whether or not the stream type or the video stream
attribute information indicates that the multiplexed data is
generated by the moving picture coding method or the moving picture
coding apparatus in each of embodiments. When it is determined that
the stream type or the video stream attribute information indicates
that the multiplexed data is generated by the moving picture coding
method or the moving picture coding apparatus in each of
embodiments, in Step exS102, decoding is performed by the moving
picture decoding method in each of embodiments. Furthermore, when
the stream type or the video stream attribute information indicates
conformance to the conventional standards, such as MPEG-2, MPEG-4
AVC, and VC-1, in Step exS103, decoding is performed by a moving
picture decoding method in conformity with the conventional
standards.
[0321] As such, allocating a new unique value to the stream type or
the video stream attribute information enables determination
whether or not the moving picture decoding method or the moving
picture decoding apparatus that is described in each of embodiments
can perform decoding. Even when multiplexed data that conforms to a
different standard is input, an appropriate decoding method or
apparatus can be selected. Thus, it becomes possible to decode
information without any error. Furthermore, the moving picture
coding method or apparatus, or the moving picture decoding method
or apparatus in the present embodiment can be used in the devices
and systems described above.
Embodiment 5
[0322] Each of the moving picture coding method, the moving picture
coding apparatus, the moving picture decoding method, and the
moving picture decoding apparatus in each of embodiments is
typically achieved in the form of an integrated circuit or a Large
Scale Integrated (LSI) circuit. As an example of the LSI, FIG. 39
illustrates a configuration of the LSI ex500 that is made into one
chip. The LSI ex500 includes elements ex501, ex502, ex503, ex504,
ex505, ex506, ex507, ex508, and ex509 to be described below, and
the elements are connected to each other through a bus ex510. The
power supply circuit unit ex505 is activated by supplying each of
the elements with power when the power supply circuit unit ex505 is
turned on.
[0323] For example, when coding is performed, the LSI ex500
receives an AV signal from a microphone ex117, a camera ex113, and
others through an AV IO ex509 under control of a control unit ex501
including a CPU ex502, a memory controller ex503, a stream
controller ex504, and a driving frequency control unit ex512. The
received AV signal is temporarily stored in an external memory
ex511, such as an SDRAM. Under control of the control unit ex501,
the stored data is segmented into data portions according to the
processing amount and speed to be transmitted to a signal
processing unit ex507. Then, the signal processing unit ex507 codes
an audio signal and/or a video signal. Here, the coding of the
video signal is the coding described in each of embodiments.
Furthermore, the signal processing unit ex507 sometimes multiplexes
the coded audio data and the coded video data, and a stream IO
ex506 provides the multiplexed data outside. The provided
multiplexed data is transmitted to the base station ex107, or
written on the recording medium ex215. When data sets are
multiplexed, the data should be temporarily stored in the buffer
ex508 so that the data sets are synchronized with each other.
[0324] Although the memory ex511 is an element outside the LSI
ex500, it may be included in the LSI ex500. The buffer ex508 is not
limited to one buffer, but may be composed of buffers. Furthermore,
the LSI ex500 may be made into one chip or a plurality of
chips.
[0325] Furthermore, although the control unit ex501 includes the
CPU ex502, the memory controller ex503, the stream controller
ex504, the driving frequency control unit ex512, the configuration
of the control unit ex501 is not limited to such. For example, the
signal processing unit ex507 may further include a CPU. Inclusion
of another CPU in the signal processing unit ex507 can improve the
processing speed. Furthermore, as another example, the CPU ex502
may serve as or be a part of the signal processing unit ex507, and,
for example, may include an audio signal processing unit. In such a
case, the control unit ex501 includes the signal processing unit
ex507 or the CPU ex502 including a part of the signal processing
unit ex507.
[0326] The name used here is LSI, but it may also be called IC,
system LSI, super LSI, or ultra LSI depending on the degree of
integration.
[0327] Moreover, ways to achieve integration are not limited to the
LSI, and a special circuit or a general purpose processor and so
forth can also achieve the integration. Field Programmable Gate
Array (FPGA) that can be programmed after manufacturing LSIs or a
reconfigurable processor that allows re-configuration of the
connection or configuration of an LSI can be used for the same
purpose.
[0328] In the future, with advancement in semiconductor technology,
a brand-new technology may replace LSI. The functional blocks can
be integrated using such a technology. The possibility is that the
present disclosure is applied to biotechnology.
Embodiment 6
[0329] When video data generated in the moving picture coding
method or by the moving picture coding apparatus described in each
of embodiments is decoded, compared to when video data that
conforms to a conventional standard, such as MPEG-2, MPEG-4 AVC,
and VC-1 is decoded, the processing amount probably increases.
Thus, the LSI ex500 needs to be set to a driving frequency higher
than that of the CPU ex502 to be used when video data in conformity
with the conventional standard is decoded. However, when the
driving frequency is set higher, there is a problem that the power
consumption increases.
[0330] In order to solve the problem, the moving picture decoding
apparatus, such as the television ex300 and the LSI ex500 is
configured to determine to which standard the video data conforms,
and switch between the driving frequencies according to the
determined standard. FIG. 40 illustrates a configuration ex800 in
the present embodiment. A driving frequency switching unit ex803
sets a driving frequency to a higher driving frequency when video
data is generated by the moving picture coding method or the moving
picture coding apparatus described in each of embodiments. Then,
the driving frequency switching unit ex803 instructs a decoding
processing unit ex801 that executes the moving picture decoding
method described in each of embodiments to decode the video data.
When the video data conforms to the conventional standard, the
driving frequency switching unit ex803 sets a driving frequency to
a lower driving frequency than that of the video data generated by
the moving picture coding method or the moving picture coding
apparatus described in each of embodiments. Then, the driving
frequency switching unit ex803 instructs the decoding processing
unit ex802 that conforms to the conventional standard to decode the
video data.
[0331] More specifically, the driving frequency switching unit
ex803 includes the CPU ex502 and the driving frequency control unit
ex512 in FIG. 39. Here, each of the decoding processing unit ex801
that executes the moving picture decoding method described in each
of embodiments and the decoding processing unit ex802 that conforms
to the conventional standard corresponds to the signal processing
unit ex507 in FIG. 39. The CPU ex502 determines to which standard
the video data conforms. Then, the driving frequency control unit
ex512 determines a driving frequency based on a signal from the CPU
ex502. Furthermore, the signal processing unit ex507 decodes the
video data based on the signal from the CPU ex502. For example, the
identification information described in Embodiment 4 is probably
used for identifying the video data. The identification information
is not limited to the one described in Embodiment 4 but may be any
information as long as the information indicates to which standard
the video data conforms. For example, when which standard video
data conforms to can be determined based on an external signal for
determining that the video data is used for a television or a disk,
etc., the determination may be made based on such an external
signal. Furthermore, the CPU ex502 selects a driving frequency
based on, for example, a look-up table in which the standards of
the video data are associated with the driving frequencies as shown
in FIG. 42. The driving frequency can be selected by storing the
look-up table in the buffer ex508 and in an internal memory of an
LSI, and with reference to the look-up table by the CPU ex502.
[0332] FIG. 41 illustrates steps for executing a method in the
present embodiment. First, in Step exS200, the signal processing
unit ex507 obtains identification information from the multiplexed
data. Next, in Step exS201, the CPU ex502 determines whether or not
the video data is generated by the coding method and the coding
apparatus described in each of embodiments, based on the
identification information. When the video data is generated by the
moving picture coding method and the moving picture coding
apparatus described in each of embodiments, in Step exS202, the CPU
ex502 transmits a signal for setting the driving frequency to a
higher driving frequency to the driving frequency control unit
ex512. Then, the driving frequency control unit ex512 sets the
driving frequency to the higher driving frequency. On the other
hand, when the identification information indicates that the video
data conforms to the conventional standard, such as MPEG-2, MPEG-4
AVC, and VC-1, in Step exS203, the CPU ex502 transmits a signal for
setting the driving frequency to a lower driving frequency to the
driving frequency control unit ex512. Then, the driving frequency
control unit ex512 sets the driving frequency to the lower driving
frequency than that in the case where the video data is generated
by the moving picture coding method and the moving picture coding
apparatus described in each of embodiment.
[0333] Furthermore, along with the switching of the driving
frequencies, the power conservation effect can be improved by
changing the voltage to be applied to the LSI ex500 or an apparatus
including the LSI ex500. For example, when the driving frequency is
set lower, the voltage to be applied to the LSI ex500 or the
apparatus including the LSI ex500 is probably set to a voltage
lower than that in the case where the driving frequency is set
higher.
[0334] Furthermore, when the processing amount for decoding is
larger, the driving frequency may be set higher, and when the
processing amount for decoding is smaller, the driving frequency
may be set lower as the method for setting the driving frequency.
Thus, the setting method is not limited to the ones described
above. For example, when the processing amount for decoding video
data in conformity with MPEG-4 AVC is larger than the processing
amount for decoding video data generated by the moving picture
coding method and the moving picture coding apparatus described in
each of embodiments, the driving frequency is probably set in
reverse order to the setting described above.
[0335] Furthermore, the method for setting the driving frequency is
not limited to the method for setting the driving frequency lower.
For example, when the identification information indicates that the
video data is generated by the moving picture coding method and the
moving picture coding apparatus described in each of embodiments,
the voltage to be applied to the LSI ex500 or the apparatus
including the LSI ex500 is probably set higher. When the
identification information indicates that the video data conforms
to the conventional standard, such as MPEG-2, MPEG-4 AVC, and VC-1,
the voltage to be applied to the LSI ex500 or the apparatus
including the LSI ex500 is probably set lower. As another example,
when the identification information indicates that the video data
is generated by the moving picture coding method and the moving
picture coding apparatus described in each of embodiments, the
driving of the CPU ex502 does not probably have to be suspended.
When the identification information indicates that the video data
conforms to the conventional standard, such as MPEG-2, MPEG-4 AVC,
and VC-1, the driving of the CPU ex502 is probably suspended at a
given time because the CPU ex502 has extra processing capacity.
Even when the identification information indicates that the video
data is generated by the moving picture coding method and the
moving picture coding apparatus described in each of embodiments,
in the case where the CPU ex502 has extra processing capacity, the
driving of the CPU ex502 is probably suspended at a given time. In
such a case, the suspending time is probably set shorter than that
in the case where when the identification information indicates
that the video data conforms to the conventional standard, such as
MPEG-2, MPEG-4 AVC, and VC-1.
[0336] Accordingly, the power conservation effect can be improved
by switching between the driving frequencies in accordance with the
standard to which the video data conforms. Furthermore, when the
LSI ex500 or the apparatus including the LSI ex500 is driven using
a battery, the battery life can be extended with the power
conservation effect.
Embodiment 7
[0337] There are cases where a plurality of video data that
conforms to different standards, is provided to the devices and
systems, such as a television and a cellular phone. In order to
enable decoding the plurality of video data that conforms to the
different standards, the signal processing unit ex507 of the LSI
ex500 needs to conform to the different standards. However, the
problems of increase in the scale of the circuit of the LSI ex500
and increase in the cost arise with the individual use of the
signal processing units ex507 that conform to the respective
standards.
[0338] In order to solve the problem, what is conceived is a
configuration in which the decoding processing unit for
implementing the moving picture decoding method described in each
of embodiments and the decoding processing unit that conforms to
the conventional standard, such as MPEG-2, MPEG-4 AVC, and VC-1 are
partly shared. Ex900 in FIG. 43A shows an example of the
configuration. For example, the moving picture decoding method
described in each of embodiments and the moving picture decoding
method that conforms to MPEG-4 AVC have, partly in common, the
details of processing, such as entropy coding, inverse
quantization, deblocking filtering, and motion compensated
prediction. The details of processing to be shared probably include
use of a decoding processing unit ex902 that conforms to MPEG-4
AVC. In contrast, a dedicated decoding processing unit ex901 is
probably used for other processing unique to an aspect of the
present disclosure. Since the aspect of the present disclosure is
characterized by inverse quantization in particular, for example,
the dedicated decoding processing unit ex901 is used for inverse
quantization. Otherwise, the decoding processing unit is probably
shared for one of the entropy decoding, deblocking filtering, and
motion compensation, or all of the processing. The decoding
processing unit for implementing the moving picture decoding method
described in each of embodiments may be shared for the processing
to be shared, and a dedicated decoding processing unit may be used
for processing unique to that of MPEG-4 AVC.
[0339] Furthermore, ex1000 in FIG. 43B shows another example in
that processing is partly shared. This example uses a configuration
including a dedicated decoding processing unit ex1001 that supports
the processing unique to an aspect of the present disclosure, a
dedicated decoding processing unit ex1002 that supports the
processing unique to another conventional standard, and a decoding
processing unit ex1003 that supports processing to be shared
between the moving picture decoding method according to the aspect
of the present disclosure and the conventional moving picture
decoding method. Here, the dedicated decoding processing units
ex1001 and ex1002 are not necessarily specialized for the
processing according to the aspect of the present disclosure and
the processing of the conventional standard, respectively, and may
be the ones capable of implementing general processing.
Furthermore, the configuration of the present embodiment can be
implemented by the LSI ex500.
[0340] As such, reducing the scale of the circuit of an LSI and
reducing the cost are possible by sharing the decoding processing
unit for the processing to be shared between the moving picture
decoding method according to the aspect of the present disclosure
and the moving picture decoding method in conformity with the
conventional standard.
INDUSTRIAL APPLICABILITY
[0341] The image decoding method and image coding method according
to an aspect of the present disclosure is advantageously applicable
to a moving picture coding method and a moving picture decoding
method.
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