U.S. patent application number 08/961988 was filed with the patent office on 2001-08-02 for digital motion picture decoding apparatus and digital motion picture decoding method.
This patent application is currently assigned to MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.. Invention is credited to SETOGUCHI, NOBUO, WATABE, AKIHIRO.
Application Number | 20010010750 08/961988 |
Document ID | / |
Family ID | 17744341 |
Filed Date | 2001-08-02 |
United States Patent
Application |
20010010750 |
Kind Code |
A1 |
SETOGUCHI, NOBUO ; et
al. |
August 2, 2001 |
DIGITAL MOTION PICTURE DECODING APPARATUS AND DIGITAL MOTION
PICTURE DECODING METHOD
Abstract
A digital motion picture decoding apparatus comprising an input
buffer memory for storing coded data to be decoded, a reproduced
picture memory for storing the decoded picture data to be
displayed, and a display picture deciding means for deciding a
reproduced picture to be output from the picture data stored in the
reproduced picture memory, further comprises: a program changing
means for changing the type of the coded data to be decoded; a
program change detecting means for detecting from the output of the
program changing means that the type of the coded data to be
decoded is changed; and a display state maintaining means for
controlling the picture data output from the reproduced picture
memory so as to maintain the display state of the reproduced
picture which is currently displayed according to the decision of
the display picture deciding means, when it is detected from the
output of the program change detecting means that the change of the
type of the coded data to be decoded makes the coded data not
continuous in time sequence.
Inventors: |
SETOGUCHI, NOBUO;
(NAGAOKAKYOU-SHI, JP) ; WATABE, AKIHIRO; (UDA-GUN,
JP) |
Correspondence
Address: |
PARKHURST & WENDEL
1421 PRINCE STREET
SUITE 210
ALEXANDRIA
VA
223142805
|
Assignee: |
MATSUSHITA ELECTRIC INDUSTRIAL CO.,
LTD.
|
Family ID: |
17744341 |
Appl. No.: |
08/961988 |
Filed: |
October 31, 1997 |
Current U.S.
Class: |
386/328 ;
348/E5.108 |
Current CPC
Class: |
H04N 21/44004 20130101;
H04N 21/4383 20130101; H04N 5/4401 20130101; H04N 21/426 20130101;
H04N 21/44016 20130101 |
Class at
Publication: |
386/46 ; 386/68;
386/111 |
International
Class: |
H04N 005/91; H04N
007/00; H04N 007/26 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 31, 1996 |
JP |
8-289521 |
Claims
What is claimed is:
1. A digital motion picture decoding apparatus comprising an input
buffer memory for storing coded data to be decoded, a reproduced
picture memory for storing the decoded picture data to be
displayed, and a display picture deciding means for deciding from
the picture data stored in the reproduced picture memory a
reproduced picture to be output, said decoding apparatus further
comprising: a program changing means for changing the type of the
coded data to be decoded; a program change detecting means for
detecting from the output of the program changing means that the
type of the coded data to be decoded is changed; and a display
state maintaining means for controlling the picture data output
from the reproduced picture memory so as to maintain the display
state of the reproduced picture being currently displayed according
to the decision of the display picture deciding means, when it is
detected from the output of the program change detecting means that
the change of the type of the coded data to be decoded makes the
coded data not continuous in time sequence.
2. The digital motion picture decoding apparatus defined in claim 1
wherein the program change detecting means detects from an output
of the program changing means a difference between a normal
reproduction state and a reproduction state after change of program
or a reproduction state at a reproduction rate different from the
normal reproduction rate.
3. The digital motion picture decoding apparatus defined in claim 1
further comprising an input buffer memory erasing means for erasing
the coded data to be decoded which is stored therein, when the
program change detecting means detects that the data subjected to
decoding is not continuous in time sequence.
4. A digital motion picture decoding apparatus comprising an input
buffer memory for storing coded data to be decoded, a reproduced
picture memory for storing decoded picture data to be displayed,
and a display picture deciding means for deciding from the picture
data stored in the reproduced picture memory a reproduced picture
to be output, said decoding means further comprising: a program
changing means for changing the type of the coded data to be
decoded; a program change detecting means for detecting from the
output of the program changing means that the type of the coded
data to be decoded is changed; a reproduced picture memory
nullifying means for nullifying the data stored in the reproduced
picture memory other than the data corresponding to the reproduced
picture being currently displayed, when it is detected from the
output of the program change detecting means that the change of the
type of the coded data to be decoded makes the coded data not
continuous in time sequence.
5. The digital motion picture decoding apparatus defined in claim 4
comprising a reproduced picture area managing means for managing
memory area information used when the decoding means writes the
decoded picture data into the reproduced picture memory, wherein
the reproduced picture memory nullifying means erases the memory
area information corresponding to the data stored in the reproduced
picture area managing means except the data corresponding to a
reproduced picture being currently displayed.
6. The digital motion picture decoding apparatus defined in claim 4
wherein the reproduced picture memory nullifying means erases the
data in the reproduced picture memory except the data corresponding
to the reproduced picture being currently displayed.
7. The digital motion picture decoding apparatus defined in claim 4
wherein picture data to be decoded next is written into a nullified
memory area of the reproduced picture memory.
8. A digital motion picture decoding apparatus comprising an input
buffer memory for storing coded data to be decoded, a reproduced
picture memory for storing decoded picture data to be displayed,
and a display picture deciding means for deciding from the picture
data stored in the reproduced picture memory a display picture to
be output, said decoding apparatus further comprising: a program
changing means for changing the type of the coded data to be
decoded; a program change detecting means for detecting from the
output of the program changing means that the type of the coded
data to be decoded is changed; and a decoding stopping means for
stopping decoding processing by the decoding means and controlling
the decoding means such that the data being in the process of
decoding at that time is written into the reproduced picture memory
as the already decoded one, when it is detected from the output of
the program change detecting means that the change of the type of
the coded data to be decoded makes the coded data not continuous in
time sequence.
9. A digital motion picture decoding method comprising the steps
of: detecting whether data is continuous in time sequence during
decoding processing; and maintaining the display state of a
reproduced picture being currently displayed when it is found in
the first step that the data is not continuous in time sequence
during the decoding processing.
10. A digital motion picture decoding method comprising the steps
of: detecting whether data is continuous in time sequence during
decoding processing; and nullifying data other than the one
corresponding to a reproduced picture being currently displayed,
when it is judged in the first step that the data is not continuous
in time sequence during the decoding processing.
11. The digital motion picture decoding method defined in claim 10
further comprising a step of stopping decoding processing and
processing the data being currently decoded at that time as the
already decoded one, when it is judged in the first step that the
data is not continuous in time sequence during the decoding
processing.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a digital motion picture decoding
apparatus and a digital motion picture decoding method for decoding
picture data coded by variable length coding for digital storage
media, broadcasting, and communication. In particular, it relates
to a digital motion picture decoding apparatus and a digital motion
picture decoding method capable of correctly decoding and
reproducing coded data which is partially discontinuous due to
change of program during the reproduction.
BACKGROUND OF THE INVENTION
[0002] Nowadays, demands for general method for coding motion
picture and its attached sound are increasing for various
applications including digital storage media, or television
broadcasting and communication. Motion Picture Experts Group (MPEG)
in the International Electrotechnical Commission (IEC) of
International Standardization Organization (ISO) has proceeded
International standardization of motion picture coding method and
already standardized several methods including ISO/IEC 13818-2
(MPEG2video).
[0003] Here a description is given, with reference to FIG. 9, of a
conventional digital motion picture decoding apparatus for decoding
the data coded by the MPEG coding method which is disclosed by
Japanese Published Patent Application Number H8-32927, for
example.
[0004] Reference numeral 900 designates a conventional digital
motion picture decoding apparatus, numeral 911 designates a channel
selecting means which takes coded video streams corresponding to
plural programs as inputs and, in response to a program select
signal input by a user, selects a bit stream corresponding to one
of the plural programs to output the bit stream as coded picture
data 901. This means is also configured to output a program change
signal at the same time. The output coded picture data 901 passes
through a code pattern detecting means 903 which is described later
and is sequentially stored in an input buffer memory 902.
[0005] The code pattern detecting means 903 is a block which
inhibits data from passing through to the input buffer memory 902
until a prescribed code pattern, I picture (intra-coded picture) of
GOP (Group of pictures), is detected based on a change detection
signal from the coded data change detecting means 904, and this
means normally allows the data to pass through during the
reproduction processing.
[0006] Reference numeral 905 designates a decoding means which
makes a request for data to the input buffer memory 902, where the
data obtained is subjected to decoding processing and then
successively stored into a predetermined reproduced picture area in
a reproduced picture memory 907.
[0007] A display picture deciding means 906 decides a reproduced
picture to be displayed according to time information of each
reproduced picture and the information about the data stored in the
reproduced picture memory 907 obtained from a time information
managing means 908 and a reproduced picture area managing means
909, outputting the picture as a reproduced picture data 910 for
reproduction and display.
[0008] Next, a description is given of the operation for a
transition from normal reproduction mode to special reproduction
mode in which reproduction speed is changed to realize high-speed
reproduction.
[0009] In response to a request for high-speed reproduction from a
user, the coded picture data 901 is transmitted to the code pattern
detecting means 903 in a format which comprises only an intra-frame
coded picture (I picture) extracted from the bit stream recorded in
record medium, and by detecting a pattern of contiguous I pictures,
it is detected that the transition to special reproduction mode has
been completed. Following this, sending data through to the input
buffer memory 902 is stopped and a clear signal is output from the
code pattern detecting means 903 to the input buffer memory 902,
whereby the data stored in the input buffer memory 902 is
erased.
[0010] When the code pattern detecting means 903 detects normal
pattern again, cancel of the special reproduction mode is
recognized and a blue-back processing which is described later is
canceled, whereby sending data to the input buffer memory 902 is
resumed.
[0011] Next, a description is given of the operation in the
above-described configuration when the coded data in the process of
reproduction becomes partially discontinuous due to change of
program.
[0012] After detecting based on a program change detection signal
that change of the coded data to be input has been performed, the
coded data change detecting means 904 sends a clear signal to the
input buffer memory 902 to clear all the data stored in the memory
902, while sending a data passing inhibit signal to the code
pattern detecting means 903 in order to inhibit data from passing
through to the input buffer memory 902 until a start code (I
picture) of an intra-frame coded picture is detected by the code
pattern detecting means 903.
[0013] At this time, blank pictures (Bu pictures) are inserted
following a bidirectional predictive coded picture B3 (B picture),
resulting in blue-back processing which provides a screen turned to
blue.
[0014] Then, when the code pattern detecting means 903 detects the
start code (I picture) of the intra-frame coded picture from the
coded picture data after the change, passing data through to the
input buffer memory 902 is permitted again and the blue-back
processing is canceled, whereby reproduction operation is started
again.
[0015] The decoding apparatus is configured to prevent reference
picture error caused by connecting data arrays of different types
at the change of coded data and avoid decoding the data left in the
buffer at the change of the coded picture data, by performing the
above-described processing.
[0016] The prior art digital motion picture decoding apparatus and
the digital motion picture decoding method have the above-described
construction which prevents reference picture error caused by
connecting different types of data arrays at the change of coded
data, but both the conventional decoding apparatus and the method
have a problem that when the coded data is changed due to the
change of program or other causes, blue-back screen is maintained
during a prescribed period of time, making a viewer feel
unconformable.
[0017] Moreover, in the case that change of coded data is not
performed on a single piece of picture data basis and the coded
data to be input is changed in the process of decoding a single
piece of picture data by means of the decoding means 905, the
operation of changing program in the middle of decoding processing
as shown in FIG. 8(a) allows a situation as shown in FIG. 8(b)
which is equal to the situation caused by inputting a data array to
which a different type of data array is connected, resulting in
decoding error and the considerably confused display resulted from
error picture.
[0018] Furthermore, as shown in FIG. 5, since the structure of the
data coded by a method employing bidirectional coding such as MPEG
coding has an order different from both the order in which the
picture data of the coded data is placed and the display order for
reproducing pictures, forward predictive coded picture (P
pictures), which is to be displayed following a sequence of
bidirectional predictive coded pictures (B pictures), is decoded
before decoding of the bidirectional predictive coded pictures (B
pictures), and the resultant decoded data is stored in the
reproduced picture memory 907. Therefore, as shown in FIG. 6), in
the configuration only capable of clearing the data in the input
buffer memory at the last stage, when the decoding processing has
been already completed at the change of the coded picture data to
be input and reproduced picture data which is not displayed yet
(P6) is stored in the reproduced picture memory because the display
time is not reached, that reproduced picture data is certainly
displayed when the display time based on time information of the
reproduced picture is reached. Therefore, with a long interval
between each display time of reproduced pictures, an extended
period of time is required before displaying the reproduced picture
data which is unnecessary (P6) and it takes much time to change the
coded picture data in the process of reproduction, whereby the
blue-back screen is displayed for an extended period of time and
makes a viewer feel uncomfortable.
SUMMARY OF THE INVENTION
[0019] An object of the invention is to provide a digital motion
picture decoding apparatus and a digital motion picture decoding
method which do not display blue-back screen during change of coded
data due to change of program or the like, in order to prevent a
viewer from feeling uncomfortable.
[0020] A further object of the invention is to provide a digital
motion picture decoding apparatus and a digital motion picture
decoding method which do not cause decoding error even when coded
data is not changed on a single piece of picture data basis and the
coded data to be input is changed when a single piece of picture
data is being subjected to decoding processing.
[0021] A still further object of the invention is to provide a
digital motion picture decoding apparatus and a digital motion
picture decoding method which require a short time before
displaying the reproduced picture data which is unnecessary and do
not take much time to change the coded picture data in the process
of reproduction, in the case that one piece of picture data, whose
display time established according to time information on a display
picture basis is not reached, has been already decoded at the
change of coded picture data, and the reproduced picture is stored
in the reproduced picture memory.
[0022] Other objects and advantages of the invention will become
apparent from the detailed description that follows. The detailed
description and specific embodiments described are provided only
for illustration since various additions and modifications within
the scope of the invention will be apparent to those of skill in
the art from the detailed description.
[0023] According to a first aspect of the present invention, a
digital motion picture decoding apparatus comprising an input
buffer memory for storing coded data to be decoded, a reproduced
picture memory for storing the decoded picture data to be
displayed, and a display picture deciding means for deciding from
the picture data stored in the reproduced picture memory a
reproduced picture to be output, further comprises: a program
changing means for changing the type of the coded data to be
decoded; a program change detecting means for detecting from the
output of the program changing means that the type of the coded
data to be decoded is changed; and a display state maintaining
means for controlling the picture data output from the reproduced
picture memory so as to maintain the display state of the
reproduced picture being currently displayed according to the
decision of the display picture deciding means, when it is detected
from the output of the program change detecting means that the
change of the type of the coded data to be decoded makes the coded
data not continuous in time sequence.
[0024] According to a second aspect of the present invention, in
the digital motion picture decoding apparatus defined in the first
aspect, the program change detecting means detects from an output
of the program changing means a difference between a normal
reproduction state and a reproduction state after change of program
or a reproduction state at a reproduction rate different from the
normal reproduction rate.
[0025] According to a third aspect of the present invention, the
digital motion picture decoding apparatus defined in the first
aspect further comprises an input buffer memory erasing means for
erasing the coded data to be decoded which is stored therein, when
the program change detecting means detects that the data subjected
to decoding is not continuous in time sequence.
[0026] According to a fourth aspect of the present invention, a
digital motion picture decoding apparatus comprising an input
buffer memory for storing coded data to be decoded, a reproduced
picture memory for storing decoded picture data to be displayed,
and a display picture deciding means for deciding from the picture
data stored in the reproduced picture memory a reproduced picture
to be output, further comprises: a program changing means for
changing the type of the coded data to be decoded; a program change
detecting means for detecting from the output of the program
changing means that the type of the coded data to be decoded is
changed; a reproduced picture memory nullifying means for
nullifying the data stored in the reproduced picture memory other
than the data corresponding to the reproduced picture being
currently displayed, when it is detected from the output of the
program change detecting means that the change of the type of the
coded data to be decoded makes the coded data not continuous in
time sequence.
[0027] According to a fifth aspect of the present invention, the
digital motion picture decoding apparatus defined in the fourth
aspect comprises a reproduced picture area managing means for
managing memory area information used when the decoding means
writes the decoded picture data into the reproduced picture memory,
and in this apparatus, the reproduced picture memory nullifying
means erases the memory area information corresponding to the data
stored in the reproduced picture area managing means except the
data corresponding to a reproduced picture being currently
displayed.
[0028] According to a sixth aspect of the present invention, in the
digital motion picture decoding apparatus defined in the fourth
aspect, the reproduced picture memory nullifying means erases the
data in the reproduced picture memory except the data corresponding
to the reproduced picture being currently displayed.
[0029] According to a seventh aspect of the present invention, in
the digital motion picture decoding apparatus defined in the fourth
aspect, picture data to be decoded next is written into a nullified
memory area of the reproduced picture memory.
[0030] According to an eighth aspect of the present invention, a
digital motion picture decoding apparatus comprising an input
buffer memory for storing coded data to be decoded, a reproduced
picture memory for storing decoded picture data to be displayed,
and a display picture deciding means for deciding from the picture
data stored in the reproduced picture memory a display picture to
be output, further comprises: a program changing means for changing
the type of the coded data to be decoded; a program change
detecting means for detecting from the output of the program
changing means that the type of the coded data to be decoded is
changed; and a decoding stopping means for stopping decoding
processing by the decoding means and controlling the decoding means
such that the data being in the process of decoding at that time is
written into the reproduced picture memory as the already decoded
one, when it is detected from the output of the program change
detecting means that the change of the type of the coded data to be
decoded makes the coded data not continuous in time sequence.
[0031] According to a ninth aspect of the present invention, a
digital motion picture decoding method comprises the steps of:
detecting whether data is continuous in time sequence during
decoding processing; and maintaining the display state of a
reproduced picture being currently displayed when it is found in
the first step that the data is not continuous in time sequence
during the decoding processing.
[0032] According to a tenth aspect of the present invention, a
digital motion picture decoding method comprises the steps of:
detecting whether data is continuous in time sequence during
decoding processing; and nullifying data other than the one
corresponding to a reproduced picture being currently displayed,
when it is judged in the first step that the data is not continuous
in time sequence during the decoding processing.
[0033] According to an eleventh aspect of the present invention,
the digital motion picture decoding method defined in the tenth
aspect further comprises a step of stopping decoding processing and
processing the data being currently decoded at that time as the
already decoded one, when it is judged in the first step that the
data is not continuous in time sequence during the decoding
processing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. 1 is a block diagram of a digital motion picture
decoding apparatus according to an embodiment of the present
invention.
[0035] FIG. 2 is a flow chart for explaining the operation during
change of program by the digital motion picture decoding apparatus
of the embodiment of the invention.
[0036] FIG. 3 is a flow chart for explaining the operation of the
decoding means during change of program in the digital motion
picture decoding apparatus of the embodiment of the invention.
[0037] FIG. 4 is a flow chart for explaining the operation for
displaying new coded data after change of program in the digital
motion picture decoding apparatus of the embodiment of the
invention.
[0038] FIG. 5 is a diagram showing an example of the structure of a
bit stream coded in a coding mode which uses a bidirectional
predictive coding such as MPEG.
[0039] FIG. 6 is a diagram showing an example of the structure of a
bit stream and an exemplary operation of the conventional digital
motion picture decoding apparatus, in the case that coded data to
be input is changed in the process of reproduction.
[0040] FIG. 7 is a diagram illustrating an exemplary operation of a
digital motion picture decoding apparatus of the present invention
under the condition illustrated in FIG. 5.
[0041] FIGS. 8(a) to 8(c) are diagrams showing the states of a
decoding means in the case that coded data is changed in the middle
of decoding one piece of picture data.
[0042] FIG. 9 is a block diagram of a prior art digital motion
picture decoding apparatus.
[0043] FIG. 10 is a conceptual diagram of a state table of
reproduced picture areas which constitute the digital motion
picture decoding apparatus according to the embodiment of the
present invention.
PREFERRED EMBODIMENT OF THE INVENTION
[0044] Hereinafter a description is given of a digital motion
picture decoding apparatus and a digital motion picture decoding
method according to the present invention with reference to
drawings.
[0045] FIG. 1 is a block diagram of a digital motion picture
decoding apparatus according to an embodiment of the invention. In
the figure, reference numeral 100 designates a digital motion
picture decoding apparatus of the invention, and numeral 104
designates a program change detecting means, which means takes
coded video streams corresponding to a plurality of coded programs
as inputs and, according to a program select signal input by a user
through a control means (remote controller) 111, selects one bit
stream corresponding to one of the plural programs to output it as
coded picture data 101.
[0046] In normal decoding operation, the input coded picture data
101 is passed through a code pattern detecting means 103 which is
described later, and stored in an input buffer memory 102.
[0047] The input buffer memory 102 has a relatively large capacity,
for example, about 400 Kb, and outputs the stored coded data
according to a request from a decoding means 105 which is also
described later.
[0048] The decoding means 105 manages an amount of data in the
input buffer memory 102 based on the amount of the data input into
this means and the amount of the data output from the means, and
controls the data input to the means itself according to the amount
of the data stored in the input buffer memory 102. Moreover, the
decoding means 105 also includes a reproduced picture memory
address management table for managing null addresses when the
decoded picture data is written into a reproduced picture memory
107 which is also described later.
[0049] The code pattern detecting means 103 is a block which
inhibits data from passing through to the input buffer memory 102
until a predetermined code pattern is detected, according to a data
passing inhibit signal from the program change detecting means 104,
and this means normally allows data to passing through during
reproduction.
[0050] The reproduced picture memory 107, which comprises SDRAM,
for example, has a capacity for storing three frames of picture
data (500 Kb.times.3=1.5 Mb) and includes divided regions M0 to M2.
The coded picture data input to the decoding means 105 to be
decoded is stored into one of the reproduced picture regions M0 to
M3 in the reproduced picture memory 107, on one display picture
basis.
[0051] The display picture deciding means 106 comprises a base time
counter for counting up with time precision equal or superior to
the time precision of the time information established on single
frame picture basis by a time information managing means 108 which
is described later, and this base time counter manages a base time
for reproduction operation. Moreover, the base time counter can
change its count according to the base time information signal
input from the decoding means 105. Then, when it is judged from a
comparison between the count of the base time counter and a value
of the time information from the reproduced picture area managing
means 109 which is described later that these values are equal or
approximately equal, this means decides a reproduced picture area
as an output area according to the data storage information from
the reproduced picture area managing means 109. Then, to output the
decoded data in this area, the deciding means outputs a signal for
selecting a reproduced picture area from which decoded data is to
be output (this signal is hereinafter referred to as an output
area-reproduced picture area select signal), to the reproduced
picture memory 107 and the reproduced picture area managing means
109.
[0052] Reference numeral 109 designates the reproduced picture area
managing means, and this managing means relates the information
indicating which reproduced picture area of the reproduced picture
memory 107 stores the decoded picture data, to a display state flag
fed back from the display picture deciding means 106 which is
described later, and performs management using a table as shown in
FIG. 10, for example.
[0053] Further in the above configuration, the control means
(remote controller) 111 implements a program changing means, and
the program change detecting means 104 implements a program change
detecting means for detecting change of program according to a
program select signal input from the control means (remote
controller) 111, and an input buffer memory erasing means for
erasing the data stored in the input buffer memory 102. The display
picture deciding means 106 and the reproduced picture area managing
means 109 implement a display state maintaining means and the
program change detecting means 104 and the reproduced picture area
managing means 109 implement a reproduced picture memory nullifying
means and a decoding stopping means.
[0054] FIGS. 2 and 4 are flow charts illustrating the processes
performed by the digital motion picture decoding apparatus, and the
operation will be described with reference to these flow
charts.
[0055] Before the description, it is assumed that among the picture
data stored in the reproduced picture memory 107, a piece of
picture data stored in reproduced picture area M1 is currently
reproduced corresponding to a specified program selected by user
input.
[0056] Next, a description is given of the operation performed in
the case that data array subjected to decoding processing becomes
non-continuous at some midpoint because coded data is changed
during the reproduction, with reference to the block diagram of
FIG. 1 and the flow chart of FIG. 2.
[0057] Program change processing in the middle of reproduction
starts as follows; in step S1, the control means (remote
controller) 111 changes a program desired to be reproduced in the
process of reproduction and outputs to the program change detecting
means 104 a program select signal for changing coded data to be
reproduced.
[0058] Then, in step S2, the program change detecting means 104
outputs to the code pattern detecting means 103 a data passing
inhibit signal for inhibiting coded data from passing through until
a prescribed code is detected, and simultaneously outputs to the
input buffer memory 102 a data clear signal for clearing all the
data currently stored in this memory 102. Further, at the same
time, this means also outputs to the decoding means 105 a decoding
stop signal for stopping the currently performed decoding, and to
the reproduced picture area managing means 109, a flag erase signal
for clearing the data in the areas other than the area for a
reproduced picture being currently displayed.
[0059] Thereafter, the program change detecting means 104 selects
coded data of a program, from the stream data arrays of plural
programs which have been input, according to the program select
signal from the control means (remote controller) 111, and starts
outputting the coded data to the code pattern detecting means
103.
[0060] In response to the input of the data passing inhibit signal,
the code pattern detecting means 103 inhibits the input coded data
from passing through to the input buffer memory 102 and waits for
the input of a sequence header code of the coded data based on
MPEG.
[0061] Further, the input buffer memory 102 clears all the stored
data in response to the input data clear signal and waits the data
input from the code pattern detecting means 103.
[0062] Furthermore, the decoding means 105 stops the currently
performed decoding processing in response to the input of the
decoding stopping signal and waits for the input of a sequence
header code. Thereafter, this means outputs a data request signal
requesting new coded data to the input buffer memory 102.
[0063] In step S3, when data is input, it is checked whether the
data is a sequence header code or not. The data which is not the
sequence header code is discarded, and a check is made for next
input data to see whether the data is a sequence header code or
not. The process in step S3 is repeated until a sequence header
code is input.
[0064] As described above, in the digital motion picture decoding
apparatus of the conventional configuration, by stopping the
decoding processing immediately after change of program, a state is
brought about which is equal to the state that different types of
data arrays connected to each other are input to the decoding
means. This results in decoding error, and considerably confused
display caused by displaying error pictures, which makes viewer
feel uncomfortable.
[0065] Further, the reproduced picture area managing means 109
clears the data in the reproduced picture memory 107 except the
data in the area for the reproduced picture being currently used as
a display output, by means of a flag erase signal. More
specifically, flags are changed so that the data storage
information about the reproduced picture memory 107
indicates--"data" except the one-about-the reproduced picture area
M1. This process resolves one of the problems occurred in the
digital motion picture decoding apparatus of the conventional
configuration that displaying unnecessary reproduced picture data
prolongs a time interval between change of the coded picture data
to be input and change of reproduced pictures.
[0066] Furthermore, data storage information and a time information
notifying signal are output to the display picture deciding means
106, the information and the signal both being the contents of the
reproduced picture area state table changed to the state after data
clear immediately after clearing the data in the reproduced picture
memory 107.
[0067] According to the data storage information and the time
information notifying signal from the reproduced picture area
managing means 109, the display picture deciding means 106 detects
that there is no data in reproduced picture areas except the one
being currently used as an output area for display, and outputs to
the reproduced picture memory 107 an output area-reproduced picture
select signal which instructs to output the data from this
reproduced picture area repeatedly because the reproduced picture
areas other than that area contains no data. This process resolves
one of the problems for the digital motion picture decoding
apparatus of the conventional configuration that blue-back display
processing (see Bu in FIG. 6) performed until the display of a new
picture after the change (see IO' in FIG. 6) causes a display state
transition which is considerably clumsy.
[0068] Next, a description is given of the operation in the process
of displaying new coded data obtained after change of program.
[0069] In step S3, the code pattern detecting means 103 analyzes
new coded data obtained from the program change detecting means 104
to detect a sequence header code and, when the sequence head code
is detected, the step is followed by step S4 in which passing coded
data through to the input buffer memory 102 is permitted again.
[0070] This step is followed by step S5, in which storing coded
data into the input buffer memory 102 is resumed with the data
following the sequence header code being initial one, and
outputting the data is started corresponding to the data request
signal from the decoding means 105.
[0071] In step S6, from the coded data which includes display order
information for single frame picture being currently decoded and
the time information about the times at which the picture should be
displayed, the decoding means 105 extracts the above information to
output it as an extracted information signal to the time
information managing means 108. If the coded data contains no time
information based on which a single frame pictures being currently
decoded is displayed, the display order information only is output
to the time information managing means 108 as an extracted
information signal. Moreover, the decoding means 105 extracts the
base time information contained in the coded data and outputs it as
a base time information signal to the display picture deciding
means 106.
[0072] Following this, the same operation as in normal reproduction
is performed: as shown in the flow chart of FIG. 3, in step S7, the
decoding means 105 judges whether the input coded data is
predictive coded data or not; when the coded data is a predictive
coded one, this step is followed by step S8 wherein a reference
picture data request signal is output to the reproduced picture
area managing means 109 to request necessary data. If the input
coded data is not a predictive coded one, decoding processing is
performed using the input coded data only.
[0073] Then, in step S9, the reproduced picture area managing means
109 checks which reproduced picture area of the reproduced picture
memory 107 stores the requested reference picture data, and in step
S10, the reproduced picture area managing means 109 outputs a
reference picture data output control signal which instructs to
output the data in the specified area as reference picture
data.
[0074] In step S11, the reproduced picture memory 107 outputs the
data in the specified area as reference picture data, according to
the instruction of the reference picture data output control
signal.
[0075] Then, in step S12, the decoding means 105 starts decoding
the predictive coding type coded data using the input reference
picture data.
[0076] In step S12-1, the decoding means 105 outputs decoded data
obtained by the decoding processing to the reproduced picture
memory 107. The reproduced picture area managing means 109 outputs
to the reproduced picture memory 107 an address signal which
instructs the area in which that decoded data is to be stored.
[0077] If the coded data in the process of decoding contains base
time information, the information is output to the display picture
deciding means 106 as base time information.
[0078] Further, the display order information for displaying a
single frame picture being in the process of decoding and the time
information based on which such picture is displayed are extracted
from the coded data and output as an extracted information signal
to the time information managing means 108. If the above-described
time information is not included in the coded data, the display
order information only is extracted and output as an extracted
information signal to the time information managing means 108.
[0079] Next, the time information managing means 108 judges whether
the time information extracted from the coded data is included in
an extracted information signal which is input, and when the time
information is included, this time information is determined as the
time information based on which the picture is to be displayed,
which picture is currently being decoded in the decoding means 105,
and output as a time information signal to the reproduced picture
area managing means 109 If the time information is not found, time
information based on which the single frame picture being currently
decoded is to be displayed is calculated from time information and
display order information for another single frame picture, both
previously input from the decoding means 105, and the display order
information for the single frame picture being currently decoded,
outputting it as a time information signal to the reproduced
picture area managing means 109.
[0080] Next, in step S16, the reproduced picture area managing
means 109 checks the contents of the reproduced picture area state
table, outputting new decoded data obtained from the decoding means
105 after the change of program to the reproduced picture areas
other than the reproduced picture area from which the display is
being output (M1), that is, M0 and M2, and from these areas the
decoded data has been cleared. The reproduced picture area managing
means 109 also changes the contents of the reproduced picture area
state table, outputting data storage information and a time
information notifying signal to the display picture deciding means
106.
[0081] Then, in step S17, the display picture deciding means 106
detects from the data storage information and the time information
notifying signal the fact that new picture is ready to be output,
outputting an output area-reproduced picture area select signal
such that the decoded data of the picture stored in one of the
reproduced picture areas will be output when the time based on the
time information for the picture is reached.
[0082] Following this step, in step S18, the reproduced picture
memory 107 outputs new decoded data obtained after the change of
program as reproduced picture data, according to the output
area-reproduced picture area select signal.
[0083] The above-described processes enable to change a picture to
be displayed, according to the content of a newly selected
program.
[0084] As described above, in the first embodiment, passing data
through to the input buffer memory 102 is inhibited when change of
program is detected, and simultaneously all the data in the input
buffer memory 102 is erased while the display picture deciding
means 106 is controlled to maintain the display picture at this
time. This disables an unnatural screen such as a blue-back screen
to be displayed for a certain period of time during the change of
program, reducing viewer's uncomfortableness.
[0085] Further, when the change of program is detected, the
information about the areas in the reproduced picture memory 107
other than that currently used as an output area for display is
cleared to treat them as null areas, whereby the display of the
unnecessary picture is prevented which will be displayed after the
change of coded data. Further, since the coded data obtained after
the change is written into the reproduced picture memory 107 more
swiftly, It is possible to reduce a time necessary to perform the
process until the reproduced picture of the coded data after the
change is displayed.
[0086] In addition, since the decoding processing performed by the
decoding means 105 is stopped and a code indicating that decoding a
single piece of picture data is completed is added to the picture
data being currently decoded, the data array of a different program
is confused with the continuous data array being in the process of
decoding, thereby preventing the occurrence of decoding error due
to this misconception and the resultant display of error
pictures.
[0087] Although in the first embodiment the code pattern detecting
means 103 and the decoding means 105 have a feature of waiting for
a sequence header code to be detected after the change of program,
any detection feature is applicable as long as it can detect a code
pattern indicating a head of a data unit for decoding processing
and this detecting target is not limited to a sequence header code.
Other code patterns such as an MPEG-based GOP header code and a
start code of an intra-frame coded picture (I picture) can be used
as long as those codes are code patterns which allow to reproduce
picture only from the coded data following the detected data
only.
[0088] Although this embodiment is configured such that the code
pattern detecting means 103 is placed as a stage followed by the
input buffer memory, the same operation can be obtained by the
following configuration that the code pattern detecting means 103
is placed as a stage following the input buffer memory 102, and the
buffer memory 102 outputs data according to the request for data
from the code pattern detecting means 103 and inhibits the data to
be sent to the subsequent decoding means 105 until the detecting
means 103 detects a predetermined code pattern.
[0089] Although in this embodiment it is assumed that the
reproduced picture memory 107 has three reproduced picture areas,
the number of the reproduced picture areas is not limited to three
and any number of reproduced picture areas are applicable as long
as the number allows the decoded reproduced picture data to be
displayed in a display order.
[0090] In addition, although in this embodiment the reproduced
picture areas in the reproduced picture memory 107 are illustrated
as contiguous areas, the structure of the reproduced picture memory
107 is not limited to this illustration and a reproduced picture
memory can be employed which divides decoded data of each single
picture data into non-contiguous areas for storage.
[0091] Although in this embodiment a decoding object is MPEG-based
coded data, the coded data as a decoding object is not limited to
this data coded based on MPEG, and any coded data is applicable as
long as this code is the one coded by bidirectional predictive
coding and therefore the data coded by any coding method other than
MPEG-based coding may be used.
[0092] The stream data input to the program change detecting means
104 is not necessary to be broadcasted and such configuration is
applicable in which required program stream data is read from
record media such as disks.
[0093] Although in this embodiment the count of the base time
counter is changed according to base time information whenever that
base time information is input to the display picture deciding
means 106, this change may be performed only when the base time
information corresponding to the initial part of each coded data to
be reproduced is input to the display picture deciding means 106,
or this change may be performed at arbitrary timing corresponding
to the input of a control signal from external unit.
[0094] Furthermore, in this embodiment, it is not necessary for the
base time information to be changed according to the data extracted
from the coded data by the decoding means 105 and external unit may
directly set the count of the base time counter to an arbitrary
value.
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