U.S. patent application number 11/425290 was filed with the patent office on 2007-01-04 for information processing apparatus and decoding control method.
Invention is credited to Takeshi Kumagaya, Katsuya Ohno.
Application Number | 20070001877 11/425290 |
Document ID | / |
Family ID | 40295132 |
Filed Date | 2007-01-04 |
United States Patent
Application |
20070001877 |
Kind Code |
A1 |
Kumagaya; Takeshi ; et
al. |
January 4, 2007 |
INFORMATION PROCESSING APPARATUS AND DECODING CONTROL METHOD
Abstract
Moving image stream data recorded on a recording medium includes
title key managing data formed of sets of pointer information items
indicating respective encipher data sections, and title keys
decoding the respective encipher data sections indicated by the
pointer information items. A playback apparatus stores the title
key managing data recorded on the recording medium in a storage
section. The playback apparatus detects change of the pointer
information item included in the moving image stream data read from
the recording medium. If the pointer information item has been
changed, the playback apparatus obtains a title key corresponding
to the pointer information item after change from the storage
section, and executes decoding of the input moving image stream
data by using the obtained title key.
Inventors: |
Kumagaya; Takeshi;
(Hachioji-shi, JP) ; Ohno; Katsuya;
(Kokubunji-shi, JP) |
Correspondence
Address: |
C. IRVIN MCCLELLAND;OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Family ID: |
40295132 |
Appl. No.: |
11/425290 |
Filed: |
June 20, 2006 |
Current U.S.
Class: |
341/50 ;
G9B/20.002 |
Current CPC
Class: |
G11B 20/00528 20130101;
H01L 2924/00 20130101; G06F 1/203 20130101; G11B 20/00086 20130101;
H01L 2924/0002 20130101; H01L 2924/0002 20130101; G06F 2200/201
20130101 |
Class at
Publication: |
341/050 |
International
Class: |
H03M 7/00 20060101
H03M007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 30, 2005 |
JP |
2005-192696 |
Claims
1. An information processing apparatus decoding a stream formed of
at least one title, each title including a pointer information item
indicating a type of the title and an encipher data section to be
decoded by a decoding key corresponding to the pointer information
item, comprising: a storing unit which stores decoding key managing
data formed of sets of pointer information items included in the
input stream and decoding keys corresponding to the pointer
information items; a comparing unit which extracts a pointer
information item included in the input stream, and compares the
extracted pointer information item with a previously extracted
pointer information item; and a decoding unit which obtains a
decoding key corresponding to the pointer information item included
in the input stream from the stored decoding key managing data, and
decodes an encipher data section included in the stream by using
the obtained decoding key when the comparing unit determines that
the extracted pointer information item is different from the
previously extracted pointer information item, the decoding unit
decoding the encipher data section included in the stream by using
the obtained decoding key when the comparing unit determines that
the extracted pointer information item agrees with the previously
extracted pointer information item.
2. An information processing apparatus according to claim 1,
wherein the pointer information items included in the decoding key
managing data include all the pointer information items included in
the input stream and all the decoding keys corresponding to the
pointer information items.
3. An information processing apparatus according to claim 1,
wherein the storing unit reads the decoding key managing data
included in the input stream before executing the decoding means,
and stores the read decoding key managing data.
4. An information processing apparatus according to claim 1,
further comprising: a storage medium selectively provided in the
information processing apparatus, wherein the storing unit stores
the decoding key managing data included in the input stream in the
storage medium, and the decoding unit obtains a decoding key
corresponding to the pointer information item included in the input
stream from the decoding key managing data stored in the storage
medium, and decoding an encipher data section included in the
stream by using the obtained decoding key in response to a
condition that the extracted pointer information item is different
from the previously extracted pointer information item, and
decoding the encipher data section included in the stream by using
the obtained decoding key in response to a condition that the
extracted pointer information item agrees with the previously
extracted pointer information item.
5. An information processing apparatus according to claim 1,
wherein the decoding unit obtains a decoding key corresponding to
the pointer information item included in the input stream from the
stored decoding key managing data, and decoding an encipher data
section included in the stream by using the obtained decoding key
in place of a decoding key previously obtained, in response to a
condition that the extracted pointer information item is different
from the previously extracted pointer information item, and
decoding the encipher data section included in the stream by using
the decoding key previously obtained, in response to a condition
that the extracted pointer information item agrees with the
previously extracted pointer information item.
6. A control method for decoding applied to an information
processing apparatus decoding a stream formed of at least one
title, each title including a pointer information item indicating a
type of the title and an encipher data section to be decoded by a
decoding key corresponding to the pointer information item,
comprising: storing decoding key managing data formed of sets of
pointer information items included in the input stream and decoding
keys corresponding to the pointer information items; extracting an
pointer information item included in the input stream, and
comparing the extracted pointer information item with a previously
extracted pointer information item; and obtaining a decoding key
corresponding to the pointer information item included in the input
stream from the stored decoding key managing data, and decoding an
encipher data section included in the stream by using the obtained
decoding key when it is determined by the comparing that the
extracted pointer information item is different from the previously
extracted pointer information item, and decoding the encipher data
section included in the stream by using the obtained decoding key
when it is determined by the comparing that the extracted pointer
information item agrees with the previously extracted pointer
information item.
7. A control method for decoding according to claim 6, wherein the
pointer information items included in the decoding key managing
data include all the pointer information items included in the
input stream and all the decoding keys corresponding to the pointer
information items.
8. A control method for decoding according to claim 6, wherein the
storing includes reading the decoding key managing data included in
the input stream before executing the decoding, and storing the
read decoding key managing data.
9. A control method for decoding according to claim 6, wherein the
storing includes storing the decoding key managing data included in
the input stream in a storage medium in the information processing
apparatus, and the decoding includes obtaining a decoding key
corresponding to the pointer information item included in the input
stream from the decoding key managing data stored in the storage
medium, and decoding an encipher data section included in the
stream by using the obtained decoding key in response to a
condition that the extracted pointer information item is different
from the previously extracted pointer information item, and
decoding the encipher data section included in the stream by using
the obtained decoding key in response to a condition that the
extracted pointer information item agrees with the previously
extracted pointer information item.
10. A control method for decoding according to claim 6, wherein the
decoding includes obtaining a decoding key corresponding to the
pointer information item included in the input stream from the
stored decoding key managing data, and decoding an encipher data
section included in the stream by using the obtained decoding key
in place of a decoding key previously obtained, in response to a
condition that the extracted pointer information item is different
from the previously extracted pointer information item, and
decoding the encipher data section included in the stream by using
the decoding key previously obtained, in response to a condition
that the extracted pointer information item agrees with the
previously extracted pointer information item.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from Japanese Patent Application No. 2005-192696, filed
Jun. 30, 2005, the entire contents of which are incorporated herein
by reference.
BACKGROUND
[0002] 1. Field
[0003] One embodiment of the invention relates to the present
invention relates to an information processing apparatus having a
function of decoding moving image stream data, and a control method
for decoding performed by the same.
[0004] 2. Description of the Related Art
[0005] Generally, in various playback apparatuses which play back
image contents recorded on DVDs (Digital Versatile Discs), disc
media such as DVDs are subjected to encoding for preventing copy of
the moving image stream data recorded on disc media such as DVDs.
An encoding method based on a CSS (Content Scramble System) method
is mainly adopted for the encipher data sections.
[0006] In the CSS method, when moving image stream data recorded on
a DVD is played back, the playback apparatuses generate moving
image stream data, such as AV (audio video) signals recorded on a
disc apparatus, and a decoding key for decoding the moving image
stream data. The playback apparatuses read out a decoding key
corresponding to an encipher data section, and decode the encipher
data section. Thereby, the playback apparatuses play back the
moving image stream data.
[0007] Recently, recording media such as DVDs may record a
plurality of moving image stream data. Therefore, the playback
apparatuses are required to prepare respective decoding keys
corresponding to the plurality of moving image stream data.
[0008] For example, Jpn. Pat. Appln. KOKAI Pub. No. 2005-92830
discloses a computer having a plurality of managing units for
managing respective identifiers included in moving image stream
data to be played back. In the computer, moving image streams to be
played back are sent by switching to a managing unit that manages
an identifier corresponding to an identifier included in the moving
image streams to be played back, and decoded in the managing unit.
Thereby, moving image stream data to be played back is continuously
played back while the identifier included in the moving image
stream data to be played back does not change.
[0009] In the meantime, if a recording medium containing a
plurality of moving image streams is played back, moving image
streams are played back. Further, in this case, if data for
decoding next encoded data to be played back is different from a
decoding key used for decoding the moving image stream being played
back, the playback apparatus has to temporarily stop playback of
the moving image stream data, and prepare a decoding key for
decoding the next encoded data to be played back. Therefore, if the
decoding key used for encoded data to be decoded is changed while
the moving image stream data is played back, the moving image
stream data may not be smoothly played back. Further, although in
Jpn. Pat. Appln. KOKAI Pub. No. 2005-92830 a plurality of managing
units are used by switching for managing respective decoding keys
used for decoding, there is the problem that it is required to add
a new managing unit every time the identifiers included in the
moving image stream data increases. Further, the recording media
themselves are required to prepare decoding keys for decoding
moving image stream data recorded in the recoding media.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0010] A general architecture that implements the various feature
of the invention will now be described with reference to the
drawings. The drawings and the associated descriptions are provided
to illustrate embodiments of the invention and not to limit the
scope of the invention.
[0011] FIG. 1 is a block diagram illustrating an example of a
system structure of an information processing apparatus according
to an embodiment of the present invention.
[0012] FIG. 2 is a diagram illustrating a structure of moving image
stream data to be played back by the information processing
apparatus of claim 1.
[0013] FIG. 3 is a diagram illustrating a structure of title key
managing data read from a recording disc by the information
processing apparatus of claim 1.
[0014] FIG. 4 is a time chart illustrating decoding processing for
decoding the moving image stream data, performed by the information
processing apparatus of claim 1.
[0015] FIG. 5 is a flowchart illustrating an example of steps of
the decoding processing for decoding the moving image stream data
performed by the information processing apparatus of claim 1.
DETAILED DESCRIPTION
[0016] Various embodiments according to the invention will be
described hereinafter with reference to the accompanying drawings.
In general, according to one embodiment of the invention, an
information processing apparatus decoding a stream formed of at
least one title, wherein each title includes a pointer information
item indicating a type of the title and an encipher data section to
be decoded by a decoding key corresponding to the pointer
information item, and the apparatus comprises: a storing unit which
stores decoding key managing data formed of sets of pointer
information items included in the input stream and decoding keys
corresponding to the pointer information items; a comparing unit
which extracts a pointer information item included in the input
stream, and detecting change of the extracted pointer information
item; and a decoding unit which obtains a decoding key
corresponding to the pointer information item included in the input
stream from the stored decoding key managing data, and decodes an
encipher data section included in the stream by using the obtained
decoding key when the comparing unit determines that the extracted
pointer information item is different from the previously extracted
pointer information item, the decoding unit decoding the encipher
data section included in the stream by using the obtained decoding
key when the comparing unit determines that the extracted pointer
information item agrees with the previously extracted pointer
information item.
[0017] First, a structure of an information processing apparatus
according to an embodiment of the present invention will be
explained with reference to FIG. 1. The information processing
apparatus is realized as a playback apparatus 1 that performs
read/write processing for recording media such as DVDs (Digital
Versatile Disc) and CDs (Compact Disc). Recording media has, for
example, moving image stream data such as AV (audio video) signals
read by the playback apparatus 1, and decoding key managing data
containing decoding keys (hereinafter referred to as "title keys")
for playing back the moving image stream data.
[0018] When the playback apparatus reads a recording medium, the
playback apparatus 1 first reads decoding key managing data
included in the moving image stream data recorded on the recording
medium, and stores the read decoding key managing data in, for
example, a storage device in the playback apparatus 1. Next, the
playback apparatus 1 detects change of pointer information item
included in the moving image stream data recorded on the recording
medium, obtains a title key corresponding to the detected pointer
information item from the decoding key managing data stored in the
storage device, and executes decoding of the input moving image
stream by using the obtained title key. Further, in the case of
detecting no change of the pointer information item included in the
moving image stream data recorded on the recording medium, the
playback apparatus 1 executes decoding of the input moving image
stream data by using the title key obtained in the previous
processing.
[0019] FIG. 1 illustrates an example of a system structure of the
playback apparatus according to an embodiment of the present
invention. The playback apparatus 1 comprises a processor 10,
encoding/decoding processing section 200, and a storage device 30,
and the like. The processor 10 has a function of reading moving
image stream data 100 transmitted from a recording medium 7, for
example. The moving image stream data 100 recorded on the recording
medium 7 is formed of at least one title. Each title is formed of a
pointer information item indicating a type of the title, and
encoded data that is decoded (deciphered) by a decoding key
corresponding to the pointer information item. The moving image
stream data 100 also includes title key managing data 101 formed of
sets of the pointer information items of the moving image stream
data 100 and decoding keys corresponding to the pointer information
items.
[0020] The processor 10 is a general-purpose apparatus that reads
the moving image stream data 100 recorded on the recording medium
7, for example, and plays back the decoded moving image stream data
transmitted from the encoding/decoding processing section 200. The
processor 10 transmits the title key managing data 101 included in
the read moving image stream data 100 to the encoding/decoding
processing 200 through, for example, a control bus 5. Further, the
processor 10 transmits the read moving image stream data 100 to the
encoding/decoding processing section 200 through a bus 3 or the
like. Furthermore, the processor 10 determines whether there is
next moving image stream data to be transmitted and played back, in
response to an interrupt signal transmitted from the
encoding/decoding processing section 200. If it determines that
there is next moving image stream data to be transmitted and played
back, the processor 10 transmits the next moving image stream data
to be played back to the encoding/decoding processing section
200.
[0021] The encoding/decoding processing section 200 comprises a
control circuit 202, an encoding/decoding section 203, a stream
interface (I/F) 204, a stream analyzing section 205, a title key
control section 206, and a storage section 207, and the like. The
control circuit 202 controls the components of the
encoding/decoding processing section 200. The control circuit 202
has a function of controlling operation of the encoding/decoding
section 203 by a control signal. Further, the control circuit 202
stores the title key managing data 101, input from the processor 10
through the control bus 5, in the storage section 207. The control
circuit 202 also has a function of storing the title key managing
data 101, input from the processor 10 through the control bus 5, in
the storage device 30.
[0022] The encoding/decoding section 203 has a function of decoding
the moving image stream data 100 input from the stream analyzing
section 205, by using the title key set in, for example, a register
in the encoding/decoding section 203. The encoding/decoding section
203 transmits the decoded moving image stream data 100 to the
stream I/F 204. Further, the encoding/decoding section 203 sets a
title key transmitted from the title key control section 206 in
place of the title key set in the register of the encoding/decoding
section 203. The stream I/F 204 is an interface that transmits the
moving image stream data 100, transmitted from the processor 10
through the bus 3, to the stream analyzing section 205. The stream
I/F 204 also transmits the decoded moving image stream data input
from the encoding/decoding section 203 to the processor 10 through
the bus 3. The stream analyzing section 205 detects whether the
pointer information item included in the moving image stream data
100 input from the stream I/F 204 has been changed or not, and
extracts the detected pointer information item. In the case of
detecting change of the pointer information item(the pointer
information item is different from the previously extracted pointer
information item), the stream analyzing section 205 extracts the
detected pointer information item, and transmits the detected
pointer information item to the title key control section 206.
Further, the stream analyzing section 205 transmits the encipher
data section indicated by the extracted pointer information item to
the encoding/decoding section 203. The title key control section
206 obtains, from the storage section 207, a title key
corresponding to the pointer information item transmitted from the
stream analyzing section 205, and transmits the obtained title key
to the encoding/decoding section 203. When transmitting a title key
to the encoding/decoding section 203, the title key control section
206 also transmits, to the processor 10, an interrupt signal
indicating that a title key has been transmitted to the
encoding/decoding section 203. The title key control section 206
also has a function of performing communications with the storage
device 30. The storage section 207 is a storage medium, such as a
nonvolatile memory. The storage section 207 stores the title key
managing data 101 transmitted by the control circuit 202. The
storage device 30 is selectively provided in the playback apparatus
1. The storage device 30 is a storage medium that stores the title
key managing data 101 transmitted by the control circuit 202.
[0023] In the playback apparatus 1, if the processor 10 reads
moving image stream data 100 from the recording medium 7, the
processor 10 executes reading of title key managing data 101
included in the read moving image stream data 100. Then, the
processor 10 transmits the read title key managing data 101 to the
encoding/decoding processing section 200 through the control bus 5.
The encoding/decoding processing section 200 stores the title key
managing data 101 transmitted from the processor 10 in the storage
section 207, under the control of the control circuit 202.
Thereafter, if the stream analyzing section 205 detects change of
the pointer information item included in the moving image stream
data input from the processor 10, the title key control section 206
obtains a title key corresponding to the new pointer information
item after change from the title key managing data 101 stored in
the storage section 207, and newly sets the obtained title key in
the register of the encoding/decoding section 203. The
encoding/decoding section 203 executes decoding of the moving image
stream data 100 input from the stream analyzing section 205, by
using the newly set title key in the register. If the pointer
information item included in the moving image stream data input
from the processor 10 is not changed (the pointer information item
agrees with the previously extracted pointer information item), the
playback apparatus 1 executes decoding of the input moving image
stream data 100 by using the title key already set in the register
in the encoding/decoding section 203.
[0024] FIG. 2 illustrates an example of a structure of the moving
image stream data 100. The moving image stream data 100 comprises
at least one title (title 1 to title n). Each title is formed of
one or more packets, and each packet is formed of a header section
and an encipher data section. The header section includes a pointer
information item as an identifier for identifying the type of the
title.
[0025] FIG. 3 illustrates an example of a structure of the title
key managing data 101. The title key managing data 101 is formed of
sets of pointer information items and title keys corresponding to
pointer information items. The pointer information items included
in the title key managing data 101 include all the pointer
information items included in the moving image stream data 100
recorded on the recording medium 7, and all the decoding keys
corresponding to the pointer information items. Specifically, the
title key managing data 101 includes all the decoding keys for
decoding the encipher data sections included in the moving image
stream data 100.
[0026] Next, explained is an example of decoding processing of
decoding the moving image stream data 100, with reference to the
time chart of FIG. 4. In the example of the decoding processing,
suppose that the moving image stream data 100 recorded on the
recording medium 7 is read, and the title key managing data 101
included in the read moving image stream data 100 is stored in the
storage section 207. The processor 10 transmits the moving image
stream data 100 formed of title 1 and title 2, etc. from the
recording medium 7 to the encoding/decoding section 200 through the
bus 3. The title 1 is formed of packets 301 and 302. The title 2 is
formed of a packet 303, etc. The header section of each of the
packets 301 and 302 includes a pointer information item #0 as an
identifier indicating that the packet 301 and the packet 302 belong
to the title 1. The header section of the packet 303 includes a
pointer information item #1 as an identifier indicating that the
packet 303 belongs to the title 2.
[0027] The processor 10 transmits the moving image stream data 100
recorded on the recording medium 7 to the encoding/decoding section
200 through the bus 3. The stream analyzing section 205 detects
whether the pointer information item of the moving image stream
data 100 transmitted through the stream I/F 204 has been changed or
not. The stream analyzing section 205 detects that the state of the
stream data has changed from the initial state, in which no pointer
information item has been detected, to the state of having the
pointer information item #0. The stream analyzing section 205
extracts the detected pointer information item #0 from the packet
301, transmits the extracted pointer information item #0 to the
title key control section 206, and the data section included in the
packet 301 to the encoding/decoding section 203. The title key
control section 206 that has received the pointer information item
#0 obtains the title key #0 corresponding to the received pointer
information item #0 from the title key managing data 101 stored in
the storage section 207, and transmits the obtained title key #0 to
the encoding/decoding section 203. The encoding/decoding section
203 sets the title key #0 transmitted from the title key control
section 206 in the register of the encoding/decoding section 203,
and decodes the data section of the packet 301 transmitted from the
stream analyzing section 205. The decoded data section of the
packet 301 is transmitted to the processor 10 through the stream
bus I/F 204. Next, the packet 302 is input to the stream analyzing
section 205.
[0028] If the detected pointer information item included in the
input packet 302 is the same as the pointer information item
(pointer information #0) previously detected, the stream analyzing
section 205 extracts the pointer information item #0 from the
packet 302, and transmits the data section included in the packet
302 to the encoding/decoding section 203. The encoding/decoding
section 203 decodes the data section included in the packet 302
transmitted from the stream analyzing section 205, by using the
title key that has been used when decoding the data section of the
packet 301. Specifically, the encoding/decoding section 203 decodes
the data section included in the packet 302, by using the title key
#0 corresponding to the previous pointer information item #0
obtained from the packet 301. The decoded data section of the
packet 302 is transmitted to the processor 10 through the stream
bus I/F 204. Next, the packet 303 is input to the stream analyzing
section 205.
[0029] If the detected pointer information item (pointer
information item #1) included in the input packet 303 has been
changed from the pointer information item (pointer information item
#0) previously detected, the stream analyzing section 205 extracts
the pointer information item #1 from the packet 303, transmits the
extracted pointer information item #1 to the title key control
section 206, and transmits the data section included in the packet
303 to the encoding/decoding section 203. The title key control
section 206 that has received the pointer information item #1
obtains a title key #1 corresponding to the received pointer
information item #1 from the title key managing data 101 stored in
the storage section 207, and transmits the obtained title key #1 to
the encoding/decoding section 203. The encoding/decoding section
203 sets the title key #1 transmitted from the title key control
section 206 in place of the title key #0 set in the register of the
encoding/decoding section 203. The encoding/decoding section 203
decodes the data section of the packet 303 transmitted from the
stream analyzing section 203, by using the title key #1 set in the
encoding/decoding section 203.
[0030] As described above, if change of the pointer information
item included in the moving image stream data is detected, a title
key corresponding to the new pointer information item after change
is obtained from the storage section 207. Then, the obtained title
key is newly set in the register of the encoding/decoding section
203, and decoding of the moving image stream data 100 is executed
by using the title key newly set in the register. On the other
hand, if no change of the pointer information item included in the
moving image stream data 100 is detected, decoding of the input
moving image stream data 100 is executed by using the title key
previously obtained by the encoding/decoding section 203. The
encoding/decoding section 203 executes decoding of the input data
section by using the title key held in the register in the
encoding/decoding section 203. The encoding/decoding section 203
can seamlessly execute decoding of the input moving image stream
data 100, by using the title key corresponding to the pointer
information item in accordance with change of the pointer
information item included in the moving image stream data.
[0031] Next, explained is an example of a process of decoding
executed by the playback apparatus 1, with reference to the
flowchart of FIG. 5. In the example of decoding, the processor 10
and the encoding/decoding processing section 200 execute decoding
in cooperation with each other.
[0032] The processor 10 transmits title key managing data 101
included in moving image stream data to be played back to the
encoding/decoding processing section 200 (step S101).
[0033] The encoding/decoding processing section 200 stores the
title key managing data 101 included in the moving image stream
data 100 transmitted from the processor 10 in the storage section
207 (step S102). The processor 10 transmits the moving image stream
data 100 to be played back to the encoding/decoding processing
section 200 (step S103). The encoding/decoding processing section
200 detects a pointer information item of the moving image stream
data 100 transmitted from the processor 10 (step S104). The
encoding/decoding processing section 200 detects whether the
pointer information item has been changed or not (step S105). In
step S105, specifically, the stream analyzing section 205 detects
the pointer information item of the input moving image stream data,
and determine whether the detected pointer information item has
been changed from the previous information item. If the pointer
information item has been changed (YES of Step S105), the
encoding/decoding processing section 200 transmits a title key
corresponding to the detected pointer information item from the
storage section 207 to the encoding/decoding section 203 (step
S106). In step S106, specifically, the stream analyzing section 205
extracts the pointer information item from the input packet, and
transmits the extracted pointer information item to the title key
control section 206. The title key control section 206 obtains,
from the storage section 207, a title key corresponding to the
pointer information item transmitted from the stream analyzing
section 205, and transmits the obtained title key to the
encoding/decoding section 203. The encoding/decoding section 203
sets the title key transmitted from the title key control section
206 in place of the title key stored in the register in the
encoding/decoding section 203.
[0034] Next, the encoding/decoding section 200 decodes the data
section by using the title key set in the encoding/decoding section
203 (step S107). In step S107, specifically, the encoding/decoding
section 203 decodes the data section input from the stream
analyzing section 205. Next, the encoding/decoding processing
section 200 transmits, to the processor 10, an interrupt signal
indicating that a title key has been transmitted to the
encoding/decoding section 203 (step S108).
[0035] The processor 10 determines whether there is next moving
image stream data to be transmitted (step S109). If there is the
next moving image stream data to be transmitted (YES of step S109),
the processor 10 executes the processing of step S103 again.
[0036] On the other hand, if no change of the pointer information
item is detected (NO of step S105), the encoding/decoding
processing section 200 decodes the input data section by using the
title key set in the encoding/decoding section 203 (step S110). In
step S110, specifically, the title key previously set in the
register of the encoding/decoding section 203 is kept set. The
encoding/decoding processing section 200 executes decoding of the
input data section by using the title key set in the register of
the encoding/decoding section 203.
[0037] As described above, according to the present invention,
title key managing data for decoding moving image stream data
recorded on a recording medium in advance is stored in the storage
section. This structure eliminates the need for the processing of
generating a decoding key that decodes the moving image stream
data. This eliminates delay in playback of moving image stream data
due to processing of generating a decoding key. Further, if the
pointer information item included in the moving image stream data
to be played back is changed, decoding is executed by using a title
key corresponding to the new pointer information item after change,
that is obtained from the stored title key managing data. If no
change of the pointer information item included in the moving image
stream data to be played back is detected, the input data section
is decoded by using the title key already set in the
encoding/decoding section 203 without setting a new title key. By
virtue of this structure, the playback apparatus 1 can efficiently
decode input moving image stream data, and play back the input
moving image stream data seamlessly.
[0038] Although the above embodiment shows the example where the
title key managing data 101 transmitted from the processor 10 is
stored in the storage section 207, the title key managing data 101
may be stored in the storage device 30, for example. This structure
enables the playback apparatus 1 to store the title key managing
data 101 even when the storage section 207 does not have an enough
available storage area. If change of the pointer information item
in the input moving image stream data is detected, the
encoding/decoding processing section 200 can execute decoding of
the moving image stream data 100, by using a title key that
corresponds to the detected pointer information item and is
obtained from the title key managing data 101 stored in the storage
device 30.
[0039] While certain embodiments of the inventions have been
described, these embodiments have been presented by way of example
only, and are not intended to limit the scope of the inventions.
Indeed, the novel methods and systems described herein may be
embodied in a variety of other forms; furthermore, various
omissions, substitutions and changes in the form of the methods and
systems described herein may be made without departing from the
spirit of the inventions. The accompanying claims and their
equivalents are intended to cover such forms or modifications as
would fall within the scope and spirit of the inventions.
* * * * *