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Claims  |
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We claim:
1. A recording of a compressed motion picture signal derived from a motion
picture signal by variable-rate coding, the motion picture signal
including pictures wherefrom signal portions of the compressed motion
picture signal are respectively derived, the signal portions including
intrinsically-decodable signal portions at irregular intervals, the
recording being structured to enable the intrinsically-decodable signal
portions to be successively reproduced when the recording is searched at
high speed, the recording comprising:
a recording medium;
machine-readable indicia formed in the recording medium to represent the
compressed motion picture signal, ones of the machine-readable indicia
representing the intrinsically-decodable signal portions constituting
respective blocks; and
additional machine-readable indicia formed adjacent each one of the blocks
of the machine-readable indicia, the additional machine-readable indicia
representing location information, the location information indicating a
location in the recording medium of at least one other of the blocks.
2. The recording of claim 1, wherein the additional machine-readable
indicia are formed in the recording medium immediately preceding each one
of the blocks.
3. The recording of claim 1, wherein the location information includes
information indicating locations in the recording medium of at least one
of the blocks preceding the one of the blocks in the recording medium and
at least one of the blocks following the one of the blocks in the
recording medium.
4. The recording of claim 1, wherein the location information includes
information indicating locations in the recording medium of plural
adjacent ones of the blocks successively disposed about the one of the
blocks in the recording medium.
5. The recording of claim 1, wherein:
the machine-readable indicia formed along the track in the recording medium
represent signal portions of the compressed motion picture signal derived
by compressing one of the pictures of the motion picture signal in one of
an intra-picture mode and an inter-picture mode, each of the
intrinsically-decodable signal portions being one of the signal portions
derived by compressing one of the pictures of the motion picture signal in
the intra-picture mode; and
wherein ones of the machine-readable indicia representing ones of the
intrinsically-decodable signal portions begin a series of the
machine-readable indicia representing a Group of Pictures.
6. A recording of a compressed motion picture signal derived from a motion
picture signal by variable-rate coding, the motion picture signal
including pictures wherefrom signal portions of the compressed motion
picture signal are respectively derived, the signal portions including
intrinsically-decodable signal portions at irregular intervals, each of
the intrinsically-decodable signal portions having a beginning, the
recording being structured to enable the intrinsically-decodable signal
portions to be successively reproduced when the recording is searched at
high speed, the recording comprising:
a recording medium;
machine-readable indicia formed in the recording medium to represent the
compressed motion picture signal, the machine-readable indicia being
divided into packs comprising plural packets, ones of the packets that
include ones of the machine-readable indicia representing at least the
beginning of ones of the intrinsically-decodable signal portions being
packets of a first type; and
additional machine-readable indicia formed in the recording medium in a
packet of a second type immediately preceding each one of the packets of
the first type, the additional machine-readable indicia in the packet of
the second type representing location information, the location
information indicating a location in the recording medium of at least one
other of the packets of the second type.
7. The recording of claim 6, wherein the recording additionally comprises
further machine-readable indicia formed in the recording medium,
first ones of the further machine-readable indicia constituting pack
headers beginning each one of the packs, ones of the first ones of the
further machine-readable indicia identifying the one of the packs as a
pack; and
second ones of the further machine-readable indicia constituting a packet
header beginning each one of the packets, ones of the second ones of the
further machine-readable indicia identifying the one of the packets as a
packet and distinguishing the packets of the first type from the packets
of the second type.
8. The recording of claim 6, wherein, in each packet of the second type,
the additional machine-readable indicia representing the location
information follows the second ones of the further machine-readable
indicia constituting the packet header.
9. The recording of claim 6, wherein the additional machine-readable
indicia in the each packet of the second type represent information
indicating the locations in the recording medium of plural packets of the
second type successively disposed about the packet of the second type.
10. The recording of claim 6, wherein the additional machine-readable
indicia in each packet of the second type represent information indicating
locations in the recording medium of at least one of the packets of the
second type preceding the packet of the second type in the recording
medium, and of at least one of the packets of the second type following
the packet of the second type in the recording medium.
11. The recording of claim 6, wherein:
the machine-readable indicia formed along the track in the recording medium
represent signal portions of the compressed motion picture signal derived
by compressing one of the pictures of the motion picture signal in one of
an intra-picture mode and an inter-picture mode, each of the
intrinsically-decodable signal portions being one of the signal portions
derived by compressing one of the pictures of the motion picture signal in
the intra-picture mode; and
wherein ones of the machine-readable indicia representing ones of the
intrinsically-decodable signal portions begin a series of the
machine-readable indicia representing a Group of Pictures.
12. A method for generating, from a variable-rate coded signal, a recording
signal for recording on a recording medium, the recording signal being
generated to enable intrinsically-decodable signal portions included at
irregular intervals in the variable-rate coded signal to be reproduced and
decoded when the recording medium is searched at high speed, the method
comprising steps of:
determining, for each one of the intrinsically-decodable signal portions in
the variable-rate coded signal, location information indicating a location
of at least one other of the intrinsically-decodable signal portions;
generating a decodable signal pointer for each one of the
intrinsically-decodable signal portions, the decodable signal pointer
including the location information determined for the one of the
intrinsically-decodable signal portions in the determining step; and
multiplexing the decodable signal pointer generated in the generating step
for each one of the intrinsically-decodable signal portions with the
variable-rate coded signal to produce the recording signal and to locate
the decodable signal pointer for each one of the intrinsically-decodable
signal portions adjacent the one of the intrinsically-decodable signal
portions in the recording signal.
13. The method of claim 12, wherein, in the multiplexing step, the
decodable signal pointer for each one of the intrinsically-decodable
signal portions is multiplexed with the variable-rate coded signal to
locate the decodable signal pointer for the one of the
intrinsically-decodable signal portions immediately ahead of the one of
the intrinsically-decodable signal portions in the recording signal.
14. The method of claim 13, wherein:
the method additionally comprises a step of recording the recording signal
on the recording medium; and
the determining step determines location information indicating a location
on the recording medium of the decodable signal pointer immediately ahead
of each of the at least one other of the intrinsically-decodable signal
portions.
15. A method for generating, from a variable-rate coded signal, a recording
signal for recording on a recording medium, the recording signal being
generated to enable intrinsically-decodable signal portions included at
irregular intervals in the variable-rate coded signal to be reproduced and
decoded when the recording medium is searched at high speed, the method
comprising steps of:
determining, for each one of the intrinsically-decodable signal portions in
the variable-rate coded signal, location information indicating a location
of at least one other of the intrinsically-decodable signal portions;
generating an entry packet for each one of the intrinsically-decodable
signal portions, the entry packet including the location information
determined for the one of the intrinsically-decodable signal portions in
the determining step; and
multiplexing the entry packet generated in the generating step for each one
of the intrinsically-decodable signal portions with the variable-rate
coded signal to produce the recording signal and to locate the entry
packet generated for each one of the intrinsically-decodable signal
portions immediately ahead of the one of the intrinsically-decodable
signal portions in the recording signal.
16. The method of claim 15, wherein:
the method additionally comprises a step of recording the recording signal
on the recording medium; and
the determining step determines, for each one of the
intrinsically-decodable signal portions, location information indicating
locations in the recording medium of the entry packets located immediately
ahead of ones of the intrinsically-decodable signal portions successively
disposed about the one of the intrinsically-decodable signal portions in
the recording medium.
17. A method of generating, from a variable-rate coded signal, a recording
signal for recording on a recording medium, the recording signal being
generated to enable intrinsically-decodable signal portions included at
irregular intervals in the variable-rate coded signal to be reproduced and
decoded when the recording medium is searched at high speed, the method
comprising steps of:
generating an entry packet for each one of the intrinsically-decodable
signal portions;
multiplexing the entry packet generated in the generating step for each one
of the intrinsically-decodable signal portions with the variable-rate
coded signal to produce the recording signal and to locate the entry
packet generated for each one of the intrinsically-decodable signal
portions immediately ahead of the one of the intrinsically-decodable
signal portions in the recording signal;
performing a first recording operation to record the recording signal;
generating location data by determining a location in the recording medium
of the entry packet located immediately ahead of each of the
intrinsically-decodable signal portions;
storing the location data; and
performing a second recording operation to record at least one of the
location data stored in the storing step into the entry packet located
immediately ahead of each one of the intrinsically-decodable signal
portions recorded in the first recording operation, the at least one of
the location data indicating the location in the recording medium of the
entry packet located immediately ahead of at least one other of the
intrinsically-decodable signal portions adjacent the one of the
intrinsically-decodable signal portions.
18. The method of claim 17, wherein:
in the first recording operation, location data indicating the locations in
the recording medium of the entry packets located immediately ahead of a
predetermined number of the intrinsically-decodable signal portions
preceding the one of the intrinsically-decodable signal portions in the
recording signal are recorded into the entry packet located immediately
ahead of each one of the intrinsically-decodable signal portions; and
the at least one of the location data recorded into the entry packet
located immediately ahead of each one of the intrinsically-decodable
signal portions in the second recording operation indicates the locations
in the recording medium of the entry packets located immediately ahead of
a predetermined number of the decodable signal portions following the one
of the intrinsically-decodable signal portions in the recording signal.
19. A method of reproducing a recording signal recorded in a recording
medium to effect a high-speed search, the recording signal being divided
into packs subdivided into packets, the recording signal including
intrinsically-decodable signal portions of a variable-rate coded signal at
irregular intervals, each of the intrinsically-decodable signal portions
having a beginning, each of the packets that includes the beginning of one
of the intrinsically-decodable portions being preceded by an entry packet
that includes location information, the high-speed search being effected
by successively reproducing and decoding the intrinsically-decodable
signal portions in the recording signal recorded in the recording medium
in response to the location information in the entry packets preceding the
intrinsically-decodable signal portions, the method comprising repeating a
sequence of steps including steps of:
reproducing a series of packets of the recording signal from a read
position on the recording medium, the series of packets of the recording
signal including an entry packet followed by a number of packets that
include one of the intrinsically-decodable signal portions;
extracting the location information from the entry packet reproduced from
the recording medium at the read position in the reproducing step, the
location information indicating a location in the recording medium of at
least one other entry packet; and
changing the read position on the recording medium to the location of one
of the at least one other entry packet in response to the location
information extracted from the entry packet in the extracting step.
20. The reproducing method of claim 19, wherein:
the method additionally comprises a step of selecting a search rate at
which the recording medium is searched;
the extracting step extracts from the entry packet location information
indicating locations in the recording medium of plural entry packets
successively preceding and following the entry packet in the recording
medium;
the extracting step includes a step of selecting, from the location
information extracted in the extracting step, selected location
information indicating the location of one other entry packet, the
selected location information being selected in response to the search
rate selected in the search rate selecting step; and
in the step of changing the read position, the read position is changed to
the read position indicated by the selected location information selected
in the location selecting step.
21. The reproducing method of claim 19, wherein the sequence of steps
additionally includes a step of decoding the intrinsically-decodable
signal portion in the series of packets of the recording signal reproduced
in the reproducing step to generate a picture of an output signal. |
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Claims |
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Description |
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FIELD OF THE INVENTION
This invention relates to an apparatus and method for processing a
variable-rate coded signal prior to recording so that high-speed searching
can be carried out on a recording medium on which the processed signal is
recorded. The invention also relates to an apparatus and method for
performing a high-speed search on a medium on which a processed
variable-rate coded signal is recorded. Finally, the invention relates to
a recording of the processed variable-rate coded signal.
BACKGROUND OF THE INVENTION
Examples of a conventional recording apparatus and a conventional
reproducing apparatus are shown in FIGS. 1 and 2. Referring to FIG. 1, the
digital video signal to be recorded is compressed and coded by the video
encoder 1, and then fed into the video signal buffer 4 in the multiplexing
circuit 3. The digital audio signal to be recorded is compressed and coded
by the audio encoder 2, and then fed into to the audio signal buffer 5 in
the multiplexing circuit 3.
The output terminals of the signal buffers 4 and 5 are connected to the
input terminals E1 and E2 of the switching circuit 6, respectively. The
output terminal F of the switching circuit 6 is connected to the input
terminal of the header addition circuit 7. The output of the header
addition circuit 7 is supplied to the digital storage medium (DSM) 10,
which includes, for example, a magneto-optical disk or a magnetic disk,
e.g., a hard disk. The control circuit 8 receives system clock signals
from the multiplexing system clock generation circuit 9, and causes the
switching circuit 6 to connect the output terminal F to the input
terminals E1 and E2 successively at a predetermined time interval. This
successively fetches video signal bytes from the video signal buffer 4 and
audio signal bytes from the audio signal buffer 5, thereby time division
multiplexing the audio and video signals.
The control circuit 8 causes the switching circuit 6 and the header
addition circuit 7 to produce a multiplexed signal having the multiplexing
system format set forth in the ISO 11172 (MPEG) standard. The multiplexed
signal includes one or more packs (PACK) and one ISO.sub.-- 11172.sub.--
end.sub.-- code, as shown in FIG. 3. The ISO.sub.-- 11172.sub.--
end.sub.-- code is a code of 32 bits and is, when represented in the
hexadecimal notation, 0x000001B9. The prefix 0x indicates hexadecimal
notation, where x is indeterminate.
Each pack includes a header, which includes a Pack.sub.-- Start.sub.--
Code, a System Clock Reference (SCR), a MUX.sub.-- Rate, and one or more
packets (Packet). The Pack.sub.-- Start.sub.-- Code of the header is a
code of 32 bits and is 0x000001B4, the prefix 0x once again indicating
hexadecimal notation. A pack has a variable length up to a maximum of
2,048 bytes.
Each packet includes a header, which includes a Packet.sub.-- Start.sub.--
Code.sub.-- Prefix, a stream.sub.-- ID, a Packet.sub.-- length, a
Presentation Time Stamp (PTS), a Decoding Time Stamp (DTS), and a packet
data portion. The Packet.sub.-- Start.sub.-- Code.sub.-- Prefix is a code
of 24 bits and is 0x000001. The Stream.sub.-- ID is a code of 8 bits and
indicates the type of the packet, as shown in FIG. 4. The Packet.sub.--
length (16 bits) indicates the length of the packet following it.
The packet data portion of each packet consists of a portion of the digital
audio signal (when the stream type indicates an audio stream) or a portion
of the video signal (when the stream type indicates a video stream).
Further, since each audio stream can have one of 32 different
stream.sub.-- IDs and the each video stream can have one of up to 16
different stream.sub.-- IDs, up to 32 different audio signals and up to 16
different video signals can be multiplexed.
A reserved stream includes, for example, subtitle data. Private.sub.--
stream.sub.-- 1 and private.sub.-- Stream.sub.-- 2 do not have defined
applications. A padding.sub.-- stream is used to increase the amount of
data.
The control circuit 8 (FIG. 1) controls adding headers and reading signal
bytes using an algorithm such as that shown, for example, in FIG. 5 so
that a total of 2,048 bytes are included in each pack in accordance with
the format described above.
Referring to FIGS. 1 and 5, at step S1, the control circuit 8 instructs the
header addition circuit 7 to generate a pack header. Then, at step S2, the
control circuit 8 waits until the sum of M4 and M5 is equal to or greater
than the number of signal bytes D included in one pack. In other words,
the control circuit 8 waits until the total number of signal bytes
accumulated in the signal buffers 4 and 5 is equal to the number of bytes
that can be accommodated by one pack, M4 represents the number of bytes of
video signal written in the video signal buffer 4, and M5 represents the
number of bytes of audio signal written in the audio signal buffer 5. D
represents a total number of signal bytes that can be accommodated in one
pack. To simplify the description, it will be assumed that D is a constant
obtained by subtracting the number of bytes in the pack headers, the
number of bytes in the video packet headers, and the number of bytes in
the audio packet headers, from the number of bytes (2,048) in a pack.
In step S3, the number of bytes P1 of video signal that will be
accommodated in the pack and the number of bytes P2 of audio signal that
will be accommodated in the pack are calculated using the following
equations:
P1=D.times.M4/(M4+M5)
P2=D-P1
Thus, P1 and P2 are calculated by distributing the total number of signal
bytes D accommodated by the pack according to the ratio of numbers of
bytes M4 and M5 accumulated in the signal buffers 4 and 5.
At step S4, after the numbers of signal bytes are determined, the control
circuit 8 instructs the header addition circuit 7 to generate a video
packet header, and to feed the video packet header to the DSM 10. Then, at
step S5, the control circuit 8 transfers P1 bytes of video signal from the
video signal buffer 4 to the DSM 10. At step S6, the control circuit 8
causes the header addition circuit to generate an audio packet header, and
to feed it to the DSM 10. At step S7, the control circuit 8 transfers P2
bytes of audio signal from the signal buffer 5 to the DSM 10. The DSM 10
records the multiplexed signal received from the multiplexing circuit 3.
At step S8, the control circuit tests whether all the video signal and all
of the audio signal have been multiplexed. If the result is NO, execution
returns to step S1. If the result is YES, execution proceeds to step S9,
at which step the program ends.
The multiplexed signal recorded on the DSM 10 in this manner is reproduced
and decoded by the reproducing apparatus shown in FIG. 2. In FIG. 2, the
header separation circuit 22 in the separation circuit 21 separates pack
headers and packet headers from the multiplexed signal read out from the
DSM 10. The header separation circuit 22 supplies the headers to the
control circuit 24, and supplies the multiplexed signal to the input
terminal G of the switching circuit 23. The output terminals H1 and H2 of
the switching circuit 23 are connected to the input terminals of the video
decoder 25 and the audio decoder 26, respectively. The control circuit 24
in the separation circuit 21 successively connects the input terminal G of
the switching circuit 23 to the output terminals H1 and H2 in accordance
with the stream.sub.-- ID of the packet header received from the header
separation circuit 22. In this way, the audio signal and the video signal
are demultiplexed from the time-division multiplexed signal, and are
supplied to the corresponding decoder.
When the video signal fed into the multiplexing circuit 3 is compressed in
accordance with the MPEG coding standard, this imposes limitations on
performing random access or searching operations. A video signal that is
compressed according to the MPEG standard includes intra-picture coded
pictures, I (intra) pictures, and two types of inter-picture coded
pictures: P (forward predictive) pictures and B (bidirectional predictive)
pictures. Of the three types of pictures, only I-pictures are compressed
independently of other pictures, and can therefore be said to be
intrinsically expandable. To decode the video signal of an I-picture
requires only the video signal of the I-picture itself, and does not
require the video signals of other pictures. However, because of this, the
coding efficiency of I-pictures is low. Since P-pictures and B-pictures
are obtained by decoding difference signals from preceding and/or
following reference pictures, the compression efficiency of such pictures
is high. However, decoding a P-picture or a B-picture requires that the
video signal of a reference picture preceding or following the picture be
decoded in addition to the video signal of the picture. Consequently,
during a search, only about two I-pictures are normally reproduced each
second. This provides a random access facility while retaining an
acceptable avenge compression efficiency.
FIG. 6 shows a diagram of a digital video signal including I-pictures,
P-pictures, and B-pictures as it is recorded on the DSM 10. The digital
video signal is divided into more than one Groups of Pictures (GOPs). Each
GOP begins with an I-picture. When the video signal is compressed at a
fixed rate, since an I-picture periodically appears at a predetermined
location, the location can be determined by calculation and the I-picture
accessed. However, when the video signal is compressed at a variable rate,
the location of the I-pictures is indeterminate, and it is thus difficult
to access the I-pictures.
When a search command is received by the reproducing apparatus shown in
FIG. 2, a main control apparatus (not shown) delivers to the control
circuit 24, the video decoder 25, and the audio decoder 26, an instruction
to transition to search mode. In search mode, the video decoder 25 decodes
only the I-pictures in the video signal received from the switching
circuit 23. Alternatively, only video signals representing I-pictures are
selected by the separation circuit 21 and fed into the video decoder 25.
The video decoder 25 then decodes the video signals that it receives.
In search mode, the control circuit 24 commands the DSM 10 to move the read
position on the disk forwards or backwards. The mount of movement of the
read position depends upon the search rate, the compression ratio, etc.;
generally, the mount of movement increases as the rate of the search
increases and as the compression ratio increases. When the read position
has moved to the selected location, the multiplexed signal is read from
the DSM 10 and fed into the separation circuit 21. The header separation
circuit 22 and the demultiplexer 23 separate the video signal and supply
it to the video decoder 25. The video decoder 65 decodes the I-picture
that appears first, and feeds it to the video output. The audio decoder 66
is muted in search mode.
In the manner just described, a search operation that successively
reproduces I-pictures is performed by carrying out repeated random
accesses. Thus, when, for example, the user commands a high-speed forward
search, the video decoder 25 searches for an I-picture by skipping a
predetermined number of frames of the video signal it receives, and then
decodes and feeds out each resulting I-picture. Alternatively, the DSM 10
can search for I-pictures, and only reproduce video signals of I-pictures
for decoding by the video decoder 25. A search operation involving a
successive reproduction of I-pictures is carried out by repeating such
operations.
A different example of a conventional recording apparatus and a different
example of a conventional reproducing apparatus are shown in FIGS. 7 and
8, respectively. Referring to FIG. 7, the digital video signal to be
recorded is fed into the video encoder 1, and the digital audio signal to
be recorded is fed into the audio encoder 2. The outputs of the video
encoder 1 and the audio encoder 2 are fed into the multiplexing circuit 3.
The output terminal of the multiplexing circuit 3 is connected to the DSM
10, where the resulting multiplexed signal is stored for a first time.
The multiplexed signal read out of the DSM 10 is fed to the Table of
Contents (TOC) addition circuit 50, which adds a TOC to the beginning of
the multiplexed signal. Generation of the TOC will be described in detail
below. The output of the TOC addition circuit 50 is fed to the input
terminal of the sector header addition circuit 51. The output of the
sector header addition circuit 51 is fed to the Error Correction Coding
(ECC) encoder 52. The output of the ECC encoder 52 is fed to the
modulation circuit 53, which feeds the resulting recording signal to the
cutting machine 54, which cuts the optical disk master 60. Plural optical
disks for distribution to consumer or professional users, such as the
optical disk 60A shown in FIG. 8, are manufactured using the optical disk
master 60.
The input terminal of the entry point storage device 33A is connected to
the output terminal of the video encoder 1, or to the video entry point
detection circuit 31, so that it receives and stores entry point
information from either one of them. The output of the entry point storage
device 33A is fed to the TOC generation circuit 56, which arranges the
format of the TOC. The TOC is fed to the TOC addition circuit 50, which
adds the TOC to the beginning of the multiplexed signal, as described
above.
The video signal to be recorded is compressed and coded by the video
encoder 1, and then fed to the multiplexing circuit 3. The audio signal to
be recorded is compressed and coded by the audio encoder 2, and then fed
to the multiplexing circuit 3. The multiplexing circuit 3 multiplexes the
coded video signal and the coded audio signal it receives using
time-division multiplexing. The multiplexed signal is fed into the DSM 10,
which stores it. This process is continued until all of the video signal
and all of the audio signal have been recorded on the DSM 10.
An output of the video encoder 1 is connected to the entry point storage
device 33A. When the video encoder 1 is capable of providing an entry
point generation signal, it provides an entry point generation signal when
it generates an I-picture. The entry point storage device 33A receives
from the video decoder 1, and stores, the entry point generation signal
generated each time the video encoder generates an I-picture.
An output of the video encoder 1 is also connected to the input terminal of
the video entry point detection circuit 31. When the video encoder 1 is
incapable of providing an entry point generation signal, or when the
digital video signal to be recorded is already encoded, the video entry
point detection circuit 31 either generates an entry point generation
signal each time an I-picture is generated, or detects the entry points in
the video signal it receives from the video encoder 1, and provides an
entry point generation signal in response. The entry point storage device
33A receives from the video entry point detection circuit 31, and stores,
an entry point generation signal each time an entry point is detected.
After the video signal and the audio signal have been coded and
multiptexed, the resulting multiplexed signal is written in the DSM 10.
Simultaneously, the entry points required to construct a TOC are all
stored in the entry point data storage device 33A. Then, processing for
adding the TOC is started.
First, the required entry points are fed from the entry point storage
device 33A to the TOC generation circuit 56. A selection is then made by
the user or a controller (not shown). The entry points fed to the TOC
generation circuit 56 are arranged in the format shown in FIG. 9. In this
example, the TOC includes the positions of N entry points. Each entry
point is indicated by a sector address of 4 bytes.
Returning to FIG. 7, the TOC generated by the TOC generation circuit 50 is
delivered to the TOC addition circuit 50, whence it is fed to the sector
header addition circuit 51 ahead of the multiplexed signal stored in the
DSM 10. Then, following the TOC, the multiplexed signal passes from the
DSM 10, through the TOC addition circuit 50, to the sector header addition
circuit 51.
As shown in FIG. 10, each sector has a sector header of 16 bytes, and
accommodates 2,048 bytes. The sector header includes the sector number of
the sector. The sector header addition circuit 51 divides multiplexed
signal received from the TOC addition circuit 50 into blocks of 2,048
bytes, and adds a sector header of 16 bytes that includes the sector
number. The output of the sector header addition circuit 51 is fed into
the error correction coding (EGG) encoder 52.
The ECC encoder 52 adds a prescribed mount of parity data to the
multiplexed signal received from the sector header addition circuit 51,
and feeds the resulting signal to the modulation circuit 53. The recording
signal from the modulation circuit 53 is fed to the cutting machine 54,
which writes the recording signal onto the optical disk master 60.
In the reproducing apparatus shown in FIG. 8, the signal recorded on the
optical disk 60 is reproduced by the pickup 61. The output signal from the
pickup 61 is fed into the demodulation circuit 62, which demodulates the
signal from the pickup 61, and feeds the demodulated signal into the ECC
circuit 63. The ECC circuit 63 detects and corrects errors in the
demodulated signal, and feeds the resulting multiplexed signal into the
demultiplexer circuit 64.
The video signal demultiplexed by the demultiplexer circuit 64 is fed into
the video decoder 65, while the audio signal is fed from the demultiplexer
circuit to the audio decoder 66. The video decoder 65 and the audio
decoder 66 individually reverse the compression of the compressed signals
to provide uncompressed video and audio output signals, respectively.
In response to an instruction from the user (not shown) to reproduce the
signal recorded on the disc, the controller 67 sends a command to the
video decoder 65 and the audio decoder 66, and provides an access command
to the drive control circuit 69. The drive control circuit 69 drives the
pickup 61 using the tracking servo circuit 70 in accordance with the
command from the controller 67 to begin reproducing from the disc.
The TOC at the beginning of the signal recorded on the disk is separated by
the demultiplexer circuit 64, fed to the controller 67, and stored in the
TOC storage device 68. The TOC is read out from the TOC storage device 68
when necessary, to be used by the controller 67.
Operation of the conventional disk reproducing apparatus shown in FIG. 8
will now be described. When the optical disk 60 is inserted, the
controller 67 delivers a first sector reading command to the drive control
circuit 69. The drive control circuit 69 drives the pickup 61 by way of
the tracking servo circuit 70 to start reproducing from the first sector
on the disk 60.
The pickup 61 illuminates the optical disk 60 with a laser beam, and
reproduces the signal recorded on the optical disk 60 using reflected
light from the disk. The signal from the pickup 61 is fed to, and is
demodulated by, the demodulation circuit 62. The demodulated signal is fed
to the ECC circuit 63, where error detection and correction are performed.
The resulting multiplexed signal from the ECC circuit is fed to the
demultiplexer circuit 64.
The TOC is recorded in first sector of the disk. The TOC is demultiplexed
by the demultiplexer circuit 64 and is fed to the controller 67. The
controller 67 stores the TOC in the TOC storage device 68, and displays
the TOC to the user (not shown) on a display (not shown).
In response to an instruction from the user (not shown) to reproduce an
item selected from the TOC, the controller 67 delivers a command to the
drive control circuit 69 to start operation. The drive control circuit 69
drives the pickup 61 by way of the tracking circuit 70 to start
reproducing at the read position on the disk 60 indicated by the user's
selection from the TOC. The drive control circuit 69 also simultaneously
delivers a command to the video decoder 65 and to the audio decoder 66 to
prepare to decode the signals reproduced from the disk.
Simultaneously with reading the TOG, the pickup 61 illuminates the optical
disk 60 with a laser beam, and reproduces the signal recorded on the disk
using reflected light from the disk. The signal from the pickup 61 is fed
to, and is demodulated by, the demodulation circuit 62. The demodulated
signal is fed to the ECC circuit 63, where error detection and correction
are performed. The resulting multiplexed signal is fed into the
demultiplexer circuit 64.
The video signal demultiplexed by the demultiplexer circuit 64 is fed to
the video decoder 65, while the audio signal demultiplexed by the
demultiplexer circuit is fed to the audio decoder 66. The video signal and
the audio signal, which are compressed, are expanded by the video decoder
65 and the audio decoder 66, respectively, to provide an uncompressed
digital video signal and an uncompressed digital audio signal.
When the video signal fed into the multiplexer 3 is compressed in
accordance with the MPEG coding standard, this imposes a limitation on
performing random access or searching operations. In particular, as
described above, a video signal compressed according to the MPEG standard
includes intra-picture coded pictures, I (intra) pictures, and two types
of inter-picture coded pictures: P (forward predictive) pictures and B
(bidirectional predictive) pictures. Of the three types of pictures, only
I-pictures are coded independently of other pictures. To decode the video
signal of an I-picture requires only the video signal of the I-picture
itself, and does not require vi | | |
