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Claims  |
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What is claimed is:
1. A method of transmitting timing-critical data of unknown transmission
rate via an asynchronous channel, comprising the steps:
(i) providing the timing-critical data subdivided into a stream of
successive critically-timed transmission units,
(ii) determining from the timing-critical data at least two items of timing
information from which the timing-critical data can be recreated,
(iii) tagging the transmission units with the items of timing information,
(iv) transmitting the transmission units tagged with the items of timing
information over the asynchronous channel,
(v) receiving from the channel the transmission units tagged with the items
of timing information,
(vi) recreating from the transmission units and the items of timing
information received in step (v) the timing-critical data.
2. The method of claim 1, wherein the timing-critical data is an MPEG data
stream, and the transmission units are transport packets.
3. The method of claim 2, wherein the channel is a digital VCR.
4. The method of claim 2, wherein the channel is a computer network, a
telephone network, or a digital interface.
5. The method of claim 1, wherein the items of timing information for one
transmission unit comprise only one pointer to a byte location of the
transmission unit and timing information associated with the byte
location.
6. The method of claim 1, wherein the timing critical data is formatted as
a data block comprising in order a block header, a block payload
comprising a plurality of the transmission units with said timing
information, and an error-checking block.
7. The method of claim 1, wherein the two items of timing information
comprise the start time and end time of a transmission unit.
8. The method of claim 1, wherein the two items of timing information
comprise in a transmission unit the location of timing-critical data and
the expected arrival time of the timing-critical data.
9. A method of transmitting timing-critical data via an asynchronous
channel, comprising the steps:
(i) providing the timing-critical data subdivided into a stream of
successive critically-timed transmission units,
(ii) determining from the timing-critical data one or more items of timing
information from which the timing-critical data can be recreated,
(iii) tagging the transmission units with the items of timing information,
(iv) transmitting the transmission units tagged with the items of timing
information over the asynchronous channel,
(v) receiving from the channel the transmission units tagged with the items
of timing information,
(vi) recreating from the transmission units and the items of timing
information received in step (v) the timing-critical data,
wherein the items of timing information for a plurality of transmission
units comprise two pointers to byte locations for some of the plurality of
transmission units and one pointer to a byte location for the remainder of
the plurality of transmission units together with timing information
associated with the respective byte location of the remainder of the
plurality of transmission units.
10. The method of claim 9, wherein the timing information for the plurality
of transmission units is stored in a data unit associated with the
plurality of transmission units.
11. The method of claim 9, wherein the two pointers point to the start and
end times respectively of said some of the plurality of transmission
units.
12. The method of claim 11, wherein the byte location pointed to by said
one pointer comprises data representing an instant of time associated with
the respective byte location of the remainder of the plurality of
transmission units.
13. The method of claim 12, wherein the plurality of transmission units are
transport packets of an MPEG information signal.
14. The method of claim 13, wherein the byte location pointed to by said
one pointer comprises a PCR.
15. The method of claim 13, wherein the plurality of transmission units are
5 in number.
16. A method of transmitting timing-critical data via an asynchronous
channel, comprising the steps:
(i) providing the timing-critical data subdivided into a stream of
successive critically-timed transmission units,
(ii) determining from the timing-critical data one or more items of timing
information from which the timing-critical data can be recreated,
(iii) tagging the transmission units with the items of timing information,
(iv) transmitting the transmission units tagged with the items of timing
information over the asynchronous channel,
(v) receiving from the channel the transmission units tagged with the items
of timing information,
(vi) recreating from the transmission units and the items of timing
information received in step (v) the timing-critical data,
wherein the timing critical data is formatted as a data block comprising in
order a block header, a block payload, and an error-correcting block, said
block payload comprising a plurality of transmission units and one tag
packet containing the timing information for the plurality of transmission
units.
17. Apparatus for transmitting timing-critical data of unknown transmission
rate via an asynchronous channel, comprising:
(i) means for receiving the timing-critical data subdivided into a stream
of successive critically-timed transmission units,
(ii) means for determining from the timing-critical data at least two items
of timing information from which the timing-critical data can be
recreated,
(iii) means for tagging the transmission units with the items of timing
information,
(iv) means for transmitting the transmission units tagged with the items of
timing information over the asynchronous channel,
(v) means for receiving from the channel the transmission units tagged with
the items of timing information,
(vi) means for recreating from the transmission units and the items of
timing information received in claim element (v) the timing-critical data.
18. The apparatus of claim 17, wherein the timing-critical data is an MPEG
data stream, and the transmission units are transport packets.
19. The apparatus of claim 17, wherein the channel comprises a computer
network, a telephone network, or a digital interface.
20. Apparatus for transmitting timing-critical data via an asynchronous
channel, comprising:
(i) means for receiving the timing-critical data subdivided into a stream
of successive critically-timed transmission units,
(ii) means for determining from the timing-critical data one or more items
of timing information from which the timing-critical data can be
recreated,
(iii) means for tagging the transmission units with the items of timing
information,
(iv) means for transmitting the transmission units tagged with the items of
timing information over the asynchronous channel,
(v) means for receiving from the channel the transmission units tagged with
the items of timing information,
(vi) means for recreating from the transmission units and the items of
timing information received in claim element (v) the timing-critical data,
(vii) said timing information for a plurality of transmission units
comprising two pointers to byte locations for some of the plurality of
transmission units and one pointer to a byte location for the remainder of
the plurality of transmission units together with timing information
associated with the respective byte location of the remainder of the
plurality of transmission units.
21. The apparatus of claim 20, further comprising means for storing said
timing information for a plurality of transmission units in a data unit
associated with said plurality of the transmission units.
22. Apparatus for transmitting timing-critical data via an asynchronous
channel, comprising:
(i) means for receiving the timing-critical data subdivided into a stream
of successive critically-timed transmission units,
(ii) means for determining from the timing-critical data one or more items
of timing information from which the timing-critical data can be
recreated,
(iii) means for tagging the transmission units with the items of timing
information,
(iv) means for transmitting the transmission units tagged with the items of
timing information over the asynchronous channel,
(v) means for receiving from the channel the transmission units tagged with
the items of timing information,
(vi) means for recreating from the transmission units and the items of
timing information received in claim element (v) the timing-critical data,
(vii) said timing critical data being formatted as a data block comprising
in order a block header, a block payload, and an error-correcting block,
said block payload comprising a plurality of transmission units and one
tag packet containing the timing information for the plurality of
transmission units. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
The invention relates to a recording arrangement for recording an
information signal in tracks on a record carrier, the recording
arrangement comprising
an input terminal for receiving the information signal,
channel encoding means for channel encoding the information signal so as to
obtain a channel signal suitable for recording in a track on said record
carrier,
writing means for writing the channel signal in the track, the channel
signal comprising subsequent or a succession of signal blocks, each signal
block comprising a first block section which comprises a synchronization
signal and a second block section which comprises a number of channel
bytes, to a record carrier obtained with the recording arrangement, and to
a reproducing arrangement for reproducing the information signal from the
record carrier.
A recording arrangement as given in the opening paragraph is known from
EP-A 492,704, to which U.S. Pat. No. 5,245,483 corresponds
The known arrangement is a recording arrangement of the helical scan type,
such as used in a digital VCR (DVCR) and records an information signal
comprising a digital audio signal and a digital video signal in audio
signal recording sectors and video signal recording sectors respectively
in subsequent tracks, where, when recording a track, the video signal
recording sector in a track comes first and is followed by the audio
signal recording sector. The order in which the sectors occur in a track
can however also be in the reverse order. Further, other sectors may be
included in a track, such as a clock run-in area located at the beginning
of a track, so as to enable a locking-in of the internal system clock on
the signals read from the track, and preamble and postamble areas that are
located between the various sectors and function as an edit gap. Reference
is made in this respect to the earlier filed European patent applications
No. 93.202.950, to which U.S. Pat. No. 5,424,878 corresponds, and No.
93.201.263, to which U.S. Pat. No. 5,400,187 corresponds.
The prior art reference documents relate to proposals for the realization
of a new digital video cassette (DVC) recorder standard, which enables the
recording and reproduction of digital video and digital audio on/from a
longitudinal magnetic record carrier such as magnetic tape. This new
digital video recorder standard will lead to new digital video
recorders/reproducers of the so-called DVC type.
BRIEF SUMMARY OF THE INVENTION
The invention aims at providing a recording arrangement which is capable of
recording other types of information signals in the known tape format as
defined in the preamble. The recording arrangement in accordance with the
invention is characterized in that the information signal is an MPEG
information signal in accordance with an MPEG format, the MPEG information
signal comprising subsequent or a succession of transport packets, that
the channel encoding means are adapted to store each time information
included in x transport packets of the MPEG information signal in the
second block section of a group of y signal blocks of the channel signal,
that the second block section of at least the first signal block of the
group of y signal blocks comprise a third block section for storing
identification information identifying the signal clock as being the first
signal block of the group of y signal blocks, and that x and y are
integers such that x.gtoreq.1 and y.gtoreq.1. More specifically, the
recording arrangement in accordance with the opening paragraph is
characterized in that the information signal is an MPEG information signal
in accordance with an MPEG format, the MPEG information signal comprising
subsequent transport packets, that the channel encoding means are adapted
to store each time information included in x transport packets of the MPEG
information signal in the second block sections of a group of y signal
blocks of the channel signal, that the second block sections of the signal
blocks comprise a third block section for storing sequence number
information relating to a sequence number of the signal blocks, and that x
and y are integers such that x.ltoreq.1 and y.gtoreq.1.
The invention is based on the following recognition. The draft Grand
Alliance HDTV System Specification dated Feb. 22, 1994, more specifically
chapters V and VI of the specification, comprises a description of a
transport system for transmitting an MPEG information signal, which
includes a data compressed digital video signal and a corresponding data
compressed digital audio signal, for broadcasting purposes or for
transmission via a cable network. The MPEG information signal is in the
form of transport packets having either an equal length or a variable
length in time. In both cases, however, a transport packet comprises 199
bytes of information, the first byte of which being a synchronization
byte.
A transmission such an MPEG information signal in the form of a recording
on a reproduction from a record carrier, such as a magnetic record carrier
as a tape, require special measures to be taken in order to realize such
kind of transmission via the known tape format. More specifically, the
invention relates to storing the transport packets in the signal blocks of
the known tape format.
Generally, it can be said that, when storing the information included in a
number of x transport packets of the MPEG information signal in a number
of y signal blocks, some unoccupied space remains available in the y
signal blocks for the storage of additional information, which additional
information relates to the specific application of recording and
reproducing the MPEG information signal on/from the record carrier. In a
specific example of the DVC format, the second block sections of five
signal blocks. Now, 11 bytes (=5.times.77-2.times.187) remain available in
the five signal blocks. Those 11 bytes can be divided over the second
block sections of the five signal blocks in various ways so as to obtain
the third block sections. One such way is that the first two bytes of all
second block sections are available as third block sections and that the
last byte available can be considered as a third block section to indicate
the boundary between the information of the two transport packets as
stored in the five signal blocks.
In the above example, identification information identifying the signal
block as being the first signal block of the group of y signal blocks can
be stored in a third block section of the first signal block in a group of
y signal blocks. Or, sequence number information (sequence numbers)
relating to the sequence of the signal blocks can be stored in the third
block sections. This sequence number can also be identified as a
continuity counter. The measures proposed result in a number of
advantages.
The advantage of using identification information identifying a signal
block as being the first signal block in a group of y signal blocks, is
that the beginning of a group can be detected, which simplifies the
read-out of the data during reproduction.
One advantage using sequence numbers is that, when reproducing the signal
blocks, it can be decided upon retrieval of the sequence numbers, whether
a signal block has been missed because of reproduction errors or not, so
that an error correction or concealment can be carried out. Another
advantage is that one may shuffle the information to be stored in the
signal blocks upon recording. Upon retrieval of the sequence numbers it is
possible to realize a corresponding deshuffling in response to the
sequence numbers retrieved so as to obtain the original data stream.
Further, having sequence numbers included in the third block sections of
the signal blocks makes it possible to repeat signal blocks in the case
that a transport packet of the MPEG data stream stored in those signal
blocks requires a higher protection against errors that can occur during
the recording and a subsequent reproduction process.
The recording arrangement as given in the opening paragraph may also be
characterized in that the information signal is an MPEG information signal
in accordance with an MPEG format, the MPEG information signal comprising
subsequent transport packets, that the channel encoding means are adapted
to store each time information included in x transport packets of the MPEG
information signal in the second block sections of a first group of y
first signal blocks of said signal blocks of the channel signal so as to
enable a normal play mode using video information stored in said first
group of y first signal blocks during a normal play reproduction mode, the
channel encoding means further being adapted to retrieve a trick mode
video signal from the MPEG information signal and being adapted to store
said trick or feature mode video signal in second block sections of a
second group of z second signal blocks of said signal blocks of the
channel signal so as to enable a trick play mode using the video
information stored in said second signal blocks, that the second block
sections of at least one signal block in each first and second group of
first and second signal blocks respectively comprise a third block section
for storing identification information indicating whether the group
comprises first signal blocks or second signal blocks, and that x, y and z
are integers such that x.gtoreq.1, y.gtoreq.1 and z.gtoreq.1. More
specifically, the information signal is an MPEG information signal in
accordance with an MPEG format, the MPEG information signal comprising
subsequent transport packets, that the channel encoding means are adapted
to store each time information included in x transport packets of the MPEG
information signal in the second block sections of a group of y signal
blocks of the channel signal, that the second block sections of at least
those signal blocks in a group of y signal blocks that comprises the start
portion of a transport packet comprise a third block section for storing
sequence number information relating to a transport packet sequence number
corresponding to the transport packet having its start portion stored in
the second block section of the signal block, and that x and y are
integers such that x.gtoreq.1 and y.gtoreq.1. This enables a reproduction
in the reproducing arrangement in a normal play mode using the first
signal blocks and a reproduction in a trick play mode using the second
signal blocks, in response to the detection of the information indicating
the groups comprising first signal blocks or second signal blocks
respectively.
The recording arrangement as given in the opening paragraph may also be
characterized in that the second block sections of all signal blocks in
each first and second group of first and second signal blocks respectively
comprise a third block section for storing identification information
indicating whether the group comprises first signal blocks or second
signal blocks. More specifically, the second block sections of a group of
y signal blocks each comprise a third block section for storing sequence
number information relating to a transport packet sequence number
corresponding to the transport packet of which information is stored in
said signal block.
Storing a packet sequence number has its advantages if an MPEG data stream
is received having a constant bit or transport rate, and comprising a
number of different video programs interleaved in the MPEG data stream.
Generally, such data stream has a too high bit rate for recording the
total data stream on the record carrier. Typically, the MPEG bit rate is
45 Mbps, whereas the record carrier typically records with a 25 Mbps bit
rate. The recording arrangement now comprises a program selector for
retrieving one video program and corresponding audio signal from the MPEG
data stream so as to obtain the MPEG information signal for recording. As
information corresponding to only one video program is included in a MPEG
transport packet, such program selector selects only those transport
packets from the MPEG data stream that comprise information corresponding
to said only one video program. That means that some packets of the
original MPEG data stream received are deleted. Upon reproduction however,
an MPEG video signal in accordance with the MPEG standard, however now
comprising only the one video program, should be regenerated or recreated.
Such regenerated data stream should have the transport packets that were
selected upon recording at the same location, that is in one or other way,
dummy packets corresponding to the packets deleted upon recording must be
inserted in the regenerated data stream. Upon recording a sequence number
is added to each transport packet received, that is: also for the packets
that will be deleted. The sequence numbers of the packets that are
selected and stored is stored in the third block section of the signal
blocks in which a transport packet is stored. Upon reproduction, a
sequence of numbers is retrieved, where subsequent numbers will not
necessarily be next higher numbers. In that situation one or more dummy
packets must be inserted so as to regenerate the replica of the original
MPEG data stream.
The recording arrangement as given in the opening paragraph can further be
characterized in that the information signal is an MPEG information signal
in accordance with an MPEG format, the MPEG information signal comprising
subsequent transport packets, the recording arrangement comprising
detection means for detecting the moment of receipt of the transport
packets and for generating timing information for each transport packet
received, the timing information for a transport packet corresponding to
said moment of receipt of said transport packet, that the channel encoding
means are adapted to each time store information included in x transport
packets of the MPEG information signal in the second block sections of a
group of y signal blocks of the channel signal, that the second block
sections of at least those signal blocks in a group of y signal blocks
that comprises the start portion of a transport packet comprise a third
block section for storing the timing information for said transport packet
having its start portion stored in the second block section of the signal
block, and that x and y are integers such that x.gtoreq.1 and y.gtoreq.1.
More specifically, the second block sections of a group of y signal blocks
each comprise a third block section for storing the timing information
corresponding to the transport packet which has information stored in the
second block section of said signal block.
Storing timing information corresponding to transport packet requires that
the recording arrangement is provided with detection means for detecting
the time of receipt of a transport packet. This measure has its advantages
if an MPEG data stream is received having a variable bit rate, and
comprising a number of different video programs interleaved in the MPEG
data stream. As has been said above, generally, such data stream has a too
high bit rate for recording the total data stream on the record carrier.
The recording arrangement now comprises a program selector for retrieving
one video program with its corresponding audio signal from the MPEG data
stream so as to obtain the MPEG information signal for recording. As
information corresponding to only one video program is included in a MPEG
transport packet, such program selector selects only those transport
packets from the MPEG data stream that comprise information corresponding
to said only one video program. By detecting and storing the timing
information corresponding to a transport packet, the reproducing
arrangement will be capable of retrieving the timing information and
recreating the MPEG information signal using said timing information.
It should be noted that the measures discussed above can be applied solely
or in combination with one another in the recording arrangement. As a
result, record carriers will be obtained having signal blocks stored in
tracks on the record carrier, the signal blocks having a first block
section which comprises a synchronization signal and a second block
section which comprises a number of channel bytes, x transport packets of
the MPEG information signal being stored in the second block sections of a
group of y signal blocks of the channel signal. Further in accordance with
the invention,
the second block section of at least the first signal block of the group of
y signal blocks comprise a third block section for storing identification
information identifying the signal block as being the first signal block
of the group of y signal blocks, or
said identification information is sequence number information and the
second block sections of a group of y signal blocks all comprise a third
block section for storing sequence number information relating to the
sequence numbers of the signal blocks, or
the second block sections of the signal blocks each comprise a third block
section for storing identification information indicating whether the
signal block comprise `normal play` data or `trick mode` data, or
the second block sections of at least those signal blocks in a group of y
signal blocks that comprises the start portion of a transport packet
comprise a third block section for storing identification information
relating to a transport packet sequence number corresponding to the
transport packet having its start portion stored in the second block
section of the signal block, or
the second block sections of at least those signal blocks in a group of y
signal blocks that comprises the start portion of a transport packet
comprise a third block section for storing the timing information for said
transport packet having its start portion stored in the second block
section of the signal block, or
third block sections comprise information resulting from a combination of
one or more of the measures listed above.
It will be apparent that a reproducing arrangement will be needed which is
adapted to each specific embodiment of the recording arrangement, so as to
enable a reproduction of the MPEG information signal recorded on the
record carrier. Such reproducing arrangement is the subject of the claims
directed to the reproduction arrangement.
The invention also includes the method of transmitting timing critical data
over an asynchronous channel without changing any of the critical timing
information; in other words, to make the asynchronous channel transparent
for the timing critical data. This is achieved, broadly speaking, by
tagging one or more of the transmission units making up the data with
timing information before sending it over the channel, and then using the
tagged information to recreate the proper data timing at the other end of
the channel. As an example, the data can be an MPEG information signal,
and the channel a DVCR. But the invention is not limited to this
application and can also be applied to asychronous channels such as a
computer network, a telephone network or a digital interface.
SUMMARY OF THE DRAWINGS
These and other aspects of the invention will be apparent from and
elucidated with reference to the embodiments described hereafter and the
accompanying drawings, in which:
FIG. 1 shows the track format of a record carrier of the DVC-type,
FIG. 2 shows schematically the contents of the video signal recording
sector in the track of FIG. 1,
FIG. 3 shows schematically the serial MPEG data stream and the format of
the transport packets included in the serial MPEG data stream,
FIG. 4 shows an example of the storage of two transport packets in five
signal blocks,
FIG. 5 shows the contents of the track when having MPEG information
recorded in it,
FIG. 6 shows one embodiment of the recording arrangement,
FIG. 7 shows one embodiment of the reproducing arrangement,
FIG. 8a shows an example of an original serial MPEG data stream having a
constant bit rate and packet rate, FIG. 8b the MPEG data stream that is
recorded, and FIG. 8c the regenerated replica of the original serial MPEG
data stream,
FIG. 9 shows one embodiment of the `normal play` processing unit in the
recording arrangement of FIG. 6,
FIG. 10 shows one example of a sequence of three groups of five signal
blocks each,
FIG. 11 shows another example of a sequence of three groups of five signal
blocks each,
FIG. 12 shows one example of the `normal play` processing unit in the
reproducing arrangement of FIG. 7,
FIG. 13a shows an example of an original serial MPEG data stream having a
variable bit rate and packet rate, FIG. 13b the MPEG data stream that is
recorded, and FIG. 13c the regenerated replica of the original serial MPEG
data stream,
FIG. 14 shows another embodiment of the `normal play` processing unit in
the recording arrangement of FIG. 6,
FIG. 15 shows another embodiment of the `normal play` processing unit in
the reproducing arrangement of FIG. 7,
FIG. 16 shows the record carrier and the read head scanning the record
carrier during a trick play mode,
FIG. 17 shows the sequence of signal blocks in a track forming the trick
play area,
FIG. 18 shows another embodiment of the invention combining the recording
and playback systems,
FIG. 19 shows an example of the input and output data streams from the
apparatus of FIG. 18,
FIG. 20 shows another example of input and output data streams from
apparatus similar to that of FIG. 18,
FIG. 21 shows one form of data block of the invention for transmission over
an asynchronous channel,
FIG. 22 shows in more detail the block payload of the data block of FIG.
21,
FIG. 23 shows various tagging options in accordance with the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
FIG. 1 shows the format of the signals as they are recorded in a track on a
magnetic record carrier by means of a helical scan video recorder of the
DVC type. The left end of the track 1 in FIG. 1 is the start of the track
and the right end of the track is the terminal part of the track. The
track comprises a number of track parts. The track part denoted by G1 is
the preamble track part. An example of the preamble track part G1 has been
described extensively in EP-A492,704.
The track part G1 is followed by tracking tone recording part TP1, which is
denoted by ITI (insert timing information) track part and which contains a
tracking tone, synchronization information and identification (or timing)
information. Further explanation of the contents of the ITI track can be
found in EP-A93.201.263.
The track part TP1 is followed by an edit gap G2. The edit gap G2 is
followed by the track part TP2, which is the audio signal recording sector
and comprises digital audio information. The edit gap G3 is followed by a
track part TP3 which is the video signal recording sector and comprises
digital video information. The edit gap G4 is followed by a track part
TP4, denoted by INDEX and which comprises among other items subcode
information, such as absolute and/or relative time information and a table
of contents (TOC). The track is terminated by the track part G5. It can be
said that the sequence order in which the parts TP1, TP2 and TP3 occur in
the tracks may be different.
The contents of the video signal recording sector TP3 is given in FIG. 2.
FIG. 2 in fact shows schematically a number of 149 horizontal lines,
denoted by j=1 to j=149, having bytes of information stored in it. The 149
lines are in fact 149 signal blocks (or sync blocks) that are stored
sequentially in the video signal recording sector TP3. 90 bytes of
information, denoted by i=1 to i=90, are stored in each signal block.
The first two bytes (i=1 and i=2) of each signal block form a
synchronization pattern of 2 bytes long. The following three bytes in each
signal block form an ID code, comprising among other items information
which indicates the sequence number of the signal block in the video
signal recording part TP3. The last eight bytes in the signal blocks form
horizontal parity information. Vertical parity information is stored in
the storage locations i=6 to i=82 inclusive of the last 11 signal blocks.
Bytes of video signal information are stored in the storage locations i=6
to i=82 inclusive of the signal blocks having the sequence numbers j=3 to
j=137 inclusive. Bytes of auxiliary data are stored in the storage
locations i=6 to i=82 inclusive of the signal blocks having the sequence
numbers j=1, 2 and 138. The signal blocks are stored sequentially in the
video signal part TP3, starting with the signal block denoted j=1,
followed by the signal block denoted j=2, and so on until the signal block
denoted j=149.
The auxiliary data for storage in the signal blocks denoted j=1, 2 and 138
can be teletext data or control data.
It should be noted here that it can be specified that the auxiliary data
will be stored in a different location in the memory. Reference is made in
this respect to EP-A492,704 FIG. 13, where the auxiliary data is stored in
the memory part denoted by III.
FIG. 3 shows schematically the MPEG data stream applied to a recording
arrangement in accordance with the invention. The MPEG data stream
comprises subsequent transport packets, denoted by . . . , P.sub.k-1, Pk,
P.sub.k+1, . . . The packets each comprise a packet header portion PH of 4
bytes long and a body portion of 184 bytes long. The transport packets can
be transmitted in a data stream having a constant bit rate. This means
that the packets are equally long, viewed in time, and are received at a
fixed packet rate. The transport packets may also be transmitted in a data
stream having a variable bit rate. In this situation, the packets need not
be of the same length, viewed in time, and may be received with a variable
packet rate. The first byte in the packet header PH is a sync byte. The
sync byte is identical for all the transport packets. The other three
bytes in the header comprise ID information, such as a packet identifier.
For a further explanation of the contents of the ID information, reference
is made to the draft Grand Alliance HDTV System Specification discussed
above specifically chapter V, paragraph 5.1 on page 27.
The body portion of the transport packets comprise each 184 bytes for
storing the video and audio information that should be transmitted in
accordance with the MPEG format. The body portion of one transport packet
can store either audio information corresponding to a certain video
signal, or the video signal. Further, in the case that a number of video
programs are transmitted via. the MPEG data stream, the body portion
stores a video signal corresponding to one of such video programs
transmitted.
One aspect of the invention now aims at recording the video signal, and the
corresponding audio signal as may be appreciated, corresponding to one of
those video programs transmitted via the MPEG data stream, on the record
carrier having the track format disclosed in FIG. 1 and 2. Information
stored in the transport packets should be stored in the signal blocks,
more specifically, in the 135 signal blocks denoted j=3 to j=137 in the
video signal recording part TP3 of a track. The two sync bytes, denoted
i=1 and 2, the ID information in the form of the three ID bytes denoted
i=3, 4 and 5, as well as the 8 horizontal parity bytes, denoted by i=83 to
90, in those signal blocks are required for a correct recording and
reproduction. As a consequence, only the 77 bytes, denoted by i=6 to 82,
in the signal blocks denoted by j=3 to 137, are available for the storage
of the transport packets of the MPEG information. The part of the signal
blocks formed by the 77 bytes i=6 to 82 is defined as being the second
block sections of the signal blocks.
As synchronization during recording and reproduction is assured by means of
the sync words in each of the signal blocks, there is no need for
transmitting the sync bytes of the transport packets via the record
carrier. So, before storing the information comprised in the transport
packets in the second block sections of the signal blocks denoted by j=3
to 135, the sync byte of all the transport packets is thrown away. As a
result only 187 bytes of information should be stored in the signal blocks
for each transport packet.
A simple calculation makes clear that two transport packets can be stored
in five signal blocks, and that 11 bytes remain available for the storage
of other information. FIG. 4 gives an example of how the two transport
packets can be stored in the second block sections of the group of five
signal blocks, denoted SB1 to SB5 in FIG. 4. FIG. 4 only shows the
contents of the second block sections of length of 77 bytes included in
the signal blocks. As can be seen in FIG. 4, the 11 bytes are divided over
the group of five signal blocks such that each second block section
comprises a third block section TB3.1 to TB3.5, of two bytes long at the
beginning of the second block sections of the five signal blocks SB1 to
SB5 respectively, and a third block section in the form of one byte,
denoted by FB, is available | | |
