Motion video signal processing for recording or reproducing – Local trick play processing – With randomly accessible medium
Reexamination Certificate
2000-05-12
2004-10-19
Kelley, Chris (Department: 2613)
Motion video signal processing for recording or reproducing
Local trick play processing
With randomly accessible medium
C386S349000, C386S349000, C360S032000
Reexamination Certificate
active
06807366
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a data recording apparatus, a data recording/reproducing apparatus, a data recording method, and a data recording/reproducing method which are applied to, for example, a case of recording image data onto a tape-shaped recording medium and reproducing the image data from the recording medium.
2. Description of the Related Art
A data recording/reproducing apparatus for recording a digital image signal onto a magnetic tape and reproducing a digital image signal from a recording medium is known as represented by a digital VTR (Video Tape Recorder). A shuffling process is performed in a recording processing unit in a digital image recording apparatus. The shuffling process is a process for setting a relation between a position of data on a screen and a recording position on the tape to a desired relation. It is the first object of the shuffling to distribute a burst error upon reproduction, thereby improving a correction ratio of the error correction by an error correction code such as a product code. The second object is to enable uncorrectable errors to be easily concealed. The third object is to enable a reproduction image to be easily seen upon high speed reproduction.
The shuffling process which is used in the conventional digital VTR will now be described.
FIG. 1
shows a track pattern on which data of one frame of the digital VTR has been recorded.
FIG. 1
shows a helical scan type VTR. Data of one frame is recorded as ten tracks T
1
to T
10
formed obliquely on the tape. Azimuths of the adjacent tracks are different.
Audio data is recorded in a center portion of each track and video data is recorded on the upper and lower sides of each track. The audio data and video data are subjected to the shuffling process and have been error correction encoded by a product code. The audio data and video data are recorded in a data format called a sync block. The sync block has a data structure in which a sync signal, a sync ID, data (audio data, a parity of an external code of the product code, or video data), and a parity of an internal code of the product code have been arranged in order from the head. For example, data of one macroblock is arranged in one sync block. The audio data and video data shown in
FIG. 1
also include the parity of the external code and auxiliary data.
FIG. 2
shows a relation between the video data of one frame and the track on which the video data is recorded. In case of an NTSC television signal of 525 lines/60 fields, valid data of one frame is constructed by 45 macroblocks in the lateral direction and 32 macroblocks in the vertical direction. One macroblock is constructed by (16×16) pixels. The macroblock is a unit of a process in case of compressing the video data by MPEG2 (Moving Picture Experts Group Phase 2). The video data is encoded as variable length data by MPEG2. However, an amount of coded data of one frame is set to be constant by a length equalizing process. In case of compressing data by MPEG2, the coded data corresponding to one macroblock becomes the variable length data. Even in this case, at least significant data in the coded data of one macroblock is arranged into a data area of each sync block.
To record the video data of one frame into each of the upper and lower areas of 10 tracks, the video data of one frame is equally divided into five data in the lateral direction and equally divided into four data in the vertical direction, so that 20 recording units are formed. Each recording unit has a size of (9×8=72 macroblocks). Among the 20 recording units, 10 recording units L
1
to L
10
of the upper half are video data that is recorded in the lower area of each track and 10 recording units U
1
to U
10
of the lower half are video data that is recorded in the upper area of each track. L
1
and U
1
are recording units which are recorded in the lower and upper areas of the track T
1
, respectively. Numerals which are added to the other recording units also correspond to the numbers of the tracks to be recorded.
As shown in
FIG. 3
, the shuffling process is performed every recording unit of (9×8) macroblocks. That is, the recording unit is further divided into six subblocks of a size corresponding to (3×4) macroblocks. In each subblock, as shown by an arrow in
FIG. 3
, three macroblocks arranged in the lateral direction are sequentially selected. When the selection of the macroblocks of one subblock is finished, the top three macroblocks of the second subblock adjacent to such a subblock are selected. When the selection of the macroblocks in the second subblock is finished and, further, the selection of the macroblocks in the third subblock is finished, the process advances to the lower leftmost subblock and the macroblocks in this subblock are selected. In this manner, the macroblocks selected in order shown by arrows in
FIG. 3
are sequentially recorded in the area on the tape.
FIG. 4
shows an example of a construction for realizing the shuffling process. The input video data is written into an RAM (Random Access Memory)
161
and the data is read out of the RAM
161
. The RAM
161
has a capacity of, for example, one frame and the video data is written into an address corresponding to the position in one frame of each macroblock. A read address in the RAM
161
is generated from a shuffling table
162
. Although not shown, a write address in the RAM
161
is generated in accordance with the position of the macroblock on an image. An output of a counter
163
for generating a sync ID is supplied to the shuffling table
162
. The position on the image of the macroblock and the recording position of the sync ID are converted into a predetermined relation by the shuffling table
162
.
For example, the macro block numbers are specified as shown in FIG.
5
A and the sync ID is specified as shown in FIG.
5
B.
FIGS. 5A and 5B
show one recording unit which is recorded on the lower or upper area of one track. The data of each macroblock is recorded in the area on the tape in the scanning direction of the head in order of the numbers of the sync IDs. Although only the sync IDs will be described for simplicity of explanation, in order to record data onto the tape in the format shown in
FIG. 1
, track IDs to distinguish 10 tracks and an ID to distinguish the upper or lower area of each track are also necessary. The macroblock numbers and the values of the sync IDs are also set to simple numbers starting from 1 for simplicity of explanation. Actually, IDs to distinguish all sync blocks in one track or in the upper area or lower area in one track are used while including a parity of an external code, auxiliary data, and the like.
In case of the digital VTR, besides a normal reproducing operation in which a tape speed upon reproduction is equalized to that upon recording, a high speed reproducing operation in which the tape speed upon reproduction is higher than that upon recording can be performed. In the high speed reproducing mode, as the tape speed rises, a relative speed between the head and the tape changes and a trace locus which is formed when the head passes on the tape is deviated from the track. Thus, although the number of tracks over which the head passes increases, the number of sync blocks which are continuously reproduced from each track decreases and the macroblocks of a plurality of frames mixedly exist on an image and are updated. The position of the macroblock which is updated at each time in the high speed reproducing mode changes depending on a difference of shuffling tables (also called shuffling patterns) in which the position of the macroblock on the image and the recording position on the tape are made to correspond. Since only a part of information recorded on the tape can be obtained in the high speed reproducing mode, in order to enable a reproduction image in the high speed reproducing mode to be easily seen, it is necessary to design the shuffling table so that information can be obtained as much as
Okubo Atsushi
Suzuki Takao
Frommer William S.
Frommer & Lawrence & Haug LLP
Kelley Chris
Smid Dennis M.
Vent Jamie
LandOfFree
Data recording apparatus, data recording/reproducing... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Data recording apparatus, data recording/reproducing..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Data recording apparatus, data recording/reproducing... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3262238