JPH0410879A - Method for recording and reproducing video signal - Google Patents

Abstract

PURPOSE:To restore a screen area to be restored even when only one part in a sync block can be taken out by arranging a low band part among orthogonally transformed-encoded codes at the front part of the sync block. CONSTITUTION:The restoration of a video signal as a special reproducing picture is attained on a sync block of which the whole is included in a range able to be scanned by a reproducing head. However, data arrangement within the sync block is made that the low band part 71 of a code orthogonal- conversion-encoded at the front part of the sync block is arranged to attain the restoration of the video signal also on a sync block 6 unable to restore the video signal. Accordingly, the video signal can be restored only by SYNC, ID and the low band part 71 in the sync block. Thus, even when only one part in the video-recorded sync block can be taken out, the whole screen area restored by video data in the sync block is not made unable to be restored, the more screen area is restored and picture quality degradation is eliminated.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a method for recording and reproducing video signals.

Conventional technology To configure a recording/playback device (VTR, video disc, etc.) that records and plays back video signals, band compression technology (or high-efficiency encoding technology) is required to reduce the amount of data of the original video signal for long-term recording. ) is used.

An example of the band compression technique is one using orthogonal transform encoding using Hadamard transform, discrete cosine transform (DCT), or the like. Orthogonal transform encoding encodes each frequency component obtained by frequency decomposing a video signal. At this time, for high-frequency components whose visual characteristics are less affected by deterioration, the method is to reduce the data amount of the original video signal by reducing the amount of data allocated. It is one of the band compression technologies.

As a conventional example, a method for recording and reproducing video signals on a VTR will be described.

Data reduced by orthogonal transform coding, which is one of the above-mentioned band compression techniques, is recorded on a tape, and is recorded by dividing it into sync blocks of a certain amount of data as the minimum synchronization unit during playback. FIG. 3 shows the data arrangement within the sync block. In the same figure, 5YN
C1 is a synchronization pattern, ID2 is identification information indicating where on the screen the recorded data should be located, etc.
ATA 3 is video data reduced by the orthogonal transform encoding.

FIG. 4 shows the arrangement of the sync blocks recorded on the tape by the VTR of this conventional example. 4a, 4b, and 4c in the figure are tracks, and the sync blocks are arranged in these tracks. Each track is the trajectory of the recording head during recording, but also the trajectory of the playback head during normal playback. In other words, during normal playback, the data reduced by the orthogonal transform encoding can be retrieved as is by scanning the playback head along the same locus that was scanned by the recording head during recording. Then, the optical video signal can be restored by performing decompression processing that is opposite to the compression processing using the orthogonal transform encoding.

Next, a method for reproducing recorded data during special playback will be described.

Reference numeral 5 in FIG. 4 shows the trajectory of the reproducing head during high-speed search, which is one of the special reproductions. Since the tape feed speed during high-speed search is faster than during normal playback, the trajectory 5 of the playback head is a trajectory that scans across a plurality of tracks. Therefore, the data that can be retrieved from the tape by the playback head is only the sync flock shown in the shaded area in the figure. Although the data reproduced at this time is different from the order of the sync blocks at the time of recording, it is possible to detect a single position on the screen using the ID information in the sync blocks mentioned above, so it is possible to restore the video signal as a special playback image. Become.

Problems to be Solved by the Invention However, in the above-mentioned conventional video signal recording and playback method,
During special playback, there are zinc blocks that can only be partially scanned with the playback head trajectory 5. For example, like the sync block 6 in FIG. 4, only the front part of the sync block can be scanned, but the entire sync block cannot be scanned. For this reason, the entire DATA located at the rear of the sync block 6 cannot be extracted, so the data necessary for the decompression process cannot be prepared, and the entire video data in the sync block 6 cannot be restored. I had an issue. Additionally, depending on the search speed, there is a high probability that data will not be updated on a particular screen for a long time, and old data will remain on the screen for a long time, seriously deteriorating the reproduced image. It was also an issue.

In view of this point, in the present invention, the DATA in the sync block
To provide a video signal recording and reproducing method capable of restoring a larger screen area using only retrievable data even if not all the retrievable data is taken out.

Means for Solving the Problems The present invention provides a method for recording and playing back a video signal obtained by orthogonal transform coding by dividing it into sync blocks, the method comprising recording and reproducing a code obtained by orthogonally transforming a video signal by dividing the code into sync blocks, the code being orthogonally transform coded at the front of the sync block. This is a video signal recording and playback method that arranges the low frequency part of the video signal.

Effect of the Invention The present invention makes it possible to restore the screen area to be restored using the video data in the sync block even if only a part of the sync block recorded on the tape can be retrieved by the method described above. It is possible to restore the screen area.

Embodiment FIG. 1 is a diagram showing data arrangement within a sync block constructed by a video signal recording method according to an embodiment of the present invention. Figures 1 and 2 are sync (SYNC) respectively.
, ID (10), which are synchronization information and identification information similar to those explained in the conventional example above. Further, 70 data (DATA) is video data compressed by orthogonal transform encoding according to this embodiment, and 71 of them is the low frequency part of the code obtained by the orthogonal transform encoding, 72 is a high frequency section other than the low frequency section 71.

FIG. 2 shows the arrangement of the sync blocks recorded on the tape by the VTR of this embodiment. 4a, 4b, and 4c in the same figure each indicate a track, and 5 indicates the trajectory of the reproducing head during high-speed search, which is one of the special reproductions, and is given the same number as in the conventional example. Further, the data that can be retrieved from the tape by the playback head trajectory 5 during special playback is shown in the shaded area in the figure.

In FIG. 2, for a sync block whose entirety is included in the scannable range of the playback head, it is possible to restore the video signal as a special playback image, as in the prior art example described above. However, in this embodiment, the video signal can be restored even for the sync block 6, for which the video signal could not be restored in the conventional example. This is because the data arrangement in the sync plotter is as shown in Figure 1, and the low frequency part 71 of the orthogonal transform encoded code is arranged at the front.
5YNC, ID, and low frequency part 7 in sync plotter
This is because the video signal can be restored using only 1.

The screen area restored only by the low frequency part 71 of the orthogonal transform encoded code lacks definition because there is no high frequency part 72, but for special playback effects such as high-speed search, the screen area is better than the definition of the screen. , it is visually preferable to display the new screen over a wider area. Therefore, as in this embodiment, the video signal can be restored even from a device such as the sync block 6 from which only a portion of the video data can be extracted, and more new screen areas can be played back on the screen, making recording and playback more effective. It's a method.

Also, even if the search speed becomes faster and the area per track that can be scanned by the playback head is reduced, the practical effect is that more screen area can be restored as described above. expensive.

As described in detail, according to the present invention, even if only a portion of a recorded sync block can be retrieved, the entire screen area that should be restored by the video data in the sync block is not rendered unrecoverable. , more screen area can be restored and image quality deterioration can be reduced. Furthermore, since it can support faster search speeds, its practical effects are great.

[Brief explanation of the drawing]

FIG. 1 is a data arrangement diagram in a sync block for explaining a video signal recording/playback method in an embodiment of the present invention, and FIG. 2 is a diagram for explaining a video signal recording/playback method in an embodiment of the present invention. FIG. 3 is a diagram showing the arrangement of sync blocks on a tape to explain the conventional video signal recording/playback method. FIG. 4 is a data layout diagram of the sync plotter to explain the conventional video signal recording/playback method. FIG. 3 is a diagram showing the arrangement of sink plotters on a tape for explanation. 1...5YNC, 2...10.70.
...DATA.

Claims (1)

[Claims] A method of recording and reproducing a code obtained by orthogonally transform-encoding a video signal by dividing it into sync blocks of a predetermined number of codes, the method comprising: recording and playing back a code obtained by orthogonally transforming a video signal; A video signal recording and playback method characterized by arranging.