JP2869291B2 - Digital recording and reproducing apparatus for video signals - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital recording / reproducing apparatus for a video signal for magnetically recording and reproducing a video signal by encoding the video signal with high efficiency, and more particularly, it is provided with means for improving the image quality at the time of variable speed reproduction such as high speed search. The present invention relates to an apparatus for digitally recording and reproducing video signals.

[0002]

2. Description of the Related Art A video signal recording and reproducing apparatus of this kind,
For example, a digital VTR is configured as shown in FIG. 11, and the configuration will be briefly described with reference to FIG.

In general, a digital VTR performs high-efficiency encoding to reduce the amount of information to be recorded on a tape after rearranging the blocks in units of a certain size (in the block shuffling 101) (high-efficiency encoding). Circuit 10
2). Next, a code (parity) for error correction is added to the highly efficient coded data (in the error correction coding circuit 103). Next, after adding a synchronization signal / ID signal for recording / reproducing (in the Sync and ID addition circuit 104), modulation is performed so as to suppress the DC component (in the modulation circuit 105) and the tape (the recording medium 106).
To record.

On the reproducing side, after performing error correction based on the demodulated data (in the demodulation circuit 107), decoding is performed in units of encoded blocks (error correction decoding 109).
At). At this time, the portion that could not be corrected by the correction circuit is not decoded, but is corrected by the decoding / modifying circuit 110.

[0005] Thereafter, the blocks are rearranged in the reverse order of the recording side (in the block deshuffling circuit 111) to reproduce the original video signal.

As a high-efficiency coding method suitable for a digital VTR, the whole screen is divided into some short blocks instead of controlling the code amount for the whole screen in order to realize a variable speed reproduction function. It is considered necessary to control the code amount so that each block has a fixed length. For example, a digital video signal recording / reproducing apparatus as disclosed in JP-A-2-220270 has been proposed. ing.

In this device, a plurality of small blocks located at positions separated from each other on a screen are collected to form a large block, and the amount of code is controlled in units of the large block to form a fixed-length block. By rearranging the corresponding small blocks included in the fixed length blocks adjacent to each other on the recording medium so as to be adjacent to each other also on the screen, the visibility of the video at the time of variable speed playback and the efficiency of the high efficiency encoding are improved. It is stated that a digital video signal recording / reproducing device compatible with this can be provided.

[0008]

However, in the means described in the prior art, the number of small blocks included in the fixed-length block is limited in terms of suppressing the information amount deviation from the viewpoint of the efficiency of high-efficiency coding. The greater the number of small blocks, the better the visibility of the video during variable-speed playback. In terms of securing continuity on the screen and preventing mosaic formation, there is a contradiction that the smaller the number of small blocks, the better. Occurs.

For example, as shown in FIG. 12 (a) for explaining the configuration of the large block and FIG. 12 (b) for explaining the arrangement on the track, one area is divided into six equal parts on the screen. Take out small blocks and compose large blocks,
After forming a fixed-length block by performing code amount control in units of the large block, recording is performed on the recording medium in units of the fixed-length block, and small blocks corresponding to each other included in adjacent fixed-length blocks on the recording medium. Are arranged adjacent to each other on the screen, the number of small blocks that can be continuously reproduced on the recording medium at the time of variable-speed reproduction is 6
One-half of the small blocks are continuous in each region, which is insufficient from the viewpoint of preventing mosaic formation related to visibility at the time of variable speed reproduction.

Conversely, the area for dividing the screen is reduced to a smaller number,
For example, in the case of dividing into two, the number of continuous blocks on the screen is one half of the number of small blocks that can be detected continuously on the recording medium, and a certain degree of continuity can be secured. A deviation is likely to occur in the information amount of each fixed-length block, causing a problem that the efficiency of high-efficiency coding is reduced.

Therefore, there is a problem in that the number of small blocks included in the fixed-length block must be determined in a compromise between the efficiency of high-efficiency coding and the visibility of video during variable-speed reproduction.

[0012]

In an apparatus for digitally recording a video signal according to the present invention, a small block forming means for collecting a plurality of sample values to form a small block, and a small block obtained by the small block forming means. Means for forming a large block by collecting a plurality of blocks, and means for forming a fixed-length block by controlling the code amount so that the total code length of the small blocks included in the large block is constant. , The fixed-length block is replaced with a small block constituting the fixed-length block.
And means for dividing the plurality of recording blocks of click as many fixed length, and a recording block processing means for recording on a recording medium by performing the rearranging of the recording block, the upper Kitai blocked In the means, a large block is composed of a plurality of small blocks that are separated from each other on the screen,
The means for dividing the upper Symbol fixed length blocks, each small block
In order from the information important for decoding
Stores in the recording block, and stores information that could not be stored in one recording block in an empty area of another recording block, above type recording block processing means,
The rearrangement is performed such that recording blocks including the main components of adjacent small blocks on the screen are also adjacent on the recording medium.

Furthermore, in the digital reproducing apparatus of a video signal to reproduce the original video signal from a signal on a recording medium which is recorded by a digital recording device of the present invention, the detected signal from the above type recording medium original When reconstructing the recording block and reconstructing the original fixed-length block, the recording block corresponding to the small blocks collected to form the fixed-length block during recording is collected so that the recording block is reversed. In addition to the rearrangement, the information stored in the free area of another recording block at the time of recording is returned to the original recording block to reconstruct the fixed-length block. The reconstructed fixed-length block is decoded to reconstruct the original large block, and the sample value included in the original small block is restored from the decoded original large block to a position corresponding to the screen and reproduced. I try to get an image.

[0014]

In the digital recording / reproducing apparatus of the present invention, a large block is formed from a plurality of small blocks located at positions separated from each other on the screen, and the high efficiency coding is performed. improves. Moreover, when dividing a fixed-length block composed of high-efficiency coding into recording blocks, information that could not be stored in one recording block was stored in an empty area of another recording block. Efficient and efficient high-density recording is performed. In recording the divided recording block signals on the recording medium, the recording blocks storing the main components of adjacent small blocks on the screen are recorded on the recording medium so as to be adjacent to each other. , video signals of adjacent blocks are securely reproduced even on the screen there especially at variable speed reproduction. The information that could not be stored in the one recording block stored in the free area of the other recording block is returned to the original recording block when the original fixed-length block is reconstructed at the time of reproduction. For reconstructing the video signal.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a block diagram of a digital video signal recording and reproducing apparatus (digital VTR) according to the present invention. In the figure, 1 is a small block means, 2 is a large block means, 3 is an orthogonal transform means, 4 is a variable length coding means, 5 is a recording blocking means, 6 is an error correction coding means, and 7 is an error correction coding means. Rearranging means, 8 is a recording medium, 9 is reverse rearranging means, 10 is error correction decoding means, 11 is recording block decomposing means, 12 is first modifying means, 13 is inverse variable length code decoding means, 14 is Inverse orthogonal transformation means, 15 is a second modification means, 16 is a large block decomposition means, and 17 is a small block decomposition means. It should be noted that the conventional Syn shown in FIG.
The means for c, ID addition / detection, and modulation / demodulation are not specifically shown because they do not directly relate to the present invention.

The operation of the digital signal recording / reproducing apparatus for video signals according to one embodiment of the present invention configured as described above will be described below.

At the time of recording, a rectangular small block is formed by combining a plurality of sample values in the horizontal and vertical directions from the digital video signal by the small block forming means 1.
Next, the large block generating means 2 takes out one small block from each of four equal areas of the screen as shown in FIG. 2 to form a large block. here,
The divided areas are A, B, C, and D, and A1, A2,..., B1, B2,.
・ ・

The video signal of each small block is orthogonally transformed by the orthogonal transform means 3 using a technique such as discrete cosine transform, and then the variable length coding means 4 changes the video signal in accordance with the information amount of each small block. Encoded. In the variable length coding means 4, the code length assigned to each small block is variable, but the fixed length block is controlled by controlling the total code length of the small blocks included in the large block to be constant. obtain.

[0020]

In one embodiment of the present invention, as shown in FIG. 3, one fixed-length block is composed of four small blocks A1, B1, C1, and D1, and four small blocks A2, B2, C2, and D2. The other fixed blocks constitute another fixed-length block, and control is performed so that the total code length of each fixed-length block becomes equal. At this time, small blocks (for example, A1 and B1) in each fixed-length block
Are small blocks (for example, A1 and A2
Etc.) are also adjacent on the screen. Therefore,
For each fixed-length block, a deviation in the amount of information hardly occurs, so that the efficiency of high-efficiency coding can be improved.

Further, the code of the fixed-length block is added to each small block after additional information, such as a code length after encoding and identification information of a quantization table, which is necessary for decoding. It is assumed that real information representing video information from low-frequency components to high-frequency components after orthogonal transformation is rearranged in order from low-frequency components.

Next, the fixed-length block is divided into a plurality of recording blocks by the recording block dividing means 5. In the recording block dividing means 5, in order to divide the main components of the information included in the fixed-length block, that is, the additional information and the real information representing the low-frequency components into separate recording blocks, the following is performed. Either method is used.

(1) Method 1 As shown in FIG. 4A, the main components of the information of each of the small blocks A to D are recorded in the recording blocks 1 to 4, respectively.
And four less important components are put together in the recording block 5.

(2) Method 2 As shown in FIG. 4B, the average of the code lengths of the small blocks A to D is used as the code length of the recording block, and A to D are arranged in the recording blocks 1 to 4. Then, a code whose code length is longer than the average and which is not completely stored in one recording block is stored in an empty area of the recording block in which the small block shorter than the average is stored.

As described above, by dividing the main components into separate recording blocks, if any of the recording blocks 1 to 4 can be detected by the reproduction system described later, the small blocks included in the recording blocks 1 to 4 are converted to large image quality. Decoding can be performed without deterioration.

In the present invention, since the desired effect of the present invention can be obtained by using any of the methods, the following description will be made only when the method 2 is used.

It should be noted that the feature of the method 1 is that each main component can be easily divided into separate recording blocks, and since the main components of the video signal are collectively recorded, only information necessary for variable speed reproduction is stored. The point is that it can be reliably detected.

The feature of the method 2 is that each main component can be easily divided into separate recording blocks, and all the recording blocks include the main components of small blocks. Sometimes, if one recording block can be reproduced, one small block is always reproduced.

Next, an error correction coding means 6 adds an error correction code for correcting an error in the reproduction system to the recording block. Here, it is assumed that double encoding is performed in the order of the outer code and the inner code to form a plurality of error correction blocks, and the inner code stores recording blocks one by one.

As an example, when four error correction blocks are configured as shown in FIG. 5A, each error correction block includes, as shown in FIG.
The recording blocks included in the large block are arranged as a unit, A1 to D1 are the first error correction blocks, A2 to D2 adjacent thereto are the second error correction blocks, and A3 to D3 are the third error correction blocks in order. A4 to D4 in the error correction block
Are arranged in the fourth error correction block.

Next, as shown in FIG. 5 (c), the blocks which have been subjected to error correction coding are divided into recording blocks by the rearrangement means 7 so that adjacent small blocks on the screen are also adjacent on the track. And record it on a recording medium.

As described above, the inner code including the main components of the adjacent small blocks on the screen is configured to be included in the separate error correction blocks, and the adjacent small blocks on the screen are also adjacent on the track. When the rearrangement is performed, the inner code is extracted one by one from the four error correction blocks in addition to the visibility of the video at the time of variable-speed reproduction described later, and a burst error in the track direction occurs in the reproduction system. In this case, the burst error is dispersed into four error correction blocks, and the length of the burst error that can be corrected by the outer code is quadrupled.

[0034]

[0035]

[0036]

Next, the operation of reproducing the digital signal recorded on the recording medium by the means described above will be described with reference to FIG.

[0038] During reproduction, when reproduction at Rutotomoni error correction decoding unit 10 rearranges the original error correction blocks when changing the reverse arrangement of the digital signal detected from the recording medium 8 means 9
Correct the error that occurred in. This error correction decoding means 10
Did not correct all errors for some reason
The recording block with an error flag.
Input to lock disassembly means 11. For this recording block
In the solving means 11, each of the fixed length blocks
Encoded data for each small block is reconstructed in the same way as when recording.
In the free area of another recording block when recording
Rearrangement is performed so that the stored code is returned to the original block.
Done. The original fixed-length block restored in this way
Are input to the first modifying means 12.

In the first modifying means 12, if the recording block containing the main component of each small block has no error and the recording block containing other unimportant components has an error, , And replaces the unimportant component with, for example, “0” and clears the error flag. If there is an error in the recording block containing the main component of each small block, the error flag is input to the second modifying means 15 at the subsequent stage. The inverse variable length decoding means 13 decodes the coded data for each small block, and the inverse orthogonal transform means 14 performs orthogonal transformation reverse to that at the time of recording to obtain a sample value for each small block.

At this time, the first modifying means 12
An image of a small block in which insignificant components have been replaced with “0” has a certain image quality, although some high-frequency components are lost. Further, the small block in which the recording block containing the main component contains an error is replaced by the sample value of the small block at the same position on the previous screen by the second modifying means 15.

The sample values for each small block obtained in this way are restored by the large block decomposing means 16 to a position corresponding to the screen, and a reproduced image is obtained.

After performing this operation, error correction is performed.
The case where the recording block 2 has no error and the recording block 3 has an error in FIG. At this time, the main component of the small block B is reproduced without error, and the high frequency component of B and the main component of the small block C have an error. Therefore, the following operation is performed. That is, the small block B replaces the error high-frequency component data with “0” to clear the error flag, and is decoded by the subsequent inverse variable length decoding means 13 and inverse orthogonal transform means 14 to obtain the small block B. Get sample values. At this time, since the decoded small block is affected by replacing the high-frequency component with “0”, the high-frequency component deteriorates, but a certain image quality can be secured. On the other hand, the small block C is replaced by the sample value of the small block at the same position on the previous screen by the second modifying means 15 because the principal component has an error.

[0043]

At the time of variable speed reproduction, the head scans across a plurality of tracks on the recording medium as shown in FIG. Since data is continuously recorded in each track using the inner code as a unit, signals can be detected to some extent continuously even during variable speed reproduction.

In one embodiment of the present invention, the inner code adjacent on the track contains the main component of the small block at the adjacent position on the screen. Since the number of inner codes detected as a result is the number of small blocks that are continuous on the screen as it is, mosaic formation on the screen can be prevented, and a variable-speed reproduction screen that is visually easy to see can be obtained.

The above is the outline of the present invention.

In general, in a digital VTR, since the amount of information to be recorded is enormous, data of one screen is divided into a plurality of tracks by a plurality of heads and recorded in consideration of a recording density on a recording medium. A so-called multi-channel / multi-segment recording method is adopted, and a case where the present invention is applied to the method will be described below.

In one embodiment of the present invention, for the sake of simplicity, it is assumed that data for one screen is divided into four tracks and recorded by the head arrangement shown in FIG.

In FIG. 7, a1 and a2 are + azimuth heads, b1 and b2 are-azimuth heads, and a1 and b1
Each time the drum makes one rotation, data for one screen is recorded, with a2 and b2 as pairs. At this time, 1
Screen data is recorded on four tracks as shown in FIG.

An example of the operation of the error correction encoding means 6 and the rearranging means 7 at this time will be described.

As described above, the error correction encoding means 7 constitutes a plurality (M) of error correction blocks. In order to interleave tracks and error correction blocks in a well-balanced manner, each error correction block 7 It is desirable to set M so that the number of inner codes of the correction block and the number of inner codes containing the main components of the small blocks are multiples of four.

Here, the description will be continued assuming that the above condition is satisfied when the number M of error correction blocks is 4. At this time, in each error correction block, as shown in FIG. 5B, the inner codes including the main components of adjacent small blocks on the screen are arranged so as to be different error correction blocks.

Next, the rearrangement means 7 arranges the inner codes including the main components of the adjacent small blocks on the screen so that they are also adjacent on the track. However, the heads of a1 and b1 or the heads of a2 and b2 are arranged. Tracks recorded and reproduced in pairs by the head are considered as one track, and rearranged as shown in FIG.

That is, A1 is set to track a1, A2 is set to track b1, A3 is set to track a1, A4 is set to track b1, A5 is set to track b1, A6 is set to track a1, A7 is set to track b1, and so on. A8 is track a1
The rearrangement is performed so that inner codes including small blocks adjacent to each other on the screen are alternately arranged on the tracks forming a pair in a sequence such as.

Here, the order in which the data of A1 to A4 and the data of A5 to A8 are arranged on the track is changed, for example, because A1, A3, A5, A7.
If the burst errors can be distributed to only two error correction blocks, the A1,
.. Are arranged in the order of A3, A6, A8,... In consideration of the fact that burst errors can be distributed to four error correction blocks.

Of course, contrary to the present embodiment, when constructing an error correction block, the order of A1 to A4 and A5 to A8 may be reversed, and when rearranged on a track, they may be arranged as they are.

At the time of variable-speed reproduction, as shown in FIG. 10, the heads scan substantially the same part of the paired tracks, and therefore, as described above, the heads alternately adjoin the paired tracks on the screen. By rearranging so that inner codes including small blocks to be arranged are arranged, small blocks twice as many as the number of inner codes that can be continuously detected by one head are continuous on the screen. Although the inner code including the main component of the adjacent small block on the screen is arranged so as to be adjacent also on the track, double small blocks can be continuously reproduced.

Therefore, the mosaic on the screen can be avoided more effectively, and a variable-speed reproduction screen which is easy to see visually can be obtained.

As described above, according to the present invention, even for various tape transports, the arrangement according to the related parameters such as the number of heads mounted on the drum and the number of tracks for recording video information of one screen is performed. By performing the replacement, a similar effect can be obtained.

In the embodiment of the present invention, the recording block and the inner code correspond one to one. However, considering the error correction capability, if the code length of the recording block is too long, It may be divided into a plurality of inner codes. Conversely, when the code length of the recording block is short and it is considered disadvantageous in terms of redundancy, a plurality of recording blocks containing the main components of adjacent small blocks on the screen may be combined to form one inner code. Good.

Further, in one embodiment of the present invention, an example in which a predetermined high-efficiency coding efficiency is obtained and a good reproduced image is obtained at the time of variable-speed reproduction has been described for a case where the screen is divided into four equal parts. Conventionally, the means for obtaining high-efficiency coding efficiency and a good variable-speed playback image have been integrally examined, and a compromise between the two was used as a design parameter of the digital VTR system. It is clear that the major feature is that both optimization studies can be performed separately, as shown in (1).

For example, considering a case in which the encoding efficiency is improved as compared with the case where the screen is divided into four equal parts in the above-described embodiment while maintaining the reproduction quality at the time of the variable speed reproduction, a method for improving the efficiency of the high efficiency encoding is as follows. In order to further reduce the information amount deviation, the number of screen divisions can be increased by more than four. Even if the number of screen divisions, that is, the number of small blocks constituting a large block increases, the reproduction image quality at the time of variable-speed reproduction can be maintained by using the method described above.

Therefore, the number of screen divisions, which has been greatly involved in variable-speed reproduction image quality, that is, the number of small blocks constituting a large block can be arbitrarily set independently of the variable-resolution reproduction image quality. Efficiency can be obtained.

[0064]

[0065]

According to the present invention, on can achieve high-density recording by improving the effect of high-efficiency encoding, a video signal of an adjacent block and securely reproduced on the screen even during variable speed reproduction, It is possible to minimize the mosaic of the reproduced video signal, which tends to occur at the time of variable-speed reproduction, and to obtain a good reproduced image which is visually easy to see. In particular, according to the present invention,
By storing information that could not be stored in one recording block in a free area of another recording block and recording and reproducing it, efficient high-density recording and reproduction can be performed by effectively utilizing the free area, and the code amount Even when a video signal having many blocks is recorded and reproduced, the deterioration of the video signal can be suppressed as much as possible.

[0066]

[0067]

[0068]

[0069]

[0070]

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of an apparatus for digitally recording and reproducing a video signal according to the present invention.

FIG. 2 is an explanatory diagram of a large block configuration of a large block unit in FIG. 1;

FIG. 3 is an explanatory diagram of a fixed-length block configuration of a variable-length encoding unit in FIG. 1;

FIG. 4 is an explanatory diagram of a recording block configuration of a recording blocking unit of FIG. 1;

FIG. 5 is an explanatory diagram of the operation of the error correction encoding means of FIG. 1;

FIG. 6 is an explanatory diagram showing a head locus at the time of high-speed reproduction of the apparatus of FIG. 1;

FIG. 7 is an explanatory diagram showing an example of an arrangement of heads for channel division recording in the apparatus of FIG. 1;

FIG. 8 is an explanatory diagram showing an example of a tape format at the time of channel division recording of the apparatus of FIG. 1;

FIG. 9 is an explanatory view showing an arrangement on a track at the time of channel division recording of the apparatus of FIG. 1;

FIG. 10 is an explanatory diagram showing a head locus at the time of high-speed reproduction at the time of channel division recording of the apparatus of FIG.

FIG. 11 is a schematic configuration diagram of a conventional digital VTR.

FIG. 12 is an operation explanatory diagram of the digital VTR of FIG. 11;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Small block means 2 Large block means 3 Orthogonal transformation means 4 Variable length coding means 5 Blocking means for recording 6 Error correction coding means 7 Rearrangement means 8 Recording medium 9 Reverse rearrangement means 10 Error correction decoding means 11 Recording block decomposing means 12 First modifying means 13 Inverse variable length decoding means 14 Inverse orthogonal transform means 15 Second modifying means 16 Large block decomposing means 17 Small block decomposing means

Claims (2)

(57) [Claims] 1. An apparatus for digitally recording a video signal, comprising: a small block forming means for collecting a plurality of sample values to form a small block; and a large block collecting a plurality of small blocks obtained by said small block forming means. Means for forming a fixed-length block by controlling the code amount so that the total code length of the small blocks included in the large block is constant ; and The small blocks that make up the fixed-length block
And means for dividing the plurality of recording blocks of a fixed length equal to the block, and recording block processing means for recording on a recording medium by performing the rearranging of the recording block, the upper Kitai blocking means in each other constitute a large block of a plurality of small blocks located apart on the screen, by a means for dividing the upper Symbol fixed length blocks, each small block
In order from the information important for decoding
Stores in the recording block, and stores one record for information that could not be stored in the block of the empty area of another recording block, in the above type recording block processing means, the main small blocks adjacent on the screen as the recording block containing the component are adjacent even on the recording medium, the digital recording apparatus of a video signal, characterized in that Ru rearranges the recording blocks. 2. A digital signal reproducing apparatus for reproducing an original video signal from a signal on a recording medium recorded by the digital signal recording apparatus according to claim 1, wherein the digital signal is detected from the recording medium. Means for reconstructing the original recording block from the signal to reconstruct the original fixed-length block; means for decoding the reconstructed fixed-length block to reconstruct the original large block; Means for restoring the sample values included in the original small block from the original large block to a position corresponding to the screen to obtain a reproduced image, wherein the means for reconstructing the original fixed-length block includes a fixed-length block at the time of recording. In order to collect the recording blocks corresponding to the small blocks collected to compose the blocks, rearrangement is performed in the reverse order of the recording so that the recording blocks corresponding to the small blocks are collected. Digital reproducing apparatus of a video signal, characterized in that to reconstruct a fixed length block by returning the information stored in the A to the original recording block.