JPH07288772A - Method and device for recording and reproducing digital picture signal - Google Patents

Abstract

PURPOSE:To obtain a reproduced picture of high quality in the case of not only a preliminarily determined limited multiple speed but also many continuously changing multiple speeds with respect to the digital VTR which records and reproduces the digital picture signal compressed by high efficiency encoding. CONSTITUTION:Data for special reproducing is continuously recorded on adjacent tracks (9 tracks in the figure), with the same recording pattern, which the reproducing head traverses at a maximum multiple speed (9-fold speed in the figure) for special reproducing, with the same recording pattern, and thereby, all multiple speeds for special reproducing to the maximum multiple speed (continuous multiple speeds from 2-fold speed to 9-fold speed in the figure) can be selected, and pictures of the same quality are reproduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for recording / reproducing a digital image signal for recording / reproducing a digital image signal compressed by high efficiency coding.

[0002]

2. Description of the Related Art In recent years, digital recording of images has been studied and put into practical use.

In digital recording, if the image is digitized as it is, the amount of information is too large, and recording and reproducing the signal requires a high running cost. In order to solve this problem, the international standard MPEG
(Motion Picture Expert Group),
High-efficiency coding using correlation is performed.

However, the helical scan type magnetic recording / reproducing apparatus (VT) equipped with a rotary drum head for digital image data whose information amount has been reduced by the high efficiency encoding.
In the case of so-called special reproduction in which recording is performed on the magnetic tape in R) and reproduction is performed while the magnetic tape is running at a speed different from that at the time of recording, the tape feed speed is changed so that the reproducing head runs across multiple tracks. become,
The image data will be obtained intermittently. This means that there is a lack of data continuity. Therefore, when performing high-efficiency coding that uses the correlation of image data and recording it on tape, during special playback, variable-speed playback of data is performed. Will be extremely difficult.

In order to overcome such a drawback, there is known a method of limiting a certain speed number for performing special reproduction and arranging data for special reproduction at a reproducible track position by a reproduction head during special reproduction. Known as technology. As such a known example, there is JP-A-4-87485.

According to Japanese Patent Laid-Open No. 4-87485, important data for decoding a digital image signal compressed by high-efficiency coding, for example, coefficient data of direct current (DC) component in DCT (discrete cosine transform) During special playback in which the tape is run at a speed that is a predetermined times the normal tape speed,
Record on the track where it is likely to be played. By recording important data like this,
During special reproduction in which the vehicle travels at a predetermined speed, important data is correctly reproduced at a high rate, so that the quality of the reproduced image can be improved.

By the way, in the above-mentioned conventional technique, since important data is recorded in a portion which is likely to be reproduced at the time of the special reproduction of the predetermined times, the quality of the reproduced image is improved at the predetermined speed of the predetermined times. Although it can be obtained, there is a problem that the rate of correct reproduction is not always high for other double speeds.

[0008]

As described above, in the conventional digital VTR, important data is recorded in a portion which is likely to be reproduced at the time of special reproduction at a predetermined speed. In terms of the number, the quality of the reproduced image can be obtained, but there is a problem that the reproduction is not always performed correctly with respect to other double speed numbers.

In view of the above problems, the present invention is not limited to a predetermined limited number of double speeds but continuously changes in a digital VTR for recording / reproducing a digital image signal compressed by high efficiency coding. It is an object of the present invention to provide a digital image signal recording / reproducing method and device capable of obtaining a high quality reproduced image for a large number of double speeds.

[0010]

The invention according to claim 1 is
In a digital image signal recording method, a digital image signal compressed by high-efficiency encoding is recorded on a belt-shaped recording medium traveling at a predetermined speed using a rotary drum head so as to form tracks sequentially obliquely to the traveling direction. ,
Important data is derived from the high-efficiency coded digital signal when the signal is decoded, and this data is recorded on the band-shaped recording medium continuously in a predetermined number of tracks in the same recording pattern. It is characterized by

According to a second aspect of the present invention, a digital image signal compressed by high efficiency coding is sequentially formed on a belt-shaped recording medium running at a predetermined speed using a rotary drum head, obliquely to the running direction. In the recording / reproducing method of a digital image signal to be recorded and reproduced as described above, important data is derived when the signal is decoded from the high-efficiency coded digital signal, and this data is recorded in the strip recording medium. When reproducing while traveling at a speed higher than the speed, at least the same number of tracks as the number of tracks traversed by the rotary drum head are continuously recorded with the same recording pattern.

According to a third aspect of the present invention, in the digital image signal recording / reproducing method according to the second aspect, the data is within one frame or one field of the digital image signal compressed by the high efficiency encoding. It is characterized in that it is derived for each frame or field from the digital image signal compressed by.

According to a fourth aspect of the present invention, in the digital image signal recording / reproducing method according to the second aspect, the data is in one frame or one field of the digital image signal compressed by the high efficiency encoding. It is characterized in that it is derived in block units from a digital image signal compressed by.

According to a fifth aspect of the present invention, a digital image signal compressed by high-efficiency coding is sequentially formed on a belt-shaped recording medium running at a predetermined speed using a rotary drum head, obliquely to the running direction. In a recording / reproducing apparatus for a digital image signal capable of recording and reproducing as described above, a data creating means for deriving data important in decoding the signal from the high efficiency coded digital signal in frame or field units And a memory means for storing the important data, the high efficiency coded digital signal is divided into recordable units on the band-shaped recording medium, and the important data from the memory means is a unit frame for high efficiency coding. Formatting means for outputting side by side so as to be arranged at a predetermined position in the configuration or unit field configuration, Recording means for recording the output from the formatting means by the rotating drum head, and reproducing means for reproducing the recording signal by the rotating drum head while traveling the belt-shaped recording medium at a speed according to a traveling control signal. And a decoding means for decoding the signal from the inverse formatting means, wherein the traveling speed of the strip recording medium at the time of reproduction is higher than that at the time of recording. And a decoding means for decoding and outputting only important data in the reproduction signal at a high speed.

According to a sixth aspect of the present invention, in the recording / reproducing method of the digital image signal according to the fifth aspect, the formatting means divides the important data into a plurality of pieces on the screen, and each divided portion is a unit. It is characterized in that it is configured to be continuously assigned to a frame configuration or each unit field configuration.

[0016]

According to the first aspect of the present invention, when the important data for decoding is recorded on the strip-shaped recording medium, the same recording pattern is continuously recorded on the adjacent tracks. Even when the vehicle travels across a plurality of tracks, it is possible to pick up and reproduce one pattern of data at the double speed at that time.

According to the second aspect of the present invention, when the same recording pattern is continuously recorded on the adjacent tracks, the number of tracks crossed by at least the same number as the number of tracks traversed by the reproducing head at the maximum double speed. Since the data is recorded, the data for one pattern can be played back up to the maximum speed number that you want to play back at double speed, so you can select the speed number for double speed playback up to that maximum speed number and play back the same quality image. It becomes possible.

According to the fifth aspect of the invention, it is possible to realize a digital VTR capable of performing special reproduction in all stages up to a predetermined maximum speed number.

[0019]

EXAMPLES Examples will be described with reference to the drawings. Before describing the method for recording / reproducing a digital image signal according to an embodiment of the present invention with reference to FIGS. 1 and 2, the structure of an image frame used in the embodiment of the present invention and the contents thereof will be described with reference to FIGS. 3 and 4. A method of segmenting an I frame will be described.

FIG. 3 shows the structure of an image frame used in the embodiment of the present invention. In FIG. 3, there are four I-frames 11 for which only intra-frame compression is performed, and three P-frames 12, 13, and 14 for which intra-frame compression or inter-frame compression is performed. 1 GOP in frame (Group of picture in MPEG)
, And this GOP is repeated. If one frame consists of 10 tracks on the magnetic tape, 1
GOP corresponds to 40 tracks.

FIG. 4 shows the segment structure of the I frame shown in FIG.

As shown in FIG. 4, the I frame is vertically divided into 8 equal parts and horizontally divided into 4 equal parts, for a total of 32 equal parts.
Numbers are 7, 8 to 15, 16 to 23, and 24 to 31. If the nth GOP is GOPn, then I of GOPn
The 0 to 7 segment in the frame is the upper 1 / I frame.
8 to 15 segments are the next ¼ of the I frame, 16 to 23 segments are the next ¼ of the I frame, and 24 to 31 segments are the last of the I frame. Each corresponds to 1/4.

FIG. 1 shows a tape format for explaining a recording / reproducing method of a digital image signal according to an embodiment of the present invention.

The tape format shown in FIG. 1 is a tape format in which a recording area for special reproduction data according to the embodiment of the present invention is added, and all double speed numbers from +2 times speed to +9 times speed for this tape format. The locus of the reproducing head when double speed reproduction is performed is shown. Here, a case is shown in which the maximum speed is set to 9 × and 9 tracks are used as the special reproduction data recording area. In the case of helical scan, the track pattern recorded on the tape is formed diagonally with respect to the tape longitudinal direction. However, in the following figures, for simplicity, the track pattern is formed in a direction orthogonal to the tape longitudinal direction. It is described.

In each of the segments 0 to 7 of the I frame of GOPn, the track (40) in which GOPn is recorded has DCT low frequency data of a data amount which can be recorded in 1/8 of one track as special reproduction data. Each track from the 1st track to the 9th track is divided horizontally into 8 equal parts, and 1 is divided into 8 equal parts.
By recording low-frequency data for a segment, I
Data of 8 segments of frames 0 to 7 is recorded on one track, and low frequency data of the same 8 segments of 0 to 7 is repeatedly recorded on each of the remaining 8 tracks as special reproduction data. . Similarly, in the case of GOPn + 1, the low-frequency data from 8 to 15 of the I-frame segment is specially recorded on each of the first to ninth tracks of the track (40 tracks) on which GOPn + 1 is recorded. Repeatedly recorded as reproduction data, and if GOPn + 2, GOPn + 2
Is recorded on each of the first to ninth tracks (40 tracks).
The low-frequency data of 16 to 23 of the frame segment is repeatedly recorded as special reproduction data, and in the case of GOPn + 3, each of the first to ninth tracks (40 tracks) in which GOPn + 3 is recorded. 24 to 31 of the I frame segment on the track
The low-frequency data up to is repeatedly recorded as special playback data.

When recording is performed in this manner, as shown in the locus of the reproducing head in FIG. 1, the data for one track of the special reproduction data recording area is traced by the head at each of the double speed numbers from +2 to +9. That is, I
(1/4 of the frame data) can be played without fail, and GOPn
, GOPn + 1, GOPn + 2, GOPn + 3, 1/4 of the I frame, that is, 1/4 of the screen is updated.

Further, FIG. 2A shows +2 for GOPn.
The head locus at the time of forward reproduction from double speed to +9 times speed is shown. Similarly, FIG. 2B shows -1 times speed to GOPn.
The head locus at the time of reverse reproduction at −7 × speed is shown. The same head locus is obtained for GOPn + 1, GOPn + 2, and GOPn + 3.

In this way, at the time of special reproduction from −7 × speed to + 9 × speed, by tracing each special reproduction data recording area (each consisting of 9 tracks) of four GOPs, an I frame is obtained for each GOP. 1/4 of the screen, that is, 1/4 of the screen is updated, and one screen of I frames is reproduced by four GOPs.

In the above embodiment, each GOP is provided with a data recording area for special reproduction for 9 tracks so that the maximum speed is 9 times, and the same data (DCT low frequency data) is recorded on all 9 tracks. However, the maximum double speed number can be further increased by further adding the special reproduction data recording area track to each GOP and recording the same data (DCT low-frequency data) on the additional track.

Next, the structure of the digital VTR for realizing the recording / reproducing method of the embodiment shown in FIG. 1 will be described.

FIG. 5 shows a digital VT according to an embodiment of the present invention.
It is a block diagram which shows the structure of R.

In FIG. 5, the A / D converter 80 converts the transmitted analog video signal to be recorded into a digital video signal and supplies it to the encoder 81. The encoder 81 forms the data of the GOP structure of FIG. 3 and DC for the I frame data in units of 8 × 8 pixels.
T (discrete cosine transform) is performed, quantization is performed and variable length coding is performed, and then output. For the P frame data, the difference between the data of the previous frame data and the data of the previous frame is compared in units of 8 × 8 pixels, and the data with the smaller data amount is selected, DCT is performed, and And output after performing variable length coding. Special reproduction data memory 83
Stores the special reproduction data as described above (FIGS. 1 to 4) in the I-frame data output from the encoder 81, and outputs it to the formatting circuit 82 in consideration of the timing. Formatting circuit 82
Divides the data output from the encoder 81 into units that can be recorded on the tape, and outputs the data from the special reproduction data memory 83 side by side so that they always come before the data of 1 GOP. Error correction circuit (ECC) 84
Outputs an error correction signal added to the data from the formatting circuit 82. The recording / reproducing device 85 is
The data from the error correction circuit 84 is recorded on the tape,
The reproduced data is output to the error correction circuit (ECC-1) 86. Error correction circuit (ECC-1) 86
Corrects an error generated in the tape head system of the data from the recording / reproducing device 85. The inverse formatting circuit 87 restores the data delimiter from the error correction circuit (ECC-1) 86 to the original and outputs it to the decoder 88. In the normal reproduction, the decoder 88 skips the special reproduction data, restores the variable-length encoded data to the original, dequantizes it, and then performs inverse DCT (inverse discrete cosine transform) and outputs it. At the time of special reproduction, only data for special reproduction is subjected to variable-length code decoding, inverse quantization and inverse DCT and output. D
The / A converter 89 converts the digital video signal output from the decoder 88 into an analog video signal.

In the above embodiment, the GOP is constructed in frame units, but it is also possible to construct it in field units in the MPEG standard, in which case the I frame and P frame are I field and P field, respectively.

Next, another embodiment of the present invention will be described with reference to FIGS.

FIG. 8 shows the structure of an image frame according to another embodiment of the present invention.

In FIG. 8, one R block that is only intra-frame compressed, and three S blocks that are intra-frame compressed or inter-frame compressed, for a total of 4 blocks.
One frame is composed of individual pieces. For each frame, the R block is arranged in a horizontally moved state as indicated by reference numerals 51, 52, 53, and 54. Therefore, in 4 frames, all of the screen is once replaced with the data compressed in the frame. . These 4 frames are 1 ROP, 51, 52,
Frames having R blocks at positions 53 and 54 are numbered 1, 2, 3, and 4, respectively.

FIG. 6 is a tape format for explaining a recording / reproducing method of a digital image signal according to another embodiment of the present invention.

The tape format shown in FIG. 6 is a tape format in which a special reproduction data recording area according to the embodiment of the present invention is added, and each of the tape formats up to +1, +2, ... The locus of the reproducing head when double speed reproduction is performed is shown. here,
The figure shows the case where the maximum speed is 9 times.

D of the amount of data that can be recorded in one track of the R block of the first frame of ROPn (nth ROP)
The CT low frequency data is repeatedly recorded on each of the first to ninth tracks (40 tracks) on which ROPn is recorded as special reproduction data. Similarly, in the case of ROPn + 1, RO
Tracks with Pn + 1 recorded (40 tracks)
In the case of ROPn + 2, the low-frequency data of the R block of the second frame is repeatedly recorded as special reproduction data on each of the first to ninth tracks of
In the case of ROPn + 3, the low-frequency data of the R block of the third frame is repeatedly recorded as the special reproduction data on each of the first to ninth tracks of the track on which ROPn + 2 is recorded (there are 40 tracks). , ROPn + 3 is recorded (40 tracks are included), the low frequency data of the R block of the fourth frame is repeatedly recorded as the special reproduction data on each of the first to ninth tracks.

When recording is performed in this manner, as shown in the locus of the reproducing head of FIG. 6, data of one track in the special reproduction data recording area is recorded by tracing the head at each of the multiple speed numbers from + 2 × to + 9 ×. That is, 1
(1/4 of the frame data) can be played without fail, and ROPn
, ROPn + 1, ROPn + 2, ROPn + 3, R blocks of one frame, that is, 1/4 of the screen are updated.

Further, FIG. 7A shows +2 for ROPn.
FIG. 7 (b) shows the head locus at the time of normal direction reproduction from double speed to +9 times speed. Similarly, FIG.
The head locus at the time of reverse reproduction at −7 × speed is shown. R
Similar head loci are obtained for OPn + 1, ROPn + 2, and ROPn + 3.

In this way, during special reproduction from −7 × speed to + 9 × speed, by tracing each special reproduction data recording area (each consisting of 9 tracks) of four ROPs, one frame is formed for each ROP. Each R block, that is, 1/4 of the screen is updated, and one screen by 4 R blocks is reproduced by 4 ROPs.

In the above embodiment, each ROP is provided with a special reproduction data recording area for 9 tracks so that the maximum speed is set to 9 times, and the same data (DCT low frequency data) is recorded on all 9 tracks. However, the maximum double speed number can be further increased by further adding the special reproduction data recording area track to each ROP and recording the same data (DCT low-frequency data) on the additional track.

Next, the structure of the digital VTR for implementing the recording / reproducing method of the embodiment shown in FIG. 6 will be described.

FIG. 9 shows a digital V of another embodiment of the present invention.
It is a block diagram which shows the structure of TR. Digital VTR
Since the configuration is the same as that in FIG. 5, the same parts as those in FIG.

In FIG. 9, the A / D converter 80 converts the transmitted analog video signal to be recorded into a digital video signal and supplies it to the encoder 81A. The encoder 81A forms the data of the ROP structure of FIG. 8 and performs DCT (discrete cosine transform) on the data of the R block in units of 8 × 8 pixels, quantizes and performs variable length coding, and then outputs. For the data of the S block, the difference between the data of the previous R block and the data of the previous R block is compared with the data of the previous R block in 8 × 8 pixel units, and the smaller data amount is selected, and DCT is performed. It is output after being quantized and variable-length coded. The special reproduction data memory 83 stores the special reproduction data as described above (FIGS. 6 to 8) for the data of the R block output from the encoder 81A, and outputs it to the formatting circuit 82 in consideration of the timing. The formatting circuit 82 divides the data output from the encoder 81A into units that can be recorded on the tape, and outputs the data from the special reproduction data memory 83 side by side so as to always come before the data of 1 ROP. Error correction circuit (EC
C) 84 adds an error correction signal to the data from the formatting circuit 82 and outputs it. The recording / reproducing device 85 records the data from the error correction circuit 84 on the tape, and outputs the reproduced data to the error correction circuit (ECC-1) 86. Error correction circuit (ECC-
1) 86 corrects an error occurring in the tape head system of the data from the recording / reproducing device 85. The inverse formatting circuit 87 restores the data delimiter from the error correction circuit (ECC-1) 86 to the original and outputs it to the decoder 88. In the normal reproduction, the decoder 88 skips the special reproduction data, restores the variable-length coded data to the original, dequantizes, and then inverse DCT (inverse discrete cosine transform).
And output. At the time of special reproduction, only data for special reproduction is subjected to variable-length code decoding, inverse quantization and inverse DCT and output. The D / A converter 89 converts the digital video signal output from the decoder 88 into an analog video signal.

In the above-mentioned embodiment, the ROP is constructed in frame units, but it may be constructed in field units.

In the embodiment described above, the case has been described in which special reproduction data is derived from a high-efficiency coded digital signal and recorded at a specific portion of the track, but the present invention is limited to special reproduction data. Instead, it can be applied to the case where important data is derived from a high-efficiency coded digital signal when the signal is decoded and the data is recorded at a specific portion of the track.

The present invention is not limited to the above-mentioned embodiments, and, for example, the number of tracks for recording special reproduction data, the number of frames constituting GOP, and RO
The number of frames that make up P, how to divide segments into I frames, how to divide blocks into one frame,
The double speed number of special reproduction can be set appropriately.

[0050]

As described above, according to the present invention, when the important data for decoding is recorded on the band-shaped recording medium, it is recorded on the adjacent tracks continuously with the same recording pattern, so that the special reproduction is performed. Sometimes even when the playhead travels across multiple tracks, the double speed will be 1
It becomes possible to pick up and reproduce the data for the pattern.

Further, when recording the same recording pattern continuously on the adjacent tracks, since the recording is performed over at least the same number of tracks as the reproducing head traverses at the maximum speed, the double speed reproduction is desired. Since one pattern of data can be reproduced up to the maximum double speed number, it is possible to continuously select the double speed number for double speed reproduction up to the maximum double speed number and to reproduce images of the same quality.

[Brief description of drawings]

FIG. 1 is a tape format and +1 for explaining a recording / reproducing method of a digital image signal according to an embodiment of the present invention.
The figure which shows the reproducing head locus at the time of double speed reproduction from double speed to +9 times speed.

FIG. 2 is a diagram for explaining a reproducing head locus during double speed reproduction from −7 × speed to + 9 × speed in the embodiment of FIG.

FIG. 3 is a diagram showing a frame structure of 1 GOP used in an embodiment of the present invention.

FIG. 4 is a diagram showing a state where the I frame in FIG. 3 is divided into segments.

FIG. 5 is a block diagram showing the configuration of a digital VTR according to an embodiment of the present invention.

FIG. 6 is a diagram showing a tape format for explaining a recording / reproducing method of a digital image signal according to another embodiment of the present invention and a reproducing head locus at the time of double speed reproduction from + 1 × to + 9 ×.

FIG. 7 is a diagram for explaining a reproducing head locus during double speed reproduction from −7 × speed to + 9 × speed in the embodiment of FIG. 6;

FIG. 8 is a diagram showing a frame structure of 1 ROP and a block structure in 1 frame used in an embodiment of the present invention.

FIG. 9 is a block diagram showing the configuration of a digital VTR according to another embodiment of the present invention.

[Explanation of symbols]

 1, 2, 3, 4 ... Frame 11 ... I frame 51, 52, 53, 54 ... R block 81, 81A ... Encoder 82 ... Formatting circuit 83 ... Special playback data memory 85 ... Recording / playback device 87 ... Reverse formatting circuit 88 ... Decoder

Claims (6)

[Claims] 1. A digital image in which a digital image signal compressed by high-efficiency coding is recorded on a belt-shaped recording medium running at a predetermined speed using a rotary drum head so that tracks are sequentially formed obliquely with respect to the running direction. In the signal recording method, important data is derived from the high-efficiency coded digital signal when the signal is decoded, and this data is continuously recorded on the band-shaped recording medium in a predetermined number of tracks and with the same recording pattern. A method for recording a digital image signal, characterized in that the recording is carried out according to. 2. A digital image signal compressed by high-efficiency encoding is recorded on a belt-shaped recording medium running at a predetermined speed using a rotary drum head so as to form tracks sequentially obliquely to the running direction and reproduced. In the method of recording / reproducing a digital image signal, important data for deriving the high-efficiency coded digital signal is derived, and the data is run at a speed higher than that at the time of recording on the strip recording medium. A recording / reproducing method of a digital image signal, wherein at the same number of tracks as the number of tracks traversed by the rotary drum head, the same recording pattern is recorded continuously when reproducing. 3. The data is derived on a frame or field basis from a digital image signal compressed within one frame or one field of the digital image signal compressed by the high efficiency coding. The method for recording / reproducing a digital image signal according to claim 2, wherein 4. The data is derived in block units from a digital image signal compressed in one frame or one field of the digital image signal compressed by the high efficiency coding. The method of recording and reproducing a digital image signal according to claim 2. 5. A digital image signal compressed by high-efficiency encoding is recorded on a belt-shaped recording medium running at a predetermined speed using a rotary drum head so as to form tracks sequentially obliquely to the running direction, and reproduced. In a recording / reproducing apparatus of a digital image signal capable of performing the above, a data creating means for deriving data important in decoding the signal from the high efficiency coded digital signal in frame or field units, and the important data Memory means for storing the high-efficiency coded digital signal is divided into recordable units on the band-shaped recording medium, and the important data from the memory means has a unit frame structure or a unit field structure for high-efficiency coding. And a formatting means for outputting the data side by side so as to be arranged at a predetermined position in the Recording means for recording the output from the recording means by the rotary drum head; reproducing means for reproducing the recording signal by the rotary drum head while traveling the belt-shaped recording medium at a speed according to a traveling control signal; And a decoding means for decoding the signal from the inverse formatting means, wherein the traveling speed of the strip recording medium during reproduction is faster than during recording. A recording / reproducing apparatus for a digital image signal, comprising: a decoding means for decoding and outputting only important data in the reproduced signal at a speed. 6. The formatting means is configured to divide the important data into a plurality of pieces on a screen and continuously divide each divided portion into each unit frame structure or each unit field structure. The method of recording and reproducing a digital image signal according to claim 5.