JPH04332283A - Recording and reproducing device for video signal - Google Patents

Abstract

PURPOSE:To time-sequentially obtain a reproduced picture in a natural flow at the time of search by separating coded data into basic data and additional data, and obtaining a search picture by the decoding processing of only the basic data. CONSTITUTION:A data separating circuit 4 divides the coded data high efficiently encoded by encoding circuit 3 into the basic data indicating the basic characteristic of the picture, and the additional data indicating the fine information. When a high efficient encoding system is, for example, the transformation- encoding system of a DCT or the like, the DC components of a DCT factor are used as the basic data, and the other DCT factors are used as the additional data. In this case, the additional data and the basic data are respectively recorded through recording heads 5 and 6 on a herical track and a linear track on a recording medium 9. At the time of the search, only the basic data reproduced by a fixed reproduction head 8 are used in order to obtain the reproduced picture. Thus, even at the time of the search, the entire basic data can be reproduced so that the resolution of a time direction can be improved.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording and reproducing apparatus for recording video signals, and more particularly to a recording and reproducing apparatus for video signals that can obtain stable reproduced images when recording and reproducing video signals with high efficiency encoding. It is.

0002

[Prior Art] With the digitization of video/audio equipment and transmission lines, research into high-efficiency encoding methods for efficiently compressing data has been actively conducted. However, using this technology,
Studies are underway to reduce the amount of data recorded and improve the efficiency of tape usage.

[0003] In general, high-efficiency encoding reduces the amount of data by removing redundancy in two-dimensional space and redundancy between frames using image correlation, and extracts image features. It consists of a step and a step of performing adaptive quantization on its features.

For example, two-dimensional D
CT (Discrete Cosine Transf.
orm), first convert the image data into N×M(N,
(M is a positive integer) pixels are divided into subblocks, and DCT is applied to each subblock to obtain DCT coefficients. Then, the DCT coefficients representing the DC and low frequency components of the image are linearly quantized as they are, or quantized after being subjected to some weighting. DC representing high frequency components of the image
Regarding the T coefficient, weighting such as 1/2 is performed to reduce the coefficient value and quantization is performed. And when quantizing,
One possible method is to reduce the total amount of data within a subblock by allocating as few bits as possible to DCT coefficients representing high frequency components.

[0005]

[Problem to be solved by the invention] High-efficiency encoding is a method that can efficiently reduce the amount of data in an information source, but
Various problems occur when recording data encoded with high efficiency.

For example, in a VTR, playback S
Not only is the NR poor, but dropouts occur, resulting in a high code error rate, and even if an error correction code is added for recording, it is difficult to ensure a sufficient data error rate after error correction processing. If there is an error in the data, the data may not be captured or the wrong video signal may be decoded.

In particular, when a video signal is recorded and reproduced with high efficiency encoding, the range of information sources represented by erroneous data becomes wider than when high efficiency encoding is not performed. The above problem occurs. In addition, if there is an error in the data that indicates the basic structure of the image among the highly efficiently encoded data, the effect on the quality deterioration of the reproduced image will be greater than if there is an error in the detailed data. Become.

[0008] Furthermore, searching is essential in a VTR, and it is necessary to decode a search image from pieces of data that are played back across video tracks. However, since data is reproduced in pieces during a search, only the inner correction code can be used, so the correction ability is drastically reduced compared to normal reproduction, the reproduction output becomes unstable, and the reproduction error rate increases. Therefore, the error rate after correction becomes higher than in normal reproduction, and the problems of error propagation and erroneous decoding of video signals become serious.

[0009]Furthermore, if an attempt is made to achieve an ultra-high-speed search that is ten times to several tens of times faster, the amount of playback data that can be acquired within one frame will be small, and the acquired data will span several frames or even tens of frames. Therefore, even if the acquired data is output sequentially, only a part of the screen will be updated, and the rest will remain the same as the data from many frames ago, resulting in a very unnatural result. .

[0010] In view of the above points, the present invention makes it possible to obtain a stable reproduced image when recording and reproducing data of a video signal encoded with high efficiency, and to obtain a reproduced image that has a more natural flow in chronological order during a search. The purpose is to provide a recording/playback device.

[0011]

[Means for Solving the Problems] The present invention solves the above-mentioned problems, and includes a means for highly efficiently encoding a video signal to obtain encoded data, and a means for obtaining encoded data from the encoded data. means for separating basic data indicating the basic configuration of the video signal and additional data indicating detailed information of the video signal; and a means for separating the additional data of the video signal and a part of the basic data or only the additional data into a recording medium using a rotating head cylinder. means for helically scanning and recording on the recording medium; means for recording part or all of the basic data of the video signal in the longitudinal direction on the recording medium using a fixed head;
The video signal recording and reproducing apparatus is characterized in that it includes at least means for decoding a search image from reproduction basic data reproduced from a recording medium using the fixed head.

0012

[Operation] With the above-described structure, the present invention separates coded data encoded with high efficiency into basic data indicating the basic structure of a video signal and additional data indicating detailed information, and divides all or part of the basic data into is recorded in the longitudinal direction of the recording medium using a fixed head, so even when searching, all the basic data recorded in the longitudinal direction of the recording medium can be reproduced, and the data length is fixed. Since the search image can be obtained by decoding only the basic data, processing is simplified, and a stable reproduced image can be obtained when searching, where the error rate of the reproduced signal increases, and when there is fast movement or scene changes. The search image becomes easier to recognize even if

[0013]

[Embodiment] (FIG. 1) is a signal processing block diagram of a video signal recording/reproducing apparatus in an embodiment of the present invention, (FIG. 2) is a recording track pattern diagram in this embodiment, and (FIG. 3) is a head at the time of search. Head trajectory pattern diagram traced by (
FIG. 4) is a waveform diagram showing a reproduction envelope during a search.

In this embodiment, in order to simplify the explanation, it is assumed that two recording heads and two reproducing heads are mounted on the rotating cylinder, and the recording heads and the reproducing heads have different azimuth angles and are 180 degrees relative to each other. The rotary cylinder is rotated at the frame frequency (that is, one frame recording track by helical scanning consists of two tracks), and one field of video signal data is digitally recorded with one recording head. This will be explained using an example. Furthermore, the processing of error correction codes for digital recording and the processing of switching between the recording head and the reproducing head on the rotary cylinder will be omitted, and a case will be described in which only the luminance signal is recorded as the video signal.

In FIG. 1, 1 is an input terminal into which a video signal is input, and 2 is an A/D for A/D converting the video signal.
Converter, 3 is an encoding circuit for highly efficient encoding of the video signal converted into the digital signal, and 4 is an encoding circuit for converting the encoded data into basic data representing the basic characteristics of the image and additional data representing detailed information. 5 is a recording head on a rotating cylinder; 6 is a fixed recording head; 7 is a data separation circuit for dividing data;
1 is a playback head on a rotating cylinder; 8 is a fixed playback head; 9 is a recording medium; 10 is a data synthesis circuit that rearranges the playback data into a combination of basic data and additional data representing information on one area of the screen; 11 12 is a decoding circuit that decodes high-efficiency encoded reproduced data; 12 is a basic data decoding circuit that decodes only basic data to obtain a reproduced image; 13;
a changeover switch 1 for switching between the output from the decoding circuit 11 and the output from the basic data decoding circuit 12;
4 is a D/A converter for D/A converting playback data, and 15 is an output terminal.

In FIG. 2, 16 is a helical track for recording additional data, and 17 is a linear track for recording basic data.

The operation of the recording/reproducing apparatus of this embodiment configured as described above will be explained. A video signal input from an input terminal 1 is A/D converted by an A/D converter 2 and input to an encoding circuit 3. In the encoding circuit 3, the video data is temporarily stored in a memory, read out from the memory in a predetermined sequence, and subjected to high-efficiency encoding processing to reduce the amount of data to be recorded. The data separation circuit 4 divides the encoded data thus encoded into basic data representing the basic features of the image and additional data representing detailed information.

As a high-efficiency encoding method, for example, dynamic range encoding is used to convert video data into m×
The dynamic range of the data contained in this block is determined by dividing it into every n pixels, and the dynamic range is requantized using a smaller number of bits, so in this case, the minimum value and dynamic range for each block are calculated. , or something similar thereto is used as basic data, and quantized data requantized for each pixel is used as additional data.

For example, in the case of transform coding such as DCT, an n×n data matrix obtained by dividing video data into subblocks for each n×n pixel on the screen and an n×n DC
Frequency conversion is performed by calculation with the T-transform matrix, and the DCT coefficient that is the result of this calculation is multiplied by a weighting coefficient whose value is smaller for the DCT coefficient of the higher frequency component to reduce the coefficient value and reduce the number of bits to be allocated. One possible method is to reduce the total amount of data, but in this case, D
The DC component of the CT coefficient is used as the basic data, and the other DC
The T coefficient is used as additional data.

These additional data and basic data are recorded on the recording medium 9 shown in FIG. 2 on the helical track 16 via the recording head 5 and on the linear track 17 via the recording head 6, respectively. In this embodiment, it is assumed that all of the basic data is recorded on the linear track 17.

Next, the reproduction process will be explained. During normal playback, from the recording medium 9 to the playback head 7 on the rotating cylinder.
The reproduction signal reproduced by the fixed reproduction head 8 and the reproduction signal reproduced by the fixed reproduction head 8 are processed in the data synthesis circuit 10 in the opposite manner to that performed in the data separation circuit 4, and the information of the same block on the screen is processed. The decoding circuit 11 decodes the reproduced signal from the basic data and additional data. This decoded data is transferred to the D/A converter 14 via the changeover switch 13.
is converted to an analog signal and output as a playback signal to terminal 1.
Output from 5.

Next, the case at the time of search will be explained. (FIG. 3) shows an example of a head trajectory that a reproducing head traces on a recording medium during a search, where 18 is the trajectory of the reproducing head 7 on the rotating cylinder, and 19 is the trajectory of the fixed reproducing head 8. (FIG. 4) shows examples of envelope waveforms from each of the playback heads. 20 is a first playback head output placed on the rotating cylinder; 21 is a second playback head placed opposite to the first playback head on the rotating cylinder;
22 is a fixed playback head output.

[0023] At the time of search, as shown in Fig. 4,
The envelope generated by the reproducing head 7 is intermittent due to the azimuth loss of the head, and the data is reproduced in pieces. Therefore, since only the inner correction code can be used for error correction, the correction ability is drastically reduced compared to normal reproduction. Furthermore, the reproduction output becomes unstable and the reproduction error rate itself increases. Therefore, the error rate after correction becomes extremely large compared to normal playback, and the problems of error propagation and erroneous decoding of video signals become serious.

[0024] Furthermore, if an attempt is made to achieve an ultra-high-speed search that is ten times to several tens of times faster, only a small amount of playback data can be acquired within one frame, and the acquired data must be sequentially output. However, only a portion of the screen is updated, and the rest of the screen remains the same as the previous data, resulting in an extremely unnatural appearance.

Therefore, during a search, only the basic data reproduced by the fixed reproduction head 8 is used to obtain a reproduced video. That is, the basic data decoding circuit 12 calculates the average value of the obtained basic data from the minimum value and dynamic range of each block, which is the basic data, in the case of dynamic range coding, for example, as high-efficiency coding. A mosaic reproduced signal is decoded, and in the case of transform encoding such as DCT, the mosaic reproduced signal is decoded from the DC component of the DCT coefficient. The decoded playback signal is passed through the changeover switch 13, converted to an analog signal by the D/A converter 14, and outputted to the output terminal 15.

As described above, according to this embodiment, a video signal is encoded with high efficiency, basic data indicating the basic structure of the image and additional data indicating detailed information are separated, and the basic data is recorded on a recording medium using a fixed head. By recording on a linear track in the longitudinal direction, all basic data can be reproduced without interruption even during a search.If decoding is performed using only basic data, the resolution in the spatial frequency direction of the image will drop, but On the other hand, resolution in the time direction improves, making it easier to recognize search images even when there is rapid movement or scene changes.

[0027] In particular, even in ultra-high-speed searches of the order of ten to several tens of times, the ease of recognition of the searched image remains the same.

When variable-length processing is used for high-efficiency encoding in order to perform more efficient encoding, fixed-length encoding is performed on the basic data and variable-length encoding is performed on the additional data. Although variable length processing is used as an efficient encoding method, the data length of the basic data part is fixed, improving error propagation characteristics for basic data, which is important for decoding highly efficient encoded data. It is possible to obtain stable reproduced images.

Furthermore, even if the data has been highly efficiently encoded including variable length processing, the search image is decoded using only the fixed length playback basic data at the time of search, so the processing becomes very simple and the playback data Even during a search when the data becomes fragmented, the correction ability is drastically reduced, and the code error rate increases, errors will not propagate to the basic data of other blocks. Compared to the case of recording on a track, the data acquisition rate is equivalently improved and a more stable search image can be obtained.

Although this embodiment does not specifically mention how to determine the number of recording heads and reproducing heads, their mounting positions, the number of revolutions of the rotating cylinder, etc., the effects of this embodiment remain unchanged in any case. do not have.

Further, in this embodiment, all of the basic data is recorded on the linear track, but a part of the basic data may be recorded on the linear track, and the remaining basic data may be recorded on the helical track. For example, in the case of DCT, DC
The DC component of the T coefficient and some coefficients representing low frequencies among the DCT coefficients representing the AC component are fixed-length encoded as basic data, the other DCT coefficients are variable-length encoded as additional data, During recording, only the DC component may be recorded on the linear track.

Furthermore, when the amount of recordable data on the linear track is smaller than the amount of basic data per frame, the basic data to be recorded on the linear track is N (N=1, 2, . . . ) of the video signal. ) Data for one frame may be recorded per frame, and the remaining basic data may be recorded on a helical track. In this case, the temporal resolution of the reproduced image during the search is reduced, but since the reproduced image is originally fast-forwarded and moves faster than usual, there is no visual problem even if the number of frames is reduced. Conversely, by reducing the number of frames, the recording data rate can be lowered, and by increasing the recording wavelength, the data error rate can be improved. Furthermore, the frequency characteristics of the fixed head can be improved by using a narrower band.

Furthermore, basic data encoding methods range from simple linear quantization to DPCM (Different
ial Pulse Code Modulat
It may be of any type up to bit reduction such as ion). Furthermore, even if the basic data is variable-length coded, the effect of improving image quality during search remains the same.

Furthermore, when searching, decoding is performed using only the basic data, but additional data that can be reproduced without data errors may be used together with the basic data for image decoding.

Furthermore, the linear track on which basic data is recorded may be multiplexed on the control track on which frame pulse signals are recorded in a general VTR. When the multiplexing method is frequency multiplexing, the two signal bands are significantly different, so they can be easily separated using a filter. The frame pulse may be digitally coded and time division multiplexed with the basic data.

Although the basic data decoding circuit 12 is provided in this embodiment for the sake of explanation, it goes without saying that this can be included in the decoding circuit 11. Further, the image at the time of search becomes a mosaic image, but as long as the encoded block is small, image quality sufficient to withstand the search can be ensured, so this does not pose much of a problem.

[0037]

As explained above, according to the present invention, encoded data obtained by highly efficient encoding of a video signal can be separated into basic data indicating the basic structure of the video signal and additional data indicating detailed information. However, all or part of the basic data is recorded in the longitudinal direction of the recording medium using a fixed head, so even when searching, all the basic data recorded in the longitudinal direction of the recording medium can be reproduced. Since the search image can be obtained by decoding only the basic data whose data length is fixed, the processing is simplified and it is possible to obtain a stable reproduced image during search when the error rate of the reproduced signal increases. This makes it easier to recognize the search image even when there is rapid movement or scene changes, and its practical effects are extremely large.

[Brief explanation of drawings]

FIG. 1 is a signal processing block diagram of a video signal recording and reproducing apparatus in an embodiment of the present invention.

FIG. 2 is a recording track pattern diagram in the same embodiment.

FIG. 3 is a diagram showing a head locus pattern traced by the head during a search.

FIG. 4 is a waveform diagram showing a playback envelope during a search.

[Explanation of symbols]

1 Input terminal 2 A/D converter 3 Encoding circuit 4 Data separation circuit 5 Recording head 6 Recording head 7 Playback head 8 Playback head 9 Recording medium 10 Data synthesis circuit 11 Decoding circuit 12 Basic data decoding circuit 13 Changeover switch 14 D/A converter 15 Output terminal 16 Helical track 17 Linear track 18 Playback head trajectory 19 on rotating cylinder Fixed playback head trajectory 20 First playback head output 21 arranged on rotating cylinder First playback head on rotating cylinder Second playback head output 22 placed opposite the playback head Fixed playback head output

Claims (3)

[Claims] 1. A means for obtaining encoded data by highly efficient encoding a video signal, basic data indicating the basic structure of the video signal and additional data indicating detailed information of the video signal from the encoded data. means for separating the additional data and basic data of the video signal or only the additional data by helical scanning onto a recording medium using a rotating head cylinder; Some or all of them include means for recording in the longitudinal direction on the recording medium using a fixed head, and means for decoding a search image from reproduction basic data reproduced from the recording medium using the fixed head at the time of search. What is claimed is: 1. A video signal recording and reproducing device comprising at least the following: 2. Basic data recorded on a recording medium using a fixed head is recorded in N periods (N=
2. The video signal recording and reproducing apparatus according to claim 1, wherein the basic data is one cycle of the data. 3. The video signal recording and reproducing apparatus according to claim 1, wherein the basic data is multiplexed on a control signal recorded on a control track formed in the longitudinal direction of the recording medium.