JPH1084530A - Reproducing device for video signal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain excellent copying with the same reproduction effect as usual correction even when a video signal is again reproduced. SOLUTION: A signal recorded on a magnetic tape 61 through a detection means 61 subject to demodulation, error correction, decoding and variable length coding is given to a recording medium 4 via a switch 91 normally, in which the signal is newly subject to error correction coding and modulation and the result is recorded on a magnetic tape 50. In the case that one synchronizing signal among three synchronizing signal blocks having been recorded on the magnetic tape 51 is in error and cannot be detected, the synchronizing signal is replaced with part of an output from a delay circuit 90 and the switch 91 is selected so as to configure a 3-synchronizing signal block configuration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal recording and reproducing apparatus for digitally recording a video signal.

[0002]

2. Description of the Related Art To compose a recording / reproducing apparatus (VTR, video disk, etc.) for recording / reproducing a video signal, a band compression technique (or a high-efficiency code) for reducing the data amount of an original video signal for long-time recording. Technology) is used.

As an example of the band compression technique, there is a technique using orthogonal transform coding such as Hadamard transform or discrete cosine transform (DCT). Orthogonal transform coding is a method of performing orthogonal transform on a video signal for each rectangular unit composed of certain pixels to encode each frequency component obtained by frequency-decomposing information in the rectangular unit. Is performed. At this time, for a high-frequency component that is less affected by deterioration in visual characteristics, the data amount of the original video signal is reduced by a method such as reducing the data allocation amount. This is one of the band compression technologies. There is also a method of assigning variable length codes having different code lengths according to the value of data obtained by orthogonal transform. In this method, a code word having a shorter code length is assigned to a value having a higher frequency of occurrence according to the frequency of occurrence of each data value, thereby reducing the entire data amount.

[0004] As a conventional example, a recording / reproducing apparatus for a video signal of a VTR will be described. FIG. 13 is a block diagram of a conventional video signal recording / reproducing apparatus, in which 10 is an input terminal for inputting a video signal, 2 is an orthogonal transform means for performing an orthogonal transform for each predetermined rectangular unit, and 3 is a variable length coding. This is constituted by a variable length encoding circuit 30 and a buffer memory 31. Numeral 4 denotes a recording means, which comprises an error correction encoding circuit, a modulation circuit and the like, and magnetically records a signal on a magnetic tape 5 through a recording head. Reference numeral 6 denotes a detection circuit, which detects a signal recorded on the magnetic tape 5 by the recording means 4 through a reproducing head, and detects the signal.
And a reverse demodulation circuit and an error correction decoding circuit. Reference numeral 7 denotes a signal for decoding or modulation decoding the signal which has been subjected to the variable length coding by the variable length coding means 3, and 8 denotes an inverse orthogonal transform means for obtaining the pixel value of the original video signal from the orthogonal transform value and outputting it. The image is sent to the terminal 11 to be a reproduced image.

A video signal such as a television signal has a fixed frame frequency (or field frequency).
A moving image is formed by periodically providing one screen every time. Therefore, the number of screens to be reproduced within a unit time in a video signal recording / reproducing apparatus must be constant. Therefore, in the recording / reproducing apparatus using the variable length encoding method, it is necessary to control the number of screens per unit time to be constant. In the configuration as in the conventional example, the data amount for one frame is fixed, but the data amount is controlled by the variable length encoding means 3. The signal which has been subjected to the variable length coding by the variable length coding circuit 30 is sent to the buffer memory 31 to detect a change in the data amount. At that time, when the change in the data amount of the variable length coded signal is large, a control signal is sent from the buffer memory 31 to the variable length coding circuit 30, and the variable length coding circuit 30 Variable-length encoding is performed so that the data amount is compressed so as to reduce it. In particular,
Generally, the data allocation is reduced by increasing the quantization step width of the output of the orthogonal transform means 2. Conversely, if there is room for the amount of data to be recorded, then the step width is reduced so that the data amount that can be recorded is effectively used.

FIG. 13 shows an example of the amount of data recorded according to the conventional example. The sync 1, sync 2,... In the figure indicate sync blocks of the minimum synchronization unit at the time of recording and reproduction, and S1, S2,. It describes the coded rectangular unit, and its size indicates the data amount. It is also assumed that an end signal (hereinafter referred to as EOB) indicating the end of the data in the rectangular unit is sent to the last hatched portion in each rectangular unit. This EO
B indicates that the last part of the signal sequence of data of each rectangular unit has a value of 0.
In the case of, the variable length decoding can be easily performed as the value 0 at the time of decoding simply by recording the EOB without recording the value 0 column, so that the data amount of the value 0 can be reduced. In the figure, the data amount is adjusted by the field-back control from the buffer memory 31. In general, the rectangular units do not match in the sync block unit (for example, the short unit Si in the sink 1 and the sink 2 does not match). Recorded separately.)

[0007]

However, in the above configuration, the amount of data to be recorded is controlled by the capacity of the buffer memory 31, but as described above, even if the fixed range of the data amount is one frame, If there are many rectangular units with a large amount of information concentrated around the frame, there is little room for data amount control, so the allocation balance is poor compared to the beginning of the frame, causing image quality degradation. There was a problem that recording might not be possible.

In addition, when an error occurs during reproduction, even if the error portion is in a small range, the variable length coding is performed, so that there is a problem that the effect of the error extends over a wide range. For example, if Sync 1 cannot be detected due to an error, it is not known at decoding time that the rectangular unit recorded at the head of Sync 2 is Si. Subsequent rectangular units cannot be detected. However, by recording an address (for example, i + 1) of a rectangular unit together in the sink 2 to reduce the error propagation, at least the rectangular unit after Si + 1 can be detected and reproduced by detecting the EOB of the rectangular unit Si. Is there. However, recording the address in a rectangular unit for each sync block is a very large redundant component, which is not effective because the amount of data allocated to the video signal is reduced.

The effect of the synchronization between the sync block and the rectangular unit also appears during special reproduction such as high-speed reproduction. At the time of high-speed reproduction, since the recording / reproducing head normally does not pass through the locus passing over the magnetic tape and diagonally spans the locus, it cannot be detected / reproduced for every arrangement of the sync blocks at the time of recording. Cannot be decoded in the order of recorded rectangular units. Therefore, there is a problem that the reproduced high-speed reproduction image is extremely deteriorated.

Next, consider the case of editing or copying a recorded video signal. These functions can be realized by re-recording from one tape on which a certain video signal is recorded to another tape. However, in the above conventional configuration,
In the case of an error, variable-length decoding and inverse orthogonal transformation are always performed, and the undetectable portion and the rectangular unit (for example, rectangular units S1 to Si if the sink 1 is incorrect) are modified at the pixel level, and the orthogonal transformation and variable conversion are performed again. There is also a problem that it is necessary to add a long coding, and it is inevitable that deterioration occurs due to repeated orthogonal transformation.

In view of the above, the present invention can reproduce a wider range on the screen even if an error occurs or there is a sync block that is not detected at the time of high-speed reproduction, and repeats the orthogonal transformation even if the editing and copying are repeated. It is an object of the present invention to provide a video signal recording / reproducing apparatus without any deterioration.

[0012]

SUMMARY OF THE INVENTION The present invention provides a detecting means for detecting a signal recorded by a recording device from a first recording medium to obtain a variable length code, and a variable length decoding for decoding the output of the detecting means to a variable length. Means for reproducing a video signal, comprising: an inverse orthogonal transform means for performing an inverse orthogonal transform on an output of the variable length decoding means; an orthogonal transform means for performing an orthogonal transform on the video signal in a first rectangular unit; A variable length coding unit configured to form a second rectangular unit with a predetermined number of one rectangular unit and performing variable length coding on the second rectangular unit, and to output the output of the variable length coding unit to a second recording unit. When copying a signal on a first recording medium to a second recording medium using a video signal recording apparatus having recording means for recording on a medium, the output of the detecting means is transmitted to the variable length decoding means. Video signal reproducing device which is sent to the recording means without going through It is.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, since the data amount of a predetermined number of rectangular units is recorded with the same configuration, the data is recorded.
Even if an error occurs, if the predetermined number of rectangular units is reduced, error propagation can be suppressed at most within the predetermined number of rectangular units, and even if the data amount cannot be accommodated, the high frequency band is lost. Since it is a component, its influence can be reduced.

Further, the signal recorded on one of the magnetic tapes can be processed without performing variable length coding / decoding and forward / reverse orthogonal transform and compensating for a rectangular unit arrangement to be modified.
The reproduction screen can be updated with new data over a wider area during high-speed playback, where only a portion of the data can be extracted because the effect on image quality deterioration due to editing and copying can be reduced, and the erroneous part is always copied after being corrected. And good image quality can be obtained.

FIG. 1 is a block diagram of a video signal recording and reproducing apparatus according to a first embodiment of the present invention. FIG. 1A shows a recording apparatus, in which 10 is an input terminal of a video signal, 2 is an orthogonal transform means for orthogonally transforming the video signal in rectangular units, and 300 is a variable length coding means. The variable length coding means 300 includes the variable length coding circuit 30 and the orthogonal transform means 2.
It comprises a data amount estimating circuit 32 for estimating the data amount of a predetermined number of rectangular units of output before performing variable length coding.
Numeral 4 denotes a recording unit which converts the output of the variable length encoding unit 300 into an error correction code and modulates the signal to be recorded on the magnetic tape 5. FIG. 2B shows a reproducing apparatus, 6 is a detecting means for detecting a signal recorded on the magnetic tape 5 through a reproducing head, and demodulating and error-correcting decoding. 700 is a variable length decoding means. It comprises a long decoding circuit 7 and an EOB insertion circuit 70. 8 is an inverse orthogonal transform circuit, and 11 is an output terminal for outputting a reproduced video signal.

The operation of the video signal recording device and the reproducing device of the present embodiment will be described. FIG. 2 shows an example of data recorded by the recording apparatus of the present embodiment, where the number of rectangular units for making the same data amount is 2n, and the data amount is three sync blocks shown in FIG. is there. Assume that the 2n rectangular units are A1, A2,..., An, B1,. Sink 1
, A fixed amount is arranged from the reduction of the rectangular unit from A1 to An, a sink 2 is arranged at a fixed amount from the reduction of the rectangular unit from B1 to Bn, and the sink 3 is arranged from A1 to An and B1 to Bn. High frequency components A′1, A′2,..., A′n, B′1,.
B'n is arranged. A hatched portion in the sink 3 is an EOB indicating an end position of each rectangular unit.

According to the above, the same number (2n) of rectangular units are always recorded in units of three sync blocks.
Even if one sync block of data cannot be detected due to an error, the range of the error propagation can be accommodated in a maximum of 2n rectangular units. At this time, it is not necessary to record the address in a rectangular unit as in the above-described conventional example. If the undetectable sync block is sync 3,
The effect of errors is only the high-frequency component of each rectangular unit, and the important low-frequency components of all 2n rectangular units can be detected and reproduced when only some of the sync blocks can be detected as in high-speed reproduction. This is effective because a wider range of reproduced images can be configured.

FIG. 3 shows a data arrangement in a case where rectangular units having an extremely large amount of information are concentrated in the recording apparatus of this embodiment. The sink 1 and the sink 2 in the same figure are exactly the same as in FIG. 2 and a fixed amount of data is arranged from 2n important reduction components in a rectangular unit. What is different is the arrangement of the sink 3, which has a very large information amount of 2n.
The high frequency components of the rectangular units cannot be accommodated in the data amount of the sink 3. In the embodiment of FIG. 3, up to a part of the high-frequency component B′m of the rectangular unit Bm can be arranged in the sink 3.
The rest of B'm and the data of B'm + 1 to B'n cannot be recorded. However, since the important low-frequency components of the rectangular units Bm to Bn are arranged in the sink 2, there is no possibility that information of the entire rectangular unit cannot be recorded as in the above-described conventional example. In this case, the entire screen can be reproduced, which is very effective.

Next, the reproducing apparatus of the present embodiment will be described. In a normal case (the data arrangement in FIG. 2), although each rectangular unit is divided into syncs 1 and 2 and a sync 3, playback processing can be performed in the same manner as in a conventional playback apparatus. However, FIG.
In such a case, the rectangular unit after B'm (variable length)
Since the codeword string is lost in the middle, the EOB insertion circuit 70 inserts (n−m + 1) EOBs from B′m to B′n immediately after the sink 3 to perform the variable length decoding. The input of the circuit 7 is arranged as data as shown in FIG. In this way, the variable-length decoding circuit 7 at the subsequent stage can prevent erroneous detection of the variable-length codeword.

The configuration of this embodiment described above is not large in terms of circuit scale, and in a recording apparatus, the high-frequency component is simply stored in the memory and the sink 3 is stored.
It is only necessary to output only the data amount of the EOB for the variable length encoding means 300. In the reproducing apparatus, the number of EOBs is counted, the sink 3 is terminated, and the insufficient EOBs are sequentially sent to the variable length decoding means. Just good and very practical.

Next, a video signal recording apparatus according to a second embodiment of the present invention will be described. FIG. 5 is a block diagram showing the configuration of the video signal recording device of the present embodiment.

In this embodiment, the EOB insertion circuit of FIG. 533 is provided in the variable length coding means 301 in the video signal recording apparatus of the first embodiment, and the other components are the same as those shown in FIG. Since they are equivalent to elements, they are assigned the same numbers.

The operation of the present embodiment will be described with reference to FIG. In a normal state (corresponding to FIG. 2), since it is the same as in the first embodiment, the description is omitted, and even if the data amount of the 2n rectangular units is compressed, it does not fit in the data amount of three sync blocks. The case will be described. This embodiment is different from the first embodiment in that 2n EOBs are always recorded in the three sync blocks. To this end, the data is extracted from the memory storing the high-frequency component from the data amount of the sink 3 in consideration of the data amount of the remaining number of EOBs. What is necessary is just to output from the conversion means 300. Since the number of EOBs is always 2n in the playback device,
Unlike the first embodiment, there is no need to add a shortage of EOB, and the configuration is simple and practical.

More effective is when the error is not that the entire sync block can be detected, but that no part of the sync block is detected. When such an error occurs in the sink 3, in this embodiment, 2n Es are always present.
Since the OB exists in the three sync blocks, the number of EOBs can be detected from the normal data excluding the error part, so that it is possible to know which rectangular unit data the error part is. That is, the error propagation range can be further reduced, which is very effective.

Next, a video signal recording device and a video signal reproducing device according to a third embodiment of the present invention will be described. FIG. 7 is a partial block diagram of a video signal recording device and a reproducing device of the present embodiment. The left part of the figure is the same as the configuration of the first and second embodiments (FIGS. 1 and 5), and a description thereof will be omitted. New components in this embodiment are a delay circuit for delaying the output of the 90 detecting means 6 by one frame and a switch circuit of 91. The present embodiment will be described below with reference to the data arrangement diagrams of FIGS. In this embodiment, V
This configuration is effective when copying a signal recorded on a recording medium, which is performed when an editing and copying function is performed in a TR or the like, onto another recording medium.

At normal times, the switch 91 outputs a signal in a variable length coded state obtained by demodulating a signal recorded on the magnetic tape 51 by the detecting means 6 and decoding the signal by steering correction. , And are again subjected to error correction encoding and modulation, and are recorded on the magnetic tape 50. In other words, there is no need to provide the inverse orthogonal transforming means 8 and the orthogonal transforming means 2 of the recording device at the subsequent stage of the detecting device 6 of the reproducing device. Since the data is recorded again on the magnetic tape 50 while the orthogonal transform means and the variable length coding means have been applied only once, it can be performed without any deterioration due to copying, which is very effective. If FIG. 8 shows a sync block in which 2n rectangular units recorded on the magnetic tape are arranged, they are copied on the magnetic tape 50 in exactly the same state.

Here, the three sync blocks (sinks 1, 2, 3) of FIG. 8 recorded on the magnetic tape 51 are described.
The operation when the sink 1 is wrong and cannot be detected will be described. The three sync blocks (sink 1 ',
2 ', 3') indicate data just one frame before the three sync blocks in FIG. 8, and the data in FIG. 9 can be obtained from the delay circuit 90 in FIG. Now, when the sink 1 cannot be detected erroneously, it is replaced by a part of the sink 1 'and the sink 3' which are the outputs of the delay circuit 90, and the three sync blocks (sinks 1 ', 2, 3) shown in FIG.
The switching operation is performed by the switch 91 so as to obtain the configuration of 3 ″).

As described above, even if the sync 1 is incorrect at the time of copying, the corrected signal (sink 1 ') is recorded on another magnetic tape 50. Therefore, even if this signal is reproduced again, the normal correction is performed. There is a reproduction effect equivalent to that of, and a good copying operation can be performed. Further, the delay circuit 90 is practical because the amount of data is small because the signal to be delayed is the data after compression.

In the present embodiment, the data amount from A'1 to A'n in the sink 3 is smaller than the data amount from C'1 to C'n in the sink 3 'to be replaced by the switch 91. In this case, only high-frequency components of p rectangular units out of C′1 to C′n, such as sink 3 ″ (only C′p is part thereof) are modified. Therefore, the numbers of variable-length codeword strings and EOBs in the sink 3 ″ do not match those in the normal state, and therefore, in order to reproduce the tape 50 copied in this manner, the first embodiment described above is used. A playback device having the EOB insertion circuit as described may be used. However, in the first embodiment, only the case of the last rectangular unit of the sink 3 has been described. However, in the case of the sink 3 ″ as shown in FIG.
If the position t of the boundary between A'n and B'n is recorded as shown in FIG.
, The same EOB insertion operation can be performed.

The effect of this embodiment is extremely effective not only in the effect of error correction at the time of copying, but also in forming a screen in high-speed reproduction of a copied tape (the magnetic tape 50 in FIG. 7). At the time of high-speed reproduction, it is not always possible to always take out three sync blocks in which 2n continuous rectangular units are arranged, so that the above-described replacement operation is frequently performed. At this time, performing the modification processing also at the time of copying as in the present embodiment means that when the sink 1 'in FIG. 10 can be taken out, at least the data (A
Since data that is very close in time from 1 to An) can be reproduced, a high-speed reproduction screen can be configured better than using data that is erroneously separated in time.

Next, a video signal recording and reproducing apparatus according to a fourth embodiment of the present invention will be described. This embodiment is similar to the third embodiment described above, and is effective when copying a signal recorded on a recording medium, which is performed at the time of executing the editing and copying functions in a VTR or the like, onto another recording medium. There is a certain configuration. FIG. 11 is a block diagram of a part of a video signal recording device and a video signal reproducing device according to the present embodiment. The left part of FIG. 11 shows the configuration of the first and second embodiments (FIGS. 1 and 5). It is omitted because it is equivalent to. This embodiment is different from the third embodiment of FIG. 7 in that the output of the delay circuit 90 is sent to the switch circuit 91 because the EOB insertion circuit 9 for inserting an EOB is used.
2 is constituted. Hereinafter, this embodiment will be described with reference to the data arrangement diagrams of FIGS. 8, 9 and 12 described above.

FIG. 12 is a diagram showing the 3rd row of the recording data sequence shown in FIG.
Data recorded on the magnetic tape 50 as a result of performing a copy operation with error correction using data of all frames (data in FIG. 9) when the sync 1 cannot be detected due to an error for the sync block. It shows the arrangement.

10 differs from FIG. 10 in that three EOBs are arranged in the last part of the high-frequency component replaced in the sink 3 ″ by the number of rectangular units from C′p to C′n. The number of EOBs in a block is set to 2n as usual.

As described above, the number of EOBs is always 2n for a magnetic tape copied with error correction.
Since the variable length decoding means does not have an EOB insertion circuit, it can be reproduced even by a reproducing apparatus. The effect at the time of high-speed reproduction is practically equivalent to that of the third embodiment.

In the third and fourth embodiments,
It has been described that the error correction is performed by using the delay circuit 90 to perform the delay operation between the previous frame and the previous frame. However, this is an example, and the operation between the next frame and the next frame, between the fields, within the frame, Although there are many effective means such as an in-field operation, in the present invention, a copying operation can be performed while performing error correction without going through a variable length decoding encoding means and an inverse orthogonal transform means.

[0036]

As described above, according to the present invention, data is recorded with the same data amount of a predetermined rectangular unit.
Even if an error occurs, if the predetermined number of rectangular units is reduced, error propagation can be suppressed at most within the predetermined number of rectangular units, and even if the data amount cannot be accommodated, the high frequency band is lost. Since it is a component, its influence can be reduced.

In addition, the signal recorded on one magnetic tape can be processed without performing variable length coding / decoding and forward / reverse orthogonal transform and compensating for a rectangular unit arrangement to be modified.
The reproduction screen can be updated with new data over a wider area during high-speed playback, where only a portion of the data can be extracted because the effect on image quality deterioration due to editing and copying can be reduced, and the erroneous part is always copied after being corrected. Therefore, the practical effect is great because good image quality can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of a video signal recording device and a playback device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a sequence of data recorded on a tape for explaining the operation of the first embodiment;

FIG. 3 is an explanatory diagram of an arrangement of data recorded on a tape for explaining the operation of the first embodiment;

FIG. 4 is an explanatory diagram of an arrangement of data recorded on a tape for explaining the operation of the first embodiment;

FIG. 5 is a block diagram of a video signal recording device according to the first embodiment of the present invention.

FIG. 6 is an explanatory diagram of an arrangement of data recorded on a tape for explaining the operation of the second embodiment;

FIG. 7 is a block diagram showing a part of a video signal recording device and a reproducing device according to a third embodiment of the present invention;

FIG. 8 is an explanatory diagram of an arrangement of data recorded on a tape for explaining the operation of the third embodiment;

FIG. 9 is an explanatory diagram of an arrangement of data recorded on a tape for explaining the operation of the third embodiment;

FIG. 10 is an explanatory diagram of an arrangement of data recorded on a tape for explaining the operation of the third embodiment;

FIG. 11 is a block diagram showing a part of a video signal recording device and a video signal reproducing device according to a fourth embodiment of the present invention.

FIG. 12 is an explanatory diagram of an arrangement of data recorded on a tape for explaining the operation of the fourth embodiment;

FIG. 13 is a block diagram of a conventional video signal recording device and playback device.

FIG. 14 is an explanatory diagram of an arrangement of data recorded on a tape for explaining an operation of a conventional example.

[Explanation of symbols]

 2 orthogonal transform means 300 variable length coding means 301 variable length coding means 4 recording means 6 detection means 700 variable length decoding means 8 inverse orthogonal transform means

Claims (2)

[Claims] 1. A detecting means for detecting a signal recorded by a recording device from a first recording medium to obtain a variable length code, a variable length decoding means for variable length decoding an output of the detecting means, and the variable length decoding A video signal reproducing apparatus comprising: an inverse orthogonal transform means for performing an inverse orthogonal transform on an output of the means.
Orthogonal transformation means for performing orthogonal transformation in rectangular units; and a second rectangular unit in which the first rectangular units are constituted by a predetermined number;
A video signal recording apparatus comprising: a variable-length encoding unit that performs variable-length encoding on a rectangular unit; and a recording unit that records an output of the variable-length encoding unit on a second recording medium.
A video signal reproducing apparatus for transmitting an output of the detecting means to the recording means without passing through the variable length decoding means when copying the signal on the recording medium to the second recording medium. 2. When the output of the detection means is sent to the recording means, if the detection means is incorrect, a signal obtained by replacing the output of the detection means with another variable-length-encoded signal is output by the recording means to another signal. 2. The video signal reproducing apparatus according to claim 1, wherein the video signal is recorded on a recording medium.