JP3321878B2 - Dubbing method of digital video signal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to dubbing of a data compressed digital video signal in a digital VTR.

[0002]

2. Description of the Related Art Broadcasting VTRs have already adopted the D1 system and D2 system.
A digital VTR of the D3 system has been commercialized. On the other hand, various formats have been proposed for practical use of digital VTRs for consumer use. FIG. 8 is a block diagram showing the configuration of a consumer digital VTR that performs data compression and recording by using discrete cosine transform (hereinafter, referred to as DCT) and variable-length coding.

In FIG. 8, an input analog component video signal (Y, RY, BY) is converted into a digital component video signal by an A / D converter 1, and a blocking circuit 2 uses a frame memory. 8 samples in the horizontal direction, 8 lines in the vertical direction (hereinafter, referred to as
(Referred to as 8 × 8 unit) as one block, and are shuffled and Y / C multiplexed. This 8
The data of × 8 units is subjected to DCT by the DCT circuit 3, and data in the time amplitude domain is converted into data in the frequency domain. The DCT-processed data is re-quantized by the encoder 4, variable-length coded by a two-dimensional Huffman code or the like, and compressed.

In this case, a predetermined number of DCT blocks (eg,
The step width in the re-quantization is set so that the total data amount for each buffering unit composed of 30 DCT blocks does not exceed a certain amount. For reference, FIG. 9 shows SYNC, ID, AUX data, QNO, which is information on the quantization step, and PARITY.
Is added to a buffering unit composed of 30 DCT blocks. In this figure, the buffering units are Y, Y, C, Y, Y, C,.
The data of each DCT block is composed of 30 DCT blocks arranged in the order of
Subsequently, the low-frequency component to the high-frequency component of the AC component are stored. An EOB (End Of Block) code is accommodated in the last part of the accommodation of the data of each DCT block. It should be noted that overflows that cannot be accommodated in one DCT block section shown in FIG.
It is accommodated in an empty area of the T block.

[0005] Next, in the framing circuit 5, a plurality of such buffering units are vertically arranged to form a block.
After adding a parity of a product code configuration which is (Error Correction Code), the data is converted into serial data by the channel encoder 7 and recorded. Conversely, during reproduction, data is detected by the channel decoder 8,
Serial / parallel conversion is performed, and error correction is performed by the ECC circuit 9. The error-corrected data is decomposed into variable-length code words by the deframing circuit 10, decoded and inverse-quantized by the decoder 11, and inversely DCT-converted by the inverse DCT circuit 12 into 8 × 8 data.

The data is subjected to deshuffling, Y / C separation, data interpolation, and the like by a deblocking circuit 13, and is returned to a digital component video signal.
The signal is converted into the original analog component video signal by the A converter 14 and output. Next, data processing in the framing circuit and the deframing circuit will be described with reference to FIG.

The data of one DCT block is a fixed-length DC
It consists of data and variable-length AC data. In FIG. 1A, AC data (represented by data with a symbol *. Hereinafter, the symbol * used in the specification and drawings of this application indicates that the data is AC data. ) Is composed of 15 pieces, and this number is D
It depends on the CT block. The framing circuit 5 of FIG. 8 blocks a plurality of such fixed-length buffering units each composed of 30 DCT blocks.

The reproduced data is subjected to error correction by the ECC circuit 9 in FIG. 8, but as shown in FIG. 10 (3), data that could not be corrected (for example, the 10th AC data * 10). ) Is added with 1-bit error information. The buffering unit to which the error information is added is decomposed by the deframing circuit 10 into word units of a variable length code including valid data and undecodable data, and error information is added. Note that (4) in this figure shows, as an example, a case where * 10 to * 15 cannot be decoded because an error has occurred in * 10.

Then, based on the added error information, interpolation for correcting the error is performed in the deblocking circuit 13. As a method for dubbing in the digital VTR configured as described above, for example, three methods A, B, and C as shown in FIG. 11 can be considered.

In FIG. 11, reference symbol A denotes ordinary analog dubbing in which a D / A conversion output of a reproducing device is input to an A / D converter of a recording device. B denotes digital dubbing in which the digital component output of the reproducing device is input to the blocking circuit 2 of the recording device via a digital interface (hereinafter, digital I / F) 15. Reference numeral C denotes digital dubbing in which data subjected to error correction by the ECC circuit 9 is input to the parity generation circuit 6 of the recorder via the digital I / F 16.

[0011]

However, in the conventional dubbing method, since A is analog dubbing, the image quality deteriorates during dubbing. In addition, B has a high transmission rate (10) because it processes an uncompressed video signal.
0 Mbps), and there is a possibility that the image quality is degraded due to DCT.

Further, C processes a compressed video signal, so that the transmission rate is reduced. However, if an error that exceeds the correction capability of the ECC circuit remains and is transmitted and recorded as it is, the framing circuit Since error information is lost in the processing after step 5, erroneous data is decoded during reproduction of the dubbing tape. Similarly, even if an error occurs on a transmission path for transmitting data from a reproducing device to a recording device for dubbing (for example, in a digital I / F), erroneous data is decoded when reproducing a dubbed tape. Would. As a countermeasure in case of dubbing by the method of C,

(1) Interpolation for error correction is performed by a digital I / F or ECC circuit. (2) The data including the parity is transmitted and recorded as it is. However, in the case of (1), a frame memory for interpolation is required. In addition, since the data has been subjected to variable length coding and blocking, interpolation is at least one.
Since the operation is performed in units of DCT blocks, valid data in the DCT block in which an error has occurred is also lost. However, during normal playback, instead of performing interpolation on the part where an error has occurred, it is conceivable to create an image with effective data (low-frequency component). In this case, the contents of the master tape and the image may change become. In the case of (2), errors are accumulated when dubbing is repeated, so that the correction capability of the ECC circuit is substantially reduced and image quality may be degraded.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of dubbing a digital video signal which solves the above-mentioned problems, can reduce a transmission rate, and does not cause deterioration in image quality during dubbing.

[0015]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a dubbing method for an apparatus for digitizing a video signal, performing discrete cosine transform, performing variable length coding, and recording in a block form. The variable-length code is decomposed into word units, an error end code is defined in the variable-length code table, and a predetermined word portion of the DCT block having the AC value error of the discrete cosine transformed data is converted into the error code. After performing error processing for dubbing by replacing with the end code, digital dubbing with compressed data is performed by recording again in blocks, and effective data processing such as interpolation detects an error end code at the next playback Do it.

As a specific procedure for performing the dubbing error process in this case, the variable length code that has been blocked by the playback device is decomposed into word units, the dubbing error process is performed, and then the block is again formed into a recording device. Or, the variable length code in the form of a block transmitted from the reproducing device is divided into words in the recording device, subjected to error processing for dubbing, and then recorded again in the form of a block. What is necessary is just to be a structure.

As specific contents of the error processing for dubbing, a predetermined code is defined, an error part is recorded by replacing this code, and processing such as interpolation is performed at the next reproduction. In particular, regarding the error portion of the AC value in the discrete cosine transformed data, it is preferable to replace this error portion with a predetermined code defined in the variable length code table, for example, an EOB code. It is suitable.

When the error part is replaced with an EOB code, the structure of the EOB code is changed to a normal EOB code.
It is effective to have a configuration having an identification signal that can distinguish between the case of using as a code and the case of using as an error code.

[0019]

According to the present invention, since the digital video signal dubbing method is configured as described above, it is possible to perform error processing of a variable length code in word units. Further, since error interpolation is not performed at the time of dubbing, it is possible to prevent image quality from being degraded due to loss of effective data at the time of error interpolation. Furthermore, since the data transmitted from the recorder to the reproducer for dubbing is compressed, the transmission rate can be reduced.

When an EOB code that is inevitably used when accommodating data of each DCT block is used as a code indicating that there is an error in the AC value,
The data after the word with an error in the AC value is
Even if the code is replaced, it is unlikely that the replacement operation will cause an overflow.

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings. (First Embodiment) FIG. 1 is a block diagram showing a dubbing method according to a first embodiment of the present invention.

In this embodiment, the output of the deframing circuit 10 is input to the decoder 11 on the reproducing apparatus side to obtain a normal reproduction output, and the dubbing error processing section (Err)
or Proc) 17, and after error processing, is input to the framing circuit 5. Framing circuit 5
Is re-blocked by the digital I / F 18
And output to the recorder. At this time, the recording system blocks other than the framing circuit 5 are in a pause state.

In the recorder, the data is input to the parity generation circuit 6 through the digital I / F 18 and is newly added with parity and the like, is recorded, and is also supplied to the deframing circuit 10 to obtain a video output for monitoring. it can. At this time, the recording system from the A / D converter 1 to the framing circuit 5 and the channel decoder 8 to the ECC circuit 9
The playback system up to this point is in a halt state. Deframing circuit 1
Since the output of 0 is decomposed into word units of a variable length code, it is possible to perform detailed operations in DCT block units or word units as error processing.

As an error processing method in the dubbing error processing unit 17, interpolation on a screen (in a frame) or a time axis (between frames) can be considered, but the following problems are considered. (1) Since DCT is performed by n × n, interpolation is performed in units of DCT blocks, and it is difficult to perform interpolation within a screen (peripheral pixels). (2) One frame of memory is required for interpolation in the time axis direction. (3) In the interpolation in units of DCT blocks, valid reproduction data in DCT blocks having errors is also lost. At the time of reproduction, it is conceivable to produce an image with effective data (low-frequency component) in addition to interpolation, so that the contents of the image differ from the master tape.

On the other hand, considering a case where only effective data is reblocked (framing) and dubbing is performed without performing interpolation, a DCT block having an error has only a halfway word, so if it is reblocked as it is, it is reproduced. Occasionally, the break of the DCT block cannot be recognized, and correct decoding cannot be performed. In this case, it is conceivable to forcibly add an EOB code. In this case, however, error information is lost, so that error interpolation cannot be performed during reproduction of the dubbed copy.

Therefore, in this embodiment, the DCT block D
When there is an error in the C value or the AC value, the error portion is replaced with a predetermined code and dubbing is performed, so that error interpolation can be performed during reproduction of the dubbed tape. The configuration will be described below. 1) When there is an error in the AC value A special code (error end code) not used in normal encoding is prepared in the table of the variable length code,
The data of the reproduced DCT block is, for example, as shown in FIG.
As shown in (4) of FIG. 2, when a non-decodable part due to an error is included, the dubbing part is converted into an error end code by the dubbing error processing unit 17 as shown in (1) of FIG. Perform the replacement operation.

By dubbing the data to which the error end code is added in this manner, all the valid reproduction data is stored, and thereby the error information is also substantially stored. When reproducing the dubbed copy, the output of the deframing circuit 10 is detected by detecting the error end code in the deframing circuit 10 to reproduce the master tape as shown in (4) of FIG. Therefore, there is no change (deterioration) in image quality due to dubbing. In addition, the error processing in the system is only the addition of an error end code. Only one data is added to the table at the time of word decomposition, and there is almost no special processing. Here, the error return code is
Long codes are allocated so as not to affect the compression efficiency.

If the error end code is replaced with an error code having a long code length as described above, the replacement operation may increase the data amount and cause an overflow. Therefore, as a countermeasure, the EOB code itself can be used as the error end code by devising the structure of the EOB code, and it is possible to avoid the occurrence of overflow due to the replacement operation. An embodiment in this case will be described in detail with reference to FIG.

FIG. 3A partially shows an example of a two-dimensional variable length code table used in this embodiment. In this table, (A, B) is that the run length value of “0” is A, and the absolute value of the quantized DCT coefficient value that appears next to the data string of “0” is B. Represents The EOB pattern (11110) is used as a sync code, and a variable length code including this pattern at the end of the code is a sync code. Therefore, when an error occurs, a break in the variable length code is detected by detecting this pattern,
Can be re-decoded.

Here, a 1-bit sign bit (s) indicating whether the DCT coefficient value is positive or negative is added to the end of all codes other than the EOB code, so that this regularity is maintained. To this end, a special bit (R) of 1 bit is added to the end of the EOB code. EOB = 11110R

When the EOB code is used as a code indicating a normal block end, the above-mentioned special bit (R) is set to "0",
As described above, when the special bit (R) is used as an error end code only at this time.
To “1”. If this operation is represented in a diagram, for example, FIG.
(B).

With this configuration, it is only necessary to check the last bit of the EOB code always used when accommodating data in the DCT block, and to determine whether the data after the error part is replaced with the EOB code. Can be determined. Although the EOB pattern is set to 11110 in the example of FIG. 3, it is needless to say that the code is not limited to such a code, and any other pattern can be used within the scope of the present invention. .

The error processing method described above replaces the code of the error occurrence part (AC part). Instead, as shown in FIG. 5A, the AC value in the DCT block is If an error occurs, the DCT
The DC value of the block may be replaced with a predetermined 9-bit error code, for example, 10000000 or 011111111. In this case, when the dubbing tape thus processed is reproduced and this error code is detected, all data of the DCT block is invalidated and interpolation is performed in the deblocking circuit 13.

2) When there is an error in the DC value The dubbing error processing unit 1
7, a 9-bit DC value not used in the DC recording area, for example, 10000000 or 0111
11111 or the like. Thus, an error code can be recorded without preparing a special code in the variable length code table and without increasing the redundancy of information. The operation in this case is shown in FIG.

FIG. 6 is a block diagram showing a dubbing method according to a second embodiment of the present invention. In the present embodiment, the output of the ECC circuit 9 is input to the deframing circuit 10 on the playback device side, and a normal playback output is obtained.
It is also sent to the digital I / F 19 and input to the recorder. At this time, the recording system block of the reproducing device is in a pause state.

On the other hand, on the recording device side, the data from the reproducing device is supplied to the deframing circuit 10 and the dubbing error processing section 17 through the digital I / F 19, and after error processing, is inputted to the framing circuit 5. You. The data re-blocked by the framing circuit 5 is input to a parity generation circuit 6, where a parity and the like are newly added and recorded. The output data of the deframing circuit 10 is also input to the decoder 11 and becomes a video output for monitoring. At this time, the recording system from the A / D converter 1 of the recorder to the encoder 4 and the channel decoder 8
The reproduction system from to the ECC circuit 9 is in a halt state.

In the first embodiment, the dubbing error processing is performed on the reproducing apparatus side. However, in the present embodiment, the dubbing error processing is performed on the recording apparatus side. The dubbing error processing unit and the framing circuit (for reproduction only) become unnecessary, and the system scale can be reduced. However, in the case of this embodiment, E
The error information (flag, etc.) obtained by the CC circuit 9 also needs to be transmitted from the reproducing device to the recording device, which increases the transmission rate. However, when a 1-bit flag is added to 8 bits, about 10% is used. It's just up.

Further, if the parity generation circuit 6 to the recording medium to the ECC circuit 9 are regarded as a data recorder, an external processor is connected to the digital I / F 19 and DAT, A
It is possible to record and reproduce other types of data such as TV and computer data. In this case, the processing from deframing to dubbing error processing to framing is unnecessary, and the digital I / F 19 and the parity generation circuit 6 are used for recording, and the ECC circuit 9 and the digital I / F are used for reproduction.
It becomes the route of 19.

Next, the configuration of a digital VTR in which the dubbing methods of the first and second embodiments can be appropriately selected and executed will be described with reference to the block diagram of FIG. (A) When the dubbing method of the first embodiment is used, a reproduced video output is obtained through the channel decoder 8 to the D / A converter 14 when the dubbing method of the first embodiment is used. The error-processed data is output to the outside through the route of the deframing circuit 10, the dubbing error processing unit 17, the framing circuit 5, the bus 22, and the digital I / F 20.

(B) When used as a reproducing device in the dubbing method of the second embodiment and a reproducing device for supplying an output to an external processor, the ECC circuit 9-bus 23-
The data to which error information is added is output to the outside through the digital I / F 20. In the case of dubbing, (A) and (B) can be switched and used depending on the configuration of the other party, and can be fixed to (A) (independent of the configuration of the recording machine). The output to the external processor 24 can automatically switch the digital I / F 20 by providing identification data (ID in the product code configuration of FIG. 9) in the recording data.

(C) On the other hand, when used as a recorder, in the case of the dubbing method of the first embodiment, data input from the outside passes through the digital I / F 20-bus 22-parity generating circuit 6-channel encoder 7. And a video output for monitoring is obtained through the digital I / F 20, bus 23, deframing circuit 10 and D / A converter 14. The same applies to the input from the external processor 24.

(D) When used as a recorder in the dubbing method of the second embodiment, the digital I / F 20
-Bus 23-deframing circuit 10-error processing unit 17 for dubbing-SW21 (lower side)-framing circuit 5
Error-processed data is recorded through a parity generation circuit 6-channel encoder 7, and a monitor video output is obtained through a deframing circuit 10 to a D / A converter 14. At this time, the bus 22 is not used. Here, the switching between (C) and (D) can be either manual switching or automatic switching based on identification data provided in the transmission data.

By using the digital VTR having the above-described configuration as a standard configuration, a device having only (B) output (and (C) input) can be used in development of a playback-only device, a camcorder, a popular device, and the like. It is. For example, playback-only machines and camcorders can be dubbed with (B) output only (D) input (standard configuration) devices, and (B) output (C) only input devices can be dubbed in combination with standard configuration devices. Such a system can be configured.

Since the transmission rate between the digital I / Fs is set to the dubbing method (addition of error information) of the second embodiment, in the case of dubbing between digital VTRs of the standard configuration, the reproduction device If the setting is made such that error processing for dubbing is performed, it is not necessary to transmit error information from the reproducing device to the recording device, and accordingly, other additional information can be transmitted to achieve higher functionality.

The error processing described above with reference to FIGS. 1, 6, and 7 relates to an error that has occurred during the recording / reproducing process on the tape. A supplementary description will be given of an error countermeasure when an error occurs on a transmission line for transmitting data (for example, digital I / F). As a countermeasure against such errors, when data is sent from the playback device to the transmission path, a check code such as CRC is attached and transmitted, and when the recording device receives this data, it is checked whether there is an error and the error is corrected. There is a way to do it. In this case, when a check code of a simple type that can be checked in units of 1 SYNC block is used, and when an error that cannot be corrected by the check code occurs on the transmission line, the following (1) or (2)
The following coping method can be adopted. (1) Replace all DC values in one SYNC block in which an error has occurred with an error code, for example, the error code shown in FIG. (2) All data in one SYNC block in which an error has occurred is set to 0 or 1.

When a SYNC block whose code has been replaced in this way is detected during reproduction of a dubbed copy tape, all data in the SYNC block is processed as invalid data, that is, the data in the SYNC block is deblocked. The circuit 13 is configured to interpolate. It should be noted that the present invention is not limited to the embodiments described above, and various modifications are possible based on the spirit of the present invention, and they are not excluded from the scope of the present invention.

For example, the process of replacing the DC value of the erroneous DCT block with a DC value not used in the DC recording area can be applied to the reproduced data in a block state. Further, the present invention can be applied to a digital VTR using other coding methods such as Hadamard transform and KL transform.

[0048]

As described above in detail, according to the present invention, a video signal is digitized, subjected to discrete cosine transform, variable-length coded, and recorded in a block for dubbing. The variable-length code is decomposed into word units, an error end code is defined in the variable-length code table, and a predetermined word portion of the DCT block having an AC value error of the discrete cosine transformed data is converted into the error end code. After performing error processing for dubbing and replacing the data, digital dubbing with compressed data is performed by recording again in blocks, and effective data processing such as interpolation is performed at the next playback, as described below. This has the effect of (1) Since the compressed data is transmitted from the recording device to the reproducing device, the transmission rate is reduced. (2) Compared to a system for transmitting a digital component video signal, it is advantageous in terms of image quality and has little waste in terms of system. (3) Reproduction equivalent to that of a master tape is possible with a simple system. (4) By using the EOB code as the error end code, the data amount does not increase even if the code replacement operation of the error part is performed, and therefore, no overflow occurs.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a dubbing method according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of an example of dubbing error processing according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating an example of a two-dimensional variable-length code table used in the present invention, and error processing relating to an AC value by the code.

FIG. 4 is a diagram illustrating an example of error processing relating to a DC value according to the present invention.

FIG. 5 is a diagram showing another example of error processing relating to an AC value according to the present invention.

FIG. 6 is a block diagram illustrating a dubbing method according to a second embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a digital VTR capable of implementing the first embodiment and the second embodiment of the present invention.

FIG. 8 is a block diagram showing a configuration of a conventional digital VTR using DCT and variable length coding.

FIG. 9 is a diagram illustrating a buffering unit in a conventional digital VTR.

FIG. 10 is an operation explanatory diagram of a framing circuit and a deframing circuit in a conventional digital VTR.

FIG. 11 is a block diagram showing a dubbing method in a conventional digital VTR.

[Explanation of symbols]

 2 blocking circuit 3 DCT circuit 4 encoder 5 framing circuit 6 parity generation circuit 7 channel encoder 8 channel decoder 9 ECC circuit 10 deframing circuit 11 decoder 12 inverse DCT circuit 13 deblocking circuit 17 error processing block for dubbing 18-20 digital I / F

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hajime Inoue 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (56) References JP-A-1-296460 (JP, A) JP-A 3-116586 (JP, A) JP-A-3-185982 (JP, A) JP-A-64-73560 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 20/18 , 20/10 H04N 5/92

Claims (7)

(57) [Claims] A digital signal is converted to a discrete signal.
And in converting, and variable length coding, in the dubbing method of the apparatus and records the blocks, decomposing the variable length code that is blocked into units of words, to define the error end code into the variable length code table, the discrete Error of AC value of cosine transformed data
Error termination of a specified word part of a certain DCT block
After performing error processing for dubbing by replacing it with code, digital dubbing with compressed data is performed by recording again in blocks, and effective data such as interpolation
A dubbing method of a digital video signal, wherein the processing is performed by detecting an error end code at the next reproduction . 2. The reproducing apparatus according to claim 1, wherein the variable length code which has been divided into blocks is decomposed into word units, error processing for dubbing is performed, and then the block is again divided and transmitted to the recording apparatus. For dubbing digital video signals. 3. The recording apparatus according to claim 1, wherein said variable length code transmitted from said reproducing apparatus is decomposed into word units, dubbing error processing is carried out, and said recording is again made into blocks. Item 3. A method for dubbing a digital video signal according to Item 1. 4. The method according to claim 1, wherein the predetermined word portion is the DCT block.
4. The DC value of the clock.
3. A method for dubbing a digital video signal according to claim 1. 5. The A of the discrete cosine transformed data
A word part having an error in the C value is replaced with a predetermined code defined in a variable length code table.
The method for dubbing a digital video signal according to claim 1 . 6. The digital video signal dubbing method according to claim 1 , wherein the error end code is an EOB code. 7. The EOB code, the dubbing method of a digital video signal according to claim 6, characterized in that it comprises an identification signal whether an error code.