JP3167663B2 - Encoding / decoding method of error correction code - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for encoding and decoding an error correction code.

[0002]

2. Description of the Related Art In recent years, a digital VCR (DVCR) for recording and reproducing a video signal as digital data has been developed. The DVCR can record a video signal based on MPEG, which is an international standard for image compression.

First, a simple format of a DVCR will be described.

FIG. 4 shows a recording format on a magnetic tape used for a DVCR. Data for 300 tracks per second is recorded on the magnetic tape. Each track is recorded in the order in which it is recorded, using ITI (Insert and Track Informat
It consists of an ion area, an audio (AUDIO) area, a video (VIDEO) area, and a subcode area.

FIG. 5 shows a format in a video area. The data is composed of a block of 77 bytes × 138 bytes (video data 135 + AUX data 3 bytes). First, the EC for error correction in the direction of 138 bytes
C2 parity (11 bytes) is added, and then ECC1 parity (8 bytes) is added in the direction of 77 bytes. Then, data of a total of 149 sync blocks are sequentially recorded in units of sync blocks.

As shown in FIG. 6, a sync pattern (2 bytes) and an ID (3 bytes) indicating the attribute of data are added before the data (77 bytes) and the ECC1 parity (8 bytes). It is composed of a total of 90 bytes and is recorded in order from the sync pattern.

A double coded Reed-Solomon code is used as an error correction code of the DVCR, and 11 bytes of ECC2 parity are generated from 135 bytes of data (ECC).
8 bytes of the ECC1 parity is 7 bytes.
Generated from 7-byte data (encoding of ECC1).

At the time of reproduction, first, 77 bytes of data + 4 of 8 bytes of ECC1 parity are used by using the ECC1 parity.
Error correction of up to 5 bytes and detection of the presence of an error of 5 bytes or more (decoding based on ECC1 parity). Also, E
Erasure correction based on the CC1 parity and erasure correction based on the ECC2 parity are performed to correct an error of up to 11 bytes out of data 135 bytes + ECC2 parity 11 bytes (decoding based on ECC2 parity).

A decoding process based on the ECC1 parity is as follows.
This is executed every time one sync block is reproduced. E
The decoding process based on the CC2 parity is executed after all the signals in the video data area have been reproduced.

[0010] MPEG signals are recorded only in the video data area of the DVCR format. The video data area includes 135 sync block areas. As shown in FIG. 7, a normal reproduction data area (NP data area), a special reproduction data area such as high-speed reproduction (TP data area), and an optional MPEG. The area is divided into an error correction code area (ECC3 area) at the time of signal recording.
The P data area is divided into a TPH data area and a TPL data area according to the reproduction speed.

The MPEG signal input to the DVCR is M
Two PEG transport packets are mapped to five sync blocks. At that time, MP
MPEG at the same timing as when EG data was input
In order to be able to output data and to prevent temporal inconsistency in MPEG data, MPEG
The time when the transport packet arrives at the DVCR is added as a time stamp.

When data for one track (125 sync blocks) are aligned, an optional ECC3 parity is added for 10 sync blocks, and an ECC2 parity and an ECC1 parity according to the DVCR format are further added and recorded.

The encoding of ECC3 generates a 10-byte parity from 125-byte data spanning between tracks.

The rate of MPEG data recordable on a DVCR based on the above format is 22.56 Mbps.
It is. When the rate of MPEG data is lower than this rate, as shown in FIG. 8, the rate is adjusted by packing the stuffing data into the remaining sync blocks in the NP data area. For example, if the MPEG signal rate is 12 Mb
In the case of ps, about half of the NP data area is stuffing data.

In the normal reproduction mode, decoding based on ECC1 parity and ECC2 parity is performed, and then decoding based on ECC3 parity is performed if ECC3 is supported. Each parity, TP data and NP data area M remaining after discarding stuffing data
The PEG transport stream is output at a time corresponding to the time stamp added at the time of recording.

In the special reproduction mode, since only a part of the data in the track is reproduced, decoding based on the ECC2 parity and the ECC3 parity is not performed. ECC1
TP data is extracted and collected from highly reliable sync blocks in which errors have been corrected by performing decoding based on parity, and an MPEG bit stream for special reproduction is created and output.

[0017]

By the way, when the rate of the MPEG signal is lower than the recordable rate of the DVCR, the stuffing data packed in the NP data area is discarded at the time of reproduction, and is not effectively used. Is not used. However, when an error occurs in the stuffing data portion, even if the error generated in the NP data portion is within the correction capability of the error correction code, it may exceed the correction capability of the error correction code as a whole,
Then, it is impossible to correct an error generated in the NP data portion during reproduction.

The TP data is used in the special reproduction mode but is not used in the normal reproduction mode, and no error correction is performed in the special reproduction mode. However, if an error occurs in the TP data portion in the normal playback mode, the error in the NP data portion may exceed the error correction code correction capability as a whole, even if the error is within the error correction code correction capability. In such a case, it is impossible to correct an error occurring in the NP data portion in the normal reproduction mode.

According to the present invention, there is provided an encoding / decoding method of an error correction code which can prevent an error in valid information from being unable to be corrected due to an error occurring in invalid information such as stuffing data. The purpose is to provide.

Further, the present invention is used in a special reproduction mode such as TP data, but is not used in a normal reproduction mode, and an error occurs in information which is not corrected in the special reproduction mode. It is an object of the present invention to provide an encoding / decoding method of an error correction code which can prevent the error of valid information from being unable to be corrected in the normal reproduction mode.

[0021]

A first encoding and decoding method of an error correction code according to the present invention is effective in encoding and decoding an error correction code in which a predetermined amount of information is added with parity. If the required information is less than the predetermined amount, a parity is generated for the predetermined amount of information after adding the known dummy information of an amount less than the predetermined amount to valid information, and an error correction code is generated. And at the time of error correction decoding, all or part of the dummy information part was replaced with the known dummy information and then the error correction code was decoded. At the time of decoding the error correction code, the dummy information was replaced with dummy information. Department
If it is determined that an error has occurred in the minute,
Assuming that an error exceeding the correctability of the positive code has occurred
Processing .

The valid information is, for example, NP and TP data in a VCR that records an MPEG signal, and the known dummy information is, for example, stuffing data in a VCR that records an MPEG signal.

[0023]

According to a second encoding / decoding method of an error correction code according to the present invention, in the encoding / decoding method of an error correction code in which parity is added to a predetermined amount of information, Includes special reproduction information that is used in the special reproduction mode but is not used in the normal reproduction mode and error correction is not performed in the special reproduction mode. Parity is generated for a predetermined amount of information after the special reproduction information is replaced with known dummy information, and error correction encoding is performed.
Thereafter, the dummy information portion is returned to the special reproduction information and supplied to the recording device. When the reproduction device performs reproduction in the normal reproduction mode, the special reproduction information portion is converted to the known dummy information. After the replacement, decoding of the error correction code is performed.

The special reproduction information is, for example, TP data in a VCR for recording an MPEG signal.

If it is determined that an error has occurred in the portion replaced with the dummy information when decoding the error correction code, it is assumed that an error equal to or higher than the correction capability of the error correction code has occurred. Is preferred.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a DVCR for recording and reproducing MPEG signals will be described below.

[1] Description of First Embodiment FIG. 1 shows the configuration of a DCVR.

[1-1] Description of Recording Operation The MPEG signal a input to the DVCR is composed of an NP data (signal for normal reproduction) generation circuit 111 and a TP data (signal for special reproduction) generation circuit 112 Is sent to the data amount control circuit 113.

The NP data generation circuit 111 generates NP data b based on the input MPEG signal a. T
The P data generation circuit 112 receives the input MPEG signal a
TP data c is generated based on

The data amount control circuit 113 receives the input M
The rate of the MPEG signal is determined based on the PEG signal a. The stuffing data generation circuit 114 outputs the stuffing data d based on the MPEG signal rate determined by the data amount control circuit 113 so as to match the DVCR recording rate. If the rate of the MPEG signal is low, the amount of stuffing data output from the stuffing data generation circuit 114 increases,
The higher the signal rate, the smaller the amount of stuffing data output from the stuffing data generation circuit 114.

The NP data b, the TP data c and the stuffing data d are arranged in the DVCR recording format (FIG. 8) by the synthesizing circuit 115 and output (signal e). ECC is added to the signal e output from the synthesis circuit 115.
An ECC3 parity, an ECC2 parity, and an ECC1 parity are added by a 3 parity generation circuit 116, an ECC2 parity generation circuit 117, and an ECC1 parity generation circuit 118. Then, this signal f is
Recorded as 0.

[1-2] Description of Operation During Reproduction The operation in the normal reproduction mode will be described below. The signal g reproduced from the tape 100 is sent to the ECC1 decoding circuit 121 and the stuffing data section detection section 122. The ECC1 decoding circuit 121 performs a decoding process (error detection / correction process) based on the ECC1 parity.

The signal h after the decoding processing based on the ECC1 parity is sent to the replacement circuit 123. In the replacement circuit 123, the stuffing data portion of the signal h after the decoding process based on the ECC1 parity is replaced with the stuffing data generated by the stuffing data generation circuit 114 at the time of recording. This allows
The error does not exist in the stuffing data portion of the signal i output from the replacement circuit 123.

The detection of the stuffing data portion is performed by the stuffing portion detection circuit 122 based on the reproduction signal and the reproduction time of the reproduction signal. For example, a method of detecting the amount and location of the stuffing data in a video AUX or the like, a method of detecting using the flag indicating the stuffing data in the stuffing data section, or a method of detecting the location where the stuffing data is inserted. It is also conceivable to determine (for example, put together in the latter half of the track) and detect it in combination with AUX and a flag.

If the stuffing data cannot be determined with certainty, the signal h after decoding based on the ECC1 parity is directly input to the ECC2 decoding circuit, and only the part that can be reliably determined as the stuffing data is converted to the stuffing data. What is necessary is just to replace with the stuffing data from the generation circuit 114.

The signal i output from the replacement circuit 123
Is sent to the ECC2 decoding circuit 124. The ECC2 decoding circuit 124 performs a decoding process based on the ECC2 parity. The signal after the decoding process based on the ECC2 parity is sent to the ECC3 decoding circuit 125.
The ECC3 decoding circuit 125 performs a decoding process based on the ECC3 parity.

ECC2 decoding circuit 124 or ECC3
At the time of decoding processing based on the decoding circuit 125, it may be determined that an error has occurred in the stuffing data that should be error-free. In such a case, it is preferable to determine that an error number exceeding the error correction capability has occurred, and to perform processing such as interpolation or setting an error flag without performing error correction processing.

The signal j output from the ECC3 decoding circuit 125 is sent to an NP data extraction circuit 126. NP
The data extraction circuit 126 discards TP data and stuffing data from the signal j, extracts only NP data, and outputs an MPEG signal k.

In the first embodiment, the portion replaced by the stuffing data by the replacement circuit 123 at the time of reproduction can be a 100% error-free signal, which is input to the ECC2 decoding circuit 124. Thus, it is possible to increase the possibility that the error of the NP data part (and the TP data part) can be corrected based on the ECC2 parity and the ECC3 parity.

The decoding process based on the ECC2 parity will be described as an example. In the decoding process based on the ECC2 parity, an error of 11 bytes out of 135 bytes can be corrected.
As shown by the signal h in FIG. 2, it cannot be corrected if there is an error of 13 bytes. However, as in the above embodiment, the signal h
If the stuffing data portion inside is replaced with a known pattern like the signal i in FIG. 2, the error in this portion disappears, so the error amount becomes 8 bytes, and the NP data is converted into E.
The correction can be performed based on the CC2 parity.

Further, according to the conventional method, even if there is no error in the NP data portion, if an error occurs concentrated in the stuffing data portion (due to a scratch on the tape, etc.), the ECC 2
It may happen that decoding cannot be performed by decoding processing based on parity or ECC3 parity. Then,
Even NP data without errors becomes unreliable.
However, in the above-described embodiment, the stuffing data portion is replaced with the original signal at the time of reproduction. Therefore, such a situation (a necessary error-free portion is not used due to an error occurring in an unnecessary portion). Can not be avoided).

[2] Description of Second Embodiment FIG. 3 shows the configuration of a DVCR.

[2-1] Description of Operation During Recording NP Data Generation Circuit 111, TP Data Generation Circuit 112
And the stuffing data generation circuit 114
The generation of NP data b, TP data c and stuffing data d from the MPEG signal a input to the DVCR is the same as in the first embodiment.

In the second embodiment, the TP data c is
It is synthesized after adding the ECC2 parity. ECC3
TP of signal e to which parity and ECC2 parity are added
In the data area, dummy TP data c ′ generated by the null TP data generation circuit 212 is inserted. That is, the NP data b generated by the NP data generation circuit 111, the dummy TP data c ′ generated by the null TP data generation circuit 212, and the stuffing data d generated by the stuffing data generation circuit 114 are:
The combination is performed by the combination circuit 115.

The signal e obtained by the synthesizing circuit 115 includes the ECC3 parity and the ECC2 parity generating circuit 1 generated by the ECC3 parity generating circuit 116.
The ECC2 parity generated by step 17 is added. The signal m to which the ECC3 parity and the ECC2 parity are added is sent to the replacement circuit 219.

In the replacement circuit 219, the TP data area (the area where the dummy TP data c 'is inserted) of the signal m is replaced with the original TP data c generated by the TP data generation circuit 112. The ECC1 parity generated by the ECC1 parity generation circuit 118 is added to the signal n output from the replacement circuit 219. The signal f obtained in this way is
00 is recorded.

[2-2] Description of Operation During Reproduction The operation in the normal reproduction mode will be described below. The signal g reproduced from the tape 100 is sent to the ECC1 decoding circuit 121 and the stuffing data section detection section 122. The ECC1 decoding circuit 121 performs a decoding process (error detection / correction process) based on the ECC1 parity.

The signal h after the decoding processing based on the ECC1 parity is sent to the replacement circuit 123. The replacement circuit 123 replaces the stuffing data portion of the signal h after the decoding process based on the ECC1 parity with the stuffing data generated by the stuffing data generation circuit 114, and replaces the TP data portion of the signal h with the stuffing data. It is replaced with a null TP signal c ′ generated by the null TP data generation circuit 212. Since the area of the TP data is fixed, whether or not the area is the TP data section can be easily determined.

Therefore, the TP data portion of the signal i output from the replacement circuit 123
T when generating C3 parity and ECC2 parity
The contents are the same as the contents of the P data area, and no error exists in this part. Also, no error exists in the stuffing data portion of the signal i.

Signal i output from replacement circuit 123
Is sent to the ECC2 decoding circuit 124. The ECC2 decoding circuit 124 performs a decoding process based on the ECC2 parity. The obtained signal is sent to the ECC3 decoding circuit 125. In the ECC3 decoding circuit 125,
A decoding process based on the ECC3 parity is performed.

ECC2 decoding circuit 124 or ECC3
At the time of decoding processing based on the decoding circuit 125, it may be determined that an error has occurred in the TP data area or the stuffing data that should be error-free. In such a case, it is preferable to determine that an error number exceeding the error correction capability has occurred, and to perform processing such as interpolation or setting an error flag without performing error correction processing.

The signal j output from the ECC3 decoding circuit 125 is sent to an NP data extraction circuit 126. NP
The data extraction circuit 126 discards TP data and stuffing data from the signal j, extracts only NP data, and outputs an MPEG signal k.

According to the second embodiment, it is possible to input a signal free of 100% error not only in the stuffing data but also in the TP data portion to the ECC2 decoding circuit. Can be further improved with ECC2 parity and ECC3 parity.

[0055]

According to the first aspect of the present invention, it is possible to avoid that an error in valid information cannot be corrected due to an error occurring in invalid information such as stuffing data. become.

According to the second aspect of the present invention, the information is used in the special reproduction mode such as the TP data, but is not used in the normal reproduction mode. It is possible to avoid that errors in valid information cannot be corrected in the normal reproduction mode due to the occurrence.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a part of a configuration of a DVCR according to a first embodiment.

FIG. 2 is an explanatory diagram for explaining that an error correction function of NP data is improved by the first embodiment.

FIG. 3 is a block diagram showing a part of the configuration of a DVCR according to a second embodiment.

FIG. 4 is a schematic diagram showing a recording format of a DVCR on a magnetic tape.

FIG. 5 is a schematic diagram showing a format in a video area.

FIG. 6 is a schematic diagram showing a structure of a sync block.

FIG. 7 is a schematic diagram showing a recording format of an MPEG signal on a DVCR.

FIG. 8 is a schematic diagram showing a state in which stuffing data is packed in an NP data area.

[Description of Signs] 111 NP data generation circuit 112 TP data generation circuit 113 data amount control circuit 114 stuffing data generation circuit 115 synthesis circuit 116 ECC3 parity generation circuit 117 ECC2 parity generation circuit 118 ECC1 parity generation circuit 121 ECC1 decoding circuit 122 stuffing Data part detection circuit 123 Replacement circuit 124 ECC2 decoding circuit 125 ECC3 decoding circuit 126 NP data extraction circuit 212 Null TP data generation circuit 219 Replacement circuit

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiroshi Murashima 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (56) References JP-A-11-31363 (JP, A) (58) ) Surveyed field (Int.Cl. ⁷ , DB name) H04N 5/91-5/956 G11B 20/10-20/18 H04N ^7/ 24-7/68

Claims (5)

(57) [Claims] 1. An encoding and decoding method for an error correction code in which parity is added to a predetermined amount of information, wherein when effective information is less than the predetermined amount, the effective amount of information is less than the predetermined amount. Parity is generated and error correction coding is performed for a predetermined amount of information after adding known dummy information to valid information. At the time of error correction decoding, all or part of the dummy information part is The error correction code is decoded after replacing with the known dummy information, and the part replaced with the dummy information when decoding the error correction code is used.
If it is determined that an error has occurred,
Processed as if an error exceeding the correction capability of the issue has occurred
Coding and decoding methods of the error correction code, characterized by. 2. The effective information is V which records an MPEG signal.
2. The method according to claim 1, wherein the dummy information is NP and TP data in the CR, and the known dummy information is stuffing data in a VCR for recording an MPEG signal. 3. A method for encoding and decoding an error correction code in which parity is added to a predetermined amount of information, wherein the predetermined amount of information is used in a special reproduction mode but is used in a normal reproduction mode. If special reproduction information is not included and error correction is not performed in the special reproduction mode, the special reproduction information of the predetermined amount of information is replaced with known dummy information. Parity is generated for the fixed amount of information and error correction coding is performed. Thereafter, the dummy information portion is returned to the special reproduction information and supplied to the recording means, and reproduction in the normal reproduction mode is performed by the reproduction means. An error correction code decoding method, wherein the error correction code is decoded after replacing the trick play information portion with the known dummy information. 4. The encoding / decoding method of an error correction code according to claim 3 , wherein the special reproduction information is TP data in a VCR for recording an MPEG signal. 5. When it is determined that an error has occurred in a portion replaced with dummy information during decoding of an error correction code, processing is performed assuming that an error equal to or higher than the correction capability of the error correction code has occurred. 5. The method according to claim 3, wherein
Encoding / decoding method of the error correction code according to any one of the above.