JPS598445A - Data transmitting method - Google Patents

Abstract

PURPOSE:To attain the transmission of data, by obtaining a maximum between two symbols of an error correcting code series and locating a redundant symbol of an error correction code series near the center position of each block to improve the burst error correcting ability and the random error correcting ability. CONSTITUTION:A recording audio signal sent from an input terminal 1 is digitized by an A/D converter 2, one field's portion is written in RAMs 3, 4 and supplied to P, Q encoder/decoder 6. The parity from the decoder 6 and a signal read out from the RAMs 3, 4 are supplied to an adder 7 to add addresses generated from an address generator 8. Further, a reproduced digital signal sent from an input terminal 16 of the reproducing signal is demodulated by an FM encoder/decoder 12 and supplied to a CRC encoder/decoder 10. Further, pointer RAMs 18, 19 and a compensating circuit 22 and the like are used to obtain a maximum between two symbols of the error correction code series, thereby improving the burst error correcting ability and the random error correcting ability.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a data transmission method applicable to recording and reproducing digital audio signals.

For example, since the /field portion of the digital audio signal accompanying the video signal is data of a predetermined location, the first
As shown in the figure, it is considered as a unit of (n symbols×m blocks), and error correction correction encoding processing is performed for each unit. Cross-interleaving has been proposed as one method for making a digital audio signal have an error-correctable code structure.

Cross interleaving is a double interleaving in which each singil of the digital information signal is included in two error correction code sequences. In the following description, P and Q sequences, which are parity code sequences, are used as error correction code sequences. This cross-interleaving can be applied to the data in the arrangement shown in FIG.

The data to which the P sequence and Q sequence are added after being subjected to the Scherrer correction coding process by this Zorock-completed cross interleaving is processed sequentially from the first program as shown by the arrows in Fig. 7. , transmitted longitudinally. During this transmission, a synchronization signal, a block address signal, and a CRC code for error detection are added and recorded for each block.

The error correction encoding method using cross interleaving is
Since each word of the digital audio signal is included in two parity sequences, it has a feature of high error correction ability. Furthermore, in this cross-interleaving error correction encoding method, the probability that error correction will be impossible differs depending on the position within the block.

For simplicity of explanation, consider the case of cross-interleaving in which coword parity is added to forward digital data.The parity sequence can be expressed as shown in FIG. In FIG. 2, the black circles indicate the /sword of each code symbol, and attention is drawn to 5o-85 with the white circle added. Further, in FIG. 2, the three words in the vertical direction are the series of one parity P, and the six words in the diagonal direction are the series of the other parity Q.

The transmission system is random, and the decoder uses parity P
When P decoding using parity Q and Q decoding using parity Q are alternately repeated multiple times, consider how many cases occur where error correction for each symbol So '' Ss becomes impossible. For example, In the case of symbol So, if the symbols located in the trapezoid containing this symbol S become error words at the same time, each of the two parity sequences will contain two error words, and this error cannot be corrected. By counting such trapezoidal patterns, it is possible to find the probability that error correction is impossible.Also, the symbols St, S2゜Ss,
Regarding S4 and S5, when the words constituting the parallelogram including this symbol are erroneous at the same time, error correction becomes impossible.

Assuming that the probability that the / word makes an error is P, the probability that error correction is impossible for each word of So''Ss is as shown below.

Po=/θP'Pl=10P' S S
P* =/ 3P' Pa =/ 'IP'S
SP
4 −/ 3P Ps =/ OP'
S S Of course, there are cases in which the S hood or higher is erroneous at the same time and error correction becomes impossible, but this probability (p5 or lower) is ignored. Furthermore, the same tendency exists not only in the case of DOW-P but also in the case of n-word uparity in general.

As mentioned above, conventional error correction encoding methods do not take into account the fact that the probability that errors cannot be corrected differs depending on the data channel.
, parity data was assigned to the position of Ss or S5. However, since the parity information data for error correction is more important, it is desirable to place the PCM data in a position where there is a low probability that correction will become impossible.

When digitizing a stereo audio signal that accompanies an N'I"SC video signal, the digital audio signal for /field is /θ30 words when the silling frequency is fh (fh is the horizontal frequency). Word control data for this 105θ word is added, (n=ff word) (m=/
3.2 blocks) (nXm = 105 words). Figure 3 shows P for this 70S word data.

A configuration example in which a parity sequence of Q is added is shown.

In FIG. 3, w and -Ws indicate a horizontal information data series, which is included in the information data series,
A parity sequence P is formed by words (x marks) having a distance of 11 blocks. This distance between cowords (D=/ll block) is the maximum possible value. However, the cycle of block change is in units of /32 blocks, so as long as the remaining distance after forming one P sequence is not smaller than the distance between the units, this distance is the maximum. be done. In this way, by maximizing the distance between the words, it is possible to increase the ability to correct burst errors.

Moreover, the other parity sequence Q is the information data sequence W! ~
It is formed by words (indicated by *) included in each of W8 and parity sequence P, and having a distance of //blocks. The distance between the cowords included in this parity sequence Q is υ smaller than in the case of the parity sequence P described above.

In the data structure shown in FIG. 3, two parity sequences P and Q are located at the end of the / block. but,/
As described above, the position at the end of the block has a low probability of making error correction impossible, and therefore it is not preferable to place a parity sequence with redundant data at this position.

Therefore, when a parity sequences P and Q are brought to the center of the block, the data structure becomes as shown in the figure. As is clear from this diagram, since one parity sequence P does not contain the data stored in the other parity sequence QK, the gap between one word contained in each of data sequence W4 and parity sequence P is Since the distance is 2g blocks, the distance between cowords cannot be set to /S block.

In consideration of the above-mentioned points, the present invention provides redundant symbols for error correction in the vicinity of the central position of a block while keeping the distance between two words of a correction code sequence at a maximum. It was designed to be arranged.

FIG. S shows a sequence in which the invention is applied to the case (n=g, m=/32) as described above.

One harness sequence P is formed by words located at equal intervals of /l blocks.

Furthermore, when forming the parity sequence Q, the information data sequences Wl-ws and the parity sequence P are extracted from each other. word is used. As shown in FIG. 3, the resulting parity is placed at the position of the block number obtained by adding 6 blocks to the block number of the symbol included in the information data series W4. Therefore, the block number of the first parity included in the parity sequence P is obtained by subtracting the SS block from this parity block number.

In such a parity sequence Q, the information data sequence W
The distance between the cowords included in each of the information data series W8 and the parity series P is 7 blocks, and the distance between the words included in the information data series W8 and the words of the parity series Q is also 7 blocks. Therefore, in the parity sequence Q, the distances between each word are equal // blocks.

Furthermore, as shown by the broken line in FIG. 5, the words of the parity sequence Q may be arranged at positions obtained by subtracting lIt from the block number of the words included in the information data sequence W4. The distance between the word of parity series Q and the word of parity series P becomes the left S block.

In the above description, the distance between the words of the parity sequence P is set to /l block. As a result, 1.20 blocks remained, and using this, as shown in Figure 6,
Five locations where the distance between cowords is /S block can be created. Furthermore, the distance between cowords of the parity sequence Q is 7.2 blocks.

Then, as shown in FIG. 6, the data of the parity sequence Q is allocated to a block number obtained by adding 70 blocks to the block number containing the / word of the data sequence W4. In this way, the distance between each unit of the parity sequence Q becomes equal to /2 blocks.

Also, as shown by the broken line in FIG. 6, the data series W
The data of the parity sequence Q may be allocated to the block number obtained by subtracting g from the block number of the word included in 4.

FIG. 7 shows the configuration of an embodiment in which the present invention is applied to the case where digital audio signals are recorded on a magnetic tape.

In FIG. 7, a recording audio signal is supplied to an input terminal indicated by 1, and is digitized by an A/D converter 2. The solid arrows in FIG. 7 indicate the direction of the signal during recording, and the broken arrows indicate the direction of the signal during reproduction.

A digital audio signal from A/D converter 2 is written to RAM 3 or RAM 4. This RAM3
and RAM 4 are each capable of storing /field's worth of digital audio signals, and while input data is being written into one RAM, the data of the previous field is read out from the other RAM.

The Q encoder/decoder 6 is supplied to form one parity, which is written to the other RAM. An address generation circuit 5 is provided to write predetermined data into the memory areas of the RAM 3 and RAM 4, and to interleap and read the data. This address generation circuit 5.

A predetermined block address is generated by an address generation circuit, ROM, and adder.

Further, the digital audio signal and parity data read from the RAM 3 or RAM 4 are supplied to the adder T, and a block address from the proxer P address generator 8 is added thereto. The output of the adder 7 is then serialized by a parallel-to-serial converter 9 and supplied to a CRC encoder/decoder 10.

For example, the CRC encoder/decoder 10 (X16+
X'' + .

In this example, since the FM modulation method is used, the output of the CRC encoder/lever-1''10 is supplied to the FM encoder/decoder 12.

Furthermore, a block synchronization signal from a synchronization signal generator 14 is added in an adder 13 and output to an output terminal 15. The digital signal taken out to this output terminal 15 is recorded on the magnetic tape by the rotary head.

In addition, 1. A digital signal reproduced from the magnetic tape is supplied to the input terminal 16, and is sent to the FM via the synchronization detection circuit 17.
The signal is supplied to encoder 4//decoder 12 and is FM demodulated. This FM demodulated playback data is supplied to a CRC encoder/decoder 1o, where each block is subjected to a Scherrer check using a CRC code, and the result is taken out as a /bit error pointer. This error pointer is stored in pointer RAMs 18 and 19. These pointer RAMs 18 and 19 correspond to RAMs 3 and 4.
An error pointer is written to each address. Yes.

A block address common to RAMs 3 and 4 is supplied from address generation circuit 5 to pointer RAMs 18 and 19.

In addition, the reproduced data is transferred to the buffer 2o and the serial/parallel converter 2
1 to RAMs 3 and 4.

This buffer 20 delays the reproduced data until an error pointer is formed as a result of the CRC check.

RAM 3 and RAM 4 operate in the same way as during recording, so that in the field where playback data is written to one of them, the playback data read from the other is corrected. . When writing reproduced data to RAM 3 or RAM 4, the error word indicated by the 2-pointer is prevented from being written. Therefore, the error pointer read from the pointer RAM 18 or 19 is supplied to the timing generator 22, which generates a control signal for the RAM 3 or 4.

The playback data read from RAM 3 or 4 is P.

The data is supplied to the Q encoder/decoder 6, where error correction is performed using parity, and the error-corrected data is written into the RAM 3 or 4 again. During this error correction, the error word only needs information that it is an error, and therefore, as described above, the error word itself is not written to the RAM 3 or 4. It is still not possible to correct errors if a single parity generation sequence contains more error words than cowords, but error correction using a parity P sequence and error correction using a parity Q sequence are performed repeatedly and alternately. In particular, the number of words in which errors cannot be corrected is reduced.

The error-corrected reproduced data read from the RAM 3 and RAM 4 is supplied to the correction circuit 23, and words whose errors cannot be corrected are subjected to average value interpolation processing. The output of the correction circuit 23 is converted into an analog signal by a D/A converter 24, and a reproduced audio signal is outputted to an output terminal 25. Note that an A/D converter 2 and an /A converter 24 are provided in correspondence with the co-channel signal.

As understood from the above explanation, this invention
By locating the redundant symbols of the error correction code series near the center position of each block while maximizing the distance between the symbols of the error correction code series, burst error correction ability and randomness can be improved. Both error correction capabilities can be improved.

Note that an adjacent code or a Reed-Solomon code can be used as the error correction code, and different codes can also be combined. In the case of these codes, more than one redundant code is used.

[Brief explanation of the drawing]

Figures 1 and 2 are route maps used to explain error correction encoding using cross interleaving, and Figures 3 and 3 are route maps used to explain error correction encoding using block-contained cross interleaving. , FIG. 5 is a route map used to explain the data structure in one embodiment of this invention, FIG. 4 is a route map used to explain the data structure in another embodiment of this invention, and FIG. 7 is a route map to which this invention is applied. FIG. 2 is a block diagram showing the configuration of an error correction encoder and an error correction decoder. 1...Audio signal input terminal, 3,
4...RAM, 6...P, Q encoder/decoder, 10...CRC encoder/decoder, 15...Output terminal for recording signal ,
16......Reproduction signal input terminal, 18゜1
9... Pointer RArVI, 23...
. . . Correction circuit, 25 . . . Output terminal for reproduced audio signal. Agent Masatoshi Sugiura

Claims (1)

[Claims] In a data transmission method in which a digital information signal is subjected to error correction coding in units of (n symbols x m blocks), the first signal containing k redundant symbols is generates an error correction code sequence, generates a second error correction code sequence having seven redundant symbols so that the distance is smaller than the distance for the (n+k) symbols, and generates a second error correction code sequence having seven redundant symbols, n symbols of each block of the signal are included in different seventh and third error correction code sequences, and redundant symbols of the seventh and third error correction code sequences are arranged near the center position of each block. A data transmission method characterized by locating.