JPS61247137A - Data transmission method - Google Patents

Abstract

PURPOSE:To prevent propagation of a data error at decoding over a long time by adding a data number closest to a specific value in a data group to a data string based on the difference between adjacent data and sending the result. CONSTITUTION:A data obtained by sampling an analog signal inputted from an input terminal 5 is converted into a DPCM data by a DPCM encoder 8, and fed to a control address generating circuit 21. The circuit 21 stores once the sampling data for one block's content and outputs a data number A0 closest to 0 level among all the data in the data block. After the DPCM data is stored by one block at a control address addition circuit 22, the number A0 is added. The DPCM data added with the number A0 is added by a redundancy bit at an error correction code addition circuit 9 and a synchronizing signal is added by a cynchronizing signal addition circuit 10, and the result is sent to a transmission line 12.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a data transmission method for transmitting a data sequence in which preceding and succeeding data are correlated with each other.

(Prior Art) In general, digital signals obtained by sampling and quantizing temporally correlated analog signals such as audio signals and video signals, and further analog-to-digital conversion, such as PCM (Pulse Code
In a data series consisting of modular data, the preceding and succeeding data have a correlation with each other. Conventionally, when transmitting such a data series via a transmission system or recording and reproducing it on a recording medium such as a magnetic tape, one of the data groups consisting of multiple pieces of information data is
One or more groups, synchronization data, and error detection and correction data constitute a data frame, and each frame is transmitted.

However, the increase in redundant data represented by synchronization data and error detection and correction data as described above, as well as the increase in the number of bits thereof, leads to an increase in the transmission signal frequency and an increase in the transmission band during data transmission. It becomes susceptible to the influence of the frequency characteristics of the transmission path and external noise, leading to an increase in errors during transmission. Furthermore, when recording on and reproducing from a recording medium such as a magnetic tape, the recording wavelength becomes shorter, making it more susceptible to signal dropouts due to the frequency characteristics of the medium, dust, scratches, etc. In addition, when increasing the number of quantization bits of each information data in order to improve the quality of received or reproduced analog signals, this also leads to an increase in the transmission frequency and a shortening of the recording wavelength. A similar problem occurs.

Bandwidth compression is a technique for reducing such an increase in data rate. There are various methods for band compression technology, but a commonly used method is the predictive differential PCM method (Difference PCM method).
It is considered to use data conversion using ferentialPCM (hereinafter referred to as DPCM).

The DPCM method is a method that predicts the next digital data using past information data, and quantizes only the difference between the predicted value and the actual data (prediction error) using a constant quantization step. When transmitting signals of the same quality, a transmission method using data conversion using the DPCM method can reduce the number of quantization bits required for transmission.

Figure 5 is a diagram showing the conventional transmission data format using the DPCM system.
3 is a differential data series, and 3 is data for error correction and detection such as well-known CRC.

FIG. 6 is a diagram showing how data is encoded and decoded using the DPCM method. In the figure, S is the input analog signal waveform, Di
, o to D i , and N-1 indicate the value of the difference from the immediately preceding data, and each data has no errors (if this is the case, the original analog signal waveform will be faithfully reproduced).

FIG. 7 is a block diagram showing a schematic configuration for realizing the system as described above. In FIG. 7, the data obtained by sampling the analog signal input from the terminal 5 is processed by the adder 7, which passes through the one-sampling period delay device 6 and the data which is not delayed.
The data is supplied to the CM encoder 8 and converted into data with a predetermined number of bits. This predetermined bit data is supplied to the error correction code addition circuit 9, and redundant bits as described above are added thereto. Furthermore, after a synchronization signal is added by the synchronization signal addition circuit 10, the transmission path (for example, a recording/reproducing device) 12 is sent via a terminal 11.
is discharged to.

On the other hand, the transmission data obtained from the transmission line 12 via the terminal 13 is separated into a synchronization signal and other data by a synchronization signal separation circuit 14, and then sent to an error correction circuit 15 based on the separated synchronization signal. Well-known error correction is performed. The error-corrected data is restored to its original analog signal waveform by a DPCM decoder 16.

<Problems to be Solved by the Invention> However, when transmitting data using such a band compression technique, a predicted value from past data becomes the determining factor for decoding. In general, this prediction method includes a one-dimensional previous value prediction method in which one piece of past data becomes the predicted value, and a linear prediction method that uses multiple pieces of past data.In either case, once the data is transmitted, When an error occurs on the road, the next data that is predictively decoded using that data also becomes an error, and the error propagates indefinitely during decoding.

FIG. 8 is a diagram showing how error propagation occurs. now.

If an error occurs at time ti,1, then D't.

l is the error data, and the subsequent restored data will be the one in which the error has been propagated as shown in the figure.

In view of the problems typified by the above, the present invention can prevent the propagation of data errors over a long period of time during decoding while maintaining the band compression effect by converting data to data based on the difference between adjacent data. The purpose is to provide a data transmission method.

<Means for Solving the Problems> In view of the above-mentioned purpose, the present invention adds the number of data closest to a specific value in a data group to a data string based on the difference between adjacent data and transmits the data. I'm doing it like that.

<Operation> According to the above configuration, using the transmitted data number,
It is possible to prevent errors from propagating during decoding for each piece of data closest to a specific value.

<Example> Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 shows a code according to the data transmission method of the present invention.

FIG. 2 is a diagram illustrating an example of a configuration for decoding. FIG. 2 is a diagram showing an example of the transmission data format according to the present invention.
ync (1) is a synchronization signal, and subsequent data can be separated based on this synchronization signal. W0～W
n-1 is n DPCM data similar to 2 in FIG. 5, and these form one data group. 3 is data for error correction and detection, such as well-known CRC, similar to 3 in FIG. Ao (4) is data indicating the number of the data closest to the 0 level before the DPCMR number among the following n DPCM data.

FIG. 3 is a diagram showing a state of decoding using the aforementioned data Ao. In FIG. 3, the (i-1) block is the data whose data number 4 is closest to the 0 level, converted into DPCM, the i block has the data number O, and the (i + 1) block has the data number 3 which is 0. It is assumed that the data closest to the level is converted into DPCM. On the other hand, the error is (i −1
) Block data number 2, i block data number 5
It is assumed that this occurs in

In FIG. 3, the solid line shows the original analog signal, and the dotted line shows the signal restored after data transmission in this embodiment.
In the i-1) block, after an error occurs at Ao=4, the i error will be corrected as shown in the figure after two sampling periods. On the other hand, A in the l block. = O, even if an error occurs in data number 5, the above-mentioned correction will not be performed within l block, and data number 3 in the next (i+1) block will be corrected.
It will be corrected at the time of. Here, the possible values of Ao are 0 to 7
Therefore, it is sufficient if AO is 3 bits. Generally, the relationship between n and m in FIG. 2 is 2≧n.

The operation of the part shown in the first figure will be explained below. The data obtained by sampling the analog signal inputted from 5 is converted into DPCM data by a DPCM encoder as in the device shown in FIG. 7, and is supplied to the control address generation circuit 21.

The control address generation circuit temporarily stores one block of sampling data, and all data cores of the data block also have data numbers (control address data) close to O level.
Output AO. The DPCM data output from the DPCM encoder 8 is also stored for one block in the control address addition circuit 22, and then the aforementioned control address data A0 is added thereto. The DPCM data to which the control address data has been added is added with the above-mentioned redundant bits in the error correction code adding circuit 9, and a synchronization signal is added in the synchronization signal adding circuit 10, and then outputted to the transmission path 12.

The data transmitted through the transmission path 12 is separated into synchronization signals by a synchronization separation circuit 14, and each data is reproduced, and these data are supplied to an error correction circuit 25. error correction circuit 2
For the data that could not be corrected in step 5, the data number AE is supplied to the control circuit 26. Further, the aforementioned control address data A0 is also supplied to the control circuit 26.

The control circuit 26 controls the <DPCM decoder 27 based on 80 and AI: as shown in the flowchart of FIG. 4, which will be described later. The output of the DPCM decoder 27 is converted into an analog signal by a digital-to-analog (D/A) converter 28, and the restored analog signal is output from the terminal 17.

Next, the operation of the control circuit 26 in FIG. 1 will be explained with reference to the timing chart shown in FIG. 4.

Here, the correction flag indicates whether or not an error has occurred in each data block. When the flag is 1, it indicates that an error has occurred, and when it is "OF1", it indicates that an error has occurred. This indicates that the correction has not occurred or that the correction has been completed.

First, this correction flag is reset to °°0'', and the control address data Ao of the data block that is about to be reproduced is stored. Next, error correction processing is performed, and there is data that could not be corrected. If it exists, set the correction flag to “1”.
'' and store the data number Aε of that data.

Next, the magnitude relationship between Ao and Aa is compared, and if AO≧A
, then after an error occurs at data number Ag, the restored data is immediately corrected to O level at data number Ao within the block. At the same time, the correction flag is also reset to 0'', and DPCM decoding continues until the next data block.

On the other hand, if Ao≦Aε, after an error occurs, 0 level correction is not performed within that data block, but correction is performed at data number AO of the next data block.

In addition, if it is determined that the above-mentioned error data does not exist, the correction data at that time is “1”.
” It is determined whether or not it remains.

If it is "1", it means that correction could not be performed in the immediately preceding data block, so 0-level correction is performed at the data number AO in the data block. Of course, if there is no error and the flag is °°O'', these processes are not performed and DPCM decoding continues.

In the above embodiment, by utilizing the fact that a data series consisting of a data group that occurs with the same probability of being positive or negative, such as an audio signal, swings around the 0 level, the data that is closest to the O level data, which is the easiest to obtain, in the data group is used. data number D
Along with PCM data.

is being transmitted to. Even if an error occurs during decoding, propagation of the accompanying error can be prevented for each piece of data closest to the 0 level.

゛In addition, in the above-mentioned embodiment, the control address data for zero level correction is one piece for each data group, but the second and third data in each data group are used in order from the data closest to the 0 level. The data number may be transmitted.

In this case, although the number of transmission bits increases slightly, it is possible to limit the propagation of errors to an even shorter period.

Although DPCM has been described as a data conversion method, the present invention can also be applied to transmission systems that perform other data conversions based on differences between adjacent data, such as adaptive predictive differential PCM (APCM). It is also possible to apply

<Effects of the Invention> As explained above, according to the present invention, the propagation of data errors over a long period of time during decoding can be prevented while maintaining the band compression effect by converting data to data based on the difference between adjacent data. This provides a data transmission method that can

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a configuration for code decoding according to the data transmission method of the present invention, FIG. 2 is a diagram showing an example of the transmission data format according to the present invention, and FIG. 3 is a diagram showing the state of decoding according to the present invention. FIG. 4 is a flowchart for explaining the operation of the control circuit in FIG. 1, FIG. 5 is a diagram showing the conventional transmission data format using the DPCM method, and FIG. FIG. 7 is a block diagram showing a schematic configuration for realizing the system as shown in FIG. 6. FIG. 8 is a diagram showing how error propagation occurs. In the figure, 1 is a synchronization signal, DPCM data, 3 is an error correction code, 4 is control address data, 8 is a DPCM encoder, 9 is an error correction code addition circuit, 21 is a control address data generation circuit, and 22 is control address data Additional circuit, 2
5 is an error correction circuit, 26 is a control circuit, and 27 is a DPCM decoder. -105 Six Domo 30

Claims (2)

[Claims] (1) A data group consisting of multiple pieces of data in a data series in which the preceding and succeeding data have mutual correlation is converted into a data string based on the difference between adjacent data, and a specific value in the data group is added to the data string. A data transmission method in which the closest data number is added to the data and transmitted. (2) The data series consists of a data group that occurs with the same probability of magnitude with respect to the specific value.
The data transmission method described in ).