JPS6113720A - Data transmission method - Google Patents

Abstract

PURPOSE:To prevent transmission of wrong data for a long period in a decoding mode by transmitting the data on the estimated value used for conversion to the head data within a group to a prescribed position of an estimated differential data string. CONSTITUTION:The input information data A is converted into the DPCM data B by a coder 7 and supplied to a selector 8 together with past (t) pieces of data C used for said conversion. Then the data B is outputted selectively and this output is supplied to an error detection/correction code coding circuit 10 and a synchronizing signal generating circuit 11. The output of the circuit 11 converts the data group containing plural pieces of data in a data series where the data at the preceding and next positions have correlation with each other into an estimated differential data string in a format where the data on the estimated value used for conversion is added to a prescribed position of the estimated differential data string against the head data within a group. Then the signals are transmitted via a modulation circuit 12.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field 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.

(Description of Prior Art) In general, a digital signal 1 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 Mod
In a data series made up of data that has been converted into ulation, the data before and after the data have a correlation with each other. Conventionally,
When transmitting such a data series through a transmission system or recording and reproducing it on a recording medium such as a magnetic tape, one or more data groups consisting of multiple pieces of information data, synchronization data, and error detection and correction data are used. Configure a data frame with
Transmission is performed for each frame.

FIG. 1 is a diagram showing an example of a conventional data frame.

In FIG. 1, data 1 at the beginning is data for synchronization, data 2 is information data, and data 3 at the end is data for error detection and correction. Here, the synchronization data 1 and the error detection and correction data 3 are redundant data necessary for transmitting digital data. For example, by increasing bit a of the error detection and correction data 3, it is possible to enhance the error detection and correction capability on the receiving side for errors occurring on the transmission path.

However, such redundant data or an increase in the number of its bits leads to an increase in the transmission signal frequency and an increase in the transmission band during data transmission, making it more susceptible to the effects 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, the frequency characteristics of the medium become more susceptible to signal dropouts due to dust, scratches, etc. Furthermore, in order to improve the quality of received or reproduced analog signals, increasing the number of quantization bits of each information data will also lead to an increase in the transmission frequency and a shortening of the recording wavelength, similar to the above. 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 ferent ial PCM (hereinafter referred to as DPCM).

The DPCM method uses past information data to calculate the next
Predict digital data and calculate the difference between the predicted value and the actual data (
This method quantizes only the prediction error (prediction error) using a fixed quantization step, and compared to the normal data transmission method described above, when transmitting signals of the same quality, it is better to use a transmission method using data conversion using the DPCM method. The number of quantization bits required for transmission can be reduced.

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, If an error occurs on the road, the next data predictively decoded using that data will also be an error, and the error will propagate to the R limit during decoding.

<Purpose of the Invention> The present invention was made in view of the above-mentioned problems, and it is possible to eliminate long-term records of data errors during decoding while maintaining the effect of band compression associated with data conversion using predicted differences. The purpose of the present invention is to provide a data transmission method that can prevent the above.

<Explanation based on examples> Hereinafter, the present invention will be explained based on examples.

FIG. 2 is a diagram showing a frame structure of transmission data as an embodiment of the present invention. In the figure 5 a + ~5ak, 5
b, ~5bk, -----, 5n, ~5nk are each DPCM data, and a group of n DPCM data is formed, and a group of n (however, n is 1 or more) forms one group. Indicates that it is in the frame. Also, 4 il ~ 4 it placed at the beginning of each group
(i=a, b, ---, n) is the first DPCMPCM data 5t+a, b, ---1- of the group.
, n) using a DPCM encoder is predicted using a prediction method such as a linear prediction method using past data. According to the above configuration, the predicted value is always determined for each group, and the error ledger is contained within each group. Furthermore, since only prediction errors are transmitted, the transmission frequency is low even when the number of quantization bits of information data and the number of redundant data bits increases, and high-quality data transmission is not possible at the same transmission frequency. It becomes possible.

FIG. 3 is a diagram showing an embodiment of a data transmission device to which the data transmission method of the present invention is applied. Information data that is correlated with data before and after A is input, and converted into DPCM data B by a DPCM encoder 7. Reference numeral 8 denotes a data selector, into which, simultaneously with D and PCM data B, past data C used for the DPCM signal conversion is input, and a control circuit 9 selects and outputs one of B and C.

10 is an error detection and correction code decoding circuit, and 11 is a synchronization signal generation circuit. The output of 11 becomes a data string having the structure shown in FIG.

12 is a modulation circuit that performs modulation suitable for the transmission path, such as MFM.
(Modified, FrequencyModu
Modulation such as ration) is applied. The output of 12 is outputted to a transmission path or a recording medium 13 via a recording element. Further, the signal that has passed through step 3 is passed through a reproducing element to a demodulation circuit 14 for demodulating the signal modulated by the modulation circuit 12.
Furthermore, 15 synchronization signal separation circuits detect and separate synchronization signals for frame recognition. Reference numeral 16 denotes an error detection/correction code decoding circuit, which performs a predetermined error detection code correction. , 17 is a data distributor, and demodulated DPCM
The past data F used in signal E signal PCM encoding is separated and output to the next stage DPCM decoder 18. 19 is a demodulation control circuit, which includes the above-mentioned distributor 17 and decoder 1;
Control 8. G is the output of decoded information data.

According to the data transmission device configured as described above, since the first data in each data group uses the past at the time of encoding as individual data, and the other data as DPCM data, the transmission of prediction errors is the main part. Therefore, the transmission frequency is low, and conversely, if the transmission frequency is the same, it is possible to add data with a large number of quantization bits and redundant data such as error detection/correction codes, etc. to improve the quality of the transmitted data. It is possible to improve the error detection and correction ability. At the same time, since the past data at the time of encoding is placed at the beginning of each group, even if an error occurs during transmission, the error record remains within each data group during decoding, and linear prediction is performed. It has the excellent feature that no erroneous records will occur for a long period of time even if the system is used.

The above was explained based on the 21st Δ frame configuration, but
It is of course possible to prevent continuous errors in decoded data by interleaving past data and DPCM data within a frame between frames or within a frame, or by multiplexing error detection/correction codes.

It should be noted that, in addition to the DpcM method used in the explanation, the present invention can obtain similar effects as long as it is a predictive coding method that uses a prediction method and creates a predicted value from past data at the time of prediction.

Further, the number of bits of the synchronization signal and the position and number of bits of the error detection/correction code within the frame shown in FIG. 2 are not limited as long as the gist of the present invention is met. Also, the past data in the code death prediction value and the number of bits, position, number of DPCM signals, 1
Similarly, there is no restriction on the number of groups within a frame.

<Description of Effects> As explained above, according to the present invention, it is possible to transmit high-quality data, reduce the number of transmitted bits, and eliminate data errors over a long period of time during decoding. The present invention provides a data transmission method that can prevent slips.

[Brief explanation of drawings]

FIG. 1 shows an example of a conventional data frame. FIG. 2 shows a frame structure of transmission data as an embodiment of the present invention. FIG. 3 shows data transmission using the data transmission method of the present invention. FIG. 1 is a diagram showing an example of an apparatus. l is data for synchronization, 3 is data for error detection and correction,
4a, ~4at, 4bl ~4bt,
-----. 4 n + ~4nt are past data, 5al
~5ak, 5J ~5bk, -----, 5nl ~5
n is predicted difference data, respectively.

Claims (1)

[Claims] Concerning a predicted value used to convert a data group consisting of a plurality of data in a data series in which the preceding and succeeding data have mutual correlation into a predicted difference data sequence, and to perform the conversion on the first data in the group. A data transmission method that adds data to a predetermined position of the predicted difference data string and transmits the data.