JPS58162142A - Transmitting system of digital signal - Google Patents

Abstract

PURPOSE:To reduce the number of bits and to prevent the accumulation of transmission errors by grouping PCM signals and transmitting the PCM signals after converting the PCM signals other than the leading PCM signals into DELTAPCM signals. CONSTITUTION:One group (frame) is composed of plural PCM signals and a PCM encoder 2 converts the PCM signals into DELTAPCM signals regarding the leading PCM signal as an initial value. A mixer 3 mixes the leading PCM signal with other DELTAPCM signals to form the center part of the frame. An error detection/correction code in the frame and a frame synchronizing signal are added to the center part by an error correction code generating circuit 4 and a synchronizing signal generating circuit 5 respectively to constitute one frame shown by the figure. The framed digital signal series are transmitted and recorded in a recording medium through a digital transmission line.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention transmits digital signals obtained by sampling analog signals such as acoustic signals and further quantizing them through a transmission system, or records and reproduces digital signals on a recording medium. It concerns the signal transmission method.
In particular, the purpose is to transmit high-quality digital signals while lowering the transmission frequency and suppressing the occurrence of errors.

Conventionally, analog signals such as acoustic signals are converted to a mu/D converter (
When recording and reproducing a digital signal (hereinafter referred to as a PGM signal) obtained by an analog-to-digital converter on a recording medium such as a magnetic tape, the PCM data is grouped into multiple pieces and further By adding a code for detection and correction and a synchronization signal, a frame as shown in FIG. 1 is constructed. In Fig. 1, 5YNO is a synchronization signal, and ORCG (CycQic Redundancy) is a type of error detection code.
This is an example of a frame structure using CheckCode). The synchronization signal and the error detection and correction code are redundant signals necessary for the transmission of digital signals. For example, by increasing the number of bits of the error detection and correction code, the error detection and correction capability can be strengthened.

However, in the case of digital signal transmission, this increase in redundant signals causes an increase in the signal frequency, making it more susceptible to the influence of the frequency characteristics of the transmission path and noise from abroad, resulting in errors during transmission. This will have negative effects such as an increase in Furthermore, when recording and reproducing on a recording medium such as a magnetic tape, the recording frequency must be high, and the recording wavelength on the recording medium must be short, resulting in signal loss due to the frequency characteristics of the medium, dust, scratches, etc. dropout). The above examples are problems related to redundant signals such as synchronization signals and error detection and correction codes, but recent PCs
In order to improve the quality of analog signals in M signal transmission and recording/playback equipment, there is a tendency to increase the number of quantization bits of PCM signals, and as the number of quantization bits increases, the transmission frequency increases as well. This leads to the shortening of the recording wavelength and causes the above-mentioned problems.

Bandwidth compression is a technique for reducing such an increase in data rate. There are various band compression techniques, but one that is often used is the differential PCM method (hereinafter abbreviated as the IPCM method). dPGMPCM method This method predicts the next digital data from the digital data of past signals, quantizes only the difference between the predicted value and the actual data (prediction error), and transmits it. In comparison, the ΔPCM method requires fewer quantization bits for transmission. Alternatively, higher quality transmission is possible using the same number of bits as the PCM method. However, in the ΔPGMPCM method, the level of the past signal becomes the determining factor during decoding in order to predict the next signal from the past signal. That is, once an error occurs, the next prediction data will also be an error, and error propagation will occur indefinitely.

The present invention makes use of the advantage of the low transmission bit number of the ΔPCM method, while at the same time preventing error propagation from occurring over a long period of time, and also makes the rise of the ΔPGMPCM signal faster. The present invention provides a digital signal transmission method characterized in that it is used for values.

FIG. 2 shows a frame structure in one embodiment of the present invention. In FIG. 2, the PCM signal and ΔPGMPCM signal are formed within one frame. Furthermore, the ΔPGM signal sequence within the frame is formed using the PCM signal as an initial value. According to the above configuration, the ΔPGMPCM signal value is always preset for each frame, and error propagation is contained within each frame. Furthermore, ΔP for each frame
Since the GMPCM signal value is set, the startup time during decoding is quick. Furthermore, since only prediction errors are mainly transmitted, the transmission frequency is low even when the number of bits increases, and conversely, high-quality digital transmission is possible at the same transmission frequency.

FIG. 3 shows an embodiment of a digital transmission device to which the digital signal transmission system of the present invention is applied. 1 is a PCM signal input terminal, 2 is a ΔPGM encoder, a mixer that combines the 3ViP CM signal and ΔPCM signal as described below, 4 is an error correction code generation circuit that adds an error detection and correction code, and 5 is a frame synchronization 6 is a modulation circuit that modulates according to the transmission system, for example, MF
M (Modified Frequency Mod
ration), and 7 is an output terminal, from which a digital signal with a frame structure as shown in Fig. 2 is output, and is then input to a digital transmission system, or sent to a magnetic tape via a recording element. etc. are recorded on recording media. On the other hand, 8 is an input terminal into which a signal from a digital transmission system or a signal reproduced from a recording medium via a reproduction element is input. 9 is a demodulation circuit that demodulates a signal modulated by a modulation method such as MFM, 1o is a synchronization signal separation circuit that separates a synchronization signal added to identify frames and synchronizes the frames, and 11 is an error detection circuit. An error correction circuit that corrects errors in a signal using a correction code, 12 is a Δpa in the frame in FIG.
A ΔPICM decoder decodes the M signal into a PCM signal, and 13 is a PGM output terminal.

Next, the operation will be explained. An analog signal such as an acoustic signal is converted into a PCM signal by a MU/D converter and inputted to a PCM signal input terminal 1. Next, use ΔPGM encoder 2 to
The M signal is converted into a ΔPGMPCM signal in units of multiple units, and the mixer 3 forms the central part of the frame shown in FIG. Furthermore, an error correction code generation circuit 4 adds an error detection and correction code (ORCG) within the frame, a synchronization signal generation circuit 6 adds a synchronization signal (5YNC) for frame synchronization, and the signals are input to a modulation circuit 6. . MFM is a well-known modulation method and is widely used in the field of magnetic recording. Then, a digital signal series having a frame structure as shown in FIG. 2 is transmitted from the output terminal via a digital transmission line or recorded on a recording medium via a recording element.

On the other hand, a modulated signal from the above-mentioned transmission line and a modulated signal obtained from the recording medium via a reproducing element are inputted to the input terminal 8 and inputted to the demodulation circuit 9 . The demodulation circuit 9 performs clock recovery from the modulated signal, and uses this clock as input to perform demodulation. Next, the synchronization signal is separated in the synchronization signal separation circuit 10, and checked for errors in the error correction circuit 11. If there is an error, it is corrected. Finally, the ΔPCM signal in the frame is decoded by the ΔPCM decoder 12 using the first PCM signal in the frame as an initial value, and the original PC
The signal is decoded into an M signal series, output to the PGM output terminal 13, and further converted to the original analog signal via a D/M converter.

The above description has been made based on the frame structure shown in FIG. 2, but errors in the paM signal that are continuous in time can also be avoided by interleaving the PCM signal and the ΔPGMPCM signal within the frame.

Note that the number of bits of the synchronization signal and the number of bits of the error detection and correction code within the frame shown in FIG. 2 are not limited as long as the gist of the present invention is met. Similarly, the number of bits and the number of PCM signals and ΔPCM signals are not limited.

As is clear from the above embodiments, the present invention mainly transmits prediction errors by converting the first data in a group into a PCM signal and converting data other than the first data into a ΔPCM signal sequence and transmitting it. Therefore, the transmission frequency is low, and conversely, if the transmission frequency is the same, the transmitted digital signal can be of high quality, such as data with a large number of quantized bits and many redundant signals used for error detection and correction. Error correction ability can be improved. At the same time, since the first data of each group is a PCM signal, even if an error occurs during transmission, it will remain within that group during decoding, and the error will not be propagated for a long time.
It has the excellent feature that the signal rises quickly. Therefore, according to the present invention, it is possible to transmit high-quality data with high error correction ability, and at the same time, it is possible to reduce the number of transmitted bits, thereby reducing the influence of frequency characteristics of the transmission system, external noise, etc. Therefore, it is possible to provide an excellent digital signal transmission system that can realize signal reproduction with few errors.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a frame structure in a conventional digital signal transmission method, FIG. 2 is a diagram showing a frame structure in an embodiment of the digital signal transmission method of the present invention, and FIG. 3 is a diagram showing a frame structure in an embodiment of the present invention. 1 is a block diagram illustrating one embodiment of a suitable digital signal transmission device; FIG. 2...ΔPGM encoder, 3...Mixer, 4...Error correction code generation circuit, 6...
... Synchronization signal generation circuit, 6 ... Modulation circuit, 9
... Demodulation circuit, 1o ... Synchronization signal separation circuit, 11 ... Error correction circuit, 12 ...
・ΔPOM delder. Agent's name: Patent attorney Toshio Nakao and 1 other person - Continued from page 1 of Johane 0 Inventor: Nobuyoshi Hihara, Matsushita Electric Industrial Co., Ltd., 1006 Kadoma, Kadoma City, Japan 0 Author: Yoshinori Amano, 1006 Kadoma, Kadoma City Address Matsushita Electric Industrial Co., Ltd.

Claims (1)

[Claims] The digital signals obtained by sampling and quantizing the analog signals are grouped into multiple groups, the first data in the group is set to the digital signal as the initial value, and the remaining digital signal series is derived from the digital signal series. The digital signal and the differential digital signal sequence are converted into a generated differential digital signal sequence, a frame is formed from the digital signal and the differential digital signal sequence, and an error detection and correction code and a synchronization signal for identifying the frame are added and transmitted. A digital signal transmission method.