JPS6064541A - Adaptive differential pcm decoder - Google Patents

Abstract

PURPOSE:To decrease the time until the effect of a line error is lost without deteriorating the S/N even when the operation parameter of a decoder reaches a value not to be formed by a coder due to the line error. CONSTITUTION:The parameter revising device 1 revises the operation parameter by using a content of a transmitted ADPCM signal and stores the revised operation parameter to a memory 2, and an ADPCM decoding processing unit 3 applies decoding processing by using the stored operation parameter and regenerates a PCM signal to transmit it to the next stage. When the operation parameter of the decoder reaches a value not formed by the coder due to a line error, a parameter supervising device 4 detects it and outputs a reset signal. The reset signal is inputted to a parameter set device 5, changes the content of the operation parameter memory 2 into a predetermined standard operation parameter and sets it.

Description

[Detailed Description of the Invention] (a) Technical Field of the Invention The present invention relates to an adaptive differential PCM (hereinafter referred to as ADPCM) decoder, in which a calculation parameter becomes a value that cannot be produced by the encoder due to a line error. An ADP that can shorten the time it takes for the effects of line errors to disappear without worsening 8/N.
Regarding a CM decoder.

Prior Art and Problems The ADPCM system predicts the next audio signal from past audio signals and compresses the transmission rate by transmitting only the prediction error to the corresponding station.

Figure 1 is a block diagram of the main parts of a conventional ADPCM decoder.

In the figure, 1 is a parameter updater, 2 is a calculation parameter memory, and 3 is an ADPCM decoding processor.

The parameter updater 1 updates calculation parameters (step size prediction coefficients, etc.) according to the contents of the sent ADPCM signal (prediction error signal), stores the updated calculation parameters in the calculation parameter memory, and stores the stored calculation parameters. Using the parameters, the ADPCM decoding processor 3 performs decoding processing to reproduce the P'CM signal and send it to the next stage. If an error occurs in the ADPCM signal due to the line, the calculation parameters of the decoder will differ from the calculation parameters of the encoder, and the PCM signal that is decoded and reproduced by substitution will have an error. Also, if an error occurs in the line, this effect will follow. In order to prevent this effect from continuing as much as possible, leakage should be applied to the encoding/decoding calculation parameters.
It is made to have. However, if the time until the influence disappears is shortened by increasing the leakage, the S/N ratio deteriorates, so it cannot be made too short.

Although leakage is provided as described above, depending on the line error, the calculation parameter updated by the input ADPCM signal may become a value that cannot be created by the encoder. In this case, the conventional ADPCM decoder has the disadvantage that it takes a long time until the influence of the line error disappears.

(c) Purpose of the Invention In view of the above-mentioned drawbacks, the purpose of the present invention is to improve the circuit speed without deteriorating the S/N when the decoder's calculation/parameter becomes a value that cannot be created by the encoder due to a line error. To provide an ADPCM decoder that can shorten the time until the influence of an error disappears.

(d) Structure of the Invention In order to achieve the above object, the present invention provides a system in which the calculation parameters updated by the contents of the ADPCM signal and stored in the calculation/parameter memory become values that are too large to be created by the encoder. It has a parameter monitor that detects this and outputs a reset signal when the parameter monitor detects this and outputs a reset signal, and a predetermined standard calculation parameter.When a reset signal is input from the parameter monitor, the contents of the calculation parameter memory are changed and set to the standard calculation parameters. A feature is that the ADPCM reprinter is equipped with a parameter setter.

(e) Examples of the invention An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram of the main parts of the ADPCM (summer unit) according to the embodiment of the present invention.

In the figure, those having the same functions as those in the η31 diagram are shown in the same arrangement, 4 is a parameter monitor, 5 is a parameter setter, and 9 is not shown.

In Fig. 2, 'A''r is different from Fig. 1. When the updated calculation parameters are stored in the calculation parameter memory 2, this calculation parameter is created in the encoder and when it becomes a value larger than 1d. It has a parameter monitor 4 that detects and outputs a reset 2= number, and a predetermined standard calculation parameter, and when a reset signal is input from the parameter monitor 4, the contents of the calculation parameter memory 2 are changed to the standard calculation parameters. This is because a setting device 5 is provided.

By doing this, when the calculation parameters of the decoder become 1 shift which cannot be created by the encoder due to a line error, the calculation parameters will be returned to the standard calculation parameters, so that the difference with the corresponding calculation parameters of the encoder will be reduced. The error will disappear quickly, and the time it takes for the effects of the line error to disappear can be shortened. In this case, the likitsuji is not shortened, so the shiko does not deteriorate.

(f) Effects of the Invention According to the present invention, when the calculation parameters of the decoder become a value that cannot be created by the encoder due to a line error, the line error is eliminated without deteriorating the SA. This has the effect of shortening the time it takes for the effects of errors to disappear, and reducing quality deterioration for lines with errors.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of main parts of a conventional adaptive differential PCM decoder, and FIG. 2 is a block diagram of main parts of an adaptive differential PCB decoder according to an embodiment of the present invention. In the figure, 1 is a parameter updater, 2 is an arithmetic parameter memory, 3 is an adaptive differential PCM analogue processor 9, 4 is a parameter monitor, and 5 is a parameter setter. 1-, Pa

Claims (1)

[Claims] In the adaptive differential PCM decoder, the calculation parameters updated according to the contents of the adaptive differential PCM signal (when the calculation parameters stored in the parameter memory reach a value that cannot be created by the encoder, this is detected and a reset signal is generated. It is characterized by comprising a parameter monitor that outputs, and a parameter set device that has predetermined standard calculation parameters and changes and sets the calculation to the parameter (when a reset signal is input from the parameter monitor). Adaptive differential PCM decoder.