JPH0993208A - Adpcm correction system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct the voice information of a specific talker by generating a replaced correction pattern from a PCM signal so as to decrease deterioration in the voice of the specific talker. SOLUTION: A demodulated ADPCM code and redundant data such as CRC are inputted to an error check section 21, from which the presence of an error is outputted. Data outputted from the error check section 21 are inputted to a data replacement section 22, a data correction device 24 and a replacement and correction pattern generating device 26. Furthermore, the demodulated ADPCM code is inputted to the data replacement device 22, and when the error check section 21 detects an error, an optional pattern is read from a replacement pattern memory and the data pattern is replaced with the read pattern. The replacement pattern and the correction pattern are generated from a PCM signal in this way, the replacement pattern and the correction pattern of each specific talker differ from each other, the deterioration in the voice of each specific talker is reduced and voice information of each specific talker is corrected. Furthermore, the patterns are corrected in duplicate by the data replacement device and the data correction device to attain efficient correction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital cordless telephone system, and in particular, when a transmission error occurs in a wireless section between a mobile station and a base station, the voice is corrected and encoded to encode it. Adaptive PCM (ADPC
M) A communication correction method to which the method is applied.

[0002]

2. Description of the Related Art In recent years, mobile terminals are required to be cordless and to digitize voice. Regarding the digitization of voice, in the wired system, the PCM system of 64 Kbps is used, and the ADPCM system of 32 kbps is currently used. The transmission path of the wireless line has a finite frequency, and it is preferable that the number of transmission bits is small in order to effectively use the frequency. In addition, since the terminal is used in common with the wired system, the 32 kbps ADPCM system used in the wired system tends to be used. When this 32 kbps ADPCM system is used in a wireless transmission system such as a cordless telephone, the occurrence of transmission errors is unavoidable, and there is a problem that the voice quality of a wired system cannot be obtained.

One of the causes of such transmission error is several H.
There is slow fading on the order of z. Then, the entire frame of the transmission data is affected by the slow fading, and the voice quality is deteriorated. If such a continuous burst error extends over several tens of msec or more, an unpleasant sensation that an impact sound is mixed in a voice signal is given. Therefore, there is a problem that such a burst error must be corrected. When an ADPCM code string containing an error is input to the ADPCM decoder, the state inside the decoder differs from those on the encoder side due to an erroneous code. As a result, a waveform different from the input voice waveform is output. For this reason, the voice quality deteriorates.

[0004]

There are some known measures against the above burst error.
The M-correction method has been the only means for improving the deterioration of voice quality, such as a muting method and a method of replacing error patterns.

FIG. 2 shows an example thereof, which replaces an ADPCM code in which an error has been detected. In FIG. 2, the code replacement circuit 12 is provided on the input side of the ADPCM decoder 13.
When an error is detected in the ADPCM code received by the error detecting unit 11, the code is replaced with a specific pattern that the ADPCM decoder 13 recovers quickly when the internal state does not match the encoder. . The 64 kbps PCM code from the ADPCM decoder 13 is supplied to the PCM decoder 14, and the analog signal from the PCM decoder 14 is attenuated by the attenuator 15.

However, in these methods, data that is not erroneous is also corrected by replacement, which may rather deteriorate the voice quality. There is also a problem in that the degree of correction varies because the characteristics of the audio signal differ depending on the specific speaker.

In a system including a wireless line such as a cordless telephone, a method of adaptively correcting an error is desired.

An object of the present invention is to reduce the influence of burst error, which is a conventional problem, and the deterioration of reproduced voice in a system such as a cordless telephone in which wireless transmission is interposed. It is an object of the present invention to provide an ADPCM correction method capable of reducing deterioration of voice.

[0009]

In order to solve the above problems, the present invention provides an error detecting means for detecting an error in demodulated adaptive differential PCM code data and redundant data, and a detected adaptive differential PCM. Data replacement means for replacing code data error, and ADP for decoding the adaptive differential PCM code data to adaptive differential PCM decoding and outputting a decoded signal
A CM decoding means, a data correcting means for correcting the PCM decoding decoded by the ADPCM decoding means, a PCM storing means for storing a few frames of a PCM code, and a replacement and correction pattern used for the data replacing means and the data correcting means. Replacement and correction pattern generation means generated from PCM code, replacement pattern storage means for storing the generated replacement pattern, correction pattern storage means for storing the correction pattern, and PCM for decoding the corrected PCM code into an analog signal. A burst error is corrected by providing a decoding means.

DP from the demodulated PCM code data
Replacement pattern for replacing CM code data and P
By providing the means for generating the correction pattern for correcting the CM data, not only the burst error is corrected, but also the data of the ADPCM code can be easily replaced and the replacement can be performed more faithfully.

Further, since the PCM code data is further corrected, it is possible to reduce the deterioration of the voice of a specific speaker and improve the sound quality of the specific speaker.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention is shown in the drawings.

Redundant data such as the demodulated ADPCM code and CRC is input to the error detector 21 and the presence or absence of an error is output. The data output from the error detector 21 is input to the data replacer 22, data corrector 24, and replacement / correction pattern generator 26. Also demodulated ADP
The CM code is input to the data replacer 22, and the error detector 2
When an error is detected by 1, the arbitrary pattern is read from the replacement pattern memory and replaced. For example,
Data of several tens of patterns are stored in the replacement pattern memory 27, and each pattern determined by the data error is replaced. If no error is detected,
The replacement by the data replacer 22 is not performed.

The 32 kbps ADPCM code subjected to the substitution processing through the data displacing unit 22 is decoded by the ADPCM decoder 23 into a 64 kbps PCM signal.

PCM decoded by the ADPCM decoder 23
When the code is input to the data corrector 24 and an error is detected by the error detector 21, the correction pattern memory 28
The pattern is read from and replaced with an arbitrary pattern.
For example, several tens of pattern data are corrected pattern memory 28.
The data is stored in, and the data is replaced for each fixed pattern. If no error is detected, the correction by the data corrector 24 is not performed.

The data output from the data corrector 24 is stored in the PCM memory 25, and the replacement pattern and the correction pattern are generated by the replacement and correction pattern generator 26 by the data stored in the PCM memory 25. The generated data is stored in the replacement pattern memory 27 and the correction pattern memory 28.

The corrected PCM signal is output from the data corrector 24. The PCM signal is input to the PCM decoder 29, and a corrected analog audio signal is obtained.

[0018]

As described above, the present invention provides a PCM
Since the replacement pattern and correction pattern are created from the signal,
The replacement pattern and correction pattern differ for each specific speaker,
It is possible to reduce the deterioration of the voice of the specific speaker and correct the voice information of the specific speaker. Further, the double correction by the data replacer and the data corrector makes it possible to correct the burst error more efficiently than the conventional correction means.

Further, in the past, replacement was performed with a specific pattern, so that good voice may be corrected in some cases. However, by creating a replacement pattern and a correction pattern at all times, good voice is mistakenly made. The probability of correction is reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of an ADPCM correction system of the present invention.

FIG. 2 is a block diagram showing a circuit configuration of a conventional ADPCM correction method.

[Explanation of symbols]

 11 error detector 12 code replacement circuit 13 ADPCM decoder 14 PCM decoder 15 attenuator 21 error detector 22 data replacer 23 ADPCM decoder 24 data corrector 25 PCM memory 26 replacement and correction pattern generator 27 replacement pattern memory 28 correction Pattern memory 29 PCM decoder

Claims (1)

[Claims] 1. An error detecting means for detecting an error in demodulated adaptive differential PCM code data and redundant data, a data replacing means for replacing a detected data error in the adaptive differential PCM code, and the adaptive differential PCM code. ADPCM that decodes the data of the above to adaptive differential PCM decoding and outputs a decoded signal
Decoding means and P decoded by the ADPCM decoding means
Data correction means for correcting CM decoding, PCM storage means for storing several frames of PCM code, substitution and correction pattern generation means for generating substitution and correction patterns used for the data replacement means and data correction means from PCM codes. A burst error is corrected by providing replacement pattern storage means for storing the generated replacement pattern, correction pattern storage means for storing the correction pattern, and PCM decoding means for decoding the corrected PCM code into an analog signal. ADPCM correction method characterized in that.