JPH07336311A - Voice decoder - Google Patents

Abstract

PURPOSE:To provide a voice decoding device capable of reducing the intermittent feeling of decoding voice in frames where code errors are continuously detected. CONSTITUTION:In a parameter interpolation device 3, when the code errors are detected in single or continuous frames, the coding parameter of the frame immediately before is replaced as the coding parameter of the current frame when an error detected continuous frame number is less than a certain fixed number. When it is more than the fixed number, a silent frame coding parameter is replaced as the coding parameter of the current frame and voice decoding is respectively performed in a voice decoder 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speech decoding apparatus for carrying out power control of decoded speech for a section in which a coding error is detected on the decoding side in a mobile communication system where a coding error occurs on a transmission line. It is about.

[0002]

2. Description of the Related Art In recent years, the practical application of digital mobile communication systems has been rapidly advanced. In such a mobile communication system, when a code error occurs on the transmission path and an error is detected that cannot be corrected even by error correction, a method (parameter interpolation) for performing speech decoding using past speech coding parameters is often used. It is used.

FIG. 2 shows the structure of a conventional speech decoding apparatus of this type. In FIG. 2, reference numeral 11 is a parameter interpolator that interpolates parameters using the reception coding parameters and error detection information, and 12 is a speech decoder that decodes speech from the interpolated coding parameters.

The operation of the speech decoding apparatus configured as above will be described below. When the parameter interpolator 11 detects an error in the reception coding parameter after the error correction, it replaces the coding parameter of the immediately preceding frame and outputs the parameter. Then, processing (muting) is performed such that the power of the decoded speech is reduced according to the number of consecutive frames in which the error is detected by the speech decoder 12. If no error is detected, the received coding parameter is output as it is, and normal speech decoding is performed.

[0005]

However, in the above-described conventional speech decoding apparatus, when an error is detected in consecutive frames, the decoded speech is nutated, so that the decoded speech is interrupted and the audible deterioration occurs. There was a problem that arises.

The present invention solves the above-mentioned conventional problems, and provides an excellent speech decoding apparatus capable of suppressing deterioration in hearing even when an error is detected in consecutive frames. To aim.

[0007]

In order to achieve the above object, the present invention, when a code error is detected in consecutive frames, encodes in a past silent frame instead of the immediately preceding encoding parameter. It is provided with means for interpolating with parameters.

[0008]

According to the present invention, therefore, when a code error is detected in consecutive frames, voice coding is performed by substituting the coding parameters of the past silent frames for the coding parameters of the immediately preceding frame. As a result, it is possible to reduce the discontinuity of the decoded speech due to muting, and suppress the auditory deterioration.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of a speech decoding apparatus according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a voice / silence determiner for determining voice / non-voice from the decoded voice, and 2 denotes a reception / coding parameter of the latest frame in which no voice is detected and no error is detected and updated. Silence frame coding parameter updater, 3 is a parameter interpolator that interpolates error detection information, a reception coding parameter, and a silence frame coding parameter as input, and 4 is a voice that decodes speech from the interpolated coding parameter It is a decoder.

The operation of the speech decoding apparatus configured as described above will be described below. First, for a frame in which no decoding error is detected by the error detection information, the parameter interpolator 3 outputs the error-corrected reception coding parameter as it is, and the speech decoder 4 decodes the speech and decodes it. Output audio. On the other hand, when a code error is detected alone or in consecutive frames, the parameter interpolator 3 will describe the coding parameter of the immediately preceding frame or the coding parameter of the immediately preceding frame as the coding parameter of the current frame in accordance with the number of error-detected consecutive frames. Replace any of the silence frame coding parameters. As a specific replacement method, the number of consecutive error detection frames nef
, A threshold constant Nth (> 0) of the number of frames is provided, and if nef <= Nth, the immediately previous coding parameter is set, and if nef> Nth, the silent frame coding parameter is set for the current frame. Replace as a parameter.

As another replacement method, the parameter interpolator 3 decodes the code representing the power information of the decoded speech in the coding parameters of the immediately preceding frame, and after the muting performed by the speech decoder 4. In a frame whose power value of is greater than the power of the decoded speech by the silent frame coding parameter, the previous parameter is replaced as the current frame parameter, and after the frame in which the silent frame is less than the decoded speech power, the silent frame is used as the current frame parameter. Replace the parameter.

Using the current frame coding parameters processed and output as described above, the voice decoder 4 performs voice decoding and outputs decoded voice. The speech decoder 4 mutes the decoded speech power according to the number of error detection consecutive frames when the immediately preceding parameter is used as the current frame parameter.

Further, the silent frame coding parameters input to the parameter interpolator 3 are the latest frame coding parameters which have been determined to be silent by the voice / silence determiner 1 and have not been error-detected. It is updated by the encoding parameter updater 2 and saved.

As described above, according to the present embodiment, when the code error is detected continuously for the number of frames N or more, the coding parameter in the past silence frame is used instead of the coding parameter immediately before. By substituting and performing voice decoding, it is possible to reduce the sense of interruption in the decoded voice due to muting, and suppress auditory deterioration.

[0015]

As is apparent from the above embodiment, the present invention is effective in the case where a code error is detected in consecutive frames.
Since a means for interpolating with the coding parameter in the past silent frame instead of the immediately preceding coding parameter is provided, it is possible to reduce the sense of interruption in the decoded speech due to muting and suppress auditory deterioration. be able to.

[Brief description of drawings]

FIG. 1 is a block diagram of a speech decoding apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram of a speech decoding apparatus in a conventional example.

[Explanation of symbols]

 1 voiced / unvoiced discriminator 2 silence frame coding parameter updater 3 parameter interpolator 4 speech decoder

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H04B 7/26 H04L 1/00 Z

Claims (2)

[Claims] 1. A speech decoding apparatus comprising means for interpolating with a coding parameter in a past silent frame instead of a coding parameter immediately before when a code error is detected in consecutive frames. 2. A sound / silence judging device for judging sound / silence from decoded speech, and a silent frame coding for updating and storing the reception coding parameter of the latest frame which has been judged as silent and has not been error-detected. A parameter updater, a parameter interpolator that interpolates parameters by using error detection information, a reception coding parameter, and a silent frame coding parameter as inputs, and a speech decoder that decodes speech from the interpolated coding parameter are provided. Speech decoding device.