JPH0736497A - Sound decoder - Google Patents

Abstract

PURPOSE:To prevent quality degradation in acoustic feeling of decoded sounds which derive at the time of sending no sound signal at silence intervals. CONSTITUTION:Decoded sound signals from a transmission code decoder 21 by which sound signs at a sound interval are decoded are outputted according to the selection by a switch 27 by changeover indicating signals out of a sound/ silence indicator 22 to which a sign of beginning of a sound interval is inputted. When a sign of beginning of a silence interval is inputted, a noise signal out of a noise signal buffer 23 is outputted. At the silence interval, correlation between a final interval signal of the sound intervals and a storing signal of the noise signal buffer 23 is calculated by a correlation calculator 24 and a noise signal approximating to a waveform with highest correlation is selected and outputted from the switch 27 via a noise power controller 26. Further, a signal power out of the noise signal buffer 23 is controlled so as to be equal to a power of a final interval of the sound interval detected by a decoded signal power detector 25 and when the signal power from the buffer 23 is stronger that in the final interval, it is made low gradually to an equal power under the control of the noise power controller 26.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to a digital mobile communication device or the like, and when the transmitting side stops the transmission of a voice signal in a silent section in order to reduce power consumption, the last waveform in the sounding section. The present invention relates to a voice decoding device that reproduces a waveform approximated by the above in a silent section and outputs a signal while maintaining continuity with a voice signal in a voiced section.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing the configuration of a speech code decoding apparatus having a function of determining the presence or absence of speech used in a digital mobile communication apparatus.

In FIG. 2, the transmitting side A has an input voice encoder 1 to which an input voice signal is supplied and a voiced / unvoiced discriminator 2.
And a signal assembler 3 that outputs a transmission code signal. The receiving side B also has a signal decomposer 4 to which the transmission code signal is input, and a speech decoding device 5 that outputs a decoded speech signal.

Next, the operation of the configuration of this conventional speech code decoding apparatus will be described. On the transmitting side A, the input voice signal is encoded by the input voice encoder 1, and the voice / non-voice determination unit 2 determines the voice / voice of the input voice signal to start the voiced section and the start of the voiceless section. Is generated. The signal assembler 3 multiplexes the output code of the input speech coder 1 and the code indicating the start of each voiced / voiceless section from the voiced / voiceless decision unit 2 to assemble a transmission code. A transmission amplifier (not shown) that transmits this transmission code stops its operation after transmission of the code for starting silence. Further, the transmission is restarted by the code indicating the start of the voiced section. This prevents power consumption in the transmitter (not shown) and reduces power consumption.

On the receiving side B, the signal decomposer 4 decomposes into a code Fa of the voice signal and a code Fb indicating the start of each of the voiced and silent sections, and outputs it to the voice decoding device 5. The voice decoding device 5 decodes the code of the voice signal transmitted in the voiced section. Since the code of the voice signal is not transmitted in the silent section, a signal that replaces the code is generated and output.

Next, the voice decoding device 5 in FIG. 2 will be described. FIG. 3 is a block diagram showing the configuration of the speech decoding apparatus. In FIG. 3, the voice decoding device 5 includes a transmission code decoder 11 to which a transmitted voice code signal is input, and a voice / silence indicator 12 to which a code indicating the start of each voiced / silent section is input. , A noise generator 13, and a switch 14 for selecting an output signal.

Next, the operation of the configuration of the voice decoding device 5 will be described. The code of the voice signal sent from the signal decomposer 4 in FIG. 2 is input to the transmission code decoder 11. A code indicating the start of a voiced section or the start of a voiced section is input to the voiced / voiceless indicator 12. After the code indicating the start of the voiced section is input, the code of the transmitted voice signal is decoded by the transmission code decoder 11, and this decoded signal is output through the switch 14. Further, after the code indicating the start of the silent period is input, the noise generator 13 generates a signal such as white noise having a constant power, and the noise signal is output through the switch 14.

[0008]

However, in the above-mentioned conventional speech decoding apparatus, since the signals of the voiced section and the silence section are independently generated, there is no continuity between the voiced section and the silence section. Therefore, when the transmitting side stops the transmission of the voice signal in the silent section in order to reduce the power consumption, a different timbre signal is reproduced and the quality of the decoded voice deteriorates.

The present invention solves such a conventional problem, and is excellent in preventing deterioration of the perceptual quality of decoded speech which is caused by not transmitting a speech signal in a silent section. An object is to provide a voice decoding device.

[0010]

In order to achieve the above object, a speech decoding apparatus of the present invention is a speech decoding apparatus provided in a speech code decoding apparatus in digital communication, and decodes a speech code signal in a voiced section. Transmission code decoding means for outputting the decoded speech signal, noise signal storage means for storing a plurality of types of noise signals, and a switching instruction signal for switching the decoded speech signal from the transmission code decoding means or the noise signal from the noise signal storage means. And a switching instruction signal for selecting the decoded voice signal from the transmission code decoding means by the selecting means when the code for starting the voiced section is input, and the silent section. In the case of the start code, the sound / silence instruction means for outputting the switching instruction signal for the selection means to select the noise signal from the noise signal storage means; The correlation between the noise signal stored in the signal and noise signal storing means of the end sections is calculated, it has a configuration and a correlation calculation unit for outputting a noise signal approximating the highest correlation waveform. Further, in addition to this configuration, a decoded signal power detection means for detecting the power of the noise signal from the noise signal storage means, and a voiced section in which the power of the noise signal from the noise signal storage means is detected by the decoded signal power detection means Noise power control means for controlling the power to be equal to the power of the final section and gradually decreasing the power to be equal to the power of the final section of the voiced section when the power of the noise signal is large.

[0011]

With such a structure, the speech decoding apparatus of the present invention approximates the last waveform of the voiced section even when the transmitting side stops transmitting the voice signal in the silent section in order to reduce power consumption. The generated waveform is reproduced in the silent section, and the signal is output while maintaining continuity with the voice signal in the sound section. As a result, it is possible to prevent deterioration of the perceptual quality of the decoded speech, which is caused by not transmitting the speech signal in the silent section.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a speech decoding apparatus of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of a speech decoding apparatus of the present invention. It should be noted that this speech decoding apparatus is arranged in place of speech decoding apparatus 5 of the speech encoding / decoding apparatus shown in FIG.

In FIG. 1, the speech decoding apparatus includes a transmission code decoder 21 to which the transmitted speech code signal is input,
A sound / silence indicator 22 to which a sound / silence section start code signal of a code indicating each start of a sound / speech section is input, and a noise signal buffer in which various noise signals indicating signals in a silence section are stored. 23) (corresponding to the noise signal storage means in the above section). The apparatus also includes a correlation calculator 24, a decoded signal power detector 25, a noise power controller 26, and a decoded speech signal from the transmission code decoder 21.
The signal from the noise power controller 26 is sent to the sound / silence indicator 2
And a switch (corresponding to the selecting means in the claims) 27 which selects and outputs the signal in response to the switching instruction signal from 2.

Next, the operation of the configuration of this embodiment will be described. The code for the start of the voiced section in the voiced / voiceless section start code signal is input to the voiced / voiceless indicator 22. The sound / silence indicator 22 switches the switch instruction signal for selecting the decoded voice signal from the transmission code decoder 21 to the switch 27.
Send to. The speech code signal transmitted at the same time is decoded by the transmission code decoder 21, and this decoded speech signal is converted by the switch 27.
Is output through. Further, when the code of the start of the soundless section in the sound / soundless section start code signal is input to the sound / silence indicator 22, a switching instruction signal is sent to the switch 27 so as to select the signal from the noise signal buffer 23. Then, the signal from the noise signal buffer 23 is output.

In this case, the noise signal buffer 23 stores various noise signals indicating signals in the silent section,
In this silent section, the correlation calculator 24 calculates the correlation between the signal in the last section of the voiced section and the various noise signals stored in the noise signal buffer 23. In this calculation, the noise signal having the highest correlation, that is, the waveform having the most approximate waveform is selected and output to the noise power controller 26.

At this time, the power of the last section of the voiced section is detected by the decoded signal power detector 25, and the power of the signal from the noise signal buffer 23 is made equal by the noise power controller 26 to the detected power. Control to be. Further, when the power is higher than necessary, the noise power controller 26 controls to gradually decrease to the same power.

As described above, according to this embodiment, the signal from the noise signal buffer 23 is similar to the signal in the last section of the voiced section. Further, since the output power is adaptively controlled, the continuity of the signal between the voiced section and the silent section is maintained, and the quality of the decoded speech is prevented from deteriorating.

[0019]

As is clear from the above description, the speech decoding apparatus of the present invention can be used in the voice section even when the transmitting side stops transmitting the voice signal in the silent section in order to reduce the consumption of the transmission power. Since the waveform that is similar to the last waveform of is reproduced in the silent section and the signal is output while maintaining the continuity with the voice signal in the sound section, the voice signal is not transmitted in the silent section. As a result, it is possible to prevent deterioration of the perceptual quality of the decoded speech that is derived.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration in an embodiment of a speech decoding apparatus of the present invention.

FIG. 2 is a block diagram showing a configuration of a speech code decoding apparatus having a speech presence / absence determining function used in a conventional digital mobile communication apparatus.

FIG. 3 is a block diagram showing a configuration of a conventional speech decoding device.

[Explanation of symbols]

 21 transmission code decoder 22 voice / silence indicator 23 noise signal buffer 24 correlation calculator 25 decoded signal power detector 26 noise power controller 27 switch

Claims (2)

[Claims] 1. A voice decoding device provided in a voice code decoding device for digital communication, comprising: a transmission code decoding means for outputting a decoded voice signal obtained by decoding a voice code signal in a voiced section; and a noise signal of a plurality of forms. A noise signal storing means for storing, a selecting means for selecting and outputting a decoded voice signal from the transmission code decoding means or a noise signal from the noise signal storing means by a switching instruction signal, and a code for starting a voiced section are input. Output a switching instruction signal for selecting the decoded voice signal from the transmission code decoding means by the selecting means, and selects the noise signal from the noise signal storing means in the case of a code of the silent section start. Means for outputting a switching instruction signal for selection by the means, a signal of the last section of the sound section in the silent section, and a noise stored in the noise signal storage section. A speech decoding apparatus comprising: a correlation calculation unit that calculates a correlation with a sound signal and outputs a noise signal that approximates a waveform having the highest correlation. 2. The decoded signal power detecting means for detecting the power of the noise signal from the noise signal storage means, and the power of the noise signal from the noise signal storage means for detecting the decoded signal power in addition to the configuration of claim 1. Noise power control means for controlling the power equal to the power of the final section of the voiced section detected by the means, and gradually reducing the power to the power equal to the power of the final section of the voiced section when the power of the noise signal is large; A voice decoding device comprising.