JP3149562B2 - Digital audio transmission equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital voice transmission device used for digital voice communication, digital mobile communication and the like.

[0002]

2. Description of the Related Art In recent years, voice transmission apparatuses have been used for mobile communications, and it has been desired to realize a high-performance VOX function, which is one method for digitizing and reducing power consumption. A conventional example of such a digital audio transmission device will be described below.

FIG. 3 shows a conventional voice coding apparatus of a digital voice transmission apparatus. In FIG.
0 is an encoder. Reference numeral 11 denotes a sound / non-speech determiner.
2 is a VOX controller. Reference numeral 13 denotes a multiplexer. FIG.
1 shows an audio decoding device of a conventional digital audio transmission device. In this figure, reference numeral 14 denotes a separator, and 15 denotes a separator.
Is a VOX controller. 16 is a code controller, and 17 is a code controller.
Is a multiplexer (MUX), and 18 is a decoder.

[0004] The operation of the digital audio transmission apparatus configured as described above will be described below. First, the speech encoding device will be described. The audio signal is subjected to data compression and encoding in the encoder 10. The sound / silence determiner 11 determines whether the input audio signal is sound or not. VOX
The controller 12 controls a state according to the state transition diagram of FIG. 5 based on the determination result of the sound / silence determiner. The multiplexer 13 creates transmission data as described below according to the state determined by the VOX controller 12. VCE: The result of the encoder is converted into transmission data. PST: A special pattern (postamble) is used as transmission data. BGN: The result of the encoder is converted into transmission data. (Data for reproducing background noise) Si: Nothing is transmitted. PRE: A special pattern (preamble) is used as transmission data.

Next, the operation of the speech decoding apparatus shown in FIG. 4 will be described. First, the separator 14 detects the preamble and postamble patterns and separates the speech code from the transmission data. The VOX controller 15 determines a voiced section and a silent section based on the preamble and the postamble, and determines the state of the speech decoding device. In the sound period, the multiplexer 17 connects the audio code from the separator to the decoder 18, and the decoder 18 outputs an audio signal. In the silent period, the code controller 16 controls the decoder 1
8 and a decoder 18 reproduces the background noise. The code controller 16 controls the code using the data of the frame next to the post-preamble, and reproduces background noise in a silent section.

[0006]

However, in such a conventional digital voice transmission apparatus, the performance of the voice / speech / no-speech determiner of the voice coding apparatus is not sufficient at the current technical level. May cause If the voiced section is erroneously determined to be silent, the voice coding apparatus transmits the voice in the voiced section as data for reproducing background noise after transmitting the post-preamble data. Therefore, since the speech decoding apparatus employs a method of repeatedly reproducing background noise in a silent section based on the data in the sound section, unusual abnormal sounds are repeated in the silent section. Had the problem that

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide an excellent digital audio transmission apparatus in which abnormal noise is less generated during background noise reproduction in a silent section.

[0008]

According to the present invention, in order to achieve the above object, a speech encoder is provided with a code converter and a multiplexer, and when transmitting background noise reproducing data, the code converter converts the data. The gist of the present invention is to connect the obtained code to a multiplexer.

[0009]

According to the above arrangement, the code transmitted for background noise reproduction is code-converted into a code that is unlikely to produce unusual abnormal noise. Therefore, it is possible to make it difficult for the audio decoding device to reproduce abnormal noise.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. Here, as the encoding and decoding methods, "Digital automobile telephone system standard RC
The following describes an example of the VSELP method defined in “RSTD-27”.

In FIG. 1, reference numeral 1 denotes a VSELP which compresses and encodes an audio signal by a VSELP method.
The voice encoder 2 is a voice / silence determiner that determines whether the input voice signal is a voice signal or a voiceless signal, and 3 controls the state based on the determination result of the voice / silence determiner 2. A VOX controller 4 for converting a coded audio signal into a code that is difficult to generate unusual noises,
5 is a multiplexer (MUX) for selecting and outputting a code-converted signal and a code-unconverted signal from the coded audio signal, and 6 is a multiplex for generating transmission data in a state determined by the VOX controller 3. It is a vessel.

The operation of the digital audio transmission apparatus configured as described above will be described with reference to FIG. First, the speech input is encoded by the VSELP speech encoder 1. At the same time, the sound / non-speech determiner 2 determines the presence or absence of sound in the voice input, and the VOX controller 3 determines the state according to the state transition diagram of FIG. The state of the multiplexer 5 is “B”.
Only when GN ", the output of the code converter 4 is connected to the multiplexer 6. The multiplexer 6 creates transmission data by a conventional method. The multiplexer 6 converts only four parameters GSPO_1 to GSPO_4. takes an integer value from 0 to 127, respectively, a common index of the table in the table and PO value of GS value is a parameter in the VSELP. transcoder 4 each four values of GSPO, P
O value is small (0.1 or less) Converted to GSPO value.
This can be easily realized by preparing a conversion data table.

The structure of the speech decoding apparatus is the same as that shown in FIG. However, in this embodiment, the decoder 1
8 uses a VSELP decoder. The code controller 16 holds the encoded data next to the postamble,
Among them, only four values of CODE_1 to CODE_4 are changed at random.

FIG. 2 is a block diagram showing a VSELP decoder. Long-term filter state 7 and probability codebook 8
, And data are selected and added from the respective codebooks by the codes of LAG and CODE, and the speech is decoded by the synthesis filter 9. LAG_1 to LAG_4, CODE_1 to CO
Each of the four codes of DE_4 represents one frame of audio as 4
The code for each divided subframe is shown. The input of the past synthesis filter 9 is fed back and held in the long-term prediction filter. The probability codebook 8 is fixed and stores white noise. VSEL
PO, which is a parameter in P, takes a value of 0 to 1, and FIG.
Determine the ratio between β and γ. When PO is small, γ becomes small and β becomes small. The GSPO code control is performed by the audio coding apparatus so that the PO for background noise reproduction is reduced. Therefore, in the speech encoding device, when the background noise in the silent section is reproduced, PO is a small value, so that the input of the synthesis filter 9 becomes white noise, and the decoded speech also becomes white noise.

As described above, according to the above-described embodiment, the speech decoding apparatus performs the VSE when reproducing background noise in a silent section.
Since the PO of the LP parameter is set to be small, the decoded sound is white noise-like, and it is possible to avoid reproducing an unusual noise that is unfamiliar.

[0016]

[0017]

As described above, according to the present invention,
By providing a transcoder and a multiplexer in the speech encoding device, if an error occurs in the voiced / silent decision unit of the speech encoding device, the speech decoding device may be unfamiliar with reproducing background noise in a silent section. An effect is obtained that an excellent digital audio transmission device capable of reducing generation of sound can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a digital audio transmission device according to the present invention.

FIG. 2 is a diagram for explaining the operation of a VSELP decoder in the embodiment.

FIG. 3 is a block diagram showing a conventional digital audio encoding device.

FIG. 4 is a block diagram showing a conventional digital audio decoding device.

FIG. 5 is a diagram for explaining the operation of a VOX controller;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Encoder (VSELP) 2 Voiced / No-Sound discriminator 3, 15 VOX controller 4 Code converter 5, 17 Multiplexer 6 Multiplexer 7 Long-term prediction state 8 Probability codebook 9 Synthesis filter 10 Encoder 14 Separator 16 Code controller 18 Decoder

Continuation of front page (56) References JP-A-5-122165 (JP, A) Young-Soo CHOI et. Al. , "A Very Low Complexity VSELP Speech Coder Using Regular Pulse Basis Vectors", IEICE TRA NS. FUNDAMENTALS, Vol. E80-A, No. 6, JUNE 1997 (58) Field surveyed (Int. Cl. ⁷ , DB name) H04B 14/00-14/06 G10L 11/02

Claims (1)

(57) [Claims] 1. A VSELP sound encoding an input audio signal.
Voice encoder and a predetermined VS of the VSELP encoded speech signal.
A code converter for converting an ELP parameter;
Determine whether voice signal is voiced or silenced
A sound / silence determiner, and a sound / silence determiner based on the determination result.
A VOX controller that is controlled in accordance with
VSELP coded speech signal and code conversion based on control signal
Select one of the converted VSELP encoded speech signals
Multiplexer to output and VSELP selected and output
A digital audio transmission device comprising: a multiplexer that performs transmission processing of an encoded audio signal .