JP2000020097A - Small power background noise generating system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce power consumption at the time of generating a background noise in a soundless state without causing sense of incongruity in an auditory sense. SOLUTION: A background noise code interpolating section 133 performs interpolation between a received background noise code stored in an encoded information storing section 121 and a received background noise code of the previous time stored in a background noise code storing section 134. A interpolated background noise code is decoded by a high efficiency voice decoding section 143. A decoded background noise signal is stored in a background noise signal storing section 154. A background noise signal stored in the background noise signal storing section 154 is successively selected and outputted by a background noise signal selecting section 153. While a background noise signal is outputted from the background noise signal selecting section 153, operation of the high efficiency voice decoding section 143 is stopped.

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, and more particularly, to a method for generating and inserting background noise in a silent state where no speech code exists.

[0002]

2. Description of the Related Art In a speech encoding apparatus, when there is no speech signal to be encoded, transmission of speech encoded information is stopped in order to reduce power consumption. In this case, in the audio decoding device on the receiving side, the sense of discontinuity between sound and silence of the decoded audio signal becomes remarkable, and in order to eliminate it,
A pseudo background noise signal is generated and output.

[0003] A background noise generation method in a conventional speech coding apparatus is described in, for example, Japanese Patent Application Laid-Open No. 5-122165, and will be briefly described here with reference to Figs. As shown in FIG. 6, the conventional background noise generation method includes an input terminal 61, a reception information storage unit 62, a reception code storage unit 63, a decoding processing unit 64, and an output terminal 65. .

[0004] The reception information storage section 62 includes an encoded information storage section 621 and a sound / non-speech information storage section 622. The reception code storage unit 63 includes a code control unit 631, a code switching unit 632, and a background noise code storage unit 633. The decoding processing unit 64 includes a high-efficiency audio decoding unit 641
It has.

The operation of the conventional example will be described below with reference to FIGS.
This will be described with reference to FIG. The received encoded information input from the input terminal 61 is stored in the encoded information storage unit 621.
The voiced / silent information input from the input terminal 61 is
It is stored in the silence information storage unit 622 (step B1).
The sign control unit 631 determines whether there is sound or no sound based on the sound / silence information input from the sound / silence information storage unit 622 (step B2).

In the case of a sound, the code control section 631 switches the coding switching section 632 to the decoding processing section 64 side (632-1 side). The high-efficiency audio decoding unit 641 decodes the received audio code stored in the encoded information storage unit 621 (Step B3), and outputs the decoded audio signal from the output terminal 65 as it is (Step B4).

When there is no sound, the code control section 631 sets the coding switching section 632 to the background noise code storage section 633 side (632-
2). The background noise code storage unit 633 stores the received background noise information (Step B5).

[0008] The high-efficiency speech decoding section 641 receives the background noise code stored in the background noise code storage section 633 and performs a decoding process (step B3), and outputs the decoded background noise signal as it is to an output terminal. The data is output from the block 65 (step B4).

[0009]

In this prior art, the high-efficiency speech decoding section always operates irrespective of the state of speech such as sound / no-speech.
Even when there is no sound, power is consumed in the same way as when there is sound.
For example, when a battery is used as a power source such as a mobile phone, there is a problem that the use time is shortened.

If the operation of the high-efficiency speech decoding unit is stopped during silence in order to reduce the power consumption of the speech decoding device, the power consumption is reduced, but as described above, the background noise signal is output. There is a problem that unnaturalness occurs when there is no sound.

An object of the present invention is to generate background noise in an audio decoding device when an audio signal does not exist (hereinafter referred to as silence), and to reduce power consumption at that time without causing a sense of incongruity. It is to provide a possible configuration.

[0012]

SUMMARY OF THE INVENTION According to the present invention, in order to reduce transmission power in a silent state where no audio signal exists,
In a background noise generation method in which a speech encoding device stops transmitting a code and a speech decoding device generates and outputs a background noise signal in a pseudo manner, the speech encoding device has a certain constant value during a silent state. A background noise having a time length is generated by encoding by a speech encoding process, and is transmitted as background noise information to the speech decoding apparatus at a certain period.

On the other hand, during the silent state, the audio decoding device decodes the background noise information having the predetermined time length received at the predetermined period by the audio decoding unit, thereby converting the background noise signal. Generated and stored in the background noise signal storage unit. Then, the stored background noise signal is repeatedly read and output during the predetermined period. In addition, while the background noise signal is repeatedly read and output, the operation of the audio decoding unit is stopped to reduce the power consumption of the audio decoding device.

The speech decoding apparatus of the present invention performs an interpolation process between the received background noise code stored in the encoded information storage unit and the previous received background noise code stored in the background noise code storage unit. A background noise code interpolation unit, a high-efficiency speech decoding unit that decodes the interpolated background noise code, a background noise signal storage unit that stores the decoded background noise signal, and a background noise signal storage unit. A background noise signal selecting section for sequentially selecting and outputting the background noise signal that has been selected, and the background noise signal selecting section sequentially selects and outputs the background noise signal stored in the background noise signal storage section. While you are
The operation of the high-efficiency speech decoding unit is stopped.

According to the present invention, the operation of the high-efficiency speech decoding unit is stopped except during interpolation processing for generating background noise during silence. Power consumption can be reduced during a period in which noise is generated and output.

[0016]

FIG. 1 is a block diagram showing a first embodiment of the present invention. The first embodiment of the low power consumption type background noise generation system according to the present invention is the
, Reception information storage unit 12, reception code processing unit 13, decoding processing unit 14, output signal processing unit 15, output terminal 1
6, and each of these components has the following functions.

The reception information storage unit 12 includes an encoded information storage unit 121 and a sound / non-sound information storage unit 122. The encoded information storage unit 121 receives the encoded information from the input terminal 11 and stores it. The sound / silence information storage unit 122 inputs the sound / silence information from the input terminal 11 and stores the information.

The reception code processing unit 13 includes a code control unit 131
, Code switching unit 132, background noise code interpolation unit 133
And a background noise code storage unit 134. The code control unit 131 controls the operations of the code switching unit 132 and the background noise code interpolation unit 133 as follows based on the sound / silence information input from the sound / silence information storage unit 122.

In the case of a sound, the received voice code stored in the coded information storage unit 121 is directly used by the decoding processing unit 1.
Output to 4. In addition, when performing the silence and the interpolation processing, the background noise code interpolation unit 133 is driven.

The background noise code interpolation unit 133 performs an interpolation process between the reception background noise code stored in the coded information storage unit 121 and the previous reception background noise code stored in the background noise code storage unit 134. , And outputs the interpolated background noise code to the decoding processing unit 14. Encoding information storage unit 12
The received background noise code stored in 1 is stored in the background noise code storage unit 134 for the next interpolation process.

In a section where silence is not performed and interpolation processing is not performed,
The background noise code interpolation unit 133 is not driven.

The decoding processing unit 14 includes a decoding control unit 141
, A decoding switching unit 142 and a high-efficiency audio decoding unit 143
And The decoding control unit 141 determines based on the sound / silence information input from the sound / silence information storage unit 122,
The operation of the high-efficiency speech decoding unit 143 is controlled as follows.

In the case of a sound, the high-efficiency speech decoding unit 143
To decode the received audio code input from the encoded information storage unit 121 and output the decoded audio signal to the output signal processing unit 1.
Output to 5

In a section in which silence and interpolation processing are performed, the high-efficiency speech decoding section 143 is driven to decode the interpolation background noise code input from the background noise code interpolation section 133, and the decoded background noise signal is output to the output signal processing section. Output to the unit 15.

In a section where silence is not performed and interpolation processing is not performed,
The high-efficiency speech decoding unit 143 is not driven.

The output signal processing unit 15 includes an output control unit 151
, Output switching section 152, background noise signal selection section 153
And a background noise signal storage unit 154. The output control unit 151 controls the operation of the output switching unit 152 and the background noise signal selection unit 153 based on the sound / silence information input from the sound / silence information storage unit 122 as follows.

In the case of a sound, the high-efficiency speech decoding unit 143
The input decoded audio signal is output from the output terminal 16 as it is.

In a section in which silence and interpolation processing are performed, the background noise signal selection section 153 is driven. The background noise signal selection section 153 stores the decoded background noise signal input from the high-efficiency speech decoding section 143 in the background noise signal storage section 154, and outputs it from the output terminal 16.

In a section where silence is not performed and interpolation processing is not performed,
The background noise signal selection unit 153 includes a background noise signal storage unit 154.
Are sequentially selected and read out, and are repeatedly output from the output terminal 16.

Here, an outline of the overall operation of the present invention will be described. This kind of background noise generation method is used in the following cases in a speech encoding / decoding device such as a mobile phone and a car phone. That is, in order to reduce the transmission power in the wireless section in a silent state where no audio signal exists, the audio encoding device stops transmitting the code,
This is a case where the speech decoding apparatus generates and outputs a pseudo background noise signal.

In this case, the speech coding apparatus performs a certain time length (hereinafter referred to as a frame, for example, 1) during a silent state.
0 msec) is generated by encoding the background noise by a speech encoding process. The background noise information is transmitted for a certain period of time (hereinafter referred to as a background noise information transmission period. For example, 1
Once every second) from the speech encoding device to the speech decoding device.

The speech decoding apparatus decodes the background noise information received once in the background noise information transmission cycle by a speech decoding process to generate a background noise signal. The generated background noise signal is stored in the background noise signal storage unit. When there is no sound, the background noise signal stored in the background noise signal storage unit is repeatedly read and output.

Next, the operation of the present invention will be described with reference to FIGS.
This will be described with reference to FIG. The received encoded information input from the input terminal 11 is stored in the encoded information storage unit 121. The sound / silence information input from the input terminal 11 is stored in the sound / silence information storage unit 122 (step A1).

Code control section 131 and decoding control section 141
And the output control unit 151 includes the sound / silence information storage unit 122.
The following control is performed based on the input sound / silence information.

First, it is determined whether there is sound or no sound (step A2). In the case of a sound, the code control unit 131 switches the coding switching unit 132 to the decoding processing unit 14 side (132-1 side) and uses the received voice code stored in the coding information storage unit 121 as it is. Output to the decoding processing unit 14.

The decoding control section 141 is provided with the decoding switching section 14
2 is switched to the high-efficiency audio decoding unit 143 side (142-1 side), the received audio code input from the encoded information storage unit 121 is decoded, and the decoded audio signal is output to the output signal processing unit 15.
(Step A3).

The output control unit 151 switches the output switching unit 152 to the output terminal 16 side (152-1 side), and outputs the decoded audio signal input from the high-efficiency audio decoding unit 143 from the output terminal 16 as it is ( Step A4).

On the other hand, when there is no sound, first, the code control unit 131, the decoding control unit 141, and the output control unit 151
Determines whether or not to perform interpolation processing (step A
5).

The judgment as to whether or not to carry out the interpolation processing is made according to FIG.
As shown in (1), it is determined by the timing of receiving background noise information during silence. That is, after receiving the background noise information, for a certain period of time (hereinafter referred to as an interpolation processing time, for example, 50 msec), the interpolation processing between the received background noise information and the previously received background noise information is performed. After the background noise information is received, the interpolation processing is not performed after the interpolation processing time has elapsed.

First, a description will be given of the operation in the case of performing the silence and the interpolation processing. The code control unit 131 sets the coding switching unit 132 to the background noise code interpolation unit 133 side (132-2).
Side), and outputs the received background noise code stored in the encoded information storage unit 121 to the background noise code interpolation unit 133.

The background noise code interpolation unit 133 performs an interpolation process between the reception background noise code stored in the encoded information storage unit 121 and the previous reception background noise code stored in the background noise code storage unit 134. , And outputs the interpolated background noise code to the decoding processing unit 14 (step A6).

Hereinafter, an example of an actual code interpolation method will be specifically described. The background noise information is information obtained by encoding background noise for one frame on the encoding device side with a highly efficient speech encoding algorithm. Examples of the type of the coded information include a code representing a loudness of a sound (hereinafter referred to as a power code) and a code representing a spectral envelope characteristic of a sound (hereinafter referred to as a spectrum code).

The background noise code interpolation process is performed by encoding the received background noise code stored in the encoded information storage unit 121 and the previous received background noise code stored in the background noise code storage unit 134. Linear interpolation is performed for each type of information.

For example, a method for linearly interpolating the background noise information A received after receiving the background noise information B will be described.

Assuming that the frame length is 10 msec and the interpolation processing time is 50 msec, the interpolation processing is 50 は 1.
0 = 5, that is, for 5 frames. In each frame within the interpolation processing time, the background noise information A and the background noise information B are added at the rate shown in the details of the interpolation processing in FIG. 3 for each type of encoded information.

At this time, as shown in the details of the interpolation processing in FIG. 3, the code of the first frame within the interpolation processing time has the lowest ratio of the background noise information B, and the code of the second frame is the first frame.
The ratio of the background noise information B is slightly larger than the code of the frame, the code of the third frame has a larger ratio of the background noise information B than the code of the second frame, and the code of the fourth frame is The configuration is such that the ratio of the background noise information B is even greater than the code of the third frame.

However, the code of the fifth frame is generated at a ratio that is exactly the middle value between the code of the fourth frame and the code of the first frame. By performing such interpolation processing, the fifth frame and the first frame within the interpolation processing time are smoothly connected. As a result, even if the background noise signal having the interpolation processing time length is repeatedly output, the discontinuity is not sensed. Is not coming out.

The above-described interpolation processing is performed, for example, by combining a power code A in the background noise information A and a power code B in the background noise information B, and a spectrum code A in the background noise information A.
And a spectrum code B in the background noise information B,.
・ Perform for each set of codes such as.

The interpolation processing may be performed on all pieces of information in the coded information, or may be performed on only a part of the information. Generally, it is more effective from the viewpoint of hearing when the interpolation processing is performed on the power code and the spectrum code.

The received background noise code stored in the coded information storage section 121 is stored in the background noise code storage section 134 for the next interpolation processing. For example, when the background noise information A is stored in the background noise code storage unit 134, the background noise information B is newly received and the coded information storage unit 121 is received.
When the background noise information B is stored in the background noise information B, the interpolation processing of the background noise information A and the background noise information B is performed during the interpolation processing time. Remember.

The decoding control unit 141 is provided with a decoding switching unit 142
Is switched to the high-efficiency speech decoding unit 143 side (142-1 side), the interpolated background noise code input from the background noise code interpolation unit 133 is decoded, and the decoded background noise signal is output to the output signal processing unit 15 ( Step A7).

The output control section 151 switches the output switching section 152 to the background noise signal selection section 153 side (152-2 side). The background noise signal selection section 153 stores the decoded background noise signal input from the high-efficiency speech decoding section 143 in the background noise signal storage section 154, and outputs it from the output terminal 16.

The background noise signal storage unit 154 stores decoded background noise signals of the number of frames of (interpolation processing time) / (frame length). For example, if the frame length is 10m
When the interpolation processing time is 50 msec, the decoded background noise signals for 5 frames are stored in the background noise signal storage unit 15.
4 (step A8).

Next, a description will be given of the operation in the case where no sound is generated and no interpolation processing is performed. If no interpolation is performed and no received code exists, the received code processing unit 13, that is, the code control unit 131, the coding switching unit 132, and the background noise code interpolation unit 133 do not operate. Further, the decoding control unit 141 sets the decoding switching unit 142 to 14
Switch to the 2-2 side so that the high-efficiency audio decoding unit 143 is not operated. That is, the decoded background noise signal is not output from the decoding processing unit 14 to the output signal processing unit 15 (step A9).

On the other hand, the background noise signal selection section 153 sequentially selects the background noise signals for the interpolation processing time stored in the background noise signal storage section 154 and outputs them from the output terminal 16. For example, when the frame length is 10 msec and the interpolation processing time is 50 msec, decoded background noise signals for 5 frames are stored in the background noise signal storage unit 154.

Therefore, the stored decoded background noise signal is converted from the first frame → the second frame → the third frame → the fourth frame → the fifth frame → the first frame → the second frame → the third frame →. .. Are sequentially output from the output terminal 16 (step A9).

As described above, since the background noise signal generated in the same silence section is repeatedly output in the section where silence is not performed and interpolation processing is not performed, there is no sense of incongruity in the sense of hearing. Since it is not necessary to operate the noise code interpolation unit and the high-efficiency speech decoding unit, power consumption can be reduced.

FIG. 4 is a block diagram showing another embodiment of the present invention. This embodiment is different in that the background noise code interpolation unit 133 in FIG. 1 is replaced with a background noise code generation unit 135. The background noise code generation unit 135 generates a code for background noise by a method other than linear interpolation, such as randomization of the code, based on the received background noise code stored in the coding information storage unit 121, The generated background noise code is output to the decoding processing unit 14.

Next, the operation of this embodiment will be described with reference to FIG.
This will be described with reference to FIG. Steps A1 and A in FIG.
The operation in the case of a sound indicated by 2, A3, A4 is the same as the operation in the case of a sound in the first embodiment indicated by steps A1, A2, A3, A4 in FIG. Is omitted.

Further, steps A1, A2, A5,
The operation in the case where no sound and no interpolation processing are performed as indicated by A9 and A10 is performed in steps A1, A2, A3, and A3 in FIG.
7, since the operation is the same as that of the first embodiment indicated by A9 when no sound and no interpolation processing are performed, the description is omitted.

The operation in the case of performing the silence and the interpolation processing in this embodiment will be described below. Referring to FIG. 5, this embodiment is different from step A6 in FIG.
Is different in that the background noise code interpolation process represented by is replaced with the background noise code generation process.

If there is no sound, first, the code control unit 131, the decoding control unit 141, and the output control unit 151 determine whether or not to execute a code generation process (step A5). The operation of determining whether or not to execute the code generation process is the same as the operation of determining whether or not to perform the interpolation process in the first embodiment, and a description thereof will not be repeated.

The code control section 131 switches the coding switching section 132 to the background noise code generation section 135 (132-2 side), and converts the received background noise code stored in the coded information storage section 121 to the background noise code generation section. Output to the unit 135.

The background noise code generation section 135 generates a code for background noise by a method other than linear interpolation based on the reception background noise code stored in the encoding information storage section 121, and generates the generated background noise code. Is output to the decryption processing unit 14 (step A11).

The background noise code generation processing is performed for a certain period of time (hereinafter referred to as a code generation processing time, for example, 50 msec) after receiving the background noise information.

Hereinafter, an example of an actual code generation method will be specifically described. As the type of encoded information, the first
In addition to the power code and the spectrum code described in the embodiment, for example, there are a pitch code indicating a vibration period of a vocal cord, an excitation signal code indicating an excitation signal, and the like.

A code for background noise is generated by randomizing these pitch codes and excitation signal codes. The background noise code generated in this way is output to the decoding processing unit 14. The received background noise code stored in the encoded information storage unit 121 is stored in the background noise code storage unit 134 during the code generation processing time.

The decoding control section 141 is provided with a decoding switching section 142.
Is switched to the high-efficiency speech decoding unit 143 side (142-1 side), the background noise code input from the background noise code generation unit 135 is decoded, and the decoded background noise signal is output to the output signal processing unit 15 (step A7).

The output control section 151 switches the output switching section 152 to the background noise signal selection section 153 side (152-2 side). The background noise signal selector 153 is a high-efficiency speech decoder 1
The decoded background noise signal input from 43 is stored in the background noise signal storage unit 154 and output from the output terminal 16.

The background noise signal storage unit 154 stores decoded background noise signals of the number of frames of (code generation processing time) / (frame length). For example, if the frame length is 1
If the code generation processing time is 0 msec and the code generation processing time is 50 msec, the decoded background noise signals for five frames are stored in the background noise signal storage unit 154 (step A8).

The method of generating a code for background noise by randomizing the code has been described above. However, the code for background noise may be generated by another method other than linear interpolation or randomization. Instead of performing the decoding process on the background noise code by the high-efficiency speech decoding unit, the decoding process may be performed by a background noise decoding unit having a function dedicated to background noise decoding.

As an example of the configuration of the background noise decoding unit, for example, a configuration in which the calculation accuracy of the decoding process of the high-efficiency speech decoding unit is reduced, a configuration in which the order of the spectral code to be calculated is reduced, and the like are considered. Further, the selection order when the background noise signal selection unit selects the background noise signal from the background noise signal storage unit may be changed.

Further, when the operation of the high-efficiency audio decoding unit 143 is switched from the stop state (142-2 side) to the driving state (142-1 side) by the decoding switching unit 142, each operation in the high-efficiency audio decoding unit is performed. The internal state of the filter may be initialized.

[0074]

According to the present invention, the operation of the high-efficiency speech decoding unit can be stopped when there is no sound, so that the power consumption of the speech decoding device when there is no sound can be reduced.

Also, according to the present invention, the background noise signal stored in the background noise signal storage section is sequentially selected and output. Therefore, even if the operation of the high-efficiency speech decoding section is stopped when there is no sound, the background noise signal is stopped. A signal can be output.

Further, since the interpolation processing is performed so that the first frame and the last frame stored in the background noise signal storage unit are smoothly connected, the background noise signal stored in the background noise signal storage unit is Even if they are sequentially selected and output, natural background noise without a sense of discontinuity can be generated.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a flowchart illustrating an operation of the exemplary embodiment of the present invention.

FIG. 3 is a diagram for explaining an interpolation processing operation in the present invention.

FIG. 4 is a block diagram showing another embodiment of the present invention.

FIG. 5 is a flowchart for explaining the operation of another embodiment of the present invention.

FIG. 6 is a block diagram showing a conventional example.

FIG. 7 is a flowchart for explaining the operation of the conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Input terminal 12 Reception information storage part 13 Reception code processing part 14 Decoding processing part 15 Output signal processing part 16 Output terminal 121 Encoding information storage part 122 Sound / silence information storage part 131 Code control part 132 Code switching part 133 Background Noise code interpolation unit 134 Background noise code storage unit 135 Background noise code generation unit 141 Decoding control unit 142 Decoding switching unit 143 High-efficiency speech decoding unit 151 Output control unit 152 Output switching unit 153 Background noise signal selection unit 154 Background noise Signal storage unit 61 Input terminal 62 Received information storage unit 63 Received code storage unit 64 Decoding processing unit 65 Output terminal 621 Encoded information storage unit 622 Sound / silence information storage unit 631 Code control unit 632 Code switching unit 633 Background noise code Storage unit 641 High-efficiency speech decoding unit

Claims (8)

[Claims] To reduce transmission power during a silent state in which no audio signal exists, an audio encoding device stops transmitting a code, and an audio decoding device generates and outputs a pseudo background noise signal. In the background noise generation method, the speech encoding apparatus encodes and generates background noise of a predetermined time length by a speech encoding process during the silent state, and performs the speech decoding at a predetermined cycle as background noise information. The speech decoding device transmits to the speech decoding device, the background noise information received at the predetermined period is decoded by a speech decoding unit to generate a background noise signal during the silent state, and the background noise signal is generated. While storing in the storage unit, the stored background noise signal is repeatedly read and output for the predetermined period, and while the stored background noise signal is repeatedly read and output,
A low power consumption type background noise generation method, wherein the operation of the speech decoding unit is stopped. 2. The speech decoding apparatus according to claim 1, wherein the speech decoding apparatus performs an interpolation process between the currently received background noise information and the previously received background noise information, and decodes the interpolated background noise information in the speech decoding unit. 2. The low-power-consumption-type background noise generation method according to claim 1, wherein the background noise signal is generated. 3. The speech decoding apparatus according to claim 2, wherein the interpolation processing between the background noise information received this time and the background noise information received last time is performed a plurality of times at different addition ratios, so that the predetermined time length is multiplied. 2. The low power consumption type background noise generation method according to claim 1, wherein the background noise signal having a time length of: 4. The low power consumption type background noise generation method according to claim 3, wherein the addition ratio is set so as not to cause a sense of discontinuity when the background noise signal is repeatedly output. . 5. The low power consumption type background noise generation method according to claim 2, wherein an interpolation process is performed on a power code and a spectrum code of the noise information. 6. The speech decoding apparatus according to claim 1, wherein the speech decoding unit performs randomization on the received background noise information, and decodes the randomized background noise code by the speech decoding unit. 2. The low power consumption type background noise generation method according to claim 1, wherein a signal is generated. 7. A speech decoding apparatus which receives background noise information transmitted from a speech encoding apparatus at a predetermined time length and at a predetermined period during a silent state in which no speech signal exists, and outputs a background noise signal. In the background, the speech decoding apparatus performs an interpolation process between the currently received background noise information stored in the encoded information storage unit and the previously received background noise information stored in the background noise code storage unit. A noise code interpolation unit, a high-efficiency speech decoding unit that decodes a background noise signal from the interpolated background noise code, a background noise signal storage unit that stores the decoded background noise signal, A background noise signal selection unit that reads and outputs the background noise signal stored in the signal storage unit, and the background noise signal selection unit sequentially reads the background noise signals stored in the background noise signal storage unit. -Option while to outputs, the high efficiency speech decoder low-power speech decoding apparatus characterized by stopping the operation of. 8. A speech decoding apparatus for receiving background noise information transmitted from a speech encoding apparatus at a predetermined time length and at a predetermined cycle during a silent state in which no speech signal exists, and outputting a background noise signal. In the speech decoding device, a background noise code generation unit that performs a randomization process on the received background noise information to generate a background noise code, and a background noise signal from the randomized background noise code , A high-efficiency voice decoding unit for decoding the background noise signal, a background noise signal storage unit for storing the decoded background noise signal, and reading and outputting the background noise signal stored in the background noise signal storage unit A background noise signal selection unit, while the background noise signal selection unit sequentially selects and outputs the background noise signal stored in the background noise signal storage unit, the high efficiency speech decoding unit Stop operation Low power consumption speech decoding apparatus characterized by.