JPH04340821A - Adaptive prediction type adpcm encoding/decoding device - Google Patents

Abstract

PURPOSE:To prevent the generation of a noise, and the distortion of a waveform by inputting a fixed PCM pattern to an ADPCM encoding circuit at the time of the absence of a voice at a transmission side, and simultaneously inputting the fixed PCM pattern to an ADPCM decoding circuit at a reception side. CONSTITUTION:A signal 112 selected by a selecting circuit 19 is ADPCM- encoded by an ADPCM encoding circuit 13, and outputted through a transmission control circuit 14 from an output terminal 2 to a transmission path 105 as an ADPCM signal 104. Moreover, a selecting circuit 16 selects an output signal 107 of a reception control circuit 15, and a signal 114 obtained by converting an output signal 113 of a fixed PCM pattern generating circuit 21 which is the same as the transmission side, into an ADPCM code by an ADPCM encoding circuit 22 which is the same with the transmission side, by a control signal 106 from the reception control circuit 15. At that time, the selecting circuit 16 selects the output signal 107 of the reception control circuit when the received signal 105 is inputted, and selects the output signal 114 of the ADPCM encoding circuit 22 when the received signal 105 is not inputted. Then, a signal 109 selected by the selecting circuit 16 is decoded, and outputted from an output terminal 4.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is an adaptive predictive ADPCM encoding device that converts an audio signal into a PCM code digital signal, and further performs adaptive predictive ADPCM encoding to convert it into a digital signal that is slower than the PCM code, and vice versa. The present invention relates to an adaptive predictive ADPCM decoding device that performs conversion, and particularly relates to an adaptive predictive ADPCM encoding/decoding device used in a device that controls transmission of a low-speed digital signal depending on the presence or absence of an audio signal.

0002

2. Description of the Related Art FIG. 3 shows a conventional adaptive predictive ADPCM encoding/decoding apparatus.

The adaptive predictive ADPCM encoding/decoding apparatus includes an adaptive predictive ADPCM encoding apparatus provided on the transmitting side and an adaptive predictive ADPCM decoding apparatus provided on the receiving side.

[0004] In the adaptive predictive ADPCM encoding device, a PCM signal 1 is obtained by PCM encoding an audio signal from an input terminal 1.
01 is received by the voice detection circuit 11 and the delay circuit 12.

The output signal 103 of the delay circuit 12 is an ADPC
ADPCM encoded by the M encoding circuit 13, and ADP
The signal is output as a CM signal 104 from the output terminal 2 to the transmission line 105 via the transmission control circuit 14.

[0006] However, the PC input in the audio detection circuit 11
When the M signal 101 is determined to be silent, the control signal 10
2, the output of the transmission control circuit 14 is stopped.

In the adaptive predictive ADPCM decoding device, the signal 105 received at the input terminal 3 is supplied to one input of the selection circuit 16 via the reception control circuit 15 . The other input of the selection circuit 16 receives a fixed ADPCM pattern (for example, a pattern of "1111" as a 4-bit ADPCM signal) 10 from the fixed ADPCM pattern generation circuit 17.
8 is supplied.

The reception control circuit 15 receives the signal 1 from the transmission side.
05 is stopped, and a control signal 106 is supplied to the selection circuit 16.

The selection circuit 16 receives a signal 105 from the transmitting side.
is supplied, the input ADPCM signal 10
7 is sent to the ADPCM decoding circuit 18. When the signal 105 from the transmitting side is stopped, the selection circuit 16 sends the fixed ADPCM pattern 108 to the ADPCM decoding circuit 18.

The ADPCM decoding circuit 18 includes the selection circuit 1
The output signal 109 from 6 is decoded into a PCM code 110 and output from output terminal 4.

FIG. 3 with reference to the time chart of FIG.
The operation of the circuit will be explained below.

In FIG. 4, 101 is a voice detection circuit 11.
and a PCM signal input to the delay circuit 12, 102
is a control signal that outputs the result of detecting whether the PCM signal input to the voice detection circuit 11 is audible or silent. 103 is an output signal of the delay circuit 12, 104 is an output signal of the ADPCM encoding circuit 13, and 105 is an output signal of the transmission control circuit 14.

106 is a control signal that outputs the detection result of the presence or absence of a signal input to the reception control circuit 15, and 107 is a signal outputted through the reception control circuit 15, which is the same as the signal 105 input to the reception control circuit 15. It's a signal. 108 is an output signal from the fixed ADPCM pattern generation circuit 17, 109 is an output signal from the selection circuit 16, and 110
is the output signal of the ADPCM decoding circuit 18.

First, in the PCM signal 101, when the silent section 201 changes to the sound section 202, the voice detection circuit 1
The control signal 102 from 1 changes from no audio 204 to audio 205. Here, the detection time T of the voice detection circuit 11
A delay occurs by a.

[0015] Furthermore, the PCM signal 101 is in a sound section 202.
When a silent period 203 occurs, the control signal 102 from the voice detection circuit 11 changes from voice presence 205 to no voice 206. Here, a delay occurs by the detection time Tb.

The transmission control circuit 14 sends the output signal 104 of the ADPCM encoding circuit 13 to the transmission line when the control signal from the voice detection circuit 11 indicates that there is voice 205, so that all the signals in the section 202 where there is a voice signal are sent to the transmission line. In order to transmit the signal, the signal is delayed by a delay time Tc in the delay circuit 12, and then ADPCM encoded and output to the transmission control circuit 14. Here, sections 207, 208 and 209 of signal 104
are the sections 201 and 20 of the section 103 of the signal 103, respectively.
2 and 203 are ADPCM encoded. Section 210 of output signal 105 of transmission control circuit 14
and 212 are sections in which no signal is sent out according to the control signal 102 from the voice detection circuit 11, and section 211 is a section in which signals are sent out.

On the receiving side, sections 213 and 215 of the control signal 106 from the reception control circuit 15 indicate a section where there is no signal 105 from the transmission line, and section 214 indicates a section where there is a signal from the transmission line.

Section 21 of the output signal 108 of the selection circuit 17
6 is a fixed ADPCM pattern.

The output signal 109 of the selection circuit 16 outputs the fixed ADPCM pattern of the signal 108 to the intervals 217 and 219 when the control signal 106 is in the intervals 213 and 215, and outputs the fixed ADPCM pattern of the signal 108 to the intervals 217 and 219 when the control signal 106 is in the interval 214.
11 signals are output to section 218.

The output signal 109 of the selection circuit 16 is ADPC
It is decoded into PCM code 110 by the M decoding circuit, and the signals in sections 217, 218, and 219 of signal 110 are PCM code 110.
are converted into signals and divided into sections 220, 221 and 2, respectively.
22.

[0021]

[Problems to be Solved by the Invention] The conventional adaptive predictive ADPCM encoding/decoding device described above is
All the ADPCM encoded signals in the M encoding circuit are not input to the ADPCM decoding circuit on the receiving side, and the ADPCM code is input to the ADPCM decoding circuit on the receiving side only when there is voice, and is fixed when there is no voice. ADPCM pattern is input.

[0022] Then, the fixed ADPCM pattern is ADP
When input to the CM decoding circuit, the ADP on the transmitting side
The internal state of the CM encoding circuit and the internal state of the ADPCM decoding circuit on the receiving side no longer match.

[0023] In such a state, even if the input PCM signal on the transmitting side has audio, the internal state of the ADPCM encoding circuit on the transmitting side and the internal state of the ADPCM decoding circuit on the receiving side must match. It takes time, and during that time A on the receiving side
There are disadvantages in that noise and waveform distortion occur in the output signal of the DPCM decoding circuit.

An object of the present invention is to provide an adaptive predictive ADPC capable of eliminating the coincidence between the internal state of the ADPCM encoding circuit on the transmitting side and the internal state of the ADPCM decoding circuit on the receiving side.
An object of the present invention is to provide an M encoding/decoding device.

Another object of the present invention is to provide an adaptive predictive ADPCM encoding/decoding device that can prevent noise from occurring and waveform distortion even when there is voice on the transmitting side. It's about doing.

[0026]

[Means for Solving the Problems] Adaptive predictive AD of the present invention
The PCM encoding/decoding device includes an adaptive predictive ADPCM encoding device provided on the transmitting side and an adaptive predictive ADPCM decoding device provided on the receiving side.

The adaptive predictive ADPCM encoding device includes a voice detection circuit that detects the presence or absence of voice from an input PCM signal and outputs a voice detection signal representing the presence or absence of voice;
a delay circuit that delays the CM signal and outputs the delayed PCM signal; and a first circuit that generates a fixed PCM pattern on the transmitting side.
a fixed PCM pattern generation circuit, and the delayed PCM pattern generation circuit.
M signal and the fixed PCM pattern are selected based on the voice detection signal, and when the voice detection signal indicates "with voice", the delayed PCM signal is selected when the voice detection signal indicates "no voice". , a first selection circuit that outputs the fixed PCM pattern as a selected PCM signal, a first ADPCM encoding circuit that converts the selected PCM signal into a transmission side ADPCM signal, and a first ADPCM encoding circuit that outputs the fixed PCM pattern as a selected PCM signal; a transmission control circuit that transmits the transmitting side ADPCM signal as a transmission signal when the detection signal indicates "sound present", and does not transmit the transmission signal when the voice detection signal indicates "no voice"; have

The adaptive predictive ADPCM decoding device receives the transmitted signal as a received signal via a transmission path, detects the presence or absence of the received signal, and outputs a reception detection signal indicating the presence or absence of the received signal, Input the received signal as it is A
a reception control circuit that outputs a DPCM signal; a second fixed PCM pattern generating circuit that generates a fixed PCM pattern on the receiving side that is the same as the fixed PCM pattern on the transmitting side; and a second fixed PCM pattern generation circuit that converts the fixed PCM pattern on the receiving side into a fixed ADPCM signal. 2 ADPCM encoding circuit and the input ADPC
M signal and the fixed ADPCM signal are selected based on the reception detection signal, and when the reception detection signal indicates "reception signal present", the input ADPCM signal is selected, and the reception detection signal indicates "no reception signal". , the fixed ADPCM pattern is used as the selected ADPCM pattern.
a second selection circuit outputting as a signal; and a second selection circuit outputting the selected A as a signal.
and an ADPCM decoding circuit that decodes the DPCM signal into a PCM signal.

[0029]

Embodiments Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an adaptive predictive ADPCM encoding/decoding apparatus according to an embodiment of the present invention.

Adaptive predictive ADPCM encoding of this embodiment/
The decoding device is an adaptive predictive ADPCM provided on the transmitting side.
Encoding device and adaptive predictive ADPC provided on the receiving side
M decoding device.

[0032] In the adaptive predictive ADPCM encoding device on the transmitting side, the PC which PCM-encoded the audio signal from the input terminal 1 is used.
M signal 101 is supplied to voice detection circuit 11 and delay circuit 12 .

The selection circuit 19 receives the output signal 1 of the delay circuit 12.
03 and the output signal of the fixed PCM pattern generation circuit 20 (for example, "11111111 as an 8-bit PCM signal)
” pattern) 111 is selected by the control signal 102 from the voice detection circuit 11. Here, the PCM signal 101
When there is a sound, the output signal 103 of the delay circuit 12 is selected, and when there is no sound, the output signal 111 of the fixed PCM pattern generation circuit 20 is selected.

The signal 112 selected by the selection circuit 19 is ADPCM encoded by the ADPCM encoding circuit 13 and A
The signal is output as a DPCM signal 104 from the output terminal 2 to the transmission line 105 via the transmission control circuit 14. However, when the voice detection circuit 11 determines that the PCM signal 101 is silent, the output of the transmission control circuit 14 is stopped by the control signal 102.

In the adaptive predictive ADPCM decoding device on the reception side, the signal 105 received at the input terminal 3 is supplied to the selection circuit 16 as an output signal 107 via the reception control circuit 15.

The selection circuit 16 receives the output signal 1 of the reception control circuit.
07 and the same fixed PCM pattern generation circuit 21 as the transmitter side
A control signal 106 from the reception control circuit 15 selects a signal 114 obtained by converting the output signal 113 of 1 to an ADPCM code by the same ADPCM encoding circuit 22 as that on the transmitting side. Here, the selection circuit 16 selects the output signal 107 of the reception control circuit when the reception signal 105 is input, and selects the output signal 114 of the ADPCM encoding circuit 22 when the reception signal 105 is not input.

The signal 109 selected by the selection circuit 16 is decoded into a PCM signal by the ADPCM decoding circuit 18 and outputted from the output terminal 4.

The operation of the apparatus shown in FIG. 1 will be explained with reference to the time chart shown in FIG.

In FIG. 2, 101 is the voice detection circuit 11.
and a PCM signal input to the delay circuit 12, 102
is a control signal that outputs the result of detecting whether the PCM signal input to the voice detection circuit 11 is audible or silent. 103 is an output signal of the delay circuit 12, 111 is an output signal from the fixed PCM pattern generation circuit 20, and 112 is a signal selected by the selection circuit 19. 104 is ADP
It is an output signal of the CM encoding circuit 13, and 105 is an output signal of the transmission control circuit 14.

106 is a control signal that outputs the detection result of the presence or absence of a signal input to the reception control circuit 15, and 107 is a signal outputted through the reception control circuit 15, which is the same as the signal 105 input to the reception control circuit 15. It's a signal. 114 is an output signal of the ADPCM encoding circuit 22, 109 is a signal selected by the selection circuit 16, and 110 is an output signal of the ADPCM encoding circuit 22;
This is an output signal of the PCM decoding circuit 18.

First, in the PCM signal 101, when the silent section 201 changes to the sound section 202, the voice detection circuit 1
The control signal 102 from 1 changes from no audio 204 to audio 205. Here, the detection time T of the voice detection circuit 11
A delay occurs by a.

[0042] Furthermore, the PCM signal 101 is in the sound section 202.
When a silent period 203 occurs, the control signal 102 from the voice detection circuit 11 changes from voice presence 205 to no voice 206. Here, a delay occurs by the detection time Tb.

The transmission control circuit 14 sends all the signals in the sound period 202 of the output signal 104 of the ADPCM encoding circuit 13 to the transmission path when the control signal from the voice detection circuit 11 indicates that there is voice 205. After delaying the signal by a delay time Tc, the signal is ADPCM encoded and output to the transmission control circuit 14.

However, as the input signal 112 of the ADPCM encoding circuit 13, the fixed PCM pattern 111 of the fixed PCM pattern generation circuit 20 is input to the sections 224 and 226 when the control signal 102 is non-audio 204 and 206 in the selection circuit 19. , when there is audio 205, section 2 of section 105
The output signal 103 of the delay circuit 12 is input to 25.

Sections 210 and 212 of the output signal 105 of the transmission control circuit 14 correspond to the control signal 10 from the voice detection circuit 11.
2 is a section in which no signal is sent out, and section 211 is a section in which a signal is sent out.

On the receiving side, sections 213 and 215 of the control signal 106 from the reception control circuit 15 indicate a section in which the signal 105 from the transmission line is not input, and section 214 indicates a section in which the signal 105 from the transmission line is input. . Section 216 of signal 114 is an ADPCM code.

The output signal 109 of the selection circuit 16 is the AD of the signal 114 when the control signal 106 is in the sections 213 and 215.
The PCM code is output to sections 217 and 219, and the control signal 1
When 06 is in section 214, the signal in section 211 of signal 107 is output to section 218.

The output signal 109 of the selection circuit 16 is ADPC
Decoded into PCM code 110 by M decoding circuit 18,
The signals in sections 217, 218 and 219 of signal 109 are P
The section 22 of the signal 110 is converted into a CM signal.
0, 221 and 222.

[0049]

[Effects of the Invention] As explained above, the present invention inputs a fixed PCM pattern into the ADPCM encoding circuit on the transmitting side when there is no voice, and simultaneously encodes the fixed PCM pattern into the ADPCM decoding circuit on the receiving side. By inputting the signal, it is possible to eliminate mismatch between the internal states of the ADPCM encoding circuit and the ADPCM decoding circuit, and to prevent the generation of noise and distortion of the waveform even if there is audio on the transmitting side. Can be done.

[Brief explanation of drawings]

FIG. 1: Adaptive predictive ADPCM according to an embodiment of the present invention.
FIG. 1 is a block diagram showing an encoding/decoding device.

FIG. 2 is a time chart for explaining the operation of the device shown in FIG. 1;

FIG. 3 is a block diagram showing a conventional adaptive predictive ADPCM encoding/decoding device.

FIG. 4 is a time chart for explaining the operation of the device shown in FIG. 3;

[Explanation of symbols]

1, 3 Input terminals 2, 4 Output terminal 11 Audio detection circuit 12 Delay circuits 13, 22 ADPCM encoding circuit 14 Transmission control circuit 15 Reception control circuit 16 Selection circuit 17 Fixed ADPCM pattern generation circuit 18 AD
PCM decoding circuit 19 selection circuit

Claims (3)

[Claims] [Claim 1] Adaptive predictive ADP provided on the transmitting side
Adaptive predictive ADP provided on the CM encoding device and receiving side
In the adaptive predictive ADPCM encoding/decoding device having a CM decoding device, the adaptive predictive ADPCM encoding device detects the presence or absence of voice from the input PCM signal, and performs voice detection indicating the presence or absence of the voice. a voice detection circuit that outputs a signal; and a voice detection circuit that delays the input PCM signal and generates a delayed PCM signal.
a delay circuit that outputs a signal; a first fixed PCM pattern generation circuit that generates a transmitting side fixed PCM pattern; and a first fixed PCM pattern generation circuit that selects the delayed PCM signal and the fixed PCM pattern based on the audio detection signal; When the audio detection signal indicates "audio present", the delayed PC
M signal, when the voice detection signal indicates "no voice", the fixed PCM pattern is transmitted to the selected PCM.
A first selection circuit outputting as a signal, and the selected P
A first AD that converts the CM signal into a transmitting ADPCM signal
The PCM encoding circuit and the voice detection signal indicate “sound present”.
a transmission control circuit that transmits the transmitting side ADPCM signal as it is as a transmission signal when the voice detection signal indicates "no voice", and does not transmit the transmission signal when the voice detection signal indicates "no voice"; The ADPCM decoding device receives the transmitted signal as a received signal via a transmission path, detects the presence or absence of the received signal, outputs a reception detection signal indicating the presence or absence of the received signal, and inputs the received signal as it is. a reception control circuit that outputs an ADPCM signal; a second fixed PCM pattern generation circuit that generates a fixed PCM pattern on the receiving side that is the same as the fixed PCM pattern on the transmitting side;
a second ADPCM encoding circuit for converting into a CM signal, selecting the input ADPCM signal and the fixed ADPCM signal based on the reception detection signal, and when the reception detection signal indicates "reception signal present"; The input ADP
a second selection circuit that outputs the fixed ADPCM pattern as the selected ADPCM signal when the reception detection signal indicates "no reception signal";
An adaptive predictive ADPCM encoding/decoding device comprising: an ADPCM decoding circuit that decodes the selected ADPCM signal into a PCM signal. 2. A voice detection circuit that detects the presence or absence of voice from an input PCM signal and outputs a voice detection signal representing the presence or absence of voice; and a delay circuit that delays the input PCM signal and outputs the delayed PCM signal. a transmitting side fixed PCM pattern generating circuit for generating a transmitting side fixed PCM pattern; and selecting the delayed PCM signal and the transmitting side fixed PCM pattern based on the voice detection signal; A transmitting side selection circuit outputs the delayed PCM signal when the voice detection signal indicates "sound present" and outputs the transmitting side fixed PCM pattern as the selected PCM signal when the voice detection signal indicates "no voice". , a transmitting side ADPCM encoding circuit that converts the selected PCM signal into a transmitting side ADPCM signal, and when the voice detection signal indicates "sound present", the transmitting side A
An adaptive predictive ADPCM encoding device comprising: a transmission control circuit that transmits a DPCM signal as it is as a transmission signal, and does not transmit the transmission signal when the voice detection signal indicates "no voice". 3. Adaptive predictive ADPC according to claim 2.
An adaptive predictive ADPCM decoding device that receives the transmission signal sent from the M encoding device via a transmission path as a reception signal, the reception device detecting the presence or absence of the reception signal and indicating the presence or absence of the reception signal. a reception control circuit that outputs a detection signal and outputs the received signal as it is as an input ADPCM signal; and a reception side fixed PC that generates a reception side fixed PCM pattern that is the same as the transmission side fixed PCM pattern.
an M pattern generation circuit, a receiving side ADPCM encoding circuit that converts the receiving side fixed PCM pattern into a fixed ADPCM signal, and the input ADPCM signal and the fixed ADPCM signal.
M signal is selected based on the reception detection signal, and when the reception detection signal indicates "reception signal present", the input ADPCM signal is selected, and when the reception detection signal indicates "reception signal not present", the input ADPCM signal is selected. Adaptive predictive ADPCM decoding characterized by comprising a second selection circuit that outputs the fixed ADPCM pattern as a selected ADPCM signal, and an ADPCM decoding circuit that decodes the selected ADPCM signal into a PCM signal. conversion device.