JPH02268045A - Voice packet communication equipment - Google Patents

Abstract

PURPOSE:To improve the S/N of a regenerative signal by sending a data while the serial number of voiced frame and non-voiced frame and end packet information, thereby allowing a receiver side to detect packet abort and executing an interpolation processing. CONSTITUTION:A transmitter 10 inputs a voice frame 100 subjected to band compression to a packet composition circuit 18 with a coder 14 via a voice frame forming circuit 12. The circuit 18 composes a count 115 obtained from a serial number provision circuit 20 and an end packet flag representing the end of the voice period obtained from a packet flag generating circuit 24 into a voice packet P, which is sent to an exchange network 60. A receiver 30 receives the packet P to detect the packet abort based on the continuity of the serial number, end packet information and an under run signal to apply interpolation processing. Thus, the S/N of the regenerative signal is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a voice packet communication device, and more specifically to a voice packet communication device that interpolates discarded voice packets.

(Prior art) In voice packet communication, in order to improve transmission efficiency, the transmitting side usually constructs voice packets of voice frames and silent frames using manually generated voice signals, and does not send silent frames as voice packets. Transmission is performed using a silent compression technique, and for voiced frames, a band compression technique based on predictive coding such as ADPC: l, t. However, in predictive coding such as ADPCJ+,
The encoder and decoder are configured to use independent internal information to predict the next sample, and the internal information is updated in a synchronized manner. - Once a packet is discarded, an asynchronous state occurs in the internal information between the encoder and the decoder, and as a result, the S/N of the reproduced output of the received audio packet continues to deteriorate significantly after the packet is discarded.

As a countermeasure for this, there is a proposal proposed by Hiroshi Tani et al., "Study of audio packetization using r ADP (J encoding"), Proceedings of the 1986 Institute of Electronics, Information and Communication Engineers Spring National Conference, B-329. Disclosed in this document. In such devices, the encoder and decoder are simultaneously reset at the beginning of each sound interval to force the internal information of the encoder and decoder to match, thereby reducing S/N degradation due to packet discards. This is limited to a maximum of l sound sections, and the deterioration of the S/N ratio is recovered in the next sound section of the combined section in which packet discard occurs.

(Problem to be Solved by the Invention) However, in the above-mentioned conventional method, an asynchronous state between the encoder and the decoder still occurs in the sound section where packet discard occurs, and therefore, S/N deterioration of the reproduced audio occurs. There was a major problem in that satisfactory audio quality could not be obtained.

SUMMARY OF THE INVENTION An object of the present invention is to provide voice packet communication equipment with excellent voice quality that minimizes deterioration of S/N even in voiced sections where such packet discard occurs.

(Means for Solving the Problems) According to the present invention, there is provided a voice frame forming means for forming a digital voice signal into a voice frame, and a voice frame forming means for forming a digital voice signal into a voice frame, and a voice frame forming means for forming a voice frame into a voice frame, and a voice frame forming means for forming a voice frame into a voice frame, and a voice frame forming means that forms a voice frame in the voice frame. a voice detection means for detecting and outputting a sound presence/absence signal representing a voiced and silent interval and a hangover signal for a voiced interval; and an encoding means for compressing and encoding a voice frame and outputting the encoded voice frame. , a serial number assigning means for assigning a series of serial numbers to the voice frames and silent frames of the voice frames, and a packet for assembling and transmitting voice packets including the voice frames and the serial numbers of the voice frames from the encoding means. an assembling means, a reset means for resetting the encoding means at the head of the sound section by a sound presence/absence signal, and an end packet information for identifying the rear part of the sound interval and outputting end packet information indicating the rear part. and an end packet information generating means, and the packet assembling means assembles and transmits an audio packet including the end packet information.

According to the present invention, the voice packet communication device also includes a voice frame, a serial number consecutively assigned to the voice frame and the silent frame, and an end packet i blue indicating the end of the voice section following the voice frame. a storage means for receiving audio packets containing information, storing the audio packets and outputting them in the order of reception, and generating an underrun signal when all the stored audio packets have been output;
packet disassembly means for disassembling a voice packet output from the means into a voice frame serial number and end packet information; detecting packet discard based on the continuity of the serial number, end packet information and underrun signal; a discard detection means for outputting a discard detection signal indicating the presence or absence of sound in audio playback and outputting a sound/absence detection signal indicating the result of the detection; , an interpolation means that outputs a sound frame from the packet decomposition means, and when a discard detection signal is output, creates interpolated data from the sound frame and outputs the interpolation data, and converts the output from the interpolation means into a digital signal. The decoding means has a decoding means that performs one summer issue, and a reset means that resets the decoding means when the sound detection signal from the discard detection means changes to sound.

(Function) According to the present invention, the transmission (jjl
1, when forming a digital audio signal into an audio frame, detects a sound section and a silent section, and forms a sound presence signal and a hangover signal. The audio frame is compressed and encoded, and a series of serial numbers are assigned to the voice frame and the silent frame. A voice packet including a voice frame and a serial number of the voice frame is assembled and transmitted. The encoding means detects the beginning of the sound section based on the sound presence/absence signal, identifies the end of the sound section, and generates end packet information. The packet assembling means adds end packet information indicating the end of the sound section, assembles a voice packet, and transmits the voice packet.

On the receiving side, such voice packets are received, recorded, and outputted in the order in which they were received. When all recorded voice packets are output, an underrun signal is generated. The audio packet output from the storage means is decomposed into a sound frame, a serial number, and end packet information. The discard detection means detects packet discard based on the continuity of serial numbers, end packet information, and underrun signal, and also detects the presence or absence of sound in audio reproduction.

When a discarded packet is not detected, a sound frame from the packet decomposition means is output, and when a discarded packet is detected, interpolated data is created from the sound frame and output. This output is decoded into a digital signal.

When the sound detection signal from the discard detection means changes to sound, the decoding means is reset. In this way, packet discard is detected based on the serial number and end packet information, and interpolation corresponding to voice and silence is performed.

(Embodiment) Next, an embodiment of the voice packet communication device according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows an embodiment of a voice packet communication device according to the present invention. The voice packet transmitting device 1 of this embodiment includes a transmitting device IO and a receiving device 30 connected via a switching network 60. The transmitting device 30 assembles the input voice signals into packets, adds a packet end flag PEF indicating the end of the sound section to the packets, and transmits the packets to the switching network 60. The receiving device 30 is connected to the switching network 6
When this packet is received via 0 and a discontinuity in the serial number or an underrun in the buffer is detected, the packet end flag indicates that the discontinuity or underrun is due to packet discard or a silent section. Depending on the identification result, interpolation is performed to indicate whether there is a sound or no sound.

The transmitting device 20 has an audio frame forming circuit 12, which forms audio signals that are continuously input from the input terminal 11 as audio frames, and outputs the audio frames from the output 100 to the audio detection circuit 22 and the encoder. output to the device 14. The audio detection circuit 22 is the audio frame forming circuit 1
2 determines whether there is a sound or no sound in the audio frame 100 output from 2, outputs a presence/no-speech signal I11 indicating the determination result to the packet assembling circuit 18 and the sending-side resent circuit 16, and generates a hangover signal 112 as a packet flag. Output to circuit 24.

Normally, the audio detection circuit 22 calculates the average power of the input audio signal, compares the calculated average power with a threshold corresponding to the power in a silent state, and there are cases where this average power is higher than the threshold. It is determined to be a sound.

In addition, in this embodiment, a protection period called hang-o-eight is provided in order to prevent a voice with low power, such as a consonant part of a voice, which is lower than a threshold value from being erroneously determined to be silent.

As shown in FIG. 3, when the voice section of the audio frame 100 begins, the presence/silence signal 111 becomes active, and when a hangover occurs thereafter, the hangover signal 111 becomes active.
2 becomes active. Both continue until the end of the sound interval. The bucketed flag generation circuit 24, which is one of the features of this embodiment, has a timer (not shown), which is activated when the hangover signal 112 output from the voice detection circuit 22 becomes active, and reset when it becomes inactive. be done. When the count value of this timer exceeds a preset value, the packet flag generation circuit 24 generates an end packet flag signal 113 of time length T.
is activated and output to the packet assembly circuit 18. This time length T usually takes a value of "2" or more. This is the value rlJ at which the end packet flag EPF becomes active for N sound frames at the trailing edge of the sound period.
This is to prevent all end packet flags from being lost due to packet discard within the 7 networks. In the example of FIG. 3, N is set to "2".

The transmitting device 10 has a serial number assigning circuit 20, which is a counter that increments by +1 each time the audio frame 100 of the packet assembling circuit 18 is input, and outputs a count value of 115 to the packet assembling circuit 18.

The transmitting side reset circuit 16 differentiates the presence/displacement signal I11 output from the voice detection circuit 22 and generates a reset pulse 116.
Output. This reset pulse 116 is generated at a timing to re-center the encoder 14 immediately before the first audio sample of each sound frame 100 input to the encoder 14 is input. The encoder 14 forcibly initializes the internal information by this reset pulse 118 and uses the audio frame 100 inputted from the audio frame forming circuit 12.
is subjected to predictive coding such as ADPCM code, compresses the band of the sound frame, and outputs it to the packet assembling circuit 18.

The packet assembling circuit 18 converts the audio frame 100 band-compressed by the encoder 14 into the count value obtained from the numbering circuit 2o! 15 and the end packet flag obtained from the end flag generation circuit 24 as an audio packet) P
Assemble. This voice packet P is transmitted to the voice detection circuit 2.
When the presence/silence signal 111 input from 2 is active, it is sent to the switching network 60.

The receiving device 30 has a receiving eight buffer 32, which receives and stores voice packets P from the exchange 1 network 60. As a result, variations in the delay time within the network 60 for each bucket P are absorbed and a predetermined delay is established. The accumulated packets P are output to the packet disassembly circuit 32 in the order of input. The buffer 32 further generates an underrun signal 311 indicating the presence or absence of the bucket) P, and outputs this to the packet discard detection circuit 38.

As shown in FIG. 4, the packet disassembly circuit 34 disassembles the input voice packet P into a voice frame 320, serial number information, and an end bar/sotofraction EPF, and sends the voice frame 320 to the interpolation circuit 38 with a serial number 312. An end packet flag signal 313 is output to the packet discard detection circuit 36.

The packet discard detection circuit 36 determines whether the frame is a voice frame or a silent frame based on the serial number information 312 and end packet flag signal 313 output from the packet disassembly circuit 34 and the underrun signal 311 output from the reception buffer 32. judgment, and detection of bucket lift discard. A sound detection signal 314 indicating the detection result of a sound frame is sent to the selection circuit 46 and the receiving side reset circuit 42.
In addition, a discard detection signal 31 indicating the detection of a discard bucket, l.
5 are output to the interpolation circuit 38, respectively.

When the discard detection signal 315 output from the packet discard detection circuit 36 does not indicate packet discard, the interpolation circuit 38 sends the f\ voice frame 320 output from the packet decomposition circuit 34 to the decoder 40 without performing the same processing. At the same time, interpolated data 321 is created using this voice frame in case packet discard occurs. When a packet discard is detected, interpolation data 321 is output to the encoder 40, and a sound frame is interpolated using the interpolation data 321.

The receiving side recent circuit 42 includes a packet discard detection circuit 36
A reset pulse 316 is outputted to the decoder 40 by differentiating the voice presence detection signal 314 outputted from the decoder 40 . This reset pulse 316 is the interpolated data 32 input to the decoder 40.
The decoder 40 is generated at a timing such that the decoder 40 is reset immediately before the first audio sample of each sound frame of 1 is input.

The decoder 40 receives the ADPCM output from the interpolation circuit 38.
etc., and outputs it to the selection circuit 46 in the form of a digital signal 31B. Further, in response to a reset pulse 316 supplied from the receiving side reset circuit 42, internal information is forcibly initialized.

The receiving device 30 has a silence reproduction circuit 44, which is a circuit for pseudo-reproducing a silent frame that was silently compressed and not transmitted by the transmitting device 10. The silence reproduction circuit 44 typically has a HOTH signal having a power substantially equal to the average power of the silence frames input to the transmitter 10 at the input terminal 11.
Noise such as spectral noise 317 is generated and output to the selection circuit 4B. When the sound detection signal 314 output from the discard detection circuit 36 indicates the presence of a sound frame, the selection circuit 46 causes the output signal 322 of the decoder 40 to be output to the output terminal 31, so that the sound detection signal 314 is If a silent frame is indicated, the output 31 of the silent reproduction circuit 44
7 is output to the output terminal 31. In this way, the discarded frame is restored with or without sound and is output from the output terminal 31.

The packet discard detection circuit 36 will be explained in more detail with reference to FIG. The packet discard detection circuit 36 is composed of a serial number continuity detection circuit 50 and a control circuit 52.

The serial number continuity detection circuit 50 detects whether there is a missing number in the serial number information 312 output from the packet disassembly circuit 34. In the example in Figure 4, the missing numbers "4""7" ~r Il" r 13
J is detected, and the missing number detection signal 411 is activated for a period substantially equal to the length of one audio frame for one missing number. The missing number detection signal 411 is input to the control circuit 52.

The control circuit 52 receives an underrun signal 311 output from the reception buffer 32, a missing number detection signal 411 output from the serial number continuity detection circuit 50, and a packet disassembly circuit 3.
Based on the end packet flag signal 313 obtained from 4, a voice detection signal 314 indicating whether the frame is a voice frame or a silent frame, and a discard detection signal 315 indicating whether or not a packet is discarded are output. In addition, as a protection against the case where all end packet flag information is lost due to packet discard, if consecutive discards of M or more buckets are detected, end flag information is lost due to packet discard. After that, the system is configured to play silence. This value M is selected in proportion to the maximum packet discard rate of the switching network 200, and is usually set in a range of about 3 to 6.

The control circuit 36 can be realized, for example, by software having a bucket loss counter and an end flag, and is executed according to the operational flow shown in FIG. 5 to generate a voice detection signal 314 and a discard detection signal 315. In this operation flow, first, it is checked whether the underrun signal 311 is active or not (500), and if not, it is checked whether the missing number detection signal 411 is active or not (502).
. When the missing number detection signal 411 is inactive, the packet loss counter is set to "0" 504), the voice detection signal 314 is set to active 50B), and the discard detection signal 315 is set to inactive (508). From here on]
The second case is when there is no disposal.

Next, in preparation for the occurrence of discard, it is checked whether the end packet flag 313 is active (510). If active, the end flag of the control circuit 36 is set to "
1” (512). That is, the a-matching section is stored. If not, the end flag is set to "O" (514), that is, the silent section is memorized and interpolated between sound and silence.

If the missing number detection signal 411 is active (502) and the underrun signal 311 is also active (500), it is checked whether the previous end flag was "1" or not (520). If not, increase the packet loss counter by +1 step (53
0), it is checked whether the value of the packet loss counter is equal to M (532). If the value is M, the end flag is set to rlJ (534). In this case and when the count of the packet loss counter is not M, the voice detection signal 314 is activated (536) and the discard detection signal 315 is activated.
Activate (538).

When the end flag indicates "1" in step 520, the packet loss counter is set to "0".
2), and make the sound detection signal 314 inactive (5).
24) Also make the discard detection signal 315 inactive (
528).

In the voice packet communication device of this embodiment, in a special case, when the first packet of a sound section is lost, the reset timings of the encoder 14 and the decoder 40 are different, so that the internal information is not synchronized. This may occur. However, since the power of the audio signal is small before the sound section,
This asynchronous state quickly recovers due to leakage when updating internal information. Therefore, no large S/N deterioration occurs. In this embodiment, the trailing edge of consecutive audio frames is also detected using an end packet flag. Therefore, when the value N is set to "2" or more in the packet flag generation circuit 24, it may not be possible to interpolate a maximum of N-1 voice buckets I at the trailing edge of a voice frame. However, since these voice packets that cannot be interpolated exist during the hangover period, and the hangover period in voice detection is inherently not strict, it is unlikely that the quality of the reproduced audio will be impaired due to the loss of packets during this period. .

(Effects of the Invention) As described above, according to the present invention, the receiving device can distinguish between a sound period and a silent period, and between a silent period and packet discard, and perform interpolation processing on discarded packets.

Therefore, the S/N of reproduced audio is improved. Furthermore, even if a temporally large packet discard occurs and the interpolation process becomes impossible, the encoder and decoder can be synchronized for each sound interval. Therefore, the quality deterioration of the reproduced audio is minimized.

[Brief explanation of drawings]

FIG. 1 is a relay system diagram showing an embodiment of the voice packet communication device according to the present invention, FIG. 2 is a functional block diagram showing an example of the configuration of the discard detection circuit in the embodiment shown in FIG. 1, and FIG. 3 is the same. FIG. 4 is an operation diagram showing an example of the operation of the transmitting device in the embodiment, FIG. 4 is an operation diagram showing an example of the operation of the receiving device in the same embodiment, and FIG. 5 is a flow diagram showing an example of the algorithm of the discard detection circuit. Explanation of symbols of main parts 19. Voice packet communication device 10, . . ., Send-E word holder 12, Voice frame forming circuit 14, . . . Encoder 113, . . . Transmitting side reset circuit 18, . . . Packet assembling circuit 20, . , , voice detection circuit 241 . Packet flag generation circuit 30, receiving device 32, receiving buffer 34, packet decomposition circuit discard detection circuit interpolation circuit

Claims (1)

[Claims] 1. Audio frame forming means for forming a digital audio signal into an audio frame; detecting a sound section in the audio frame followed by a sound frame and a silent section followed by a silent frame; and a voice detecting means for outputting a sound/absence signal representing a silent section and a hangover signal for the voiced section; an encoding means for compressing and encoding the voice frame and outputting the encoded voice frame; a serial number assigning means for assigning a series of serial numbers to the voice frames and silent frames; and a packet assembling means for assembling and transmitting the voice packets including the voice frames from the encoding means and the serial numbers of the voice frames. A voice packet communication device comprising: a reset means for resetting the encoding means at the beginning of the sound section using the sound presence/absence signal; and an end for identifying the rear part of the sound section and indicating the rear part. an end packet information generating means for outputting packet information, wherein the packet assembling means assembles and transmits an audio packet including the end packet information. 2. The apparatus according to claim 1, wherein the end packet information generating means outputs the end packet information during a period during which the plurality of audio packets are output from after the output of the hangover signal until the end of the sound section. An audio packet communication device characterized by: 3. Receive a voice packet including a voice frame, a serial number given consecutively to the voice frame and the silent frame, and end packet information indicating the end of the voice section following the voice frame, and receive the voice packet; storage means for storing and outputting the voice packets in the order of reception and generating an underrun signal when all the stored voice packets are output; packet disassembly means for disassembling into end packet information; detecting packet discard based on the continuity of the serial number, the end packet information and the underrun signal; and outputting a discard detection signal indicating the packet discard; a discard detection means for detecting voice or silence and outputting a sound/absence detection signal indicating the result of the detection; and when the discard detection signal is not output from the discard detection means, a voice frame from the packet disassembly means; and when the discard detection signal is output, an interpolation means for creating interpolation data from the sound frame and outputting the interpolation data, and a decoding means for decoding the output from the interpolation means into a digital signal. and a reset means for resetting the decoding means when the sound presence/absence detection signal from the discard detection means changes to sound. 4. The apparatus according to claim 3, wherein when the discard detection means detects the discard of a series of packets exceeding a predetermined number, the display of the sound/absence detection signal becomes silent. Packet communication device.