JPH0983524A - Assembling/dissolving method for cell of sound signal frame - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cell assembling/dissolving method of a sound signal frame which can precisely reproduce sound and can suppress the deterioration of sound quality even if cell transfer delay fluctuation and the abolishment of a sound cell occur. SOLUTION: A cell assembling part 7 stores sequence numbers for the respective sound signal frames 4 and cell position information showing sound/silence information 6 corresponding to the prescribed number of the sound signal frames 4 which are immediately before, in a sound transmission cell 8 and transmits them at intervals of a prescribed period. A received cell analysis part 15 inspects the reception cells 1 in the order of the sequence number at intervals of a prescribed period, and judges the abolished cell or the silent cell from cell position information of the subsequent received cell 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of assembling and disassembling a voice signal frame cell, and particularly for assembling a voice signal frame into a voice cell or disassembling a voice cell to reproduce a voice signal frame in an ATM communication device. The present invention relates to a method for assembling and disassembling a voice signal frame cell.

[0002]

2. Description of the Related Art Generally, in the case of transmitting an analog voice signal through an ATM communication network performing data transmission in an asynchronous mode, first, the analog voice signal is encoded to generate a voice signal frame of a predetermined length, and then, These voice signal frames are converted into ATM cells (hereinafter referred to as cells), that is, cells are assembled and transmitted. On the other hand, the received cell is framed, that is, cell disassembled to restore a voice signal frame, and the voice signal frame is decoded to reproduce the original voice signal.

Conventionally, as a method of assembling and disassembling a voice signal frame, the cell transfer is stopped when the voice signal frame shows no sound, and the receiving side does not receive a voiced cell for a predetermined period. In this case, a method has been proposed in which a silent audio signal frame is generated by determining that it is a silent interval, and the silent interval of the original audio signal is compressed and transmitted (for example, "voice packet communication"). Factors and Countermeasures for Voice Communication in Japan, "IEICE, Exchange Research Group, SE87-103, etc.).

Further, a voiced section of the voice signal is recognized by detecting voiced / non-voiced voice of the input voice signal in units of a predetermined sample, and voiced out of voice cells assembled from the voice signal. Various control information indicating the start cell corresponding to the start position of the section, the end cell corresponding to the end position, the order of the voice cells corresponding to the voiced section, and the start cell of the silent section are stored in each voice cell. Audio signals are efficiently transmitted by identifying and reproducing the voice cells by referring to the control information on the receiving side (see, for example, JP-A-4-7824).
No. 8).

[0005]

Therefore, in such a conventional method for assembling and disassembling a voice signal frame cell, the transmission of a voice cell indicating a silent section is simply stopped and the voice cell indicating a voice section is received. Since the voice signal is reproduced in accordance with it, the cell delay fluctuation that occurs depending on the congestion state in the communication network is not taken into consideration.For example, when the voice cell at the head of the voiced section is delayed due to the fluctuation. However, there is a problem in that it is not possible to accurately reproduce the voice because the silent section immediately before the voice cell is extended and the voiced section is delayed.

According to the latter method, in particular, for example, when the last cell of a voiced section is discarded in the network, it is distinguished whether the following voice cell is discarded or is not transmitted due to a silent section. However, there is a problem in that it is impossible to interpolate a voice signal for a discarded voice cell, it is impossible to prevent deterioration of reproduced voice, and voice quality deteriorates. The present invention is intended to solve such a problem, and even when cell transfer delay fluctuation or voice cell discard occurs, it is possible to more accurately reproduce voice and suppress deterioration of voice quality. It is an object to provide a cell assembling and cell disassembling method for an audio signal frame.

[0007]

In order to achieve the above object, a method of assembling a voice signal frame cell according to the present invention includes a voice signal frame transmission buffer for temporarily storing each voice signal frame and each voice signal frame transmission buffer. Sound of signal frame /
A voice presence / absence frame identifying unit that outputs voice presence / absence information indicating silence is provided, and the voice signal frame and the voice presence / absence information corresponding thereto are provided at predetermined intervals from the voice signal frame transmission buffer and the presence / absence voice frame identifying unit. Are read out, sequence numbers are generated for each read audio signal frame in the order in which they were read, and if the voiced / silent information corresponding to the read voice signal frame indicates voiced, The cell position information indicating the sound / silence of a predetermined number of audio signal frames read out immediately before is generated, and a cell is assembled based on the audio signal frame, the sequence number and the cell position information.

Accordingly, the voice signal frame and the voiced / non-voiced information corresponding thereto are read out from the voice signal frame transmission buffer and the presence / absence sound frame identification section at predetermined intervals, and for each read voice signal frame. Sequence numbers are generated in the order
When the voiced / non-voiced information corresponding to the read voice signal frame indicates voiced, cell position information indicating voiced / non-voiced of a predetermined number of voice signal frames read immediately before the voice signal frame is generated. , The cell is assembled based on the voice signal frame, the sequence number and the cell position information.

Further, the speech signal frame cell disassembling method according to the present invention has an address corresponding to a sequence number indicating the order of the speech signal frames, and sequentially stores the received speech cells at the address corresponding to the sequence number. A cell reception buffer is provided, and the contents of each address in the reception buffer are inspected in sequence number order at predetermined intervals. If the contents indicate a valid voice cell, it is judged as a voiced cell and a voiced voice signal is output. If the frame is generated and the content does not indicate a valid voice cell, it is determined whether the cell is a silent cell or a discarded cell based on the predetermined cell position information included in the following voice cells in sequence number order, and the silence cell is determined. Alternatively, an audio signal frame indicating discard is generated.

Therefore, the contents of each address in the receiving buffer are inspected in sequence number order at predetermined intervals.
When this content indicates a valid voice cell, it is determined to be a voiced cell and a voiced voice signal frame is generated, and when the content does not indicate a valid voice cell, the following voices are arranged in sequence number order. It is determined whether the cell is a silent cell or a discarded cell based on the predetermined cell position information included in the cell, and a voice signal frame indicating silence or discard is generated.

[0011]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an ATM communication device by a cell assembling and disassembling method of a voice signal frame according to an embodiment of the present invention, in which (a) shows a transmitting side and (b) shows a receiving side. .

In the figure, 2 is an input voice signal 1.
An encoder that encodes and outputs as a predetermined voice signal frame, detects voiced / non-voiced voice signals, adds voiced / non-voiced information to each voice signal frame, and outputs the encoder. A voice signal frame transmission buffer for temporarily storing the voice signal frame from the voice signal 2 from the voice signal frame 4 by extracting voiced / non-voiced information from the voice signal frame from the encoder 2. A presence / absence sound frame identification unit for identification.

A reference numeral 7 sequentially reads the audio signal frames 4 from the audio signal frame transmission buffer 3 in accordance with a predetermined timing, and outputs the voiced sound output from the presence / absence sound frame identification section 5 in synchronization with each audio signal frame 4. / Silence information 6
When a voice is indicated, a voice cell is assembled based on various voice cell control information and is output to the network side as a transmission cell 8, and when a silence is indicated, cell assembly and cell transmission are not performed. It is a cell assembly unit that compresses silent cells.

Further, 12 is a buffer write control unit for sequentially storing the receiving cells 11 at predetermined addresses of the cell receiving buffer 13, 14 is the content of each address of the cell receiving buffer 13, and the content is a voiced cell, Received cell analysis unit 15 that analyzes whether the cell is a silent cell or a discarded cell
And a voice signal frame reproducing unit 16 for reproducing and outputting various voice signal frames 17 according to the analysis result from the receiving cell analyzing unit 15, and 18 for decoding the reproduced voice signal frame 17. Is a decoding unit that reproduces an audio signal.

Next, referring to FIG. 2, a cell assembling operation of a voice signal frame will be described as an operation of the present invention. FIG. 2 is a timing chart showing a cell assembling operation of a voice signal frame. First, the audio signal 1 is input to the encoder 2 (see FIG. 1), where it is sequentially encoded into a predetermined audio signal frame, and the voice signal 1 of the audio signal 1 corresponding to each audio signal frame is transmitted. Silence is detected, and sound / silence information based on the detection result is added to the audio signal frame and output.

The voice signal frame is temporarily stored in the voice signal frame transmission buffer 3 and the presence / absence voice frame identification section 5 extracts voiced / non-voiced information. The cell assembling unit 7 includes the voice signal frame transmission buffer 3
A voice signal frame 4 having a predetermined length is read out every period T from, and voiced / silent information 6 output from the presence / absence voice frame identification unit 5 is taken in synchronization with this to assemble a voice cell.

When the audio signal frame is based on the 16KLD-CELP system, the cycle T is 20 ms corresponding to one cell, and the audio signal frame 4 (20 ms minutes = 40 bytes) of this cycle T length is sequentially read. To be done.
In addition, the cell assembling unit 7 uses the read audio signal frame 4
Sequence number (SNC: Sequence Number of Ce
ll) is generated, and the voiced / silent information 6 input in synchronization with each voice signal frame 4 is sequentially stored, and the voiced / silent information 6 corresponding to the predetermined number of voice signal frames 4 read immediately before is generated. Cell location information (CTI: Cell Tra)
nsmission Information) is generated.

A voice cell as shown in FIG. 3 is generated on the basis of the voice signal frame 4 and various control information. The audio signal frame 4 has a payload part (PAYLO
AD), and the sequence number and cell position information are stored in the SNC field and CTI of the header part, respectively.
Stored in the field. The sizes of the SNC field and the CTI field depend on the capacity of the delay fluctuation absorption buffer and the allowable delay time based on each coding method.

For example, a voice cell arriving after exceeding the delay allowable time has a large delay from the original voice signal.
It does not make much sense to transfer cell location information for such a voice cell. In the case of FIG. 3, 5 bits are provided as the SNC field and the CTI field. Further, each bit of the cell position information is voiced (= “1”) / silent (= “0”) for each of the five audio signal frames 4 processed immediately before the audio cell in which the cell position information is stored. Is shown.

Therefore, as shown in FIG. 2, if there is a silent frame before the voice signal frame 4 of sequence number # 1, this CTI becomes "00000", and each bit of this CTI increases as the sequence number increases. Shifts to the left, and CTI with sequence number # 3
Becomes “00011”. Also, the CTI of sequence number # 6 following the silent voice signal frames # 4 and # 5 is "1.
1100 ".

In this way, the audio signal frames generated in accordance with the audio signal 1 are read in every predetermined length, sequence numbers # 1 ... Are assigned, and the audio signal frames corresponding to the individual audio signal frames 4 are provided. When the sound / silence information 6 indicates silence, the voice cell is not assembled and sent (not sent). On the other hand, when the sound / silence information 6 indicates sound, the above sequence number and cell position are set. A voice cell containing information is assembled and output as a transmission cell 8.

Next, with reference to FIG. 4, a cell disassembling operation in the case of disassembling a reception cell into a voice signal frame will be described. FIG. 4 is a timing chart showing a cell disassembling operation into audio signal frames. In particular, as an example, the fluctuation occurs in the transmission cell 8 transmitted from the transmitting side in the predetermined cycle T due to the congestion state of the communication network, and the voiced cell with the sequence number # 3 is discarded. explain.

Buffer write controller 12 (see FIG. 1)
Sequentially stores the receiving cell 11 at a predetermined address of the cell receiving buffer 13 based on the sequence number stored in the header of the receiving cell 11. In the cell reception buffer 13, as shown in FIG. 5, the reception cell 11 corresponds to the sequence numbers # 1 to # 32 of the reception cell 11.
Addresses 0 to 31 for storing are fixedly assigned.

The received cell analysis unit 15 of the cell disassembly unit 14 is
In order to absorb the delay fluctuation at the time of cell transfer, the first inspection is performed after delaying the timing by the delay fluctuation absorption time α after first receiving the voiced cell after receiving the signaling signal. After that, in a predetermined cycle T, the stored contents of the addresses are inspected in the order of addresses of the cell reception buffer 13, that is, in the order of sequence numbers indicating the order of the voice signal frames. Therefore, as the read address,
Since the address where the voice cell is not received, that is, the address corresponding to the silent cell or the discarded cell is also inspected every cycle T, the silent section is reproduced correctly.

When valid data is stored in the inspection target address of the cell reception buffer 13, it is determined that there is sound and the content is read and output to the audio signal frame reproduction unit 16. In response to this, the audio signal frame reproduction unit 16 reproduces a predetermined audio signal frame 17 and outputs it to the decoding unit 18, where it is decoded into an audio signal 19 and output.

On the other hand, when valid data is not stored in the check target address of the cell reception buffer 13, the cell position information stored in the header portion of the reception cell subsequent to the reception cell is inspected, It judges whether the receiving cell is a voiced cell or a silent cell, and if it indicates a voiced cell, it is judged as a discarded cell that has been discarded in the communication network. Judge as a cell,
This is notified to the audio signal frame reproduction unit 16.

That is, as shown in FIG. 4, when the voiced cell of sequence number # 3 is not received by the receiving side,
Next, the cell position information “11100” is referred to from the header portion of the received cell 11 having the sequence number # 6 received, and the third bit from the right corresponding to the sequence number # 3 is “1”.
Since it indicates (= voiced), it is determined as a discarded cell. Similarly, since the 2nd and 1st bits from the right corresponding to the sequence numbers # 4 and 5 indicate "0" (= silence), it is determined to be a silence cell.

In response to this, the audio signal frame reproducing section 1
In 6, the voice signal frame 17 indicating discard or silence is generated and output to the decoding unit 18. Here, in the case of discard, the voice signal frame interpolation process is performed from the immediately previous voice signal frame 17, and an appropriate voice signal frame interpolation process is performed. The audio signal 19 is output, and in the case of silence, a predetermined audio signal 1 indicating silence.
9 will be output.

As described above, on the transmitting side, the sequence number for each voice signal frame and the cell position information indicating the voiced / non-voiced information corresponding to the predetermined number of voice signal frames immediately before are stored in the voiced cells and predetermined. It transmits every cycle, and the receiving side inspects the received cells in sequence number order at every predetermined cycle, and if a valid voice signal frame is not obtained, discards cells or silent cells from the cell position information of the following receiving cells. Since the decision is made, even if cell transfer delay fluctuations or voice cell discards occur, audio can be played back accurately without causing playback delays, and audio signal frame interpolation processing is effectively used to degrade voice quality. Can be suppressed.

[0030]

As described above, according to the present invention, as a method of assembling a voice signal frame cell, sequence numbers are generated in the order of reading for each voice signal frame, and the sequence numbers are read immediately before the voice signal frame. Generating cell position information indicating the presence / absence of a predetermined number of audio signal frames, and assembling a cell based on these audio signal frames, sequence numbers, and cell position information only when the audio signal frame is audio. It is the one. As a cell decomposition method for a voice signal frame, a cell reception buffer that has an address corresponding to a sequence number indicating the order of voice signal frames and sequentially stores received voice cells at an address according to the sequence number is provided. , The contents of each address in the receive buffer are checked in sequence number order, and if the content does not indicate a valid voice cell, the specified cells included in the following voice cells in sequence number order A silent cell or a discarded cell is determined based on the position information, and a voice signal frame indicating silence or discard is generated.

Therefore, the contents of the cell reception buffer are inspected in sequence number order at a predetermined cycle regardless of the presence or absence of a reception cell, and a voice signal frame indicating sound, silence, or discard is generated according to the inspection result. Therefore, even if cell transfer delay fluctuation or voice cell discard occurs, it is possible to accurately reproduce the voice without causing a reproduction delay. In addition, the transmitting side reliably notifies the receiving side of the occurrence status of voiced and silent cells, and the silent cells and the discarded cells are distinguished, and the voice signal frame when the voice signal frame is decoded into the voice signal. It is possible to effectively use the interpolation process to suppress the deterioration of the voice quality.

[Brief description of drawings]

FIG. 1 is a block diagram of an ATM communication device according to a method of assembling and disassembling a voice signal frame cell according to an embodiment of the present invention.

FIG. 2 is a timing chart showing a cell assembling operation of a voice signal frame.

FIG. 3 is an explanatory diagram showing a configuration example of a voice cell.

FIG. 4 is a timing chart showing a cell disassembling operation into audio signal frames.

FIG. 5 is an explanatory diagram showing a configuration example of a cell reception buffer.

[Explanation of symbols]

1 ... Voice signal, 2 ... Encoder, 3 ... Voice signal frame transmission buffer, 4 ... Voice signal frame, 5 ... Presence / absence sound frame identification unit, 6 ... Voice / silence information, 7 ... Cell assembly unit, 8 ...
Transmission cell, 11 ... Reception cell, 12 ... Buffer write control section, 13 ... Cell reception buffer, 14 ... Cell disassembly section, 15
... reception cell analysis unit, 16 ... audio signal frame reproduction unit, 1
7 ... Voice signal frame, 18 ... Decoding unit, 19 ... Voice signal.

Claims (2)

[Claims] 1. A communication device that encodes an input voice signal to sequentially generate voice signal frames, sequentially assembles voice cells from these voice signal frames, and transmits the voice cells at a predetermined cycle. A voice signal frame transmission buffer and a presence / absence sound frame identification unit for outputting sound / silence information indicating sound / silence of each voice signal frame The audio signal frame and corresponding voiced / non-voiced information corresponding to the audio signal frame are read out at predetermined intervals, and a sequence number is generated for each read audio signal frame in the order of reading, corresponding to the read audio signal frame. When the voiced / non-voiced information that indicates that the voice is present, the predetermined number read immediately before the voice signal frame. It generates cell position information that indicates a voice / silence audio signal frame, the speech signal frame, cell assembly method of speech signal frame, characterized in that it has to assemble the cell based on the sequence number and cell location information. 2. A voice cell having a voice signal frame is received and disassembled to generate various voice signal frames according to the contents thereof, and a predetermined voice signal is reproduced by decoding the various voice signal frames. In a communication device that outputs as a signal, a cell reception buffer that has an address corresponding to a sequence number indicating the order of voice signal frames and sequentially stores received voice cells at an address according to the sequence number is provided at predetermined intervals. Check the contents of each address in the receive buffer in the order of the sequence number, and if this content indicates a valid voice cell, judge that it is a voiced cell and generate a voiced voice signal frame. If no voice cell is indicated, it is a silence cell based on the predetermined cell position information included in the voice cells that follow in sequence number order. To determine whether the disposal cell,
A method for cell decomposition of a voice signal frame, wherein a voice signal frame indicating silence or discard is generated.