JP2009065607A - JITTER BUFFER CONTROL METHOD AND VoIP TERMINAL - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a jitter buffer control method for reducing sound quality deterioration such as sound interruption, and a VoIP terminal which implements the method. <P>SOLUTION: A jitter buffer control method according to the present invention includes: dividing sound data into a plurality of divided units when storing the sound data in a jitter buffer; setting a thinning incomplete flag for each divided unit; monitoring the total amount of sound data in the jitter buffer; and applying thinning processing to at least one divided unit to which the thinning incomplete flag is set, and changing and setting the thinning incomplete flag of the relevant divided unit into a thinning complete flag when the total amount of sound data exceeds a predetermined threshold. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a jitter buffer control method in a VolP terminal that performs voice communication using VoIP technology, and to such a VolP terminal.

  In voice communication using the VolP technology, voice data is encoded in a predetermined encoding format and then packetized, usually at intervals of 20 msec to 10 msec, and transmitted toward a VoIP network such as the Internet. However, depending on the congestion state of the VoIP network, packet transmission at an interval of 10 msec to 20 msec is not necessarily guaranteed, and jitter and delay inevitably occur. Therefore, in general, a VolP terminal is provided with a jitter buffer to absorb jitter at the time of packet reception. However, since the audio data for the packet corresponding to the jitter is directly delayed, the packet is discarded when the number of packets in the jitter buffer exceeds a certain threshold.

  For example, in the cited document 1, a technique is provided in which a packet deletion area and a packet addition area are provided in the FIFO constituting the jitter buffer, and control is performed so that packets are deleted or packets are added according to the amount of accumulated packets in the FIFO. In addition, a technique for increasing the processing speed by changing the clock frequency according to the amount of packets in the jitter buffer is disclosed.

Further, Cited Document 2 discloses a technique for determining whether or not a decimation or decimation is necessary from the jitter value of a received packet, and performing a decimation or decimation process on a frame basis for audio data in a buffer.
JP 2004-274572 A JP 2005-64873 A

  However, depending on the conventional technique, there is a problem that the audio data is interrupted because several tens to several hundreds of continuous audio data pieces are lost due to discarding in units of packets or frames.

  An object of the present invention is to provide a jitter buffer control method for reducing voice quality degradation such as voice interruption and a VoIP terminal for executing such a method.

  A jitter buffer control method according to the present invention is provided in a VoIP terminal comprising a jitter buffer for accumulating audio data included in a received packet, and an audio decoding unit for extracting and decoding the audio data stored in the jitter buffer. A jitter buffer control method, wherein when audio data is stored in the jitter buffer, the audio data is divided into a plurality of division units, and a thinning incomplete flag setting step for setting a thinning incomplete flag for each division unit; The total amount of audio data in the jitter buffer is monitored, and when the total amount of audio data exceeds a predetermined threshold, thinning processing is performed on at least one division unit for which the decimation incomplete flag is set and the division unit Thinning completion flag change setting step for changing the thinning incomplete flag to the thinning completion flag , Characterized in that it comprises a.

  A VoIP terminal according to the present invention is a VoIP terminal comprising a jitter buffer that accumulates audio data included in a received packet, and an audio decoding unit that extracts and decodes the audio data accumulated in the jitter buffer. A decimation incomplete flag setting means for dividing the audio data into a plurality of division units and setting a decimation incomplete flag for each division unit when the jitter buffer accumulates audio data, and a total amount of audio data in the jitter buffer When the total amount of audio data exceeds a predetermined threshold, at least one division unit for which the thinning incomplete flag is set is thinned and the thinning incomplete flag for the division unit is thinned And a decimation completion flag change setting means for changing and setting the flag.

  According to the jitter buffer control method and the VoIP terminal according to the present invention, the thinning process for deleting the audio data pieces is performed for each audio data division unit when jitter occurs. Thereby, voice quality deterioration such as voice interruption is reduced.

  Embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows an embodiment of the present invention and shows the entire configuration including a VoIP terminal. Here, the VoIP terminal 30 is a terminal connected to the VoIP network 10 and having a voice communication function using the VoIP technology. The VoIP terminal 30 includes a packet receiving unit 40, a jitter buffer 50, an audio decoding unit 60, and a jitter buffer control unit 70.

  The packet receiver 40 receives a received packet arriving from the VoIP network 10 and accumulates audio data included in the packet in the jitter buffer 50 under the control of the jitter buffer controller 70. The jitter buffer 50 is a memory that performs a FIFO operation, and operates so that the audio data portion that has arrived and accumulated first is taken into the audio decoding unit 60 first. The audio decoding unit 60 takes in the audio data accumulated from the jitter buffer 50 and applies a decoding process to the audio data to restore the audio.

  The jitter buffer control unit 70 controls the writing operation and the reading operation of the jitter buffer 50. The jitter buffer control unit 70 includes a counter 71 for counting audio data accumulated in the jitter buffer 50 in units of packets, which is a division unit, and a threshold table 72 in which thresholds for the number of packets that give an execution timing of the thinning process are set. , A thinning rate table 73 in which a thinning rate for giving a rate at which the audio data pieces are thinned, and a thinning execution flag G indicating whether the thinning processing is being executed are included. In the present embodiment, when the value of the thinning execution flag G is 1, it indicates that execution of the thinning process is requested or is being executed, and when the value is 0, execution is not requested or is being executed. It shall represent that it is not.

  FIG. 2 shows a configuration example of the jitter buffer shown in FIG. In the example of this figure, audio data of a plurality of division units DD1 to DD10, each of which is for one packet, are stored, and 10 packets are stored as a whole. One decimation completion flag F is given to the division unit corresponding to one packet. When the value of the thinning completion flag F is 1, it indicates that the thinning process has already been performed for the division unit. When the value of the thinning completion flag F is 0, the thinning completion flag F is set to the division unit as a thinning incomplete flag. This indicates that the thinning process has not yet been performed.

  One division unit to which the decimation completion flag F is assigned is not limited to audio data for one packet, and even for audio data for a plurality of packets, the audio data for one packet is further divided to complete each decimation. A flag F may be given.

  FIG. 3 shows one division unit shown in FIG. The example division unit DDn (n is a positive integer) is composed of, for example, 100 audio data pieces. Also, assuming that the thinning process is performed with a thinning rate of 0.1, one voice data piece (filled in the figure) is deleted from ten voice data pieces as shown in the figure. Yes. One piece of audio data can be audio data for one sampling in audio encoding, or audio data that has been sampled for a predetermined number.

  In addition, various forms of how the audio data pieces are deleted discretely for one division unit are assumed. For example, a mode in which N consecutive (N is a positive integer) audio data pieces at an arbitrary position in one division unit is deleted is also assumed. The determination of the specific deletion mode and the value of the thinning rate needs to be made based on actual experimental results. For example, if 50 consecutive or discrete audio data pieces are deleted from 100 continuous audio data pieces in the division unit DDn, the influence on the quality of the reproduced audio is not negligible, so the thinning rate does not exceed 50%. It is desirable to do so. Moreover, even if the thinning rate is low (for example, 10%), if a continuous audio data piece (for example, 91st to 100th of the audio data pieces in FIG. 3) is deleted, a partially collected audio data piece is deleted. In other words, since it becomes easier to affect the quality of the voice than to delete the distributed audio data pieces, it is desirable to distribute the audio data pieces to be deleted.

  FIG. 4 shows a processing procedure of audio data storage processing in the jitter buffer control method according to the present invention. When the voice packet arrives at the packet receiving unit of the VoIP terminal, the packet receiving unit accumulates only the voice data portion from the received packet in the jitter buffer.

  The jitter buffer controller 70 always monitors whether or not a received packet has newly arrived (step S1). When the packet receiving unit accumulates the audio data in the jitter buffer, the jitter buffer control unit 70 uses the audio data corresponding to the received packet as one division unit as a control operation for the packet receiving unit, and the decimation completion flag F Is set to 0 and the counter is incremented by 1 (step S2). Although not shown in the flowchart of this figure, the jitter buffer control unit 70 decrements the counter by 1 when the audio decoding unit takes in audio data for one packet. Therefore, the total amount of audio data accumulated in the jitter buffer can be recognized from the counter value.

  Next, the jitter buffer control unit 70 determines whether or not the value of the counter is equal to or greater than a threshold value (step S3). The counter value varies depending on the occurrence of jitter. For example, when a plurality of packets delayed due to jitter arrive at the packet receiving unit in a short time, the processing of the audio decoding unit is not in time and the audio data stays in the jitter buffer, and the counter value becomes, for example, a threshold value of 10 or more There is a case.

  If the counter value is equal to or greater than the threshold value in step S3, the thinning execution flag G is set to 1 (step S4), and the process returns to step S1. When the value of the thinning execution flag G is set to 1, a thinning process described later is executed. On the other hand, if the counter value is not equal to or greater than the threshold value, the jitter buffer control unit 70 returns to step S1 and waits until a new received packet arrives at the packet receiving unit of the VoIP terminal.

  FIG. 5 shows a processing procedure of the thinning process in the jitter buffer control method according to the present invention. Such thinning-out processing is executed by the jitter buffer control unit 70, but can be executed in parallel with the audio data storage processing shown in FIG.

  The jitter buffer controller 70 always monitors whether or not the thinning execution flag G is 1 (step S31). If the thinning execution flag G is 0, the monitoring in step S31 is continued, and if it is 1, the following thinning process is executed.

  First, the jitter buffer control unit 70 extracts a division unit (for one packet) whose decimation completion flag is 0 from the jitter buffer (step S32). FIG. 6 is referred to for a state in which a division unit with the thinning completion flag set to 0 remains. Next, some audio data pieces in the division unit are deleted according to the thinning rate (step S33). Next, a thinning completion flag is set to 1 for the division unit (step S34). FIG. 7 is referred to for the state in which the thinning completion flag F is set to 1 for all the division units. For example, if the thinning rate is 0.1, the audio data pieces are deleted at a rate of 1 out of 10 audio data pieces (see FIG. 3).

  Next, the jitter buffer control unit 70 determines whether there is another division unit whose decimation completion flag F is 0 (step S35). If there is, the processes in steps S33 and S34 are repeated for the division unit. On the other hand, if there is no division unit whose decimation completion flag F is 0, the jitter buffer control unit 70 sets the decimation execution flag G to 0 and ends the decimation process (step S36).

  As a result of the thinning process by the jitter buffer control unit 70, there is less audio data to be decoded than the audio decoder unit, so the audio decoder unit obtains audio data for one packet as a division unit from the jitter buffer at a timing earlier than usual. The delay will be recovered.

  In the above embodiment, several tens to several hundreds of audio data pieces that are consecutive at a time are not deleted, but the audio data pieces are deleted for each division unit of the audio data, and the audio data pieces are lost. Are distributed and do not concentrate in one place. Further, since a thinning completion flag is set for the thinned division unit, double thinning processing is not performed. As a result, it is possible to increase the speed of the audio decoding process while suppressing deterioration of the audio quality such as audio interruption.

  It should be noted that the embodiment of the present invention is not limited to a mode in which the thinning process is executed for all the division units for which the thinning completion flag F is 0. Embodiments of the present invention include a mode in which thinning processing is performed on at least one division unit, and further, for example, the number of division units on which thinning processing is performed is adjusted according to how much the total amount of audio data exceeds a threshold. You may do it. Further, the thinning process may be performed with priority over a new division unit or an old division unit.

It is a block diagram which shows the Example of this invention and shows the whole structure containing the VoIP terminal by this invention. It is the schematic which shows the structural example of the jitter buffer shown by FIG. FIG. 3 is a schematic diagram showing one division unit shown in FIG. 2. It is a flowchart which shows the process sequence of the audio | voice data storage process in the jitter buffer control method by this invention. It is a flowchart which shows the process sequence of the thinning process in the jitter buffer control method by this invention. It is a figure which shows the state of the jitter buffer with the division | segmentation unit which has not completed the thinning-out process. It is a figure which shows the state of the jitter buffer which the thinning-out process completed about all the division units.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 VoIP network 30 VoIP terminal 40 Packet receiving part 50 Jitter buffer 60 Voice decoding part 70 Jitter buffer control part 71 Counter 72 Threshold table 73 Decimation rate table F Decimation completion flag G Decimation execution flag

Claims (6)

A jitter buffer control method in a VoIP terminal comprising: a jitter buffer for accumulating audio data included in a received packet; and an audio decoding unit for extracting and decoding the audio data accumulated in the jitter buffer,
When accumulating audio data in the jitter buffer, the audio data is divided into a plurality of division units, and a thinning incomplete flag setting step for setting a thinning incomplete flag for each division unit;
The total amount of audio data in the jitter buffer is monitored, and when the total amount of audio data exceeds a predetermined threshold, at least one division unit for which the decimation incomplete flag is set is extracted and thinning processing is performed on the division unit And a decimation completion flag change setting step for changing the decimation incomplete flag of the division unit to a decimation completion flag,
A jitter buffer control method comprising:   2. The jitter buffer control method according to claim 1, wherein the thinning completion flag change setting step performs the thinning processing according to a thinning rate set in advance.   3. The jitter buffer control method according to claim 1, wherein the thinning incomplete flag setting step divides the audio data for one reception packet as one division unit. A VoIP terminal comprising: a jitter buffer that accumulates audio data included in a received packet; and an audio decoding unit that extracts and decodes audio data accumulated in the jitter buffer,
When the jitter buffer accumulates audio data, the audio data is divided into a plurality of division units, and a thinning incomplete flag setting means for setting a thinning incomplete flag for each division unit;
The total amount of audio data in the jitter buffer is monitored, and when the total amount of audio data exceeds a predetermined threshold, the decimation process is performed on at least one division unit for which the decimation incomplete flag is set and the division unit A thinning completion flag change setting means for changing the thinning incomplete flag to a thinning completion flag;
VoIP terminal characterized by including.   5. The VoIP terminal according to claim 4, wherein the thinning completion flag change setting unit performs the thinning process according to a thinning rate set in advance.   6. The VoIP terminal according to claim 4, wherein the thinning incomplete flag setting means divides the audio data for one received packet as one division unit.

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