JP3996819B2 - Audio transmission system, receiving terminal, transmitting terminal, decoding processing apparatus, and audio transmission method used therefor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In a network system such as the Internet, the present invention encodes and compresses audio data and voice from a transmitting terminal to a receiving terminal connected via the network and transmits the IP data, and the receiving terminal decodes the audio data and voice. TECHNICAL FIELD The present invention relates to an audio transmission system that reproduces and reproduces, a receiving terminal, a transmitting terminal, a decoding processing device, and an audio transmission method used therefor.
[0002]
[Prior art]
Conventionally, in the encoding process and decoding process of audio data, an overflow or underflow of the input buffer of the receiving terminal due to a difference in data processing speed that occurs when the frequency of the encoding clock and the decoding clock cannot be synchronized. The flow can be avoided by thinning out the data during the decoding process at the receiving terminal, or by stopping the process of reading the encoded data from the input buffer to the decoder or the decoding process of the decoder itself. It was. An example of such an audio transmission system is that described in Japanese Patent Application Laid-Open No. 2001-189933.
[0003]
FIG. 8 is a block diagram showing a schematic configuration of a receiving terminal of a conventional audio transmission system. In the audio transmission system shown in FIG. 8, encoded data transmitted from the transmission terminal is accumulated in the input buffer 801. The encoded data stored in the input buffer 801 is input to the decoder 802 and subjected to decoding processing. This decoded data is input to the regenerator 803 and output as regenerated data.
[0004]
An input buffer control unit 804 is provided to avoid overflow or underflow in the input buffer 801 during the decoding process. The input buffer control unit 804 checks the remaining amount of encoded data in the input buffer 801 (hereinafter referred to as “the remaining amount of the input buffer 801”), and the remaining amount of the input buffer 801 is equal to or greater than a predetermined threshold. In this case, it is determined that there is a possibility of overflow, and an instruction to discard the first encoded data stored in the input buffer 801 is given.
[0005]
In this case, the input buffer control unit 804 discards unconditionally if the remaining amount of the input buffer 801 is 95% or more. On the other hand, if the remaining amount of the input buffer 801 is not less than 70% and not more than 95%, the encoded data is temporarily input to the decoder 802, the decoded data is input to the regenerator 803, and the decoded data level generation unit 805 is input.
[0006]
The decoded data level generation unit 805 generates a level value of the input decoded data, and outputs the level value to the input buffer control unit 804. The input buffer control unit 804 determines whether the decoded data is a silence level based on the level value input from the decoded data level generation unit 805. If the decoded data is a silence level, the input buffer control unit 804 instructs to discard the decoded data input to the regenerator 803.
[0007]
On the other hand, when the remaining amount of the input buffer 801 is equal to or less than a predetermined threshold, it is determined that there is a possibility of underflow, the decoding process is stopped for the decoder 802, and the regenerator 803 is stopped. To instruct the repeated reproduction of the currently input decoded data.
[0008]
In this case, if the remaining amount of the input buffer 801 is 5% or less, the decoder 802 is unconditionally instructed to stop the decoding process, and the decoding currently input to the regenerator 803 is performed. Instructs repeated playback of data. On the other hand, if the remaining amount is not less than 5% and not more than 30%, the encoded data is temporarily input to the decoder 802, and the decoded data is input to the regenerator 803, while being input to the decoded data level generation unit 805. .
[0009]
Since the level value generated by the decoded data level generation unit 805 is input, the input buffer control unit 804 determines whether the decoded data is a silence level based on this level value. If the decoded data is a silence level, the input buffer control unit 804 instructs the decoder 802 to stop the decoding process and instructs the reproducer 803 to repeatedly reproduce the decoded data currently input. To do.
[0010]
As described above, in the conventional audio transmission system, the received data is discarded and the decoded data is repeatedly reproduced while monitoring the remaining amount of the input buffer 801 at the receiving terminal. As a result, the remaining amount of the input buffer 801 is kept constant, the overflow and underflow of the input buffer 801 that may occur because the encoding clock and the decoding clock cannot be synchronized, and the regenerator 803 Auditory degradation of the output playback data is suppressed.
[0011]
[Problems to be solved by the invention]
However, in the conventional audio transmission system, the discard of the encoded data and the repeated reproduction of the decoded data for maintaining the remaining amount of the input buffer 801 are performed in units of frames which are units of decoding processing. For this reason, the encoded data is discarded or the decoded data is repeatedly reproduced in units of several tens of msec, and there is a problem that annoying noise due to signal discontinuity occurs.
[0012]
In particular, in the conventional audio transmission system, the synchronization between the transmission timing clock for transmitting the encoded data from the transmission terminal to the IP network and the reception timing clock for the reception terminal to receive the encoded data from the IP network is not considered. . For this reason, in the receiving terminal, a situation may occur in which overflow or underflow occurs in the receiving buffer in which encoded data from the IP network is accumulated before the input buffer 801. In this case, there is a problem that encoded data is continuously lost before overflow or underflow is avoided in the input buffer 801.
[0013]
The present invention has been made in view of such problems, and avoids loss of data due to a difference in processing speed between a receiving terminal and a transmitting terminal while suppressing generation of annoying noise due to signal discontinuity. It is an object of the present invention to provide an audio transmission system that can be used, a reception terminal, a transmission terminal, a decoding processing device, and an audio transmission method used therefor.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, an audio transmission system according to the present invention calculates a time difference between time information acquired from a transmission terminal connected via a communication line and time information of the reception terminal at the reception terminal, While controlling the amount of decoding processing in the receiving terminal according to the time difference, the amount of decoding data stored in the output buffer where decoding data is stored and the decoding in the output buffer at the time of previous processing A difference amount from the accumulated amount of data is obtained, and the data output amount from the output buffer to the regenerator is adjusted according to the difference amount.
[0015]
As a result, the amount of decoding processing at the receiving terminal is controlled in accordance with the time difference between the transmitting terminal and the receiving terminal, so that overflow and underflow in the buffer of the receiving terminal can be avoided, while in the output buffer Since the data output amount to the regenerator is adjusted with the increase or decrease of the data storage amount, the generation of annoying noise due to the difference between the write amount to the output buffer and the read amount of the regenerator can be suppressed. .
[0016]
An audio transmission system according to a first aspect of the present invention is an audio transmission system that encodes and compresses audio data from a transmission terminal to a reception terminal connected via a communication line, and transmits the audio data. Includes a packet transmission unit that transmits an encoded data packet obtained by encoding audio data, and a time measurement unit that measures time information of the transmission terminal in response to a request from the reception terminal. A packet receiving unit that receives an encoded data packet; a decoding processing unit that decodes the encoded data packet; and a regenerator that reads out data decoded by the decoding processing unit and reproduces audio data; A time acquisition unit that acquires time information of the transmission terminal, and a decoding processing amount of the decoding processing unit based on the time information acquired by the time acquisition unit A configuration comprising: an input buffer management unit that controls; and an output buffer management unit that monitors a read amount of decoded data by the regenerator and adjusts an output amount of the decoded data from the decoding processing unit to the regenerator. take.
[0017]
According to this configuration, since the decoding processing amount in the decoding processing unit is controlled by the input buffer management unit according to the time difference between the transmitting terminal and the receiving terminal, overflow and underflow in the buffer in the receiving terminal Can be avoided. Further, since the output buffer management unit adjusts the output amount of the decoded data to the regenerator in accordance with the read amount of the decoded data by the regenerator, the decoded data amount in the decoding processing unit and the read data by the regenerator Generation of annoying noise caused by the difference from the amount can be suppressed.
[0018]
According to a second aspect of the present invention, in the audio transmission system according to the first aspect, the decoding processing unit stores an input buffer for storing encoded data from the packet receiving unit, and an input buffer. A configuration is provided that includes a decoder that decodes the encoded data, and an output buffer that stores the decoded data decoded by the decoder.
[0019]
According to a third aspect of the present invention, in the audio transmission system according to the second aspect, the decoder uses a data size, which is a decoding processing unit of encoded data, as a reference value, and data smaller than the reference value. While selecting the size, the same data size as the reference value or a data size larger than the reference value, adjusting the output amount and writing to the output buffer, the regenerator outputs the data size output by the decoder The decoded data is read out from the output buffer with the same data size.
[0020]
According to these configurations, the output amount of the decoded data from the output buffer to the regenerator can be adjusted from a data size smaller than the data size as a decoding processing unit to a size larger than the data size. Therefore, it is possible to prevent buffer overflow and underflow caused by the difference between the amount written by the decoder and the amount read by the regenerator with an appropriate data size, and to suppress the generation of noise.
[0021]
According to a fourth aspect of the present invention, in the audio transmission system according to the second or third aspect, the input buffer management unit calculates a time difference between the time information of the transmitting terminal and the time information of the receiving terminal. Then, a configuration is adopted in which the decoding processing amount of the decoding processing unit is controlled by controlling the input amount of encoded data from the input buffer to the decoder in accordance with the time difference.
[0022]
According to this configuration, the decoding processing amount of the decoding processing unit is controlled by controlling the input amount of the encoded data from the input buffer to the decoder according to the time difference between the transmitting terminal and the receiving terminal. . As a result, the difference between the transmission timing at which the transmission terminal transmits the encoded data and the reception timing at which the reception terminal receives the encoded data can be absorbed by controlling the decoding processing amount. It is possible to avoid overflow and underflow of the reception buffer for storing the encoded data packet. As a result, a situation in which encoded data is lost can be avoided in advance.
[0023]
According to a fifth aspect of the present invention, in the audio transmission system according to the fourth aspect, the time acquisition unit acquires time information of the transmission terminal at regular time intervals, and the input buffer management unit acquires the time acquisition Encoding the time difference with respect to the acquisition interval of time information by the unit and adjusting the timing at which the decoder acquires encoded data from the input buffer according to the ratio A configuration that controls the amount of data input is adopted.
[0024]
According to this configuration, the decoding is performed by adjusting the timing at which the decoder acquires the encoded data from the input buffer according to the ratio of the time difference between the transmitting terminal and the receiving terminal with respect to the time information acquisition interval by the time acquisition unit. The amount of encoded data input to the encoder is controlled. As a result, the encoded data is input to the decoder when a certain amount of encoded data is accumulated in the input buffer, so that overflow or underflow of the reception buffer that accumulates encoded data packets from the communication line is prevented. It can be avoided.
[0025]
According to a sixth aspect of the present invention, in the audio transmission system according to any one of the second to fifth aspects, the output buffer management unit includes a storage amount of decoded data in the output buffer at a current time, A difference amount from the accumulated amount of decoded data in the output buffer at the time of processing is obtained, and a data output amount from the output buffer to the regenerator is adjusted according to the difference amount.
[0026]
According to this configuration, the amount of data output from the output buffer to the regenerator is adjusted in accordance with the amount of difference in the amount of decoded data stored in the output buffer. The generation of annoying noise caused by the difference from the read amount from the output buffer of the device can be suppressed.
[0027]
According to a seventh aspect of the present invention, in the audio transmission system according to the sixth aspect, the output buffer management unit is configured to output the output at the time when the accumulated amount of decoded data in the output buffer at the present time has been processed previously. When the accumulated amount of decoded data in the buffer exceeds the amount of data output to the regenerator, the output at the time when the accumulated amount of decoded data in the output buffer at the present time has been processed before is reduced. A configuration is adopted in which the amount of data output to the regenerator is increased when the stored amount of decoded data in the buffer falls below.
[0028]
According to this configuration, the amount of data output from the output buffer to the regenerator is increased or decreased in accordance with the difference in the amount of decoded data stored in the output buffer. The generation of annoying noise caused by the difference from the read amount from the output buffer of the device can be suppressed.
[0029]
According to an eighth aspect of the present invention, in the audio transmission system according to the sixth or seventh aspect, the output buffer management unit includes a write destination address indicating a termination address of the decoded data written by the decoder; A management table in which information including a read source address indicating a start address of decoded data read by the regenerator is registered, and a value obtained by subtracting the read source address from the write destination address is used to decode encoded data A configuration is adopted in which the storage amount of decoded data in the output buffer at the present time is calculated by dividing the data size, which is a processing unit, as a reference value by the reference value.
[0030]
According to this configuration, the storage amount of the decoded data in the output buffer at the present time is calculated using the write destination address and the read source address registered in the management table provided in the output buffer management unit, so that it can be performed quickly and reliably. The storage amount of the decoded data in the output buffer at the present time can be obtained.
[0031]
According to a ninth aspect of the present invention, in the audio transmission system according to the eighth aspect, the write destination address and the read source address are equal to the reference value regardless of increase or decrease in the data size output from the decoder. Adopting a structure of adding and updating.
[0032]
According to this configuration, the write destination address and the read source address are updated by adding the reference value regardless of the increase or decrease in the data size output by the decoder. Address update work can be performed.
[0033]
A receiving terminal according to a tenth aspect of the present invention is a receiving terminal that receives encoded and compressed audio data from a transmitting terminal connected via a communication line, and is encoded data in which audio data is encoded A packet receiving unit that receives a packet; a decoding processing unit that decodes the encoded data packet; a regenerator that reads data decoded by the decoding processing unit and reproduces audio data; and the transmission terminal A time acquisition unit for acquiring the time information, an input buffer management unit for controlling a decoding processing amount of the decoding processing unit based on the time information acquired by the time acquisition unit, and decoded data by the regenerator And an output buffer management unit that adjusts the output amount of the decoded data from the decoding processing unit to the regenerator.
[0034]
According to this configuration, since the decoding processing amount in the decoding processing unit is controlled by the input buffer management unit according to the time difference between the transmitting terminal and the receiving terminal, overflow and underflow in the buffer in the receiving terminal Can be avoided. Further, since the output buffer management unit adjusts the output amount of the decoded data to the regenerator in accordance with the read amount of the decoded data by the regenerator, the decoded data amount in the decoding processing unit and the read data by the regenerator Generation of annoying noise caused by the difference from the amount can be suppressed.
[0035]
According to an eleventh aspect of the present invention, in the receiving terminal according to the tenth aspect, the decoding processing unit includes an input buffer for storing encoded data from the packet receiving unit, and a code stored in the input buffer. The decoder includes a decoder that decodes the encoded data and an output buffer that stores the decoded data decoded by the decoder.
[0036]
According to a twelfth aspect of the present invention, in the receiving terminal according to the eleventh aspect, the decoder uses a data size that is a decoding processing unit of encoded data as a reference value, and a data size smaller than the reference value. The data size that is the same as the reference value or larger than the reference value is selected, the output amount is adjusted and written to the output buffer, while the regenerator has the data size output by the decoder A configuration is adopted in which decoded data is read from the output buffer with the same data size.
[0037]
According to these configurations, the output amount of the decoded data from the output buffer to the regenerator can be adjusted from a data size smaller than the data size as a decoding processing unit to a size larger than the data size. Therefore, it is possible to prevent buffer overflow and underflow caused by the difference between the amount written by the decoder and the amount read by the regenerator with an appropriate data size, and to suppress the generation of noise.
[0038]
According to a thirteenth aspect of the present invention, in the receiving terminal according to the eleventh or twelfth aspect, the input buffer management unit calculates a time difference between the time information of the transmitting terminal and the time information of the receiving terminal, A configuration is adopted in which the decoding processing amount of the decoding processing unit is controlled by controlling the input amount of encoded data from the input buffer to the decoder according to the time difference.
[0039]
According to this configuration, the decoding processing amount of the decoding processing unit is controlled by controlling the input amount of the encoded data from the input buffer to the decoder according to the time difference between the transmitting terminal and the receiving terminal. . As a result, the difference between the transmission timing at which the transmission terminal transmits the encoded data and the reception timing at which the reception terminal receives the encoded data can be absorbed by controlling the decoding processing amount. It is possible to avoid overflow and underflow of the reception buffer for storing the encoded data packet. As a result, a situation in which encoded data is lost can be avoided in advance.
[0040]
According to a fourteenth aspect of the present invention, in the receiving terminal according to the thirteenth aspect, the time acquisition unit acquires time information of the transmission terminal at regular time intervals, and the input buffer management unit is configured to acquire the time acquisition unit. The ratio of the time difference with respect to the time information acquisition interval is determined, and the encoded data to the decoder is adjusted by adjusting the timing at which the decoder acquires the encoded data from the input buffer according to the ratio. The configuration is used to control the input amount.
[0041]
According to this configuration, the decoding is performed by adjusting the timing at which the decoder acquires the encoded data from the input buffer according to the ratio of the time difference between the transmitting terminal and the receiving terminal with respect to the time information acquisition interval by the time acquisition unit. The amount of encoded data input to the encoder is controlled. As a result, the encoded data is input to the decoder when a certain amount of encoded data is accumulated in the input buffer, so that overflow or underflow of the reception buffer that accumulates encoded data packets from the communication line is prevented. It can be avoided.
[0042]
A transmitting terminal according to the fifteenth aspect of the present invention is a transmitting terminal that encodes and compresses audio data to a receiving terminal connected via a communication line, and transmits the encoded audio data. A configuration is provided that includes a packet transmission unit that transmits a data packet and a time measurement unit that measures time information of the transmission terminal in response to a request from the reception terminal according to any of the tenth to fourteenth aspects.
[0043]
According to this configuration, since the time information at the transmitting terminal is measured in response to a request from the receiving terminal according to any of the tenth to fourteenth aspects, the processing of these receiving terminals can be executed smoothly. .
[0044]
A decoding processing device according to a sixteenth aspect of the present invention is a decoding processing device mounted on a receiving terminal that receives audio data encoded and compressed from a transmitting terminal connected via a communication line, An input buffer for storing the encoded data transmitted from the transmitting terminal, a decoder for decoding the encoded data stored in the input buffer, and the decoded data decoded by the decoder A time difference between the output buffer, the time information of the transmitting terminal and the time information of the receiving terminal is calculated, and the input amount of encoded data from the input buffer to the decoder is controlled according to the time difference. The difference between the input buffer management unit, the amount of decoded data stored in the output buffer at the current time, and the amount of decoded data stored in the output buffer at the time of previous processing The calculated, employs a configuration and an output buffer management unit for adjusting the data output amount to the regenerator from the output buffer in accordance with the difference amount.
[0045]
According to these configurations, the decoding processing amount of the decoding processing unit is controlled by controlling the input amount of the encoded data from the input buffer to the decoder according to the time difference between the transmitting terminal and the receiving terminal. The Thereby, since the difference in the encoded data amount corresponding to the time difference is absorbed by the input buffer, it is possible to avoid overflow and underflow of the reception buffer for storing the encoded data packet from the communication line.
[0046]
Further, since the data output amount from the output buffer to the regenerator is adjusted according to the difference in the accumulated amount of decoded data in the output buffer, the write amount from the decoder to the output buffer and the output buffer of the regenerator The generation of annoying noise caused by the difference from the read amount from can be suppressed.
[0047]
In the audio transmission method according to the seventeenth aspect of the present invention, audio data is encoded and compressed from a transmitting terminal to a receiving terminal connected via a communication line and transmitted, and the receiving terminal decodes the audio data. An audio transmission method for reproducing,
Requesting acquisition of time information of the transmitting terminal from the receiving terminal, responding to the request with time information from the transmitting terminal in response to the request, the time information of the transmitting terminal and the time information of the receiving terminal A time difference is calculated, and a decoding processing amount in the receiving terminal is controlled according to the time difference.
[0048]
According to this method, since the amount of decoding processing at the receiving end terminal is controlled according to the time difference between the transmitting terminal and the receiving terminal, overflow and underflow in the buffer in the receiving terminal can be avoided. .
[0049]
According to an eighteenth aspect of the present invention, in the audio transmission method according to the seventeenth aspect, the time information of the transmitting terminal is obtained from the receiving terminal at regular time intervals, and the ratio of the time difference to the time information obtaining interval is obtained. And the amount of decoding processing is controlled by adjusting the timing of decoding processing at the receiving terminal according to the ratio.
[0050]
According to this method, the amount of decoding processing at the receiving terminal is controlled by adjusting the timing of decoding processing at the receiving terminal according to the ratio of the time difference between the transmitting terminal and the receiving terminal with respect to the time information acquisition interval. . Thereby, since a decoding process is performed when a certain amount of encoded data is accumulated, it is possible to avoid overflow and underflow of a reception buffer that accumulates encoded data packets from the communication line.
[0051]
According to a nineteenth aspect of the present invention, in the audio transmission method according to the seventeenth or eighteenth aspect, an amount of decoded data stored in an output buffer in which decoded data decoded by the receiving terminal is stored is determined. Calculating, obtaining a difference amount between the current accumulated amount and the accumulated amount of the decoded data in the output buffer at the previous processing time, and outputting the data output amount from the output buffer to the regenerator according to the difference amount Is to adjust.
[0052]
According to a twentieth aspect of the present invention, in the audio transmission method according to the nineteenth aspect, the accumulated amount of decoded data in the output buffer at the present time is the amount of decoded data in the output buffer at the time of previous processing. While the amount of data output to the regenerator is reduced when the accumulated amount exceeds, the accumulated amount of decoded data in the output buffer at the present time is the amount of decoded data in the output buffer at the time of previous processing. When the accumulated amount falls below, the data output amount to the regenerator is increased.
[0053]
According to this method, the amount of data output from the output buffer to the regenerator is increased or decreased according to the amount of difference in the amount of decoded data stored in the output buffer. The generation of annoying noise caused by the difference from the read amount from the output buffer by the device can be suppressed.
[0054]
According to a twenty-first aspect of the present invention, there is provided a receiving terminal program for receiving encoded and compressed audio data from a transmitting terminal connected via a communication line, wherein the computer transmits the encoded data transmitted from the transmitting terminal. A packet receiving means for receiving a data packet; a decoding processing means for decoding the encoded data packet; a reproducing means for reading the data decoded by the decoding processing means to reproduce audio data; and the transmission Time acquisition means for acquiring time information of the terminal, input buffer management means for controlling the decoding processing amount of the decoding processing means based on the time information acquired by the time acquisition means, and decoding by the reproduction means Output buffer management means for monitoring the amount of data read and adjusting the output amount of decoded data from the decoding processing means to the reproducing means A receiving terminal program for functioning.
[0055]
According to a twenty-second aspect of the present invention, there is provided a transmission terminal program for encoding and compressing audio data to a reception terminal connected via a communication line, and transmitting the computer by encoding the audio data. A packet transmission means for transmitting a data packet and a program of a transmission terminal for functioning as time measurement means for measuring time information of the transmission terminal in response to a request of the program of the reception terminal of the twenty-first aspect.
[0056]
Embodiments according to the present invention will be specifically described below with reference to the drawings.
[0057]
FIG. 1 is a block diagram showing a schematic configuration of an audio transmission system according to an embodiment of the present invention, and a transmission terminal and a reception terminal constituting the audio transmission system.
[0058]
An audio transmission system 100 shown in FIG. 1 connects a transmitting terminal 110 that encodes and transmits audio data and a receiving terminal 120 that reproduces the encoded data after decoding the encoded data via an IP network 150. Configured.
[0059]
The transmission terminal 110 packetizes data obtained by encoding audio data (hereinafter referred to as “encoded data”) and transmits the packetized data to the IP network 150, and the transmission terminal 110 in response to an acquisition request from the reception terminal 120. And a time measurement processing unit 112 that measures time information within the time.
[0060]
More specifically, the transmission processing unit 110 includes a packet transmission unit 113 that packetizes the encoded data and transmits the packetized data to the IP network 150. Further, the time measurement processing unit 112 includes a time measurement unit 114 that measures time information in the transmission terminal 110 in response to an acquisition request from the reception terminal 120.
[0061]
The receiving terminal 120 receives the encoded data packetized from the IP network 150 and depackets it, a decoding processing unit 122 that decodes the encoded data received by the receiving processing unit 121, and a decoding And a playback device 123 that plays back the data decoded by the data processing unit 122 (hereinafter referred to as “decoded data”) as audio data.
[0062]
More specifically, the reception processing unit 121 includes a packet receiving unit 124 that receives encoded data packetized from the IP network 150 and depackets it. In addition, the decoding processing unit 122 includes an input buffer 125 that stores the encoded data depacketized by the packet receiving unit 124, a decoder 126 that decodes the encoded data stored in the input buffer 125, and a decoding An output buffer 127 for storing the decoded data decoded by the device 126 is provided.
[0063]
The receiving terminal 120 also includes an input control processing unit 128 that controls the input amount of encoded data input from the input buffer 125 to the decoder 126, and the decoded data output from the output buffer 127 to the regenerator 123. An output monitoring processing unit 129 that monitors the output amount, and a timer 130 that counts timer values referred to by the input control processing unit 128 and the output monitoring processing unit 139 are provided.
[0064]
More specifically, the input control processing unit 128 is input from the input buffer 125 to the decoder 126 based on the time information acquired from the transmission terminal 110 and the time information acquired by the time acquisition unit 131. An input buffer management unit 132 is provided for controlling the input amount of encoded data. The output monitoring processing unit 129 includes an output buffer management unit 133 that monitors the output amount of the decoded data output from the output buffer 127 to the regenerator 123. The output buffer management unit 133 includes a DMA transfer management unit 134 that controls DMA (Direct Memory Access) transfer from the output buffer 127 to the regenerator 123.
[0065]
The DMA transfer management unit 134 includes the DMA transfer management table 200 shown in FIG. 2, and controls DMA transfer based on information registered in the DMA transfer management table 200.
[0066]
As shown in FIG. 2, the DMA transfer management table 200 includes a write source block address 201, a write destination block address 202, a write block size 203, a read source block address 204, a read destination block address 205, a read block size 206, a reference A DMA data size 207 and a DMA correction size 208 are registered.
[0067]
The write source block address 201 is the address of the output buffer 127 where the decoder 126 starts to write the decoded data, and the write destination block address 202 is the output buffer 127 which finishes writing the decoded data by the decoder 126. In the write block size 203, the data block size when the decoded data by the decoder 126 is written in the output buffer 127 is registered. Note that a DMA transfer size described later is registered in the write block size 203.
[0068]
Further, the read source block address 204 has an address of the output buffer 127 from which the regenerator 123 starts reading the decoded data, and the read destination block address 205 has the output buffer 127 from which the regenerator 123 finishes reading the decoded data. In the read block size 206, the size of the data block when the regenerator 123 reads the decoded data from the output buffer 127 is registered. Note that a DMA transfer size described later is registered in the read block size 206.
[0069]
Further, the reference DMA data size 207 is a data size obtained by dividing the decoded data size in the decoder 126 by N (N is an integer of 2 or more), and the DMA correction size 208 is the output from the output buffer 127 to the regenerator 123. Arbitrary numerical values up to the data size obtained by dividing the DMA transfer size by 2 are registered. Note that the reference DMA data size constitutes a reference value of the data size that is a unit of decoding processing of encoded data in the decoder 126.
[0070]
The timer 130 includes a timer management table 300 shown in FIG. The input control processing unit 128 and the output monitoring processing unit 129 are activated according to the timer value registered in the timer management table 300.
[0071]
As shown in FIG. 3, a time acquisition timer value 301 and a decoding wait timer value 302 are registered in the timer management table 300. The time acquisition timer value 301 is referred to when the input control processing unit 128 is activated, and the decoding wait timer value 302 is referred to when the decoding processing unit is activated.
[0072]
Hereinafter, in the audio transmission system 100 having the above configuration, an operation until the audio data transmitted from the transmission terminal 110 is reproduced by the reception terminal 120 will be described with reference to the flowcharts shown in FIGS.
[0073]
FIG. 4 is a flowchart when transmitting encoded data from the transmission terminal 110 to the reception terminal 120. FIG. 5 is a flowchart when the receiving terminal 120 performs the decoding process of the encoded data. FIG. 6 is a flowchart for monitoring the output buffer 127 of the decoding processing unit 122 in the receiving terminal 120. FIG. 7 is a flowchart for obtaining time information from the transmission terminal 110 and controlling the input amount of encoded data to the decoder 126 based on the time information.
[0074]
First, a flow when transmitting encoded data from the transmission terminal 110 to the reception terminal 120 will be described with reference to FIG. 4A shows an operation flow of the transmission terminal 110, and FIG. 4B shows an operation flow of the reception terminal 120.
[0075]
When transmitting encoded data from the transmission terminal 110 to the reception terminal 120, the transmission processing unit 111 is activated in the transmission terminal 110. First, the transmission processing unit 111 acquires encoded data obtained by encoding audio data instructed by the operator of the transmission terminal 110 (ST401). The acquired encoded data is input to the packet transmission unit 113.
[0076]
The packet transmitter 113 packetizes the encoded data as a RTP (Real-time Transport Protocol) data packet (ST402), and transmits the data packet to the receiving terminal 120 (ST403).
[0077]
In the audio transmission system 100 according to the present embodiment, when transmitting encoded data from the transmission terminal 110 to the reception terminal 120, a well-known RTP / RTCP (RTP Control) defined by RFC1889 is used as a data communication protocol. Protocol).
[0078]
After transmitting the RTP data packet, transmission processing section 111 waits for acquisition of encoded data again until the next encoded data is input (ST404). When encoded data is input, the process returns to ST401, and the processes up to ST404 are repeated.
[0079]
On the other hand, receiving terminal 120 always waits for reception of a data packet from transmitting terminal 110 (ST405). In the reception terminal 120, the reception processing unit 121 is always activated, and reception of the data packet is monitored by the reception processing unit 121.
[0080]
If the data packet is transmitted from transmitting terminal 110, in reception processing section 121, packet receiving section 124 receives the data packet (ST406). If a data packet is received, packet receiving section 124 depackets the data packet (ST407). The depacketized encoded data is written to the input buffer 125 (ST408).
[0081]
When the encoded data has been written to input buffer 125, reception processing section 121 returns the process to ST405 and repeats the processes up to ST408.
[0082]
Next, the flow at the time of performing the decoding process of the encoded data in the receiving terminal 120 is demonstrated using FIG. Note that the flow shown in FIG. 5 is executed by the decoding processing unit 122 in the receiving terminal 120.
[0083]
In order to perform the decoding process, the receiving terminal 120 activates the decoding processing unit 122, but the decoding processing unit 122 uses the timer set with the decoding waiting timer value 301 on the timer management table 300. It is activated when 130 times out (ST501).
[0084]
When activated, the decoding processing unit 122 acquires the encoded data accumulated at the head of the input buffer 125 and inputs the encoded data to the decoder 126 to perform a decoding process on the acquired encoded data ( ST502).
[0085]
Next, decryption processing section 122 sets the address of the memory where the decrypted data obtained by the decryption processing is recorded as write source block address 201 of DMA transfer management table 200 (ST503). Here, the reason why the address of the memory in which the decoded data is recorded is set as the write source block address 201 is to use it when DMA transfer to the output buffer 127 of the decoded data.
[0086]
After setting the write source block address 201, the decoding processing unit 122 adds the reference DMA data size 207 to the current address written to the write destination block address 202 of the DMA transfer management table 200 (ST504). . That is, the address is updated to the address indicated by adding the reference DMA data size 207 to the address currently registered in the write destination block address 202.
[0087]
Next, decoding processing section 122 activates DMA and transfers the decoded data to output buffer 127 (ST505). At this time, the decoding processing unit 122 performs DMA transfer with reference to the write block size 203 indicating the DMA transfer size. If the write block size 203 is not registered, DMA transfer is performed using the reference DMA data size 207 as the DMA transfer size.
[0088]
After starting the DMA transfer of the decoded data, the decoding processing unit 122 waits until receiving an interrupt indicating that the DMA transfer is completed (hereinafter referred to as “DMA transfer completion interrupt”) from the output buffer 127 (ST506).
[0089]
If a DMA transfer completion interrupt is accepted, decoding processing section 122 determines whether or not DMA transfer of decoded data to output buffer 127 has been completed for the decoded data size (ST507). If the decoding data size has not been completed, the process returns to ST504 and the processes up to ST507 are repeated.
[0090]
In the receiving terminal 120 in the audio transmission system 100 according to the present embodiment, the DMA transfer to the output buffer 127 is performed in units of the reference DMA data size obtained by dividing the decoded data size by N (N is an integer). For this reason, the decoding processing unit 122 determines whether or not the processing has been completed for the decoded data size in ST507, so that the DMA transfer is completed with a size smaller than the decoded data size as a decoding processing unit. It is preventing.
[0091]
If the DMA transfer to the output buffer 127 is completed for the decoded data size, the decoding processing unit 122 sets the decoding waiting timer value 302 read from the timer management table 300 in the timer 130 (ST508), and the processing To ST501.
[0092]
Next, a flow when monitoring the output buffer 127 of the decoding processing unit 122 in the receiving terminal 120 will be described with reference to FIG. 6 is executed by the output monitoring processing unit 129 in the receiving terminal 120.
[0093]
In order to monitor the output buffer 127, the receiving terminal 120 activates the output monitoring processing unit 129. The output monitoring processing unit 129 DMA-transfers the decoded data from the output buffer 127 to the regenerator 123. It is activated by a completion interrupt that is output after (ST601).
[0094]
When activated, in the output buffer management unit 133 of the output monitoring processing unit 129, the DMA transfer management unit 134 calculates the number of remaining blocks currently remaining in the output buffer 127 (hereinafter referred to as “current number of remaining blocks”). (ST602). The DMA transfer management unit 134 uses the information registered in the DMA transfer management table 200 to calculate the current number of remaining blocks according to the following formula.
Current number of remaining blocks = (write destination block address 202−read source block address 204) / reference DMA data size 207
[0095]
Since the current remaining block count is calculated using the write destination address 202 and the read source address 204 registered in the DMA transfer management table 200 in this way, the current remaining block count can be obtained quickly and reliably.
[0096]
Next, the output monitoring processor 129 and the calculated number of remaining blocks and the number of remaining blocks at the beginning of DMA transfer of the decoded data to the regenerator 123 (hereinafter referred to as “initial number of remaining blocks”). (ST603). The initial number of remaining blocks is stored in the DMA transfer management unit 134 during the DMA transfer.
[0097]
If the initial number of remaining blocks is equal to the current number of remaining blocks, DMA transfer management section 134 sets the DMA transfer size to reference DMA data size 207 (ST604).
[0098]
On the other hand, when the initial number of remaining blocks is larger than the current number of remaining blocks, DMA transfer management section 134 sets the DMA transfer size to a value obtained by adding DMA correction size 208 to reference DMA data size 207 (ST605).
[0099]
If the initial number of remaining blocks is larger than the current number of remaining blocks, that is, it means that the number of remaining blocks has decreased because the recovered clock of the regenerator 123 exceeds the decoded clock of the decoder 126. To do. For this reason, the DMA transfer size is set to a value obtained by adding the DMA correction size 208 to the reference DMA data size 207, and the DMA transfer size for one time to the regenerator 123 is increased.
[0100]
On the other hand, when the initial number of remaining blocks is smaller than the current number of remaining blocks, DMA transfer management section 134 sets the DMA transfer size to a value obtained by subtracting DMA correction size 208 from reference DMA data size 207 (ST606). ).
[0101]
If the initial number of remaining blocks is smaller than the current number of remaining blocks, this means that the number of remaining blocks has increased because the recovered clock of the regenerator 123 is lower than the decoded clock of the decoder 126. To do. For this reason, the DMA transfer size is set to a value obtained by subtracting the DMA correction size 208 from the reference DMA data size 207 to reduce the size of one DMA transfer to the regenerator 123.
[0102]
The DMA transfer size is the same as the read block size 206 and the write block size 203 registered in the DMA transfer management table 200. Therefore, the DMA transfer management unit 134 sets the DMA transfer size obtained in ST604 to ST606 to the read block size 206 and the write block size 203.
[0103]
After setting the DMA transfer size as in ST604 to ST606, the DMA transfer management unit 134 adds the reference DMA data size 207 to the current address written in the read source block address 204 of the DMA transfer management table 200 (ST607). ). That is, the address currently registered in the read source block address 204 is updated to the address indicated by adding the reference DMA data size 207 to the address.
[0104]
Next, DMA transfer management section 134 activates DMA and transfers the decoded data to regenerator 123 (ST608). At this time, the DMA transfer management unit 134 performs DMA transfer using the transfer size calculated in ST604 to ST606 as the DMA transfer size.
[0105]
After starting the DMA transfer of the decoded data, the DMA transfer manager 134 waits until receiving a DMA transfer completion interrupt from the regenerator 123 (ST609). If a DMA transfer completion interrupt is accepted, DMA transfer management section 134 returns the process to ST601 and repeats the processes up to ST609.
[0106]
In this way, the data output amount from the output buffer 127 to the regenerator 123 according to the difference between the current number of remaining blocks and the initial number of remaining blocks in the output buffer 127 is determined from the reference DMA data size that is a decoding processing unit. Since the data output amount from the decoder 126 to the output buffer 127 is also adjusted accordingly, the write amount from the decoder 126 to the output buffer 127 can be adjusted from a small data size to a large data size. And an unpleasant noise caused by the difference between the read amount from the output buffer 127 by the regenerator 123 can be suppressed.
[0107]
Next, a flow for acquiring time information from the transmission terminal 110 and controlling the input amount of encoded data to the decoder 126 based on the time information will be described with reference to FIG. 7A shows the operation flow of the transmission terminal 110, and FIG. 7B shows the operation flow of the reception terminal 120. 7A is executed by the time measurement processing unit 112 in the transmission terminal 110, and the flow shown in FIG. 7B is executed by the input control processing unit 128 in the reception terminal 120.
[0108]
In order to request time information from the transmission terminal 110, the input control processing unit 128 is activated in the reception terminal 120. The input control processing unit 128 sets the time acquisition timer value 301 on the timer management table 300. When the timer 130 is timed out, it is started (ST701).
[0109]
When activated, in the input control processing unit 128, the time acquisition unit 131 transmits a time information acquisition request to the transmission terminal 110 (ST702). The time information acquisition request is made by a time information acquisition request message based on ICMP (Internet Control Message Protocol) known as RFC 792, an NTP (Network Time Protocol) known as RFC 1305, or the like.
[0110]
When the time information acquisition request is received by transmission terminal 110, time information acquisition response is returned from transmission terminal 110, and time acquisition section 131 receives this (ST703).
[0111]
If the time information acquisition response is received, the time acquisition unit 131 passes the time information included therein to the input buffer management unit 132. Upon receiving this time information, input buffer management section 132 calculates the difference between the current time at receiving terminal 120 and the time at transmitting terminal 110 (ST704). Specifically, the time difference is calculated by obtaining the difference between the current time information at the receiving terminal 120 and the time information acquired from the transmitting terminal 110.
[0112]
Note that the time difference calculated here indicates a time lag between the transmission terminal 110 and the reception terminal 120 from the previous time information acquisition time to the current time information acquisition time. In other words, this indicates the accuracy difference between the transmission timing clock at the transmission terminal 110 and the reception timing clock at the reception terminal 120.
[0113]
After calculating the time difference in ST704, input buffer management section 132 sets the time acquired from transmitting terminal 110 as the current time of receiving terminal 120 (ST705).
[0114]
Next, input buffer management section 132 calculates correction factor σ of decoding wait timer value 302 (ST706). The input buffer management unit 132 calculates the correction rate σ of the decoding wait timer value 302 by the following equation.
σ = Δt / ΔT
Note that the time difference calculated in ST704 is Δt, the time acquisition timer value 301 registered in the timer management table 300 is ΔT, and the correction rate of the decoding wait timer value 302 is σ.
[0115]
The input buffer management unit 132 corrects the decoding wait timer value 302 registered in the timer management table 300 using the correction rate σ of the decoding wait timer value 302 calculated in ST706, and sets the corrected value. It is updated to a new decoding wait timer value 302 (ST707). The input buffer management unit 132 calculates the corrected decoding wait timer value using the following equation.
ΔTf ′ = (1−σ) × ΔTf
Note that the correction rate calculated in ST706 is σ, the current decoding wait timer value 302 is ΔTf, and the corrected decoding wait timer value is ΔTf ′.
[0116]
By correcting the decoding wait timer value 302 in this way, the processing interval of the decoding process in the receiving terminal 120 shown in FIG. 5 is changed. As a result, the processing speed of the encoded data input from the input buffer 125 to the decoder 126 can be synchronized with the transmission timing clock of the transmission terminal 110. As a result, it is possible to avoid overflow or underflow of the reception buffer that stores the encoded data packet from the IP network 150, and as a result, it is possible to reliably avoid the situation where the encoded data is lost.
[0117]
Finally, the input buffer management unit 132 sets the time acquisition timer value 301 read from the timer management table 300 in the timer 130 (ST708), and returns the process to ST701.
[0118]
On the other hand, the transmission terminal 110 always waits for reception of a time information acquisition request from the reception terminal 120. In the transmission terminal 110, the time measurement processing unit 112 is always activated, and reception of a time information acquisition request is monitored by the time measurement processing unit 112.
[0119]
If a time information acquisition request is received (ST709), time measurement processing section 112 measures current time information of transmission terminal 110 (ST710), and transmits the measured time information to reception terminal 120 as a time acquisition response. (ST711). After transmitting the current time information as a time acquisition response to the receiving terminal 120, the time measurement processing unit 112 returns the process to ST709 and repeats the processing up to the processing 711.
[0120]
As described above, according to the audio transmission system 100 of the present embodiment, the reception terminal 120 requests the transmission terminal 110 to acquire time information, and calculates the time difference between the reception terminal 120 and the transmission terminal 110 at regular intervals. . Then, the processing speed for the encoded data input to the decoder 126 is corrected by synchronizing the transmission timing clock of the transmission terminal 110 and the reception timing clock of the reception terminal 120 according to the calculated time difference.
[0121]
As a result, when an overflow is expected in the reception buffer in which the data packet of the encoded data is accumulated prior to the input buffer 125, the decoding processing interval of the decoder 126 is shortened while an underflow is expected. In this case, the decoding processing interval of the decoder 126 is expanded. As a result, overflow and underflow of the reception buffer can be prevented in advance.
[0122]
Further, according to the audio transmission system 100 of the present embodiment, the write destination block address 202 of the DMA transfer performed between the decoder 126 and the output buffer 127 and between the output buffer 127 and the regenerator 123 are performed. The reading source block address 204 of the DMA transfer to be performed is monitored, and a difference in processing speed between writing by the decoder 126 and reading by the regenerator 123 is calculated. Then, the DMA transfer size is increased / decreased according to the calculated difference in processing speed, and the processing amount of the regenerator 123 is increased / decreased.
[0123]
Thereby, the read interval of the decoded data read from the output buffer 127 is synchronized with the write interval to the output buffer 127, and the write block size 203 from the decoder 126 to the output buffer 127 and from the output buffer 127 to the regenerator 123 are synchronized. The boundary size of the read source block address 204 is always kept constant. For this reason, since the remaining amount of the decoded data in the output buffer 127 can be maintained constant, an overflow or underflow of the output buffer 127 can be prevented in advance.
[0124]
As will be apparent to those skilled in the art, the present invention can be implemented using a typical commercially available digital computer and microprocessor programmed according to the techniques described in the above embodiments. Further, as will be apparent to those skilled in the art, the present invention includes a computer program created by a person skilled in the art based on the technique described in the above embodiment.
[0125]
Also included within the scope of the invention are computer program products that are storage media containing instructions that can be used to program a computer that implements the invention. This storage medium is a disk such as a floppy (R) disk, optical disk, CDROM and magnetic disk, ROM, RAM, EPROM, EEPROM, magnetic optical card, memory card or DVD, but is not limited to these. Absent.
[0126]
【The invention's effect】
As described above, according to the present invention, it is possible to avoid data loss due to a difference in processing speed between a receiving terminal and a transmitting terminal while suppressing generation of annoying noise due to signal discontinuity. Play.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of an audio transmission system according to an embodiment of the present invention, and a transmission terminal and a reception terminal constituting the audio transmission system.
FIG. 2 is a configuration diagram of a DMA transfer management table provided in a receiving terminal in the audio transmission system according to the embodiment.
FIG. 3 is a configuration diagram of a timer management table provided in a receiving terminal in the audio transmission system according to the embodiment.
FIG. 4 is a flowchart for transmitting encoded data from a transmission terminal to a reception terminal in the audio transmission system according to the embodiment.
FIG. 5 is a flowchart when decoding processing is performed in the receiving terminal of the audio transmission system according to the embodiment.
FIG. 6 is a flowchart when monitoring the output buffer of the decoding processing unit in the receiving terminal of the audio transmission system according to the embodiment;
FIG. 7 is a flowchart for obtaining time information from the transmission terminal of the audio transmission system according to the embodiment and controlling the input amount of encoded data to the decoder based on the time information.
FIG. 8 is a block diagram showing a schematic configuration of a receiving terminal of a conventional audio transmission system.
[Explanation of symbols]
100 audio transmission system
110 Sending terminal
120 receiving terminal
111 Transmission processing unit
112 Time measurement processor
113 Packet transmitter
114 Time measurement unit
121 Reception processing unit
122 Decoding processing unit
123 Regenerator
124 packet receiver
125 input buffers
126 Decoder
127 Output buffer
128 Input control processor
129 Output monitoring processor
130 timer
131 Time acquisition unit
132 Input buffer management unit
133 Output buffer management unit
134 DMA transfer manager
200 DMA transfer management table
300 Timer management table

Claims (22)

An audio transmission system that encodes and compresses audio data from a transmitting terminal to a receiving terminal connected via a communication line,
The transmission terminal includes a packet transmission unit that transmits an encoded data packet obtained by encoding audio data, and a time measurement unit that measures time information of the transmission terminal in response to a request from the reception terminal, A packet receiving unit that receives the encoded data packet, a decoding processing unit that decodes the encoded data packet, and a reproduction that reads the data decoded by the decoding processing unit and reproduces audio data A time acquisition unit that acquires time information of the transmission terminal, an input buffer management unit that controls a decoding processing amount of the decoding processing unit based on the time information acquired by the time acquisition unit, An output buffer management unit that monitors the read amount of the decoded data by the regenerator and adjusts the output amount of the decoded data from the decoding processing unit to the regenerator. Audio transmission system according to claim. The decoding processing unit includes an input buffer for storing encoded data from the packet receiving unit, a decoder for decoding the encoded data stored in the input buffer, and the decoder The audio transmission system according to claim 1, further comprising an output buffer for storing decoded data. The decoder uses a data size that is a decoding processing unit of encoded data as a reference value, a data size that is smaller than the reference value, a data size that is the same as the reference value, or a data size that is larger than the reference value. While selecting and adjusting the output amount and writing to the output buffer, the regenerator reads the decoded data from the output buffer with the same data size as the data size output by the decoder The audio transmission system according to claim 2. The input buffer management unit calculates a time difference between the time information of the transmission terminal and the time information of the reception terminal, and an input amount of encoded data from the input buffer to the decoder according to the time difference The audio transmission system according to claim 2 or 3, wherein the decoding processing amount of the decoding processing unit is controlled by controlling the decoding process. The time acquisition unit acquires time information of the transmitting terminal at a fixed time interval, and the input buffer management unit obtains a ratio of the time difference with respect to the time information acquisition interval by the time acquisition unit, and according to the ratio 5. The audio transmission system according to claim 4, wherein the input amount of the encoded data to the decoder is controlled by adjusting a timing at which the decoder acquires the encoded data from the input buffer. . The output buffer management unit obtains a difference amount between the accumulation amount of the decoded data in the output buffer at the current time and the accumulation amount of the decoded data in the output buffer at the time of the previous processing, and determines the difference amount 6. The audio transmission system according to claim 2, wherein a data output amount from the output buffer to the player is adjusted accordingly. The output buffer management unit stores data to the regenerator when the amount of decoded data stored in the output buffer at the current time exceeds the amount of decoded data stored in the output buffer at the time of previous processing. While reducing the output amount, the data stored in the regenerator when the accumulated amount of decoded data in the output buffer at the current time is lower than the accumulated amount of decoded data in the output buffer at the time of the previous processing. The audio transmission system according to claim 6, wherein the output amount is increased. The output buffer management unit registers information including a write destination address indicating the end address of the decoded data written by the decoder and a read source address indicating the start address of the decoded data read by the regenerator. The output buffer at the present time by dividing a value obtained by subtracting the read source address from the write destination address by using the data size that is a decoding processing unit of encoded data as a reference value 8. The audio transmission system according to claim 6, wherein an accumulation amount of the decoded data is calculated. 9. The audio transmission system according to claim 8, wherein the write destination address and the read source address are updated by adding the reference value regardless of increase or decrease in the data size output by the decoder. . A receiving terminal for receiving encoded and compressed audio data from a transmitting terminal connected via a communication line;
A packet receiving unit that receives an encoded data packet in which audio data is encoded, a decoding processing unit that decodes the encoded data packet, and data that is decoded by the decoding processing unit to read audio data An input buffer management for controlling a decoding processing amount of the decoding processing unit based on the time information acquired by the time acquisition unit And an output buffer management unit that monitors the read amount of the decoded data by the regenerator and adjusts the output amount of the decoded data from the decoding processing unit to the regenerator. Terminal. The decoding processing unit includes an input buffer for storing encoded data from the packet receiving unit, a decoder for decoding the encoded data stored in the input buffer, and the decoder The receiving terminal according to claim 10, further comprising an output buffer for storing decoded data. The decoder uses a data size that is a decoding processing unit of encoded data as a reference value, a data size that is smaller than the reference value, a data size that is the same as the reference value, or a data size that is larger than the reference value. While selecting and adjusting the output amount and writing to the output buffer, the regenerator reads out the decoded data from the output buffer with the same data size as the data size output from the decoder The receiving terminal according to claim 11. The input buffer management unit calculates a time difference between the time information of the transmission terminal and the time information of the reception terminal, and an input amount of encoded data from the input buffer to the decoder according to the time difference The receiving terminal according to claim 11, wherein the decoding processing amount of the decoding processing unit is controlled by controlling The time acquisition unit acquires time information of the transmitting terminal at a fixed time interval, and the input buffer management unit obtains a ratio of the time difference with respect to the time information acquisition interval by the time acquisition unit, and according to the ratio 14. The receiving terminal according to claim 13, wherein the input amount of the encoded data to the decoder is controlled by adjusting a timing at which the decoder acquires the encoded data from the input buffer. A transmission terminal that encodes and compresses audio data to a reception terminal connected via a communication line,
A packet transmission unit that transmits an encoded data packet obtained by encoding audio data, and a time measurement unit that measures time information of the transmission terminal in response to a request from the reception terminal according to any one of claims 10 to 14. A transmission terminal comprising: A decoding processing device mounted on a receiving terminal that receives audio data encoded and compressed from a transmitting terminal connected via a communication line,
An input buffer for storing the encoded data transmitted from the transmitting terminal, a decoder for decoding the encoded data stored in the input buffer, and the decoded data decoded by the decoder A time difference between the output buffer, the time information of the transmitting terminal and the time information of the receiving terminal is calculated, and the input amount of encoded data from the input buffer to the decoder is controlled according to the time difference. Determine the difference between the input buffer management unit, the amount of decoded data stored in the output buffer at the current time, and the amount of decoded data stored in the output buffer at the time of previous processing, and according to the difference And an output buffer management unit for adjusting a data output amount from the output buffer to the regenerator. An audio transmission method in which audio data is encoded and compressed and transmitted from a transmitting terminal to a receiving terminal connected via a communication line, and the audio data is decoded and reproduced by the receiving terminal,
Requesting acquisition of time information of the transmitting terminal from the receiving terminal, responding to the request with time information from the transmitting terminal in response to the request, the time information of the transmitting terminal and the time information of the receiving terminal An audio transmission method characterized by calculating a time difference and controlling a decoding processing amount in the receiving terminal according to the time difference. The time information of the transmitting terminal is acquired from the receiving terminal at regular time intervals, the ratio of the time difference to the time information acquisition interval is obtained, and the timing of the decoding process at the receiving terminal is adjusted according to the ratio 18. The audio transmission method according to claim 17, wherein the decoding processing amount is controlled by this. The storage amount of the present decoded data in the output buffer in which the decoded data decoded by the receiving terminal is stored is calculated, and the current storage amount and the decoded data in the output buffer at the time of previous processing are calculated. 19. The audio transmission method according to claim 17 or 18, wherein a difference amount with respect to a storage amount is obtained, and a data output amount from the output buffer to the player is adjusted according to the difference amount. When the accumulated amount of decoded data in the output buffer at the current time exceeds the accumulated amount of decoded data in the output buffer at the time of previous processing, the data output amount to the regenerator is reduced. Increasing the amount of data output to the regenerator when the amount of decoded data stored in the output buffer at the current time is less than the amount of decoded data stored in the output buffer at the time of previous processing; 20. The audio transmission method according to claim 19, wherein: A program for a receiving terminal that receives audio data encoded and compressed from a transmitting terminal connected via a communication line,
A computer reads packet data receiving means for receiving an encoded data packet transmitted from the transmitting terminal, decoding processing means for decoding the encoded data packet, and data decoded by the decoding processing means. A playback unit that plays back audio data, a time acquisition unit that acquires time information of the transmission terminal, and a decoding processing amount of the decoding processing unit based on the time information acquired by the time acquisition unit. A receiving terminal for functioning as an input buffer management means and an output buffer management means for monitoring the read amount of the decoded data by the reproducing means and adjusting the output amount of the decoded data from the decoding processing means to the reproducing means Program. A transmission terminal program that encodes and compresses audio data to a reception terminal connected via a communication line,
23. A computer functioning as packet transmission means for transmitting an encoded data packet in which audio data is encoded, and time measurement means for measuring time information of the transmission terminal in response to a request for a program of the reception terminal according to claim 21. Program of the sending terminal for.

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