JP4834013B2 - Transmission device, transmission program, reception device, and reception program - Google Patents

Description

  The present invention relates to a technique for calculating a transmittable band while performing data transmission and adjusting the amount of data to be transmitted in a communication network in which the transmittable band varies with time.

  Conventionally, transmission systems using a best-effort communication network (for example, the Internet) have been widely used. As a communication procedure for data transmission through such a communication network, TCP (Transmission Control Protocol) including a mechanism for confirming a reception response and a mechanism for performing congestion control is widely used.

  By using a TCP communication procedure, it is possible to maintain the reliability of data transmission and the fairness of the bandwidth used. However, this procedure is not suitable for real-time transmission for transmitting streaming data such as video and audio because the time required for data transmission is not taken into consideration.

  Real-time transmission in the Internet communication network can be realized by transmitting packet data defined by this procedure by using a communication procedure based on UDP (User Datagram Protocol). Further, on the assumption that data transmission such as video and audio is performed, a communication procedure by RTP (Real Time Transfer Protocol) is known and widely used.

  However, UDP and RTP only define the type of data that is generally required. The user can individually select the mechanism for recovering lost data and the mechanism for controlling the flow rate of transmitted data. Must respond.

  As a mechanism for recovering missing data in a communication network, a data retransmission mechanism called ARQ (Automatic Repeat Request), a mechanism called FEC (Forward Error Correction) that transmits a packet having error correction capability in advance, and the like are used. ing. As for congestion control, a communication system based on TFRC (TCP Friendly Rate Control) has been proposed in order to calculate a transmission rate according to the state of a communication network.

  The TFRC communication method calculates the same transmission rate as when TCP transmission is performed from the round-trip time length of the communication network, the packet loss rate, and the packet size, and is appropriate according to the state of the communication network. It is possible to calculate a safe transmittable band.

  By the way, when considering the type and nature of data transmitted using a communication network, the data can be classified into the following two types. The first data is data in which the total amount of data to be transmitted is determined in advance and it is not necessary to consider the data transmission time interval. For example, character data is applicable. The second data is data that does not have a predetermined total amount of data to be transmitted for transmission and needs to take into account the time interval of data transmission, that is, data that needs to be transmitted in real time. For example, data such as video and audio is applicable.

  In the system for transmitting the first data described above, the flow rate is adjusted according to the state of congestion, and data transmission is temporarily stopped to avoid data loss and to be fair with other communications. And the deterioration of the congestion state can be prevented.

  In contrast, in the above-described system for transmitting the second data, the amount of data can be adjusted by a compression technique. However, the higher the degree of compression, the lower the quality of the video and audio, so that the encoding rate (compression rate) is as high as possible. It is required to be transmitted with. In addition, it is necessary to continue to transmit data without interruption, and data transmission cannot be temporarily stopped. Depending on the state of the communication network that changes from time to time, the transmittable bandwidth is accurately calculated at that time, and the compression rate of data such as video and audio is adjusted so that it falls within that bandwidth. It is possible to transmit data such as video and audio with the highest quality according to the state.

  In order to transmit high-quality video and audio data within the required time without error, depending on the state of the communication network, the transmittable bandwidth is calculated, and video and audio data is stored within that bandwidth. A rate control technique is used to compress.

  The rate control method using TCP is performed by adjusting the window size indicating the amount of data that can be accepted by the receiving apparatus. Specifically, when a loss such as data loss occurs, the window size is significantly narrowed, that is, the amount of receivable data is reduced, thereby reducing the amount of transmitted data and avoiding congestion. According to this rate control method, the window size is adjusted according to the state of the communication network from time to time. However, since the size adjustment range is large, a large number of users can use the communication bandwidth fairly. The bandwidth cannot be used to the maximum. In addition, it is not always possible to guarantee the use of a certain band for data having real-time characteristics such as video and audio data.

  Further, the rate control method by TFRC is performed by estimating a use band when transmission is performed by a TCP procedure in a communication network and controlling a transmission data amount. According to this rate control method, it is possible to maintain fairness with other users who are transmitting data by TCP, but it is not possible to calculate the maximum value of the usable bandwidth of the communication network, and In addition, it is not possible to guarantee bandwidth utilization for real-time data, for example, stream data.

  On the other hand, without using a general TCP procedure, an increase in loss is detected while increasing the transmission amount of stream data, and an upper limit of the transmission amount of data is obtained by detecting the occurrence of continuous loss. There is a technique (see, for example, Patent Document 1).

JP 2005-269236 A

  However, in a communication network such as the Internet configured by collecting traffic by a plurality of terminals, the loss generation amount and the continuous loss amount constantly change. For this reason, when the amount of data to be transmitted is changed with a certain loss occurrence amount as a threshold, the data transmission amount at that time is not necessarily the maximum amount that can be transmitted.

  Similarly, even if the amount of loss increases, as long as the loss can be recovered using a technique such as retransmission or error correction, data with a high encoding rate is sent by increasing the amount of data to be transmitted. There are cases where it is possible. Thereby, high-quality video / audio data can be transmitted.

  In the above-mentioned Patent Document 1, for example, when the frequency of loss occurs, the amount of data when the loss occurs continuously, etc. is detected with a certain threshold, and the encoding rate is changed according to the value The encoding rate varies depending on the state of the communication network, but the amount of data that can be transmitted at that time does not indicate the maximum value. The communication network is subject to a bandwidth limitation by a router, a failure, or changes depending on a congestion state caused by other factors. That is, the transmittable band in the communication network changes according to the change in the state of the communication network.

  Therefore, in view of these problems, the object of the present invention is to accurately calculate the transmittable bandwidth in accordance with changes in the congestion state etc. in the communication network, and to transmit video or audio data with higher quality. And a transmission program, a reception program, and a reception program.

  In order to achieve the object, the invention of claim 1 compresses data to be transmitted at a predetermined encoding rate, outputs an encoded data, and transmits the encoded data to a receiving device via a communication network. A transmission terminal comprising: a transmission terminal, wherein the transmission terminal stores a buffer for storing encoded data output by the encoder; and loss information for specifying encoded data not received by the reception device, A reception unit that receives from the reception device, and a retransmission data generation unit that reads encoded data specified by the loss information received by the reception unit from the buffer, generates the retransmission data, and calculates the amount of the retransmission data And the encoding rate based on the amount of retransmission data calculated by the retransmission data generation unit. Determining whether the encoding rate is increased, and determining a target rate based on the determination result, and an encoded data amount calculating unit calculating the amount of encoded data output by the encoder And addition data for generating addition data based on the encoding data amount calculated by the encoding data amount calculation unit, the retransmission data amount calculated by the retransmission data generation unit, and the target rate calculated by the determination unit The data generation unit, the encoded data output by the encoder, the retransmission data generated by the retransmission data generation unit, and the addition data generated by the addition data generation unit are transmitted to the receiving device at the target rate. And a transmission unit.

  Further, the invention of claim 2 is the transmission apparatus according to claim 1, wherein when the determination unit increases the target rate, the target rate and the amount of retransmission data after the target rate is increased. The encoding rate is calculated based on this, and when it is determined that the encoding rate is increasing, the target rate is further increased.

  Further, the invention according to claim 3 is the transmission apparatus according to claim 1, wherein when the determination unit increases the target rate, the target rate and the amount of retransmission data after the target rate is increased. The encoding rate is calculated based on this, and when it is determined that the encoding rate has not increased, the target rate is lowered.

  According to a fourth aspect of the present invention, in the transmission apparatus according to the first aspect, when the determination unit decreases the target rate, the target rate and the amount of retransmission data after the target rate is decreased. The encoding rate is calculated based on this, and when it is determined that the encoding rate is increasing, the target rate is further lowered.

  Further, according to a fifth aspect of the present invention, in the transmission apparatus according to the first aspect, when the determination unit decreases the target rate, the target rate and the amount of retransmission data after the target rate is decreased. The encoding rate is calculated based on this, and when it is determined that the encoding rate has not increased, the target rate is increased.

  Further, the invention of claim 6 is the transmission apparatus according to any one of claims 1 to 5, wherein the addition data generation unit is configured such that a sum of an encoding data amount, a retransmission data amount, and an addition data amount is a target rate. Thus, the addition data is generated.

  Further, the invention of claim 7 is a transmission program by a transmission device for transmitting encoded data compressed at a predetermined encoding rate by an encoder to a reception device via a communication network, and a computer constituting the transmission device includes: A process for storing encoded data output by the encoder in a buffer, a process for receiving loss information for identifying encoded data not received by the receiving apparatus, and a process for receiving from the receiving apparatus, and the received loss information. The encoded data is read from the buffer and generated as retransmission data, the amount of retransmission data is calculated, and the encoding rate is calculated based on the calculated amount of retransmission data, and the encoding rate increases. Or not, and based on the determination result, Processing for calculating a target rate, processing for calculating the amount of encoded data output by the encoder, processing for generating addition data based on the calculated encoded data amount, retransmission data amount and target rate, and the encoder And a process of transmitting the encoded data output by the above, the calculated retransmission data, and the addition data to the receiving device at the target rate.

  According to an eighth aspect of the present invention, there is provided a receiving apparatus comprising: a receiving terminal that receives encoded data transmitted by a transmitting apparatus via a communication network; and a decoder that decodes the encoded data and outputs original data. A receiving unit that receives encoded data, retransmission data, and addition data transmitted via a communication network by the transmitting device according to any one of claims 1 to 6, and the receiving unit Based on the encoding data and retransmission data separated by the separation unit, the encoding data and retransmission data transmitted by the transmission device based on the encoding data and retransmission data separated by the separation unit, Loss information for detecting encoded data and retransmission data that have not been received by the receiving unit and identifying these data It includes a loss detection unit for generating, and the encoded data and the retransmission data separated by the separating unit, characterized in that to decode the decoder.

  The invention according to claim 9 is the receiving apparatus according to claim 8, wherein the loss information detecting unit transmits the encoded data transmitted by the transmitting apparatus based on the sequence number added to the encoded data and the retransmission data. Among the retransmission data, the encoded data and the retransmission data that are not received by the receiving unit are detected, and a sequence number added to these data is generated as loss information.

  The invention of claim 10 is a reception program by a receiving device that receives encoded data transmitted via a communication network by a transmitting device and decodes the encoded data into original data by a decoder, the receiving device A process of receiving encoded data, retransmission data and addition data transmitted via a communication network by a transmission apparatus that executes the transmission program according to claim 7, and the received encoded data and retransmission Based on the separated encoding data and retransmission data, the process of separating the data and the addition data, and detecting the encoded data and retransmission data not received among the encoded data and retransmission data transmitted by the transmission device, A process of generating loss information for identifying these data; The encoded data and the retransmission data serial separated, characterized in that to execute a process of decoding by the decoder.

  As described above, according to the present invention, the transmission device generates retransmission data from the loss information indicating data not received by the reception device, calculates the encoding rate from the retransmission data, and calculates the target from the increase / decrease result of the encoding rate. The rate is calculated, and the encoded data, the retransmission data, and the added data are transmitted to the receiving device so that the target rate is obtained. As a result, the encoding rate and the target rate become values according to changes in the congestion state and the like in the communication network, and the transmittable bandwidth can be accurately calculated. Therefore, data such as video or audio can be transmitted with higher quality.

The best mode for carrying out the present invention will be described below in detail with reference to the drawings.
[Transmission system]
First, the transmission system will be described. FIG. 1 is an overall view showing a configuration of a transmission system including a transmission device and a reception device according to an embodiment of the present invention. The transmission system 1 includes a transmission device 2, a reception device 3, and a communication network 4, and the transmission device 2 and the reception device 3 are connected via the communication network 4 to transmit and receive data.

  The transmission device 2 compresses (encodes and encodes) the video / audio data and transmits the compressed data to the reception device 3 via the communication network 4. The video / audio data is compressed in order to efficiently use the communication network 4. When data loss occurs in the communication network 4, the transmission device 2 generates retransmission data and performs retransmission. Here, when the communication network 4 is a best-effort network such as the Internet, for example, the frequency of loss changes according to the state at that time, and the amount of data that can be transmitted in a certain period varies.

  The receiving device 3 receives the data transmitted from the transmitting device 2 via the communication network 4 and performs decoding (decoding). When the received data is missing, that is, when missing data (loss data) exists, loss information for requesting retransmission of data is transmitted to the transmission device 2. For example, when data transmission / reception is performed using RTP, the loss information is a sequence number indicating the location of the loss data.

[Transmitter]
The transmission device 2 includes an encoder 5 and a transmission terminal 6. The encoder 5 receives the encoding rate from the transmission terminal 6, compresses the video / audio data according to the encoding rate, and outputs the encoded data. The encoder 5 can output encoded data having a quality close to that of the original video / audio data as the compression processing is performed at a higher encoding rate, but the amount of encoded data increases. On the other hand, as the compression process is performed at a lower encoding rate, encoded data with a degraded quality compared to the original video / audio data is output, but the amount of encoded data decreases.

  The transmission terminal 6 receives the encoded data from the encoder 5 and transmits it to the reception device 3 via the communication network 4. Further, the transmission terminal 6 receives the loss information from the reception device 3, generates retransmission data according to the loss information, and retransmits it. Further, the transmission terminal 6 generates and transmits addition data in addition to the encoded data and the retransmission data so that the total transmission data amount becomes a target rate calculated by a procedure described later. The addition data is for the purpose of adjusting the amount of transmission data, and any data content may be used.

  Further, the transmission terminal 6 adds a sequence number to the encoded data by using a procedure defined by RTP, for example. Thereby, the receiving device 3 can uniquely identify the encoded data from the sequence number added to the encoded data, and can specify the loss data. Further, the transmission terminal 6 calculates the encoding rate according to the procedure described later, and controls the encoder 5.

[Receiver]
The receiving device 3 includes a receiving terminal 7 and a decoder 8. The receiving terminal 7 receives the encoded data, the retransmission data, and the addition data from the transmitting terminal 6 of the transmitting apparatus 2, repairs the loss of the encoded data by the retransmission data, outputs the encoded data to the decoder 8, and receives the received encoded data Then, loss data is identified from the retransmission data, loss information indicating the location of the loss data is generated, and transmitted to the transmission device 2. The receiving device 3 can transmit loss information to the transmitting device 2 while maintaining consistency with RTP by using a procedure defined by, for example, RTCP (RTP Control Protocol).

  The decoder 8 receives the encoded data from the receiving terminal 7, generates the original video / audio data by decoding the encoded data, and outputs it.

[Sending terminal]
Next, the transmission terminal 6 provided in the transmission device 2 will be described in detail. FIG. 2 is a block diagram showing a configuration of the transmission terminal 6 shown in FIG. The transmission terminal 6 includes a header generation unit 61, a buffer 62, an encoded data amount calculation unit 63, a retransmission data generation unit 64, an addition data generation unit 65, an addition data header generation unit 66, a transmission unit 67, a reception unit 68, and a determination unit. 69 is provided.

  The header generation unit 61 receives the encoded data from the encoder 5, adds a header to the encoded data, and outputs the encoded data with the header added to the transmitting unit 67. The header is used in the receiving terminal 7 of the receiving device 3 to identify the encoded data and the later-described retransmission data and addition data.

  The buffer 62 receives the encoded data from the encoder 5 and accumulates a certain amount of encoded data. A certain amount of encoded data stored in the buffer 62 is read by the retransmission data generation unit 64 and used for retransmission of the encoded data. Accordingly, the buffer 62 stores an amount of encoded data corresponding to the time from when the transmitting terminal 6 transmits encoded data until it receives loss information from the receiving device 3 and generates retransmission data.

  The encode data amount calculation unit 63 receives the encode data from the encoder 5, calculates the encode data amount, and outputs the encode data amount to the addition data generation unit 65.

  The reception unit 68 receives loss information from the reception terminal 7 and outputs the loss information to the retransmission data generation unit 64 and the determination unit 69.

  The retransmission data generation unit 64 receives the loss information from the reception unit 68, uses the loss information to specify the information of the encoded data to be retransmitted, reads the encoded data from the buffer 62 according to the loss information, Generate. For example, a sequence number is added to the encoded data, and the loss information is information including the sequence number. That is, the retransmission data generation unit 64 reads the encoded data to which the sequence number is added from the buffer 62 using the sequence number indicated by the input loss information as a key, and generates retransmission data. Then, retransmission data generation unit 64 adds a header to the retransmission data, and outputs the retransmission data with the header added to transmission unit 67. The header is used to identify retransmission data, encoded data, and addition data described later. In addition, the retransmission data generation unit 64 calculates a retransmission data amount from the generated retransmission data and outputs it to the addition data generation unit 65 and the determination unit 69.

  The determination unit 69 receives the loss information from the reception unit 68 and the retransmission data amount from the retransmission data generation unit 64, and calculates a target rate and an encoding rate according to a procedure described later. Then, the target rate is output to the added data generation unit 65, and the encode rate is output to the encoder 5. Thereby, the encoder 5 is controlled by the encoding rate output from the determination unit 69.

The addition data generation unit 65 inputs the encoding data amount from the encoding data amount calculation unit 63, the retransmission data amount from the retransmission data generation unit 64, and the target rate from the determination unit 69, and adds the data so as to satisfy the following expression: The amount of data is calculated to generate addition data.
Target rate = encoded data amount + retransmitted data amount + added data amount The added data is output to the added data header generation unit 66. Note that the addition data is data that is added to transmit the encoded data or the like at the target rate. Therefore, as described above, data having no meaning in itself such as dummy data may be used.

  The addition data header generation unit 66 receives the addition data from the addition data generation unit 65, adds a header to the addition data, and outputs the addition data with the header added to the transmission unit 67. The header is used to identify added data, encoded data, and retransmission data.

  The transmission unit 67 transmits the encoded data to which the header is added from the header generation unit 61, the retransmission data to which the header is added from the retransmission data generation unit 64, and the addition data to which the header is added from the addition data header generation unit 66, respectively. These data are input and transmitted to the receiving device 3 via the communication network 4.

[Receiving terminal]
Next, the receiving terminal 7 provided in the receiving device 3 will be described in detail. FIG. 3 is a block diagram showing the configuration of the receiving terminal 7 shown in FIG. The reception terminal 7 includes a reception unit 71, an addition data separation unit 72, a buffer 73, a header removal unit 74, a loss detection unit 75, and a transmission unit 76.

  The receiving unit 71 receives encoded data, retransmission data, and addition data from the transmission terminal 6 via the communication network 4. The addition data separation unit 72 receives these data from the reception unit 71 and separates them into encoded data, retransmission data, and addition data. The addition data separation unit 72 accumulates the separated encoded data and retransmission data in the buffer 73.

  The buffer 73 receives the encoded data and retransmission data from the addition data separation unit 72 and accumulates a certain amount of encoded data and retransmission data. A certain amount of encoded data and retransmission data stored in the buffer 73 is read by the header removing unit 74 and used for outputting encoded data without loss. Therefore, the buffer 73 temporarily stores the input encoded data from when the lossy encoded data is input until the lossy retransmission data is input from the addition data separation unit 72. In this case, the lost retransmission data is accumulated in the buffer 73, so that the loss is recovered. Then, the buffer 73 outputs the encoded data and the retransmission data to the header removing unit 74 after a predetermined time has passed since the encoded data was input. Alternatively, the header removal unit 74 reads the encoded data and the retransmission data from the buffer 73 after the predetermined time has elapsed. In this case, it is assumed that the header removal unit 74 inputs in advance information related to the timing at which the buffer 73 has input the encoded data in order to count a predetermined time.

  The header removing unit 74 reads the encoded data and retransmission data from the buffer 73, removes the header added to the encoded data and retransmission data, returns the original encoded data, and outputs it to the decoder 8.

  The loss detection unit 75 receives the encoded data and the retransmission data from the addition data separation unit 72, detects and specifies the data that has not yet been received, that is, loss data, and loss information necessary for specifying the loss data (For example, when encoded data is transmitted by RTP, the content of the loss information is a sequence number of unreceived data (loss data)), and outputs the generated data to the transmitting unit 76. For example, the loss detection unit 75 arranges the sequence numbers added to the encoded data and the retransmission data in ascending or descending order, determines whether or not there is a missing sequence number, and if it is determined that there is a missing, When data is detected, loss information including the missing sequence number is generated.

  The transmission unit 76 inputs loss information from the loss detection unit 75 and transmits the loss information to the transmission device 2 via the communication network 4. Here, the loss information may be encoded data and retransmission data itself lost in the communication network 4, or information such as a loss ratio, the number of losses, and the position of the loss data.

(Decision part)
Next, the processing of the determination unit 69 in the transmission terminal 6 provided in the transmission device 2 will be described in detail. As shown in FIG. 2, the determination unit 69 receives loss information from the reception unit 68 and the retransmission data amount from the retransmission data generation unit 64, calculates a target rate and an encoding rate based on the loss information, The rate is output to the addition data generation unit 65, and the encode rate is output to the encoder 5. Specifically, the amount of retransmission data is calculated from the loss information, and the encoding rate is calculated by subtracting the amount of retransmission data from the target rate previously calculated (by sampling). Then, the calculated encoding rate is stored in a storage unit (not shown). Then, the encoding rate calculated this time is compared with the encoding rate calculated last time read from the storage unit, and the target rate is increased or decreased by a preset amount according to the comparison result. Details will be described later.

  Here, the target rate determines all data amounts (total output data amounts) transmitted from the transmission terminal 6, and is set so that the encoding rate always increases according to the current state of the communication network 4. Is done. Details will be described later. The transmission terminal 6 transmits the addition data in addition to the encoded data and the retransmission data so that the total amount of data to be transmitted becomes the target rate. In this case, when the sum of the encoded data and the retransmission data exceeds the target rate, the addition data is not transmitted, and the total of the encoded data and the retransmission data becomes the total output data amount of the transmission terminal 6. The encoding rate is a value obtained by subtracting the amount of retransmission data calculated from the loss information from the target rate, and the encoder 5 is controlled by this value.

[Transmission terminal processing]
Next, processing of the transmission terminal 6 will be described. The transmission terminal 6 performs mode 1 and mode 2 processing, as will be described later. First, the mode will be described. This mode indicates processing of the transmission terminal 6 and is classified into mode 1 and mode 2 according to the occurrence of loss in the communication network 4. Mode 1 refers to processing in a state where the encoding rate increases by increasing the target rate, and mode 2 refers to processing in a state where the encoding rate increases by decreasing the target rate.

  First, the processing of the transmission terminal 6 in mode 1 will be described. When increasing the target rate, the transmission terminal 6 transmits addition data in addition to the encoded data and retransmission data so that the total output data amount becomes the target rate. Then, the transmission terminal 6 receives the loss information from the reception terminal 7, whereby the retransmission data generation unit 64 can calculate the amount of retransmission data when transmitted at the target rate. The determination unit 69 can recover the loss of the encoded data with the retransmission data by using the value obtained by subtracting the retransmission data amount from the current target rate as the encoding rate.

  Here, if the loss increases as the target rate is increased and the amount of retransmission data increases more than the target rate is increased, the encoding rate is a value calculated by subtracting the amount of retransmission data from the current target rate. Therefore, it is reduced compared to the previous encoding rate. In this case, the transmission terminal 6 shifts to the mode 2 process and lowers the target rate. On the other hand, when the target rate is increased, loss increases, and when the amount of retransmitted data does not increase more than the target rate is increased, the encoding rate increases compared to the previous encoding rate. In this case, the transmission terminal 6 repeats the mode 1 process to increase the target rate.

  Next, processing of the transmission terminal 6 in mode 2 will be described. For example, when there is a bandwidth limitation in the communication network 4, the transmission terminal 6 sets a target rate exceeding the bandwidth limitation value and transmits encoded data of the total output data amount corresponding to the target rate. All data transmitted exceeding the bandwidth limit is lost, and the ratio of retransmission data in the total output data amount increases. Then, although the encode rate decreases, the encode data decreases as a result of the decrease in the encode rate, and as a result, the amount of retransmission data calculated by the loss information decreases.

  Here, when the target rate is lowered, the loss is reduced, and when the amount of retransmission data is reduced more than when the target rate is lowered, the encoding rate is increased compared to the previous encoding rate. In this case, the transmission terminal 6 lowers the target rate again. On the other hand, when the target rate is lowered, the loss is reduced, and when the retransmission data amount is not reduced more than when the target rate is lowered, the encoding rate is reduced as compared with the previous encoding rate. In this case, the transmission terminal 6 shifts to the mode 1 process and increases the target rate.

  Next, details of the processing of the transmission terminal 6 in the above-described mode 1 and mode 2 will be described using FIG. 4 and FIG. FIG. 4 is a flowchart showing processing of the transmission terminal 6 in mode 1 and mode 2. FIG. 5 is a diagram illustrating a configuration of data transmitted by the transmission terminal 6. In FIG. 4, the configuration of transmission data at the start of processing (all data transmitted by the transmission terminal 6) is (401) in FIG. The process of mode 1 is step S1 to step S4, and the process of mode 2 is step S5 to step S8.

  In step S1, the transmission terminal 6 increases the target rate at the determination unit 69, generates a predetermined amount of addition data based on the target data at the addition data generation unit 65, and encodes the data and retransmission data at the transmission unit 67. And the addition data is transmitted. The configuration of the transmission data at that time is (402).

  In step S <b> 2, the transmission terminal 6 receives the loss information at the reception unit 68, and the retransmission data generation unit 64 calculates the retransmission data amount from the loss information. In step S <b> 3, the transmission terminal 6 calculates the encode rate by subtracting the retransmission data amount from the current target rate in the determination unit 69, and outputs it to the encoder 5 to control the encoder 5. When the encoding rate calculated in step S3 is higher than the previous encoding rate, the configuration of the transmission data is (403).

  In step S4, the transmission terminal 6 determines in the determination unit 69 whether or not the encoding rate calculated in step S3 is higher than the previous encoding rate. Here, since it is determined that the current encoding rate is higher than the previous encoding rate (step S4, Yes), the process proceeds to step S1 to increase the target rate. The configuration of the transmission data at that time is (404).

  Then, the transmission terminal 6 calculates the encoding rate in step S3 after step S2, and controls the encoder 5. When the encoding rate calculated in step S3 is lower than the previous encoding rate, the configuration of the transmission data is (405).

  In step 4, the transmission terminal 6 determines whether or not the encoding rate calculated in step S3 is higher than the previous encoding rate in the determination unit 69. Here, since it is determined that the current encoding rate has not increased from the previous encoding rate (No in step S4), the process proceeds to step S5, and the target rate is lowered. In this case, the encoding rate is decreased in step 3, and the amount of retransmission data requested from the receiving terminal 7 is expected to decrease. If the amount of retransmission data is reduced by lowering the target rate, the encoding rate will increase.

  In step 5, the transmission terminal 6 lowers the target rate at the determination unit 69, generates a predetermined amount of addition data based on the target data at the addition data generation unit 65, and encodes data and retransmission data at the transmission unit 67. Send. The configuration of the transmission data at that time is (406).

  In step S6, the transmission terminal 6 receives the loss information at the reception unit 68, and the retransmission data generation unit 64 calculates the retransmission data amount from the loss information. In step S <b> 7, the transmission terminal 6 calculates the encode rate by subtracting the retransmission data amount from the current target rate in the determination unit 69, and outputs it to the encoder 5 to control the encoder 5. When the encoding rate calculated in step S7 is higher than the previous encoding rate, the configuration of the transmission data is (407).

  In step S8, the transmission terminal 6 determines in the determination unit 69 whether or not the encoding rate calculated in step S7 is higher than the previous encoding rate. Here, since it is determined that the current encoding rate is higher than the previous encoding rate (step S8, Yes), the process proceeds to step S5 to lower the target rate. The configuration of the transmission data at that time is (408).

  Then, the transmission terminal 6 calculates the encoding rate in step S7 after step S6, and controls the encoder 5. When the encoding rate calculated in step S7 is lower than the previous encoding rate, the configuration of the transmission data is (409).

  In step 8, the transmission terminal 6 determines in the determination unit 69 whether or not the encoding rate calculated in step S7 is higher than the previous encoding rate. Here, since it is determined that the current encoding rate has not increased from the previous encoding rate (No in step S8), the process proceeds to step S1 to increase the target rate. The configuration of the transmission data at that time is (410). As described above, the transmission terminal 6 repeats the same steps as described above by increasing / decreasing the target rate and increasing / decreasing the encoded data.

〔simulation result〕
Next, simulation results of the transmission system 1 shown in FIG. 1 will be described with reference to FIGS. This simulation is a loss generated using a simulator in the configuration of the transmission system 1 shown in FIG. 6 and 7, the vertical axis indicates the rate (Mbps) and the loss rate (%), and the horizontal axis indicates the time (sec). (A) shows the transmission rate (target rate) of the data transmitted by the transmission apparatus 2, (B) shows the reception rate of the data received by the reception apparatus 3, and (C) is provided in the transmission apparatus 2. The encoding rate calculated by the determination unit 69 of the transmission terminal 6 is shown, and (D) shows the rate (output rate) of the encoded data (data after NULL packet deletion) output by the encoder 5 provided in the transmission apparatus 2. (E) shows the loss rate of data generated by the simulator in one second.

  FIG. 6 (1) shows the change when the loss rate is fixed at about 10%, and it can be seen that (A) the transmission rate, (B) the reception rate, and (C) the encode rate are all increased. . At this time, the transmission terminal 6 is performing the process of the mode 1 shown in FIG. That is, the target rate is increased, the loss rate is maintained at a constant 10%, and the encoding rate is increased accordingly.

  FIG. 6 (2) shows a situation where the communication network 4 is band-limited at 30 Mbps, and (A) the transmission rate, (B) reception rate, and (C) the encoding rate are not increased, and the increase / decrease It turns out that it repeats. At this time, the transmission terminal 6 repeats the processing of mode 1 and mode 2 shown in FIG. That is, since the target rate has increased or decreased, the encoding rate has also increased or decreased.

  Note that (C) the encoding rate does not correspond to (D) the rate (output rate) of the encoded data output by the encoder 5 because the latter output rate is the video / audio data encoded by the encoder 5. This is because it differs depending on the type of.

  FIG. 7 (1) shows the change when the loss rate is fixed at about 5%, and it can be seen that (A) the target rate which is the transmission rate is stable at the set maximum rate of about 40 Mbps. . At this time, the transmission terminal 6 repeats the processing of mode 1 and mode 2 shown in FIG.

  FIG. 7 (2) shows a situation in which the communication network 4 is band-limited at about 30 Mbps ((B) reception rate is stable at about 30 Mbps), (A) transmission rate, (B) It can be seen that both the reception rate and (C) encoding rate are reduced compared to (1). At this time, since the amount of retransmission data is increased due to loss information, the encoding rate is decreased.

  FIG. 7 (3) shows the situation resulting from the bandwidth limitation of the communication network 4 at 30 Mbps, and it can be seen that (A) the target rate, which is the transmission rate, has decreased. At this time, since the encoding rate has decreased in the mode 1 process shown in FIG. 4, the transmitting terminal 6 shifts to the mode 2 process and lowers the target rate. In this case, the loss is reduced in the communication network 4 as the target rate is lowered, and the amount of retransmission data is reduced. The encoding rate is increased by the amount that the amount of retransmitted data is reduced.

  In FIG. 7 (4), it can be seen that (A) the target rate, which is the transmission rate, is lowered as in (3). At this time, the transmission terminal 6 shows the result of the bandwidth limitation of the communication network 4 that is reducing the target rate when the encoding rate is increased in the mode 2 processing shown in FIG. (A) It turns out that the target rate which is a transmission rate is falling. At this time, since the encoding rate has decreased in the mode 1 process shown in FIG. 4, the transmitting terminal 6 shifts to the mode 2 process and lowers the target rate.

  The transmission device 2 and the reception device 3 are each configured by a computer having a volatile storage medium such as a CPU and a RAM, a non-volatile storage medium such as a ROM, and an interface. The header generation unit 61, buffer 62, encoded data amount calculation unit 63, retransmission data generation unit 64, addition data generation unit 65, addition data header generation unit 66, transmission unit 67, reception unit of the transmission terminal 6 provided in the transmission device 2 68 and the determination unit 69 are realized by causing the CPU to execute a program describing these functions. Each function of the reception unit 71, the addition data separation unit 72, the buffer 73, the header removal unit 74, the loss detection unit 75, and the transmission unit 76 of the reception terminal 7 included in the reception device 3 is a program that describes these functions. This is realized by executing the above. These programs can also be stored and distributed in a storage medium such as a magnetic disk (floppy disk, hard disk, etc.), optical disk (CD-ROM, DVD, etc.), semiconductor memory, or the like.

  As described above, according to the embodiment of the present invention, the transmission terminal 6 included in the transmission device 2 performs the mode 1 process in which the encoding rate is increased by increasing the target rate and the encoding rate by decreasing the target rate. The target rate can be determined so as to increase the encoding rate by repeating the mode 2 processing for increasing. Accordingly, the transmission terminal 6 can accurately calculate a transmittable band and transmit the video / audio data in accordance with a change in the congestion state or the like in the communication network 4.

  Further, according to the embodiment of the present invention, when the transmission terminal 6 provided in the transmission device 2 increases the target rate, the transmission terminal 6 adds the additional data and transmits it, and the retransmission required based on the received loss information The amount of data is calculated, and the encoding rate is controlled so that the encoded data and the retransmission data are within the target rate range. As a result, loss of encoded data can always be recovered by retransmission data. That is, the encoding rate calculated by the transmission terminal 6 is a rate corresponding to the maximum amount of encoded data on the assumption that it can be recovered by retransmission data. Therefore, the transmission terminal 6 can transmit the video / audio data with higher quality in the communication network 4 in which the congestion state or the like changes.

  The present invention has been described above with the embodiment raised, but the present invention is not limited to the embodiment described above, and various modifications can be made without departing from the technical idea thereof. In the embodiment, as illustrated in FIG. 1, the transmission system 1 includes the single transmission device 2, the single reception device 3, and the communication network 4. The number of receiving devices 3 is not limited. In the above embodiment, data transmitted and received in the transmission system 1 has been described as video / audio data. However, the present invention is not limited to video / audio data, and may be other data.

  In the embodiment, the determination unit 69 calculates the target rate and the encoding rate based on the loss information, outputs the target rate to the addition data generation unit 65, and outputs the encoding rate to the encoder 5. When the preset upper limit value is exceeded, the upper limit value may be output to the added data generation unit 65 as the target rate. In this case, since the maximum value of the target rate is limited, the amount of data transmitted to the communication network 4 is limited, and the exclusive use of the communication network 4 by the transmission device 2 can be avoided. That is, the communication network 4 can be shared with other transmission devices in a balanced manner.

1 is an overall view showing a configuration of a transmission system including a transmission device and a reception device according to an embodiment of the present invention. It is a block diagram which shows the structure of the transmission terminal with which the transmitter by embodiment of this invention was equipped. It is a block diagram which shows the structure of the receiving terminal with which the receiver by embodiment of this invention was equipped. It is a flowchart which shows the process of a transmission terminal. It is a figure which shows the structure of the data transmitted by a transmitter. It is a figure which shows the simulation result of a transmission system. It is a figure which shows the simulation result of a transmission system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmission system 2 Transmission apparatus 3 Reception apparatus 4 Communication network 5 Encoder 6 Transmission terminal 7 Reception terminal 8 Decoder 61 Header generation part 62 Buffer 63 Encoded data amount calculation part 64 Retransmission data generation part 65 Addition data generation part 66 Addition data header generation part 67 Transmission Unit 68 Reception Unit 69 Determination Unit 71 Reception Unit 72 Addition Data Separation Unit 73 Buffer 74 Header Removal Unit 75 Loss Detection Unit 76 Transmission Unit

Claims (10)

In a transmission apparatus comprising: an encoder that compresses data to be transmitted at a predetermined encoding rate and outputs the encoded data; and a transmission terminal that transmits the encoded data to the reception apparatus via a communication network.
The transmitting terminal is
A buffer for storing encoded data output by the encoder;
A receiving unit that receives loss information for identifying encoded data that has not been received by the receiving device from the receiving device;
The encoded data specified by the loss information received by the receiving unit is read from the buffer and generated as retransmission data, and a retransmission data generation unit that calculates the amount of the retransmission data;
A determination unit that calculates an encoding rate based on the retransmission data amount calculated by the retransmission data generation unit, determines whether or not the encoding rate is increased, and calculates a target rate based on the determination result When,
An encoding data amount calculation unit for calculating the amount of encoding data output by the encoder;
Addition data generation for generating addition data based on the encoding data amount calculated by the encoding data amount calculation unit, the retransmission data amount calculated by the retransmission data generation unit, and the target rate calculated by the determination unit And
A transmission unit that transmits the encoded data output by the encoder, the retransmission data generated by the retransmission data generation unit, and the addition data generated by the addition data generation unit to the reception device at the target rate; A transmission apparatus comprising: The transmission apparatus according to claim 1,
When the target rate is increased, the determination unit calculates an encode rate based on the target rate and the amount of retransmission data after the target rate is increased, and determines that the encode rate is increasing A transmission device characterized in that the target rate is further increased. The transmission apparatus according to claim 1,
When the target rate is increased, the determination unit calculates an encoding rate based on the target rate and the amount of retransmission data after the target rate is increased, and determines that the encoding rate has not increased. A transmitter characterized in that the target rate is sometimes lowered. The transmission apparatus according to claim 1,
When the target rate is lowered, the determination unit calculates an encode rate based on the target rate and the amount of retransmission data after the target rate is decreased, and determines that the encode rate is increased A transmission device characterized in that the target rate is further lowered. The transmission apparatus according to claim 1,
The determination unit calculates an encoding rate based on the target rate and the amount of retransmission data after decreasing the target rate when the target rate is decreased, and determines that the encoding rate has not increased. A transmitter characterized in that the target rate is sometimes raised. In the transmission device according to any one of claims 1 to 5,
The transmission apparatus, wherein the addition data generation unit generates addition data so that a sum of an encoding data amount, a retransmission data amount, and an addition data amount becomes a target rate. A transmission program by a transmission device that transmits encoded data compressed at a predetermined encoding rate by an encoder to a reception device via a communication network, the computer constituting the transmission device,
A process of storing the encoded data output by the encoder in a buffer;
Processing for receiving loss information for identifying encoded data not received by the receiving device from the receiving device;
A process of reading the encoded data specified by the received loss information from the buffer and generating it as retransmission data, and calculating the amount of the retransmission data;
A process of calculating an encoding rate based on the calculated retransmission data amount, determining whether the encoding rate is increased, and calculating a target rate based on the determination result;
Processing for calculating the amount of encoded data output by the encoder;
Based on the calculated encoded data amount, retransmission data amount, and target rate, processing for generating addition data;
A transmission program for executing the process of transmitting the encoded data output by the encoder, the calculated retransmission data, and the addition data to the receiving device at the target rate. In a receiving device including a receiving terminal that receives encoded data transmitted via a communication network by a transmitting device, and a decoder that decodes the encoded data and outputs original data,
The receiving terminal is
A receiving unit that receives encoded data, retransmission data, and addition data transmitted via a communication network by the transmission device according to any one of claims 1 to 6,
A separation unit that separates encoded data, retransmission data, and addition data received by the reception unit;
Based on the encoded data and retransmission data separated by the separation unit, the encoded data and retransmission data that are not received by the receiving unit are detected from the encoded data and retransmission data transmitted by the transmission device, and these A loss detection unit that generates loss information for specifying data, and
A receiving apparatus that causes the decoder to decode encoded data and retransmission data separated by the separating unit. The receiving device according to claim 8, wherein
The loss information detection unit, based on the sequence number added to the encoded data and the retransmission data, among the encoded data and the retransmission data transmitted by the transmission device, the encoded data and the retransmission data that are not received by the receiving unit And a sequence number added to the data is generated as loss information. A reception program by a reception device that receives encoded data transmitted via a communication network by a transmission device and decodes the encoded data into original data by a decoder, the computer constituting the reception device,
A process of receiving encoded data, retransmission data, and addition data transmitted via a communication network by a transmission device that executes the transmission program according to claim 7;
A process of separating the received encoded data, retransmission data and addition data;
Loss information for detecting encoded data and retransmission data that have not been received from the encoded data and retransmission data transmitted by the transmission device based on the separated encoded data and retransmission data, and specifying these data Processing to generate
A reception program for executing the process of decoding the separated encoded data and retransmission data by the decoder.

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