JP2016119557A - Video transmission device and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continue video transmission even if the quality of a radio transmission line is reduced, when performing the video transmission at a fixed radio transmission rate.SOLUTION: A redundancy/compression rate calculation part 14 of a video transmission device 3 calculates redundancy and a compression rate on the basis of a reception rate, a retransmission rate and preset settings (transmission rate, target reception loss rate, maximum redundancy and minimum redundancy) in such a manner that a total quantity of compression data packets and redundant data packets with respect to data of video signals and audio signals in a predetermined size becomes constant. A compression coding part 11 generates the compression data packets by performing compression coding on the video signals and the audio signals in accordance with the calculated compression rate. A redundant packet generation part 13 generates the redundant data packets with respect to the compression data packets in accordance with the calculated redundancy. An IP packet transmission part 17 transmits the compression data packets and the redundant data packets.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a video transmission apparatus and program for transmitting data such as video via a transmission line, and in particular, transmits using a transmission line whose physical quality such as C / N fluctuates and whose transmission band is not guaranteed. Regarding technology.

  Conventionally, when data such as video is transmitted using a transmission path in which physical quality such as C / N varies, the transmission band is not guaranteed because the transmittable band varies. For this reason, when the quality of the transmission path is lowered and the transmission band is reduced, transmission delay and packet loss occur, and transmission errors such as video freeze and block noise occur.

  In order to avoid the occurrence of such transmission errors, various methods have been proposed. For example, when transmitting video using a wireless LAN transmission path, the transmission band is calculated by acquiring the wireless transmission speed from the wireless LAN device, and the video is transmitted so that the actual video transmission is within this transmission band. A method of controlling the encoding rate for compressing the image is known (see Patent Document 1). As a result, when the quality of the wireless LAN transmission path is lowered, the encoding rate is lowered and the amount of video transmission data is reduced. Therefore, transmission delay and packet loss can be suppressed, and occurrence of transmission errors can be suppressed.

  On the other hand, in the wireless LAN standard (standard conforming to the IEEE 802.11 series), there are few errors by changing the wireless transmission speed according to the quality of the wireless transmission path such as the strength of the wireless reception signal and the reception C / N. A device for realizing IP transmission has been devised.

JP 2012-249005 A

  However, in the wireless LAN standard described above, when the IP transmission is performed at the minimum wireless transmission speed that is set, and the quality of the wireless transmission path is reduced, the wireless transmission speed cannot be reduced. In such a situation, a packet loss occurs and a transmission error occurs.

  In addition, when a special video transmission device that can select only one type of wireless transmission rate is used, or a device that uses the wireless LAN standard, the wireless transmission rate is fixed to one type without switching. Similarly, when a video transmission device is used, a packet loss occurs and a transmission error occurs.

  In addition, when the technique of Patent Document 1 described above is applied to a video transmission apparatus that performs IP transmission at a constant wireless transmission speed (one kind of wireless transmission speed), there is only one kind of wireless transmission speed acquired from the wireless LAN apparatus. Does not change. For this reason, the encoding rate for compressing the video cannot be controlled, packet loss occurs as the quality of the wireless transmission path deteriorates, and the received video is interrupted.

  Accordingly, the present invention has been made to solve the above-described problems, and the purpose of the present invention is to continue video transmission even when the quality of the wireless transmission path is deteriorated when video transmission is performed at a constant wireless transmission speed. Is to provide a video transmission apparatus and program.

  In order to achieve the above object, a video transmission apparatus according to the present invention compresses and encodes video and audio signal data to generate a compressed data packet, generates a redundant data packet for the compressed data packet, and the compressed data packet. And a redundancy / compression rate calculation unit for calculating redundancy and compression rate in a video transmission device that transmits a redundant data packet via a wireless transmission path that can be transmitted at a predetermined constant wireless transmission rate; A compression encoding unit that compresses and encodes data of a predetermined size of the video and audio signals at a compression rate calculated by the redundancy / compression rate calculation unit, and generates a compressed data packet; and the redundancy / compression rate A redundancy data path for the compressed data packet generated by the compression encoding unit with the redundancy calculated by the calculation unit. A packet for transmitting a compressed data packet generated by the compression encoding unit and a redundant data packet generated by the redundant packet generating unit at a speed lower than the wireless transmission rate. A transmission unit, wherein the redundancy / compression rate calculation unit is configured so that a total amount of compressed data packets and redundant data packets for data of a predetermined size of the video and audio signals is constant. When the quality is lowered, the redundancy is increased and the compression rate is lowered, and when the quality of the wireless transmission path is improved, the redundancy is lowered and the compression rate is raised.

  The video transmission apparatus according to the present invention may further receive a reception rate calculated by a video reception apparatus that receives the compressed data packet and the redundant data packet, and a retransmission request for the compressed data packet and the redundant data packet. A packet reception unit that receives from the apparatus; and a retransmission rate calculation unit that calculates a retransmission rate based on a retransmission request received by the packet reception unit, wherein the redundancy / compression rate calculation unit is configured to receive the packet Calculating a reception loss rate based on the reception rate received by the unit and a preset transmission rate, calculating the redundancy based on the reception loss rate and a preset target reception loss rate, and Based on the redundancy, the retransmission rate calculated by the retransmission rate calculation unit, and the transmission rate set in advance, Calculating the compression rate, and wherein the.

  Further, in the video transmission device according to the present invention, the redundancy / compression rate calculation unit further sets the maximum redundancy as the redundancy when the calculated redundancy is larger than a preset maximum redundancy. When the calculated redundancy is smaller than a preset minimum redundancy, the minimum redundancy is set to the redundancy.

  Furthermore, a program according to the present invention causes a computer to function as the video transmission device.

  As described above, according to the present invention, when video transmission is performed at a constant wireless transmission speed, the transmission ratio of both data is made constant while keeping the total amount of compressed data and redundant data constant according to the quality of the wireless transmission path. Was changed. Specifically, when the quality of the radio transmission path is lowered, the compressed data is reduced and the redundant data is increased, so that the receiving side can improve the error correction capability of the compressed data. Therefore, the interruption of the video can be reduced and the video transmission can be continued.

It is the schematic which shows the whole structure of the transmission system containing the video transmission apparatus by embodiment of this invention. It is a block diagram which shows the structure of the video transmission apparatus by embodiment of this invention. It is a flowchart which shows the redundancy and compression rate calculation processing by a redundancy / compression rate calculation part. It is a flowchart which shows the detail of the redundancy calculation process (step S303) by a redundancy / compression rate calculation part. It is a figure explaining operation | movement of the video transmission apparatus by embodiment of this invention. It is a block diagram which shows the structure of a video receiver.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.
[Transmission system]
First, a transmission system including a video transmission device according to an embodiment of the present invention will be described. FIG. 1 is a schematic diagram showing the overall configuration of the transmission system. The transmission system 1 includes a video camera 2, a video transmission device 3, IP wireless transmission devices 4 and 5, a video reception device 6, and a video monitor 7.

  The transmission system 1 transmits video captured by a video camera 2 in water (for example, in the sea) and audio collected by a microphone (not shown) included in the video camera 2 to the video transmission apparatus 3 and IP wireless transmission. The video is transmitted to the video receiver 6 via the devices 4 and 5, and the video is displayed on a video monitor 7 provided outside and underwater, and the sound is reproduced from a speaker (not shown) provided in the video monitor 7. . The video camera 2, the video transmission device 3, the IP wireless transmission devices 4 and 5, and the video reception device 6 are provided so as to be movable in water.

  The video camera 2 (and microphone) and the video transmission device 3 conform to standards such as SDI (Serial Digital Interface), HDMI (registered trademark) (High-Definition Multimedia Interface). Connected by wired cable. The video receiving device 6 and the video monitor 7 (and speaker) are also connected by a similar wired cable. The video transmission device 3 and the IP wireless transmission device 4 are connected by a LAN cable, and the same applies to the IP wireless transmission device 5 and the video reception device 6. Further, the IP wireless transmission device 4 and the IP wireless transmission device 5 are connected by, for example, an IP wireless transmission path in which visible light communication is performed.

  The video transmission device 3 inputs a video signal captured by the video camera 2 and inputs a voice signal picked up by a microphone, and compresses and encodes the video signal and the voice signal at a predetermined compression rate. Generate IP packets of compressed data, generate IP packets of redundant data with a predetermined redundancy, and output these IP packets to the IP radio transmission apparatus 4 at a predetermined transmission rate.

  Here, the video transmission device 3 improves the quality of the IP wireless transmission path so that the total amount of the compressed data IP packet and the redundant data IP packet with respect to the predetermined size data of the input video signal and audio signal is constant. The corresponding compression rate and redundancy are calculated. Then, the video transmission device 3 generates an IP packet of compressed data using the compression rate, and generates an IP packet of redundant data using the redundancy.

  As a result, an IP packet of compressed data and an IP packet of redundant data having a transmission ratio corresponding to the quality of the IP wireless transmission path are generated. The quality of the IP wireless transmission path is determined based on, for example, a change in the reception rate calculated by the video reception device 6 that has received the IP packet from the video transmission device 3. When the reception rate is lowered, it is determined that the quality of the IP wireless transmission path is lowered, and by reducing the compression rate and increasing the redundancy, the amount of compressed data IP packets decreases, and the amount of redundant data IP packets increases. Will increase. When the reception rate is increased, it is determined that the quality of the IP wireless transmission path is improved, and by increasing the compression rate and decreasing the redundancy, the amount of compressed data IP packets increases, and the amount of redundant data IP packets increases. Decrease.

  The IP wireless transmission device 4 receives an IP packet from the video transmission device 3 and performs a modulation process using a visible light carrier wave to convert the IP packet of the electric signal into the IP packet of the optical signal. Then, the IP wireless transmission device 4 transmits the modulated IP packet of the optical signal to the IP wireless transmission device 5 via the IP wireless transmission path at a predetermined physical transmission rate (wireless transmission rate). Send.

  It is assumed that the predetermined transmission rate when the video transmission device 3 outputs the IP packet to the IP wireless transmission device 4 is equal to or lower than a certain wireless transmission speed in the IP wireless transmission path. That is, the sum of the compressed data IP packet and the redundant data IP packet generated by the video transmission device 3 is less than or equal to the wireless transmission speed in the IP wireless transmission path that can be transmitted at a predetermined wireless transmission speed. Sent.

  The IP wireless transmission device 5 receives an IP packet of an optical signal from the IP wireless transmission device 4 via an IP wireless transmission path at a predetermined physical transmission rate (wireless transmission rate), and receives the optical signal. In order to convert the IP packet into an IP packet of an electrical signal, a demodulation process using a visible light carrier is performed. Then, the IP wireless transmission device 5 outputs the demodulated IP packet to the video reception device 6.

  The video receiving device 6 receives the IP packet from the IP wireless transmission device 5, performs error correction of the corresponding compressed data IP packet using the redundant data IP packet, and decodes the error-corrected compressed data IP packet Thus, the original video signal and audio signal are restored. Then, the video reception device 6 outputs the restored video signal to the video monitor 7 and outputs the restored audio signal to the speaker.

  Thereby, the video receiver 6 can receive the IP packet of the compressed data and the IP packet of the redundant data having a transmission ratio according to the quality of the IP wireless transmission path, and can perform error correction. For example, when the quality of the IP wireless transmission path is deteriorated, the amount of compressed data IP packets is decreased and the amount of redundant data IP packets is increased. Can be reduced.

  Therefore, when an image captured by the video camera 2 in water is displayed on the video monitor 7 and the sound collected by the microphone is continuously reproduced by the speaker, the operator watching the video monitor 7 Underwater video and audio can be observed continuously.

[Video transmitter 3]
Next, the video transmission device 3 shown in FIG. 1 will be described. FIG. 2 is a block diagram illustrating a configuration of the video transmission device 3. The video transmission device 3 includes a compression encoding unit 11, a retransmission packet generation unit (retransmission packet generation and retransmission rate calculation unit) 12, a redundant packet generation unit 13, a redundancy / compression rate calculation unit 14, an IP packet reception unit 15, A reception data extraction unit 16 and an IP packet transmission unit 17 are provided.

  The compression encoding unit 11 of the video transmission device 3 inputs the uncompressed video signal and the audio signal from the video camera 2 and the microphone, and also inputs the compression rate from the redundancy / compression rate calculation unit 14, and the video according to the compression rate. The data of the signal and the audio signal is compression encoded.

  The compression encoding unit 11 adds a sequence number to the compression encoded video data and audio data (compressed data), converts the compressed data with the sequence number into an IP packet, and generates a compressed data packet. Then, the compression encoding unit 11 outputs the generated compressed data packet to the retransmission packet generation unit 12, the redundant packet generation unit 13, and the IP packet transmission unit 17.

  As a compression encoding method, a standard method such as MPEG is used, for example. The sequence number is added according to a standard such as RTP.

  The retransmission packet generation unit 12 receives the compressed data packet from the compression encoding unit 11 and the retransmission request sequence number from the received data extraction unit 16, and temporarily stores the input compressed data packet in a buffer (not shown). To accumulate. The retransmission request sequence number indicates the sequence number of the IP packet requested to be retransmitted from the video reception device 6.

  The retransmission packet generation unit 12 compares the input retransmission request sequence number with the sequence number included in the compressed data packet stored in the buffer, identifies a compressed data packet having the same retransmission request sequence number and sequence number, and specifies The compressed data packet is read from the buffer and output to the redundant packet generator 13 as a compressed data packet for retransmission.

  Further, the retransmission packet generator 12 calculates the data amount per unit time for the retransmission data packet (compressed data packet and redundant data packet) corresponding to the input retransmission request sequence number, and uses the calculated value as a retransmission rate for redundancy. Output to the degree / compression rate calculation unit 14. That is, the retransmission packet generation unit 12 calculates the data amount of the retransmission data packet corresponding to the retransmission request sequence number input per unit time, and sets the calculated value as the retransmission rate.

  The redundant packet generation unit 13 inputs the compressed data packet from the compression encoding unit 11 and also receives the compressed data packet for retransmission from the retransmission packet generation unit 12, and buffers the compressed data packet and the compressed data packet for retransmission ( (Not shown) temporarily. Further, the redundant packet generation unit 13 receives the redundancy from the redundancy / compression rate calculation unit 14.

  The redundant packet generation unit 13 reads the compressed data packet and the compressed data packet for retransmission from the buffer, and in accordance with the redundancy, the compressed data packet (the compressed data with the sequence number added) included in the compressed data packet and the compressed data packet for retransmission. ) To generate redundant data for error correction. Then, the redundant packet generation unit 13 converts the redundant data into IP packets and generates redundant data packets.

  The redundant data is generated from the compressed data by using a preset method, for example, FEC (Forward Error Correction). In addition, a method of generating a plurality of redundant data packets by copying the compressed data packet is also used.

  The redundant packet generator 13 outputs the redundant data packet generated for the compressed data packet input from the compression encoder 11 to the IP packet transmitter 17. The redundant packet generation unit 13 also uses the IP packet transmission unit 17 as a retransmission data packet including the compressed data packet for retransmission input from the retransmission packet generation unit 12 and the redundant data packet generated for the compressed data packet for retransmission. Output to.

  The redundancy / compression rate calculation unit 14 inputs preset setting values (transmission rate, target reception loss rate, maximum redundancy, minimum redundancy, retransmission wait period) and receives the reception rate from the reception data extraction unit 16. And a retransmission rate from the retransmission packet generator 12. The reception rate is a rate calculated for the IP packet received by the video reception device 6 from the video transmission device 3 via the IP wireless transmission devices 4 and 5.

  The transmission rate included in the set value is a maximum throughput value calculated from the wireless transmission speed of the IP wireless transmission path, and the target reception loss rate is the compressed data received by the video reception device 6 and the redundant data received. Is the target value of the ratio between the final missing data after error correction using. The maximum redundancy and the minimum redundancy are the maximum value and the minimum value of the ratio of the redundant data amount to the compressed data amount. The retransmission wait period is set to the same value as the retransmission wait period set by the video receiver 6.

  The redundancy / compression rate calculation unit 14 receives the video signal and audio input by the video transmission device 3 based on the set values (transmission rate, target reception loss rate, maximum redundancy, minimum redundancy), reception rate, and retransmission rate. The compression rate and the redundancy are calculated so that the total amount of the compressed data packet and the redundant data packet for the data of a predetermined size of the signal is constant. Then, the redundancy / compression rate calculation unit 14 outputs the calculated compression rate to the compression encoding unit 11 and outputs the calculated redundancy to the redundancy packet generation unit 13.

  Since the quality of the IP radio transmission path is reflected in the reception rate and the retransmission rate, the compression rate and the redundancy are calculated to values according to the quality of the IP radio transmission path. For example, when the quality of the IP wireless transmission path is lowered, the reception rate is lowered and the retransmission rate is raised. When the quality of the IP wireless transmission path is improved, the reception rate is raised and the retransmission rate is lowered.

  The redundancy / compression rate calculation unit 14 reduces the amount of compressed data packets and increases the amount of redundant data packets by lowering the compression rate and increasing redundancy when the quality of the IP wireless transmission path is reduced. Let Thereby, the error correction capability can be improved in the video receiver 6. On the other hand, the redundancy / compression rate calculation unit 14 increases the amount of compressed data packets by increasing the compression rate and decreasing the redundancy when the quality of the IP wireless transmission path is improved, thereby increasing the amount of redundant data packets. Decrease. As a result, the video receiver 6 can implement error correction according to the quality of the IP wireless transmission path. Details of the redundancy / compression rate calculation unit 14 will be described later.

  Further, the redundancy / compression rate calculation unit 14 outputs (sends) a set of the compressed data packet and the redundant data packet corresponding to the compressed data packet from the video transmission device 3 within the time of the retransmission waiting period included in the set value. The transmission timing is determined so that a transmission timing signal (not shown) is output to the IP packet transmission unit 17.

  The IP packet receiver 15 inputs (receives) an IP packet from the video receiver 6 via the IP wireless transmission device 5, the IP wireless transmission path, and the IP wireless transmission device 4, and receives the input IP packet as a received data extraction unit 16. Output to.

  The reception data extraction unit 16 inputs an IP packet from the IP packet reception unit 15, extracts a reception rate and a retransmission request sequence number from the IP packet, outputs the reception rate to the redundancy / compression rate calculation unit 14, and transmits a retransmission request sequence. The number is output to the retransmission packet generator 12.

  The reception rate and retransmission request sequence number included in the IP packet are described according to a standard such as RTCP, for example.

  The IP packet transmission unit 17 inputs the compressed data packet from the compression encoding unit 11 and also receives the redundant data packet and the retransmission data packet (the compressed data packet for retransmission and the redundant data packet) from the redundant packet generation unit 13. Then, the IP packet transmission unit 17 associates the input compressed data packet and the redundant data packet and temporarily stores them in a buffer (not shown), and also temporarily stores the input retransmission data packets in the buffer. .

  The IP packet transmitter 17 reads the compressed data packet, the redundant data packet, and the retransmission data packet from the buffer at a preset transmission rate. Then, the IP packet transmission unit 17 outputs (transmits) these IP packets to the video reception device 6 via the IP wireless transmission device 4, the IP wireless transmission path, and the IP wireless transmission device 5.

  The transmission rate is a value equal to or lower than the wireless transmission speed set by the IP wireless transmission devices 4 and 5, and is set in advance to a maximum throughput value that can send IP packets to the IP wireless transmission path.

  The IP packet transmitter 17 receives the transmission timing signal from the redundancy / compression rate calculator 14 and reads out and outputs a compressed data packet from the buffer according to the transmission timing signal. Thereby, the set of the compressed data packet and the redundant data packet corresponding to the compressed data packet can be output from the video transmission device 3 within the time of the retransmission waiting period.

(Redundancy / compression rate calculator 14)
Next, the redundancy / compression rate calculation unit 14 shown in FIG. 2 will be described in detail. FIG. 3 is a flowchart showing redundancy and compression rate calculation processing by the redundancy / compression rate calculation unit 14.

  First, the redundancy / compression rate calculation unit 14 inputs the reception rate from the reception data extraction unit 16 and the retransmission rate from the retransmission packet generation unit 12 (step S301). Further, the redundancy / compression rate calculation unit 14 inputs preset setting values (transmission rate, target reception loss rate, maximum redundancy, minimum redundancy, retransmission wait period) (step S302).

  The redundancy / compression rate calculator 14 calculates the redundancy based on the reception rate and the set value (transmission rate, target reception loss rate, maximum redundancy, minimum redundancy) (step S303).

FIG. 4 is a flowchart showing details of the redundancy calculation processing (step S303) by the redundancy / compression rate calculation unit 14. First, the redundancy / compression rate calculation unit 14 calculates the reception loss rate by the following formula based on the reception rate and the set value (transmission rate) (step S401).
[Equation 1]
Reception loss rate = 1− (reception rate / transmission rate) (1)

The redundancy / compression rate calculation unit 14 calculates the redundancy by the following formula based on the reception loss rate and the set value (target reception loss rate) calculated in step S401 (step S402).
[Equation 2]
Redundancy = log (target reception loss rate) / log (reception loss rate) (2)

  The redundancy / compression rate calculation unit 14 determines whether or not the redundancy calculated in step S402 is larger than a set value (maximum redundancy) (step S403). If the redundancy / compression rate calculation unit 14 determines in step S403 that the redundancy is greater than the set value (maximum redundancy) (step S403: Y), the redundancy is set to the redundancy that is the set value. If it is determined (step S404) that the redundancy is not greater than the set value (maximum redundancy) (step S403: N), the process proceeds to step S405.

  The redundancy / compression rate calculation unit 14 proceeds from step S403 or step S404 to determine whether the redundancy is smaller than a set value (minimum redundancy) (step S405). When the redundancy / compression rate calculation unit 14 determines in step S405 that the redundancy is smaller than the set value (minimum redundancy) (step S405: Y), the redundancy is set to the redundancy. (Step S406), and the process of step S303 ends. On the other hand, if the redundancy / compression rate calculation unit 14 determines in step S405 that the redundancy is not smaller than the set value (minimum redundancy) (step S405: N), the process of step S303 ends.

  In this way, the redundancy / compression rate calculation unit 14 sets the maximum redundancy, which is the set value, as the redundancy when the redundancy is greater than the set value (maximum redundancy) by the processing in steps S403 to S406. When the redundancy is smaller than the set value (minimum redundancy), the minimum redundancy that is the set value is set as the redundancy. Thereby, since the redundancy is a value within a range from the set value (maximum redundancy) to the set value (minimum redundancy), the compression rate described later is also a value within a predetermined range. A certain quality of video and audio can be restored. Therefore, the set values (maximum redundancy and minimum redundancy) can be said to be parameters that determine the quality of video and audio in the video receiver 6.

Returning to FIG. 3, the redundancy / compression rate calculation unit 14 performs the redundancy calculation processing in step S303 and then, based on the redundancy calculated in step S303, the input retransmission rate, and the set value (transmission rate). The compression rate is calculated by the following equation (step S304).
[Equation 3]
Compression rate = (transmission rate / redundancy) −retransmission rate (3)

  The redundancy / compression rate calculation unit 14 outputs the redundancy calculated in step S303 to the redundancy packet generation unit 13, and outputs the compression rate calculated in step S304 to the compression encoding unit 11 (step S305).

  In this way, the redundancy / compression rate calculation unit 14 receives reception that reflects the preset setting values (transmission rate, target reception loss rate, maximum redundancy, minimum redundancy) and the quality of the IP wireless transmission path. Based on the rate and retransmission rate, the compression rate and redundancy are calculated.

[Operation of Video Transmission Device 3]
FIG. 5 is a diagram for explaining the operation of the video transmission device 3. (A) And (b) has shown the IP packet sequence output by the video transmission apparatus 3 and transmitted via an IP wireless transmission path. “Pressure” is a compressed data packet, and “Redundant” is a redundant data packet.

  The total amount indicates an amount obtained by adding the data amount of the compressed data packet and the data amount of the redundant data packet generated with respect to the data of a predetermined size of the video signal and the audio signal input by the video transmission device 3. When the video transmission device 3 outputs an IP packet, the total amount of the compressed data packet and the redundant data packet is always constant with respect to data of a predetermined size of the video signal and the audio signal input by the video transmission device 3.

  Comparing (a) and (b), the ratio of the compressed data amount to the total amount is higher in (a) than (b), and the ratio of the redundant data amount to the total amount is higher than (a). (B) is higher. Each of the IP packet sequence (a) and the IP packet sequence (b) is output from the video transmission device 3 so as to be transmitted at a speed equal to or lower than a certain wireless transmission speed on the IP wireless transmission path. .

  First, it is assumed that the quality of the IP wireless transmission path is deteriorated (step S502) in a situation where transmission is performed at the transmission ratio (a) (step S501). When the quality of the IP wireless transmission path is lowered, it becomes difficult for the video reception device 6 to receive the IP packet, so that the reception rate is lowered and the retransmission rate is raised (step S503).

  Then, the reception loss rate of the equation (1) increases, the redundancy of the equation (2) increases, and the compression rate of the equation (3) decreases (step S504). As a result, the amount of compressed data packets generated by the compression encoding unit 11 decreases, the amount of redundant data packets generated by the redundant packet generation unit 13 increases, and is transmitted at a transmission ratio as shown in (b). Is performed (step S505). Thereby, the error correction capability can be improved in the video receiver 6.

  Next, it is assumed that the quality of the IP wireless transmission path is improved (step S512) in a situation where transmission is performed at the transmission rate of (b) (step S511). If the quality of the IP wireless transmission path is improved, it becomes easier for the video reception device 6 to receive an IP packet, so that the reception rate increases and the retransmission rate decreases (step S513).

  Then, the reception loss rate of the equation (1) decreases, the redundancy of the equation (2) decreases, and the compression rate of the equation (3) increases (step S514). As a result, the amount of compressed data packets generated by the compression encoding unit 11 increases, the amount of redundant data packets generated by the redundant packet generation unit 13 decreases, and is transmitted at a transmission ratio as shown in (a). Is performed (step S515). As a result, the video receiver 6 can implement error correction according to the quality of the IP wireless transmission path.

  In this case, the total amount of the compressed data packet and the redundant data packet (the total amount of the compressed data and the redundant data) with respect to the data of a predetermined size of the video signal and the audio signal input by the video transmission device 3 is expressed by the above formula (1) (2 ) And (3), even if the reception rate and retransmission rate change according to the quality of the IP wireless transmission path, it is constant.

  As described above, according to the video transmission device 3 according to the embodiment of the present invention, the redundancy / compression rate calculation unit 14 is a compressed data packet for data of a predetermined size of the video signal and the audio signal input by the video transmission device 3. In addition, the compression rate and the redundancy are calculated so that the total amount of redundant data packets is constant. Specifically, the redundancy / compression rate calculation unit 14 receives the reception loss rate using the equation (1) based on the reception rate received from the video reception device 6 and a preset setting value (transmission rate). And the redundancy is calculated by the above equation (2) based on the calculated reception loss rate and a preset setting value (target reception loss rate). The compression rate is calculated in (3) based on the retransmission rate according to the frequency of the retransmission request sequence number received from the receiving device 6 and a preset setting value (transmission rate). The compression encoding unit 11 performs compression encoding of the video signal and the audio signal according to the calculated compression rate to generate a compressed data packet, and the redundant packet generation unit 13 performs compression according to the calculated redundancy. A redundant data packet is generated for the data packet, and the IP packet transmitter 17 transmits the compressed data packet and the redundant data packet.

  Here, the quality of the IP wireless transmission path is reflected in the reception rate and the retransmission rate, and when the quality of the IP wireless transmission path decreases, the reception rate decreases and the retransmission rate increases. In the embodiment of the present invention, the transmission ratio between the compressed data and the redundant data is changed according to the quality of the IP wireless transmission path. Specifically, when the quality of the IP wireless transmission line is degraded, the compression rate is lowered to increase the redundancy, the amount of compressed data packets is decreased, and the amount of redundant data packets is increased. The error correction capability of the compressed data can be improved.

  Therefore, when video transmission is performed at a constant wireless transmission speed, the video reception device 6 can also freeze the transmission video, block noise, and transmission even when the physical quality such as C / N of the IP wireless transmission path varies. Audio interruptions and the like can be reduced, and transmission of video and the like can be continued.

[Video receiver 6]
Next, the video receiver 6 shown in FIG. 1 will be described. FIG. 6 is a block diagram illustrating a configuration of the video reception device 6. The video reception device 6 includes an IP packet receiving unit 21, a reception buffer unit 22, a decoding unit 23, a reception rate measuring unit 24, a missing packet determining unit 25, and an IP packet transmitting unit 26.

  The IP packet receiving unit 21 of the video reception device 6 inputs (receives) an IP packet from the video transmission device 3 via the IP wireless transmission device 4, the IP wireless transmission path, and the IP wireless transmission device 5. A certain compressed data packet and redundant data packet are output to the reception buffer unit 22. Further, the IP packet receiving unit 21 outputs a reception timing signal including the timing at which the IP packet is input (received) and the data amount thereof to the reception rate measuring unit 24.

  The reception buffer unit 22 receives the compressed data packet and the redundant data packet from the IP packet receiving unit 21 and accumulates them in the buffer, reads the sequence number included in the compressed data packet, and outputs it to the missing packet determination unit 25. In addition, the reception buffer unit 22 performs error correction on the compressed data packet corresponding to the redundant data packet using the redundant data packet.

  The error correction processing corresponds to the redundant data generation processing method performed by the redundant packet generation unit 13 of the video transmission device 3. For example, when redundant data is generated using the FEC technique, the reception buffer unit 22 uses the redundant data included in the redundant data packet to generate a compressed data packet corresponding to the redundant data packet. Performs recovery processing of the contained compressed data. If the redundant data packet is copied from the compressed data packet, the reception buffer unit 22 corrects the error of the compressed data packet using the redundant data packet, and then the same sequence number as the sequence number included in the compressed data packet ( A redundant data packet including a duplicate sequence number) is discarded.

  The reception buffer unit 22 inputs a preset reception delay time, and after the reception delay time elapses from a predetermined timing when the compressed data packet is input and stored, the compressed data packet (error correction) is ordered in the sequence number included in the compressed data packet. The later compressed data packet) is read from the buffer and output to the decoding unit 23.

  The reception delay time is a time required for the reception buffer unit 22 to perform error correction of compressed data using redundant data.

  The decoding unit 23 receives the compressed data packet from the reception buffer unit 22, decodes the compressed data included in the compressed data packet, restores and outputs the original video signal and audio signal.

  The reception rate measurement unit 24 receives the reception timing signal from the IP packet reception unit 21 and calculates the data amount per unit time based on the reception timing and the data amount included in the reception timing signal. Then, the reception rate measurement unit 24 uses the calculated value as the reception rate, generates an IP packet describing the reception rate, and outputs the generated IP packet to the IP packet transmission unit 26.

  The reception rate included in the IP packet is described according to a standard such as RTCP.

  Missing packet determination unit 25 inputs a preset retransmission waiting period and also receives a sequence number from reception buffer unit 22 and is missing based on the input sequence number in the period of the retransmission waiting period. Detect sequence numbers.

  Specifically, the missing packet determination unit 25 determines the continuity of the sequence numbers rearranged in numerical order within the retransmission wait period from the sequence number input timing. The missing packet determination unit 25 determines that there is no missing packet when the sequence numbers are consecutive. On the other hand, if there are non-consecutive sequence numbers, the missing packet determination unit 25 determines that there is a missing packet, sets the missing sequence number as a retransmission request sequence number, and sets an IP packet in which the retransmission request sequence number is described. The generated IP packet is output to the IP packet transmitting unit 26.

  As a result, when the error correction processing of the compressed data packet accumulated in the reception buffer unit 22 is not completed within the retransmission wait period, that is, the compressed data packet cannot be recovered using the redundant data packet within the retransmission wait period. In such a case, retransmission of the IP packet is requested.

  The missing packet determination unit 25 outputs the IP packet describing the retransmission request sequence number (after requesting retransmission of the IP packet), and then the same as the retransmission request sequence number from the reception buffer unit 22 within the retransmission waiting period. It is determined whether or not a sequence number has been input. If the same sequence number as the retransmission request sequence number is input, the missing packet determination unit 25 determines that the missing packet has been retransmitted and received. On the other hand, if the same sequence number as the retransmission request sequence number is not input, the missing packet determination unit 25 determines that the missing packet has not been received, and sends the IP packet describing the same retransmission request sequence number to the IP packet transmission unit 26. Output again.

  As a result, the error-corrected compressed data packet stored in the reception buffer unit 22 is inspected for the sequence number included in the compressed data packet, and the missing sequence number is again displayed in the cycle of the retransmission wait period. Detected.

  The retransmission request sequence number included in the IP packet is described according to a standard such as RTCP. The retransmission wait period is a time for waiting for the retransmission request IP packet after the video reception device 6 requests the video transmission device 3 to retransmit the IP packet.

  The IP packet transmission unit 26 inputs the IP packet in which the reception rate is described from the reception rate measurement unit 24, and also receives the IP packet in which the retransmission request sequence number is described from the missing packet determination unit 25. Are temporarily stored in a buffer (not shown). Then, the IP packet transmission unit 26 reads the IP packet from the buffer at a preset transmission rate, and outputs the IP packet to the video transmission device 3 via the IP wireless transmission device 5, the IP wireless transmission path, and the IP wireless transmission device 4. (Send.

  The transmission rate is a value equal to or lower than the wireless transmission rate set by the IP wireless transmission devices 4 and 5, and a maximum throughput value capable of sending IP packets is set in advance, and the IP packet transmission unit of the video transmission device 3 This is the same value as the transmission rate used in FIG.

  As described above, according to the video reception device 6, the reception buffer unit 22 uses the redundant data packet to perform error correction of the compressed data packet corresponding to the redundant data packet, and a predetermined reception delay time elapses. Later, the compressed data packet (compressed data packet after error correction) is read out from the buffer and output in the order of the sequence numbers included in the compressed data packet, and the decoding unit 23 receives the compressed data packet and decodes the compressed data, The original video signal and audio signal were restored.

  Here, the quality of the IP wireless transmission path is reflected by the video transmitting apparatus 3 on the amount of compressed data packets and the amount of redundant data packets. Specifically, when the quality of the IP wireless transmission path deteriorates, the compressed data The amount of packets decreases and the amount of redundant data packets increases.

  Therefore, when video transmission is performed at a constant wireless transmission speed, when the quality of the IP wireless transmission path is deteriorated, the video reception device 6 uses the increased redundant data packet to correct the error of the reduced compressed data packet. Therefore, the error correction capability of the compressed data can be improved. In other words, transmission video freeze, block noise, transmission audio interruptions, etc. can be reduced even with changes in physical quality such as C / N of the IP wireless transmission path, and transmission of video etc. can be continued. Is possible.

  Note that a normal computer can be used as the hardware configuration of the video transmission device 3 and the video reception device 6 according to the embodiment of the present invention. The video transmission device 3 and the video reception device 6 are configured by a computer including a volatile storage medium such as a CPU and a RAM, a nonvolatile storage medium such as a ROM, an interface, and the like. Compression encoding unit 11, retransmission packet generation unit 12, redundant packet generation unit 13, redundancy / compression rate calculation unit 14, IP packet reception unit 15, received data extraction unit 16, and IP packet transmission unit provided in video transmission device 3 Each of the 17 functions is realized by causing the CPU to execute a program describing these functions. The functions of the IP packet receiving unit 21, the receiving buffer unit 22, the decoding unit 23, the reception rate measuring unit 24, the missing packet determining unit 25, and the IP packet transmitting unit 26 provided in the video receiving device 6 also have these functions. Each is realized by causing the CPU to execute the described program. These programs are stored in the storage medium and read out and executed by the CPU. Further, these programs can be stored and distributed in a storage medium such as a magnetic disk (floppy (registered trademark) disk, hard disk, etc.), optical disk (CD-ROM, DVD, etc.), semiconductor memory, etc., via a network. You can also send and receive.

The present invention has been described with reference to the embodiment. However, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the technical idea thereof. For example, in the above embodiment, the redundancy / compression rate calculation unit 14 of the video transmission device 3 inputs the maximum redundancy and the minimum redundancy used for calculating the redundancy as preset setting values. However, it may be calculated based on values of a preset transmission rate and compressed data rate setting range. Specifically, the redundancy / compression rate calculation unit 14 inputs a preset transmission rate, minimum compression rate, and maximum compression rate, and based on the transmission rate and minimum compression rate, the maximum redundancy is calculated according to the following equation. And the minimum redundancy is calculated by the following formula based on the transmission rate and the maximum compression rate.
[Equation 4]
Maximum redundancy = transmission rate / minimum compression rate (4)
[Equation 5]
Minimum redundancy = Transmission rate / Maximum compression rate (5)

  In the embodiment, the redundancy / compression rate calculation unit 14 of the video transmission device 3 increases the compression rate and decreases the redundancy when the quality of the IP wireless transmission path is improved, thereby reducing the amount of compressed data packets. To increase the amount of redundant data packets. On the other hand, the redundancy / compression rate calculation unit 14 increases the compression rate and sets the redundancy to 0 when the quality of the IP wireless transmission path is sufficiently improved (for example, when the reception rate is equal to or higher than a predetermined value). Thus, the amount of compressed data packets may be increased and the amount of redundant data packets may be set to zero.

DESCRIPTION OF SYMBOLS 1 Transmission system 2 Video camera 3 Video transmission device 4, 5 IP wireless transmission device 6 Video reception device 7 Video monitor 11 Compression encoding part 12 Retransmission packet generation part 13 Redundant packet generation part 14 Redundancy / compression rate calculation parts 15 and 21 IP packet receiver 16 Received data extractor 17, 26 IP packet transmitter 22 Receive buffer 23 Decoder 24 Receive rate measurer 25 Missing packet determiner

Claims (4)

Video and audio signal data is compression-encoded to generate a compressed data packet, a redundant data packet is generated for the compressed data packet, and the compressed data packet and the redundant data packet are set to a predetermined constant wireless transmission rate. In a video transmission device that transmits via a wireless transmission path that can be transmitted,
A redundancy / compression rate calculator for calculating redundancy and compression rate;
A compression encoder that compresses and encodes data of a predetermined size of the video and audio signals at the compression rate calculated by the redundancy / compression rate calculator, and generates a compressed data packet;
A redundancy packet generation unit that generates a redundancy data packet for the compressed data packet generated by the compression encoding unit with the redundancy calculated by the redundancy / compression rate calculation unit;
A packet transmission unit that transmits the compressed data packet generated by the compression encoding unit and the redundant data packet generated by the redundant packet generation unit at a speed equal to or lower than the wireless transmission rate;
The redundancy / compression rate calculator is
When the quality of the wireless transmission path is reduced so that the total amount of compressed data packets and redundant data packets for the predetermined size data of the video and audio signals is constant, the redundancy is increased and the compression rate is decreased. When the quality of the wireless transmission path is improved, the video transmission apparatus is characterized in that the redundancy is reduced and the compression rate is increased. The video transmission device according to claim 1,
A packet reception unit that receives from the video reception device a reception rate calculated by the video reception device that receives the compressed data packet and the redundant data packet, and a retransmission request for the compressed data packet and the redundant data packet;
A retransmission rate calculation unit that calculates a retransmission rate based on the retransmission request received by the packet reception unit, and
The redundancy / compression rate calculator is
A reception loss rate is calculated based on the reception rate received by the packet receiver and a preset transmission rate, and the redundancy is calculated based on the reception loss rate and a preset target reception loss rate. And the compression rate is calculated based on the redundancy, the retransmission rate calculated by the retransmission rate calculation unit, and a preset transmission rate. The video transmission device according to claim 2,
The redundancy / compression rate calculator is
Further, if the calculated redundancy is greater than a preset maximum redundancy, the maximum redundancy is set to the redundancy, and if the calculated redundancy is less than a preset minimum redundancy, The video transmission apparatus characterized in that the minimum redundancy is set to the redundancy.   A program for causing a computer to function as the video transmission device according to any one of claims 1 to 3.

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