JP2008301309A - Encoding rate control method, transmission apparatus to control encoding rate, program storage medium, and integrated circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that, when a packet error is caused by the deterioration of a transmission line status or by the effect of multi-path fading in wireless video transmission, the transmission buffer of a transmission apparatus overflows and a video interruption occurs. <P>SOLUTION: In the present invention, a video bit rate calculated from remaining buffer capacity of the transmission buffer of the transmission apparatus and an overflow reaching time is compared with measured transmission throughput and determined to determine a suitable video bit rate and video bit rate is converted. Thus, overflow of the transmission buffer is prevented and the video interruption during wireless video transmission is avoided. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a coding rate control method for adaptively converting a coding rate of a media signal such as a video signal or an audio signal in accordance with a deterioration or favorable change in a transmission path state of a network, and a transmission apparatus therefor. is there.

  In wireless transmission such as IEEE802.11 wireless LAN (Local Area Network) or Bluetooth (registered trademark), propagation path noise, fading due to radio wave direct wave and reflected wave multipath propagation path, thermal noise of circuit board, Due to many causes such as radio wave interference of other wireless systems, a packet error that cannot correctly receive a transmitted packet occurs. Further, even in wired transmission such as PLC (Power Line Communication) that is power line communication, a packet error occurs due to the influence of noise from an electrical appliance.

  When a continuous packet error (hereinafter referred to as a burst error) occurs during real-time transmission of an MPEG (Moving Picture Experts Group) video signal, a VoIP (Voice over Internet Protocol) audio signal, or the like, the MPEG video signal When the VoIP audio data is reproduced, the video or audio is interrupted.

  One cause of this is an overflow of the transmission buffer of the transmission apparatus.

  The amount of data stored in the transmission buffer of the transmission device is the difference between the input data amount per unit time to the buffer that is the video bit rate and audio bit rate and the output data amount per unit time from the buffer that is the transmission throughput Varies depending on Here, the transmission throughput represents the number of successful transmission bits per unit time, and is equivalent to the effective transmission rate (bps).

  When a packet error occurs, the transmission apparatus stores again the packet that has been errored for retransmission in the transmission buffer. If the probability of successful packet transmission temporarily decreases due to the occurrence of a burst error, the amount of output data per unit time from the transmission buffer decreases, but the amount of input data per unit time to the transmission buffer does not change. Therefore, an overflow of the transmission buffer of the transmission device occurs.

  FIG. 24 is a diagram illustrating how the transmission buffer 501 overflows due to the occurrence of a burst error. The state (L) in FIG. 24 shows a normal stable communication state in which no burst error has occurred. In this state, the difference between the transmission throughput and the video bit rate is almost equal, and the fluctuation of the accumulated packet amount accumulated in the transmission buffer 501 is small.

  The state (M) in FIG. 24 shows a state when a burst error occurs. The transmission throughput is reduced due to the occurrence of a burst error, and the amount of data output from the transmission buffer 501 per unit time is reduced. Therefore, the amount of accumulated packets accumulated in the transmission buffer 501 increases rapidly.

  The state (N) in FIG. 24 shows a state in which data continues to be accumulated in the transmission buffer 501 due to continued burst errors, and the amount of accumulated packets exceeds the maximum accumulation amount of the transmission buffer 501 and overflow has occurred. . Overflowed packets are discarded and not transmitted, causing video interruptions and audio interruptions.

  Further, the cause of the video interruption or the audio interruption during the reproduction of the MPEG video signal or the VoIP audio data is not limited to the overflow of the transmission apparatus. When a transmission error is reduced due to the occurrence of a burst error and the amount of data input per unit time to the reception buffer of the receiving device is reduced, the amount of stored packets stored in the receiving buffer of the receiving device is rapidly reduced. If an underflow occurs when the amount of stored packets stored in the reception buffer becomes 0 due to continued burst errors, video interruptions and audio interruptions are caused.

  As a technique for solving the above problem, for example, there are methods disclosed in Patent Document 1 and Patent Document 2.

  FIG. 25 is a diagram illustrating a configuration of the moving image distribution device 601 and the moving image reproduction device 602 described in Patent Document 1.

  In the method described in Patent Document 1, the moving image distribution apparatus 601 transmits moving image data including measurement information from the moving image data transmission unit 603 with a bandwidth larger than the bandwidth being distributed. The moving image playback device 602 measures the bandwidth that can be used by the bandwidth measuring / notifying unit 605 based on the time required to receive the moving image data including the measurement information and the number of packets received within this time. To the moving image distribution apparatus 601. The moving image distribution device 601 switches the bit rate of the moving image data by the bit rate switching means 604 based on the notification from the moving image reproduction device 602.

In the method described in Patent Document 2, the transmission apparatus measures the number of bytes of media data accumulated in the buffer every predetermined time dT, and measures the buffer input rate BRin. The transmission device calculates the buffer output rate BR from the measured buffer input rate BRin, the number of bytes B1 to BN of media data stored in the buffer, and the measurement time interval dT.
Buffer output rate BR = buffer input rate BRin−buffer accumulation variation (B1−BN) / variation time interval (dT × n)
And the determined buffer output rate BR is set as a coding rate.

When the transmission throughput (bps) decreases due to the occurrence of a burst error or the like as shown in FIG. 26 by the method described in Patent Document 1 or the method described in Patent Document 2, the bit rate (bps) of the media signal is reduced. ) (For example, by adjusting the video bit rate (bps) or the audio bit rate (bps)) to the transmission throughput, it is possible to prevent the transmission buffer from overflowing.
JP 2004-357226 A JP 2006-115306 A

  However, in the method of Patent Document 1, the bandwidth is measured for a certain period of time in order to measure the bandwidth based on the time required to receive the moving image data including the measurement information and the number of packets received within this time. Takes time. Furthermore, in the method of Patent Document 1, as the measurement accuracy of the bandwidth is increased, the time required for measurement increases, and the start of control is delayed accordingly. Therefore, the transmission buffer may overflow during bandwidth measurement.

  In addition, when the transmission throughput rapidly decreases due to a burst error, the method of Patent Document 1 performs control to match the video bit rate with the measured transmission throughput, so that the image quality is severely deteriorated. For this reason, a visual discomfort is given to the user who views the video.

  Similarly to the method of Patent Document 1, when the transmission throughput is suddenly reduced due to the occurrence of a burst error, the method of Patent Document 2 performs a control for adjusting the video bit rate to the measured transmission throughput, so that the image quality is severely deteriorated. Become. For this reason, a visual discomfort is given to the user who views the video.

  In addition, when the video content is not a constant bit rate (CBR) content but a variable bit rate (VBR) content, the buffer storage fluctuation rate constantly fluctuates, so the buffer output rate BR, that is, There is a possibility of estimating transmission throughput incorrectly.

  For example, when the video bit rate increases due to VBR content, the buffer storage amount increases. Even when no burst error has occurred, the method of Patent Document 2 erroneously estimates that the buffer output rate BR, that is, the transmission throughput, has been reduced, and performs control to lower the video bit rate.

  Therefore, control is performed to deteriorate the image quality due to the VBR content even in a transmission state in which no burst error occurs and the transmission throughput is high.

  The present invention solves the above-described conventional problems, and calculates the video bit rate from the remaining buffer capacity and overflow arrival time of the transmission buffer, or the buffer storage capacity and underflow arrival time of the reception buffer, and measures the measured transmission throughput. The purpose of this is to determine the optimal video bit rate by comparing and determining both, and avoiding the overflow of the transmission buffer or the underflow of the reception buffer, and suppressing the occurrence of video interruptions and audio interruptions. To do.

  In order to solve the above-described problem, a first coding rate control method according to the present invention provides a media signal coding rate in a network system that transmits a media signal via a network according to a transmission path state of the network. The method includes the step of stepping down and following the encoding rate of the media signal stepwise at a rate higher than the effective transmission rate when the effective transmission rate is reduced due to deterioration of the transmission path state. .

  A second coding rate control method according to the present invention is a method for controlling a coding rate of a media signal according to a transmission path state of the network in a network system that transmits a media signal via a network. Monitoring the remaining buffer capacity from the transmission buffer; calculating the bit rate of the media signal from the remaining buffer capacity and the arrival time until overflow when the remaining buffer capacity reaches a certain threshold; Converting the encoding rate to the bit rate of the media signal.

  A third coding rate control method according to the present invention is a method for controlling a coding rate of a media signal according to a transmission path state of the network in a network system that transmits a media signal via a network. Monitoring the remaining buffer capacity from the transmission buffer; calculating the bit rate of the media signal from the remaining buffer capacity and the arrival time until overflow when the remaining buffer capacity reaches a certain threshold; and the effective transmission rate. A step of measuring the throughput, and a step of comparing and determining the calculated bit rate of the media signal and the measured throughput, and a step of converting the encoding rate to a larger value in the comparison and determination step. It is characterized by.

  According to a fourth encoding rate control method of the present invention, in a network system composed of a media signal server device, a transmission device, and a display device, the encoding rate of the media signal is set according to the transmission path state of the network. A method for controlling, wherein the transmission device monitors a remaining buffer capacity from a transmission buffer, and when the transmission device reaches a certain threshold value, the remaining buffer capacity and an arrival time until an overflow occurs. The step of calculating the bit rate of the media signal from the step, the step of measuring the throughput at which the transmission device is an effective transmission rate, and the step of comparing and determining the bit rate of the media signal calculated by the transmission device and the measured throughput And the transmission device signifies the larger value in the comparison and determination step. To convert the coding rate, the steps and the media signaling server for notifying the rate conversion request to a media signaling server device receives the rate conversion request, characterized in that it comprises a step of converting the coding rate.

According to a fifth encoding rate control method of the present invention, in the encoding rate control method according to claims 2 to 4, the media signal bit rate calculation means includes:
Media signal bit rate (bps) = remaining buffer capacity (bit) / overflow arrival time (sec)
It is further characterized by being calculated by.

  According to a sixth encoding rate control method of the present invention, in a network system composed of a media signal server device, a transmission device, and a display device, the encoding rate of the media signal is set according to the transmission path state of the network. A method of controlling, wherein the transmission apparatus monitors a buffer storage capacity from a reception buffer, and when the transmission apparatus reaches a certain threshold value, the buffer storage capacity and an arrival time until an underflow are used to determine a medium. A step of calculating a bit rate of a signal; a step of notifying a media signal server device of a rate conversion request to convert a coding rate into a bit rate of the media signal calculated by the transmission device; Receiving the rate conversion request, converting the encoding rate; And wherein the Mukoto.

  According to a seventh encoding rate control method of the present invention, in a network system composed of a media signal server device, a transmission device, and a display device, the encoding rate of the media signal is set according to the transmission path state of the network. A method of controlling, wherein the transmission apparatus monitors a buffer storage capacity from a reception buffer, and when the transmission apparatus reaches a certain threshold value, the buffer storage capacity and an arrival time until an underflow are used to determine a medium. A step of calculating a bit rate of a signal, a step of measuring a throughput at which the transmission device is an effective transmission rate, a step of comparing and determining the bit rate of the media signal calculated by the transmission device and the measured throughput, and In the comparison and determination step, the transmission apparatus sets the encoding value to the larger value. To convert the windows, and the media signaling server and the step of notifying the rate conversion request to a media signaling server device receives the rate conversion request, characterized in that it comprises a step of converting the coding rate.

An eighth encoding rate control method according to the present invention is the encoding rate control method according to any one of claims 6 to 7, wherein the media signal bit rate calculation means includes:
Media signal bit rate (bps) = buffer storage capacity (bit) / underflow arrival time (sec)
It is further characterized by being calculated by.

  A ninth coding rate control method according to the present invention is the coding rate control method according to any one of claims 1 to 8, wherein the media signal is MPEG-2 TS data or MPEG-4 AVC / H. It is further characterized by being H.264 data.

  The tenth coding rate control method according to the present invention is characterized in that, in the first to eighth coding rate control methods, the media signal is audio data.

  According to an eleventh coding rate control method of the present invention, in the first to eighth coding rate control methods, the network transmission path state is a wireless network transmission path state, and the wireless network is IEEE 802.11. It is further characterized by conformity to standards.

  The first transmission apparatus according to the present invention transmits a media signal to a network by controlling a coding rate of the media signal according to a transmission path state of the network in a network system that transmits the media signal via a network. The transmission apparatus comprises a means for stepping down and following the media signal encoding rate at a rate higher than the effective transmission rate when the effective transmission rate is reduced due to deterioration of the transmission path state.

  The second transmission apparatus according to the present invention transmits a media signal to a network by controlling a coding rate of the media signal in accordance with a transmission path state of the network in a network system that transmits the media signal via a network. A remaining buffer capacity monitoring means for monitoring the remaining buffer capacity of the transmission buffer, and a media signal bit rate calculating means for calculating a bit rate of the media signal from the remaining buffer capacity and an arrival time until overflow. Bit rate conversion means for converting an encoding rate at the calculated media signal bit rate.

  A third transmission apparatus according to the present invention transmits a media signal to a network by controlling a coding rate of the media signal according to a transmission path state of the network in a network system that transmits the media signal via a network. A remaining buffer capacity monitoring means for monitoring the remaining buffer capacity of the transmission buffer, and a media signal bit rate calculating means for calculating a bit rate of the media signal from the remaining buffer capacity and an arrival time until overflow. A bit for converting the coding rate into a larger value by a throughput measuring means for measuring a throughput which is an effective transmission rate, a comparison determining means for comparing and comparing the calculated media signal bit rate and the measured throughput. And rate conversion means. To.

  A fourth transmission device according to the present invention controls a media signal encoding rate according to a network transmission path state in a network system including a media signal server device, a transmission device, and a display device. A transmission apparatus for transmitting a media signal to a network, and calculating a bit rate of the media signal from a remaining buffer capacity monitoring means for monitoring a remaining buffer capacity of a transmission buffer, the remaining buffer capacity and an arrival time until an overflow The media signal bit rate calculation means, the throughput measurement means for measuring the throughput that is the effective transmission rate, the comparison determination means for comparing and comparing the calculated media signal bit rate and the measured throughput, and the comparison determination means, the larger value To convert the coding rate, the media signal service Characterized in that it comprises a means for notifying the device.

According to a fifth transmission apparatus of the present invention, in the second to fourth transmission apparatuses, the media signal bit rate calculation means includes:
Media signal bit rate (bps) = remaining buffer capacity (bit) / overflow arrival time (sec)
It is further characterized by being calculated by.

  A sixth transmission apparatus according to the present invention controls a media signal encoding rate according to a network transmission path state in a network system including a media signal server apparatus, a transmission apparatus, and a display apparatus. A transmission device for receiving a media signal from a network, a buffer storage capacity monitoring means for monitoring a buffer storage capacity of a reception buffer, and a medium for calculating a bit rate of the media signal from the buffer storage capacity and an arrival time until underflow And a means for notifying a media signal server device in order to convert a coding rate into the calculated media signal bit rate.

  A seventh transmission device according to the present invention controls a media signal encoding rate according to a transmission path state of a network in a network system including a media signal server device, a transmission device, and a display device. A transmission device for receiving a media signal from a network, a buffer storage capacity monitoring means for monitoring a buffer storage capacity of a reception buffer, and a medium for calculating a bit rate of the media signal from the buffer storage capacity and an arrival time until underflow The signal bit rate calculating means, the throughput measuring means for measuring the throughput which is the effective transmission rate, the comparison determining means for comparing and comparing the calculated media signal bit rate and the measured throughput, and the comparison determining means, the larger value To convert the coding rate, the media signal service Characterized in that it comprises a means for notifying the device.

According to an eighth transmission apparatus of the present invention, in the sixth to seventh transmission apparatuses, the media signal bit rate calculation means includes:
Media signal bit rate (bps) = buffer storage capacity (bit) / underflow arrival time (sec)
It is further characterized by being calculated by.

  According to a ninth transmission apparatus of the present invention, in the first to eighth transmission apparatuses, the media signal includes MPEG-2 TS data or MPEG-4 AVC / H. It is further characterized by being H.264 data.

  According to a tenth transmission apparatus of the present invention, in the first to eighth transmission apparatuses, the media signal is audio data.

  According to a twenty-second aspect of the present invention, in the first to eighth transmission apparatuses, the transmission path state of the network is a transmission path state of a wireless network, and the transmission apparatus is a wireless transmission apparatus compliant with the IEEE 802.11 standard. It is further characterized by being.

  As an example of the program storage medium of the present invention, all or part of any one of the first to eleventh encoding rate control methods is executed by a computer.

  As an example of the integrated circuit of the present invention, all or a part of any one of the first to eleventh encoding rate control methods is integrated.

  According to the present invention, since the video bit rate is controlled so as to prevent the transmission buffer overflow of the transmission device or the reception buffer underflow of the reception device, it is possible to suppress the occurrence of video interruption.

  In the present invention, in order to calculate the video bit rate from the remaining buffer capacity and overflow arrival time of the transmission buffer of the transmission device or the buffer storage capacity and underflow arrival time of the reception buffer of the reception device, the video bit rate is included in the transmission throughput. By controlling to reduce the video bit rate step by step according to the buffer capacity without performing the control to adjust the image immediately, it is possible to suppress a sudden reduction in image quality, and the visual discomfort of the viewer user Can be removed.

  Also, in the present invention, the remaining buffer capacity and overflow arrival time of the transmission buffer of the transmission device, or the video bit rate calculated from the buffer storage capacity and underflow arrival time of the reception buffer of the reception device are compared with the measured transmission throughput. By determining and determining the larger value as the optimum video bit rate, even if the remaining buffer capacity and buffer storage capacity fluctuate in a short cycle due to the influence of increase / decrease in the bit rate of VBR content, If the transmission throughput is always a large value, the transmission throughput value is adopted as the optimum video bit rate by the comparison judgment control of the present invention, so that it is possible to reduce image quality degradation. For example, even when the video bit rate increases due to VBR content and the remaining buffer capacity of the transmission buffer decreases, the present invention uses the video bit rate calculated from the remaining buffer capacity and the overflow arrival time and the measured transmission throughput. In order to make a comparison and adopt a large value, the measured transmission throughput value is employed, and it is possible to prevent a wasteful reduction in the video bit rate due to the influence of the VBR content, that is, deterioration in image quality.

  Embodiments of the present invention will be described below with reference to the drawings.

  In the following first to fifth embodiments, MPEG-2 transport stream (MPEG-2 TS) or MPEG-4 AVC (Advanced Video Coding) / H. An example of a video signal such as H.264 will be described. Therefore, although described as a method of controlling the video bit rate as the encoding rate, it is also possible to apply as a method of handling audio as a media signal and controlling the audio bit rate.

  In Embodiments 1 to 5, a burst error that is a continuous packet error is described as an example as a cause of deterioration in the transmission path state in which the accumulation amount of the transmission buffer or the reception buffer changes. The cause of the deterioration is not limited to this, and may be a random error that is a discrete packet error occurrence.

  FIG. 1 shows the relationship between the video bit rate, transmission throughput, and transmission buffer 501 according to the present invention divided into state (A), state (B), state (C), and state (D). The transmission throughput represents the number of successful transmission bits per unit time, and is equivalent to the effective transmission rate (bps).

  The state (A) in FIG. 1 is a stable communication state in which the occurrence of packet errors is small, and the difference between the transmission throughput that is the output rate from the transmission buffer 501 and the video bit rate that is the input rate to the transmission buffer 501 is the difference. There is almost no state.

  When a burst error occurs in the state (A) of FIG. 1, the state (B) of FIG. 1 is obtained. In state (B), due to the occurrence of a burst error, the transmission throughput decreases and the output rate from the transmission buffer 501 decreases, so the amount of data stored in the transmission buffer 501 increases. If this state continues, the transmission buffer 501 overflows. Therefore, in the present invention, the video bit rate that is the input rate to the transmission buffer 501 is converted to prevent the transmission buffer 501 from overflowing.

  The state (C) in FIG. 1 shows a state where a burst error has occurred and the possibility of overflow is recognized, and the video bit rate is reduced.

  In the present invention, as shown in FIG. 2, when a burst error occurs, the video bit rate is adjusted based on the buffer storage capacity and the transmission throughput, instead of controlling the video bit rate to match the transmission throughput immediately. Decrease. Therefore, in the present invention, the situation where the video bit rate is higher than the transmission throughput continues temporarily. On the other hand, in the conventional video bit rate control method shown in FIG. 26, when a burst error occurs, the video bit rate is converted so that it immediately matches the transmission throughput.

  The state (C) in FIG. 1 is a state in which the video bit rate is lowered stepwise, and the video bit rate and the transmission throughput are almost equal. The state (D) in FIG. 1 is a state in which the burst error has been completed. When the burst error ends, the transmission throughput increases, so the amount of data stored in the transmission buffer 501 decreases. When the amount of accumulated data decreases, the state of FIG. 1 is again obtained by converting the video bit rate to increase.

(Embodiment 1)
The first embodiment will be described with reference to FIGS.

  FIG. 3 is a functional block diagram showing an example of the configuration of the transmission apparatus 1 equipped with the bit rate conversion function according to Embodiment 1 of the present invention.

  The wireless transmission / reception unit 2 has a function of transmitting and receiving packet signals wirelessly. For example, the wireless communication device is compliant with IEEE802.11, Bluetooth (registered trademark), or the like.

  The wired transmission / reception unit 3 has a function of transmitting / receiving packet signals by wire. For example, it is a wired communication device compliant with Ethernet (registered trademark) or IEEE1394.

  The bit rate conversion unit 4 has a function of converting the bit rate of the video signal. This bit rate conversion function includes the ability to decode compressed and encoded video signals and audio signals and re-encode them to different bit rates, or without decoding compressed and encoded video signals and audio signals. In addition, any conversion method such as a transcoding function for re-encoding to a different bit rate may be used. The bit rate conversion unit 4 converts the bit rate of the video signal received by the wired transmission / reception unit 3 and outputs it to the wireless transmission buffer 9.

  The wireless transmission buffer 9 is a buffer that accumulates the packets output from the bit rate conversion unit 4 until they are transmitted from the wireless transmission / reception unit 2.

  The throughput measuring unit 5 has a function of measuring the current transmission throughput. For example, the calculation can be performed by measuring how many packet signals have been successfully transmitted within a certain unit time.

  The remaining buffer capacity monitoring unit 6 monitors the remaining storable buffer capacity (hereinafter referred to as the remaining buffer capacity) obtained by subtracting the current accumulated capacity from the maximum accumulated amount (accumulated quantity until overflow) of the wireless transmission buffer 9. Has the function of

  The video bit rate calculation unit 7 has a function of calculating the video bit rate from the remaining buffer capacity in the remaining buffer capacity monitoring unit 6 and an arbitrarily set overflow arrival time (OFT: OverFlow Time).

Here, the video bit rate calculated by the video bit rate calculation unit 7 is a value of the video bit rate that consumes the remaining buffer capacity in the overflow arrival time (OFT). The video bit rate is
Video bit rate (bps) = remaining buffer capacity (bit) / overflow arrival time OFT (sec)
Can be calculated as

  Therefore, by changing to the calculated video bit rate, overflow does not occur until the overflow arrival time. The transmission throughput measurement time is sufficiently shorter than the overflow arrival time (OFT).

  The comparison determination unit 8 has a function of comparing and determining the video bit rate calculated by the video bit rate calculation unit 7 and the transmission throughput measured by the throughput measurement unit 5. The comparison determination unit 8 adopts a larger value as the optimum video bit rate as a result of the comparison determination between the two, and notifies the bit rate conversion unit 4 to change and control the video bit rate.

  FIG. 4 is a diagram showing an example of a network connection configuration according to Embodiment 1 of the present invention. The transmission apparatus 1 of this embodiment and an AV (Audio Visual) server 11 are connected by wires such as Ethernet (registered trademark) or IEEE1394, and the transmission apparatus 1 and transmission apparatus 12 are connected wirelessly such as IEEE802.11. The device 12 and the display device 13 are connected by a wired connection such as Ethernet (registered trademark) or IEEE1394. The AV server 11 stores video content and the like, for example, a hard disk recorder, a Blu-ray (registered trademark) recorder, a personal computer, or a personal computer peripheral device. The display device 13 is a display or the like. The transmission device 12 is a transmission device that can be connected to the transmission device 1 based on a wireless standard such as IEEE 802.11, and does not need to have the function according to the present invention.

  FIG. 5 is a diagram showing an operation flow of the transmission apparatus 1 according to Embodiment 1 of the present invention.

  A burst error occurs, packets are accumulated in the wireless transmission buffer 9, and the transmission buffer accumulation amount increases, so that the buffer accumulation amount reaches a certain threshold (eg, rate conversion execution point 1) (S1 in FIG. 5). .

  In the transmission apparatus 1, the remaining buffer capacity monitoring unit 6 acquires the remaining buffer capacity (S2 in FIG. 5).

  In the transmission apparatus 1, the throughput measurement unit 5 acquires a measurement value of the transmission throughput (S3 in FIG. 5).

  In the transmission apparatus 1, the video bit rate calculation unit 7 calculates the video bit rate from the remaining buffer capacity and the overflow arrival time (S4 in FIG. 5).

The calculation method at this time is as described above,
Video bit rate = remaining buffer capacity / overflow arrival time (OFT)
Is used. The transmission throughput measurement time is sufficiently shorter than the overflow arrival time (OFT).

  In the transmission apparatus 1, the comparison determination unit 8 compares and determines the transmission throughput measured in S3 of FIG. 5 and the video bit rate calculated in S4 of FIG. 5, and determines the video bit rate for changing the larger value. (S5 in FIG. 5).

  The transmission apparatus 1 notifies the video bit rate determined in S5 of FIG. 5 to the bit rate changing unit 4 and changes the video bit rate (S6 of FIG. 5).

  As described above, in the first embodiment of the present invention, a plurality of accumulation amount thresholds (rate conversion execution points) are provided in the wireless transmission buffer 9 (for example, rate conversion execution points 2 and 3), and each time the threshold is exceeded. Then, the operation shown in FIG. 5 is executed.

  FIG. 6 is a graph showing the relationship between the amount of accumulation in the transmission buffer 9 of the transmission apparatus 1, the elapsed time, and the video bit rate in the first embodiment of the present invention. The horizontal axis represents the elapsed time, and the vertical axis represents the accumulated amount of the transmission buffer 9.

  In Embodiment 1 of the present invention, the video bit rate can be lowered stepwise by executing the operation flow of FIG. 5 at the threshold values of rate conversion execution points 1 to 3. FIG. 6 shows a state in which the video bit rate is lowered stepwise and the buffer accumulation amount is increased stepwise.

  The operation flow will be described below using specific numerical examples.

  Here, the operation when the video bit rate is 12 Mbps and the transmission throughput becomes 3 Mbps due to the occurrence of a burst error will be described. The maximum accumulation amount of the transmission buffer is 500 (packet), the rate conversion execution point 1 is the accumulation amount 100 (packet), the rate conversion execution point 2 is the accumulation amount 350 (packet), and the rate conversion execution point 3 is the accumulation amount 450 (packet). And Further, it is assumed that the overflow arrival time OFT is set to 500 msec. Let 1 packet size be 1500 bytes.

  The transmission device 1 reaches 100 the rate conversion execution point 1 due to the occurrence of a burst error and reaches the rate conversion execution point 1 (S1 in FIG. 5).

In S2 of FIG. 5, the remaining buffer capacity is
Remaining buffer capacity = 500 (maximum accumulation amount) −100 (current accumulation amount) = 400 (packet)
Remaining buffer capacity = 400 (packet) = 400 (packet) × 1500 (bytes) × 8 (bits) = 4800000 (bits)
It becomes.

  In S3 of FIG. 5, the measured value of the transmission throughput is 3 Mbps.

In S4 of FIG. 5, the calculated video bit rate is
Video bit rate = 4800000 bits (remaining buffer capacity) /0.5 sec (OFT) = 9.6 Mbps
It becomes.

  In S5 of FIG. 5, a comparison determination result of transmission throughput 3 Mbps <calculated video bit rate 9.6 Mbps is obtained.

  In S6 of FIG. 5, the video bit rate is converted to 9.6 Mbps.

  As a result of the above operation, as shown in FIG. 6, the buffer accumulation speed after the point when rate conversion execution point 1 is reached is slower than the previous buffer accumulation speed. This operation is similarly performed every time the transmission buffer accumulation amount reaches the rate conversion execution point 2 and the rate conversion execution point 3.

  As described above, in the first embodiment of the present invention, even when the transmission throughput is reduced due to the occurrence of a burst error or the like, the video bit rate can be reduced stepwise.

  When the occurrence of a burst error ends in a short period, in the conventional example, the video bit rate is reduced to the transmission throughput as shown in FIG. 7A, but in the present invention, it is shown in FIG. 7B. Thus, it is possible to cope without reducing the video bit rate to the transmission throughput. As described above, by gradually reducing the video bit rate based on the remaining buffer capacity, it is possible to suppress deterioration in image quality due to the occurrence of a burst error compared to the conventional case.

  In the first embodiment of the present invention, three threshold values are set for the transmission buffer accumulation amount as rate conversion execution points 1 to 3, and the operation flow of FIG. 5 is performed every time the transmission buffer accumulation amount reaches each threshold value. However, the setting of the threshold value is not limited to three points, and the rate conversion execution point may be set to any number such as 1 to N.

  In the first embodiment of the present invention, thresholds are set for the transmission buffer accumulation amounts as rate conversion execution points 1 to 3, and the operation flow of FIG. 5 is performed each time the transmission buffer accumulation amount reaches each threshold value. However, as shown in the flowchart of FIG. 8, it is possible to always operate in real time or to operate at regular intervals without setting a rate conversion execution point. Here, the contents of the operation steps S2 to S6 in FIG. 8 are the same as the operation steps S2 to S6 in FIG.

(Embodiment 2)
A second embodiment of the present invention will be described with reference to FIGS.

  The difference between the second embodiment and the first embodiment is that the transmission device 1 with the rate conversion function and the AV server 11 are integrated on the video transmission side, and the transmission device 12 and the display device 13 are also integrated on the video reception side. This is an integrated configuration.

  FIG. 9 shows an example of a network connection configuration according to Embodiment 2 of the present invention.

  In FIG. 9, the transmission apparatus mounted AV server 21 and the transmission apparatus mounted display device 22 according to Embodiment 2 of the present invention are connected wirelessly such as IEEE 802.11. Examples of the transmission apparatus-mounted AV server 21 include a wireless transmission function-equipped personal computer and a wireless transmission function-equipped hard disk recorder. Examples of the transmission device-mounted display device 22 include a wireless transmission function-equipped plasma display and a wireless transmission function-equipped liquid crystal display.

  The transmission device-mounted display device 22 is a transmission device-mounted display device that can be connected to the transmission device-mounted AV server 21 based on a wireless standard such as IEEE 802.11, and does not need to have the function according to the present invention. .

  FIG. 10 is a functional block diagram showing an example of the configuration of the transmission apparatus-installed AV server 21. 10, the same components as those in FIG. 3 are denoted by the same reference numerals, and the description thereof is omitted.

  The video content storage unit 23 has a function of storing video content. For example, a hard disk recorder capable of storing video content, a VHS recorder, a DVD recorder, a Blu-ray (registered trademark) recorder, and the like can be given. The bit rate conversion unit 4 converts the bit rate of the video signal output from the video content storage device 23 and outputs it to the wireless transmission buffer.

  The details of the video bit rate conversion control operation of the transmission apparatus mounted AV server 21 in the second embodiment are the same as the video bit rate conversion control operation of the transmission apparatus 1 in the first embodiment, and the operation steps of FIG. 5 or FIG. The description is omitted.

  Similar to the first embodiment, in the second embodiment, the video bit rate can be lowered step by step even when the transmission throughput is lowered due to the occurrence of a burst error or the like.

  When the occurrence of a burst error ends in a short period, in the conventional example, the video bit rate is reduced to the transmission throughput as shown in FIG. 7A, but in the present invention, it is shown in FIG. 7B. Thus, it is possible to cope without reducing the video bit rate to the transmission throughput. As described above, by gradually reducing the video bit rate based on the remaining buffer capacity, it is possible to suppress deterioration in image quality due to the occurrence of a burst error compared to the conventional case.

(Embodiment 3)
The third embodiment will be described with reference to FIGS.

  The third embodiment differs from the first embodiment in that the rate conversion function is not installed in the transmission apparatus but is installed in the AV server. Accordingly, when the transmission apparatus wants to convert the video bit rate, it notifies the AV server of a control signal for requesting a bit rate change. The AV server converts the video bit rate according to the notification of the bit rate change request.

  About the same component as Embodiment 1, the description is abbreviate | omitted using the same code | symbol.

  FIG. 11 shows an example of a network connection configuration according to the third embodiment of the present invention.

  In the third embodiment of the present invention, the transmission device 25 and the AV server (with a rate conversion function) 26 are connected by a wire such as Ethernet (registered trademark) or IEEE 1394, and the transmission device 25 and the transmission device 12 are IEEE 802.11 or the like. The transmission device 12 and the display device 13 are connected by wire such as Ethernet (registered trademark) or IEEE1394. The configurations of the transmission device 12 and the display device 13 are the same as those in the first embodiment.

  The AV server (with a rate conversion function) 26 stores video content and the like, for example, a hard disk recorder, a Blu-ray (registered trademark) recorder, a personal computer or a personal computer peripheral device. Further, it has a function of converting the video bit rate and a function of receiving and analyzing the bit rate change request 27 from the transmission device 25.

  FIG. 12 is a functional block diagram illustrating an example of the configuration of the transmission device 25 according to the third embodiment. 12, the same components as those in FIGS. 3 and 10 are denoted by the same reference numerals, and the description thereof is omitted.

  The wireless transmission buffer 9 of the transmission device 25 stores the video signal received by the wired transmission / reception unit 3 until it is transmitted from the wireless transmission / reception unit 2. The bit rate conversion request notification unit 28 has a function of creating a bit rate conversion request 27 from the video bit rate determined by the comparison determination unit 8 and notifying the AV server (with a rate conversion function) 26.

  FIG. 13 shows an operation flow of the transmission device 25. About the same step element as FIG. 5, FIG. 8 of Embodiment 1, the same code | symbol is used and description is abbreviate | omitted. 13 are the same operations as S1 to S5 in FIG. 5 of the first embodiment.

  In S7 of FIG. 13, a bit rate conversion request notifying unit 28 creates a bit rate conversion request 27 based on the video bit rate determined by comparison and determination in S5 of FIG. 13, and AV server (with a rate conversion function) 26 is notified.

  Upon receiving the bit rate conversion request 27, the AV server (with a rate conversion function) 26 converts the video bit rate according to the request.

  FIG. 14 shows an operation flow when the rate conversion is executed in real time without providing a threshold, unlike the case where the rate conversion is executed with the thresholds of the rate conversion execution points 1 to 3 in FIG.

  The step elements S2 to S5 and S7 in FIG. 14 are the same as the step elements S2 to S5 and S7 in FIG. 13, and the difference between FIG. 14 and FIG. In addition, it is to operate in real time.

  In the first embodiment, the second embodiment, and the third embodiment of the present invention, the video bit rate is changed at the three threshold values of the rate conversion execution points 1 to 3, but it is limited to these three points. The threshold value of the rate conversion execution point may be any number such as 1 to N.

  In the first embodiment, the second embodiment, and the third embodiment of the present invention, the video bit rate is changed at the three threshold values of the rate conversion execution points 1 to 3, but it is limited to these three points. Instead, the video bit rate may be converted and controlled in real time without providing a threshold value.

  In the first embodiment, the second embodiment, and the third embodiment of the present invention, the wireless transmission buffer is a buffer for the wireless communication section. However, the present invention is not limited to this, and the video content storage device system The transmission buffer for applications or the transmission buffer for applications may be used.

  In the first, second, and third embodiments of the present invention, the video bit rate is adaptively converted when a burst error occurs in the wireless transmission interval. However, the video bit rate may be adaptively converted when a burst error occurs in a wired transmission section such as a PLC network.

  In the first embodiment, the second embodiment, and the third embodiment of the present invention, the throughput measurement is measured by the transmission device on the transmission side. However, the present invention is not limited to this, and the unit time is measured by the transmission device on the reception side. It is also possible to measure the throughput from the number of successful reception packets and notify the transmission device on the transmission side.

  In the first embodiment, the second embodiment, and the third embodiment of the present invention, the video signal bit rate conversion method is described as the media signal. However, the media signal is not limited to this video signal. Other media signals such as an audio bit rate of the audio signal may be used.

  In the first embodiment, the second embodiment, and the third embodiment of the present invention, when the burst error occurs, the transmission buffer accumulation amount increases and the video bit rate is adaptively converted. It is not limited to burst errors that cause packet errors in general, but due to the occurrence of random errors that cause packet errors discretely or the deterioration of transmission path conditions, the amount of transmission buffer storage increases, and video bits The rate may be converted adaptively.

  In the configuration of the apparatus according to the first and second embodiments of the present invention, the throughput measuring unit 5 and the comparison / determination unit 8 are not required, and the video bit rate calculation unit 7 performs the remaining buffer capacity and the overflow arrival time (OFT). The video bit rate value calculated based on the above may be directly input to the bit rate conversion unit 4. In this case, the comparison of the measurement throughput and the calculated video bit rate is not performed, and the video bit rate is converted using the calculated video bit rate value.

  In the configuration of the apparatus according to the third embodiment of the present invention, the throughput measurement unit 5 and the comparison determination unit 8 are unnecessary, and the video bit rate calculation unit 7 calculates the remaining buffer capacity and the overflow arrival time (OFT). The video bit rate value may be directly input to the bit rate conversion request notification unit 28. In this case, the comparison of the measurement throughput and the calculated video bit rate is not performed, and the video bit rate is converted using the calculated video bit rate value.

  In the first embodiment, the second embodiment, and the third embodiment of the present invention, the case where the media signal encoding rate (video bit rate) decreases as shown in FIG. 6 is described. However, the present invention is not limited to this. However, the present invention may be applied when the remaining buffer capacity of the transmission buffer increases and the encoding rate (video bit rate) increases.

  In the first embodiment, the second embodiment, and the third embodiment of the present invention, the case where the encoding rate (video bit rate) of the media signal gradually decreases as shown in FIG. In the case where the remaining buffer capacity of the transmission buffer decreases, the encoding rate (video bit rate) is determined by the method of Embodiment 1, Embodiment 2, or Embodiment 3 of the present invention. When the remaining buffer capacity increases (ie, the buffer storage capacity increases), the time when the buffer storage capacity falls below a threshold (for example, rate conversion execution point 1) The encoding rate (video bit rate) may be controlled to increase (return) to the maximum instead of stepwise.

  In the operations of the first embodiment, the second embodiment, and the third embodiment of the present invention, the order of the operation flow from S1 to S6 in FIG. 5 is not limited to this order, and S1 → S3 → The order of the operation flow may be S2 → S4 → S5 → S6 or S1 → S2 → S4 → S3 → S5 → S6.

  In the operations of the first embodiment, the second embodiment, and the third embodiment of the present invention, the order of the operation flow from S2 to S6 in FIG. 8 is not limited to this order, and S2 → S4 → The order of the operation flow may be S3 → S5 → S6.

  In the operations of the first embodiment, the second embodiment, and the third embodiment of the present invention, the order of the operation flow from S1 to S5 and S7 in FIG. 13 is not limited to this order, and S1 → The order of the operation flow may be S3 → S2 → S4 → S5 → S7 or S1 → S2 → S4 → S3 → S5 → S7.

  In the operations of the first embodiment, the second embodiment, and the third embodiment of the present invention, the order of the operation flow from S2 to S5 and S7 in FIG. 14 is not limited to this order, and S2 → The order of operation flow may be S4 → S3 → S5 → S7.

  The configurations of the first embodiment, the second embodiment, and the third embodiment of the present invention may be configured such that all or part of the functions are recorded on a program recording medium and executed by a computer.

  The configurations of the first embodiment, the second embodiment, and the third embodiment of the present invention may be realized by an LSI (Large Scale Integration) that is typically an integrated circuit. These may be individually made into one chip, or may be made into one chip so as to include all or part of the structure. An integrated circuit may be referred to as an IC, a system LSI, a super LSI, an ultra LSI, or the like depending on the degree of integration. Further, the method of the integrated circuit is not limited to the LSI, and may be realized using a dedicated circuit or a general-purpose processor. Further, a Field Programmable Gate Array (FPGA) or a reconfigurable processor that can reconfigure the connection and setting of circuit cells inside the LSI may be used. Further, if integrated circuit technology comes out to replace current semiconductor technology as a result of the advancement of semiconductor technology or a derivative other technology, it is naturally also possible to carry out function block integration using this technology. For example, biotechnological applications can be considered.

(Embodiment 4)
The fourth embodiment will be described with reference to FIGS. 15 to 20.

  The first to third embodiments are methods for preventing the overflow of the transmission buffer of the transmission device on the video transmission side, and the remaining buffer capacity of the transmission buffer is used. This is a method for preventing the underflow of the reception buffer of the transmission apparatus, and uses the buffer storage capacity of the reception buffer.

  About the same component as Embodiment 1 to Embodiment 3, the same code | symbol is used and description is abbreviate | omitted.

  FIG. 15 shows an example of a network connection configuration according to the fourth embodiment of the present invention.

  The transmission apparatus (with a rate conversion function) 41 of the present invention and the AV server 11 are connected by a wire such as Ethernet (registered trademark) or IEEE1394, and the transmission apparatus (with a rate conversion function) 41 and the transmission apparatus 31 of the present embodiment are connected. The transmission apparatus 31 and the display apparatus 13 are connected by a wired connection such as Ethernet (registered trademark) or IEEE 1394. The AV server 11 and the display device 13 are the same as those in the first embodiment.

  FIG. 16 is a functional block diagram illustrating an example of the configuration of the transmission device 31 on the video reception side.

  The reception buffer 32 has a function of temporarily buffering the video signal received from the wireless transmission / reception unit 2. The reception buffer 32 is in a more stable state as the packet accumulation amount increases. Conversely, when the packet accumulation amount decreases and underflow occurs, there is no video signal to be sent to the wired transmission / reception unit 3 and video interruption occurs. The output rate from the reception buffer 32 is determined by the video bit rate, and the input rate to the reception buffer 32 is determined by the transmission throughput. The difference between the input / output data amounts is accumulated in the reception buffer 32. The transmission throughput represents the number of successful transmission bits per unit time, and is equivalent to the effective transmission rate (bps).

  The buffer capacity monitoring unit 33 has a function of monitoring the current amount of data stored in the reception buffer 32 (hereinafter referred to as the current buffer storage capacity).

  The video bit rate calculation unit 34 has a function of calculating the video bit rate from the current buffer storage capacity in the buffer capacity monitoring unit 33 and a certain arbitrarily settable underflow arrival time (UFT: UnderFlow Time).

This calculated video bit rate is the value of the video bit rate that consumes the current buffer storage capacity in underflow arrival time (UFT). The video bit rate is
Video bit rate (bps) = current buffer storage capacity (bit) / underflow arrival time UFT (sec)
Calculated by

  Therefore, by changing to the calculated video bit rate, the underflow does not occur until the underflow arrival time.

  The throughput measuring unit 35 has a function of measuring the current transmission throughput. For example, it is possible to measure how many packet signals have been successfully received within a certain unit time. The transmission throughput measurement time is sufficiently shorter than the underflow arrival time (UFT).

  The comparison determination unit 8 has a function of comparing and determining the video bit rate calculated by the video bit rate calculation unit 34 and the transmission throughput measured by the throughput measurement unit 35. The comparison determination unit 8 adopts a larger value as the optimum video bit rate as a result of the comparison determination between the two, and notifies the bit rate conversion request notification unit 28 to change and control the video bit rate.

  FIG. 17 is a functional block diagram illustrating an example of the configuration of the transmission device 41 on the video transmission side.

  The bit rate conversion request analysis unit 42 has a function of receiving and analyzing the bit rate conversion request notification 27 transmitted by the transmission device 31. The bit rate conversion request analysis unit 42 issues a video bit rate conversion instruction to the bit rate conversion unit 4 based on the value of the video bit rate described in the bit rate conversion request notification. Thereby, the video bit rate is converted.

  FIG. 18 shows an operation flow of the transmission device 31 and the transmission device 41.

  When a burst error occurs, the number of packets received from the transmission device 41 decreases, the packet storage amount of the reception buffer 32 of the transmission device 31 decreases, and the reception buffer storage amount reaches a certain threshold (rate conversion execution point 1). (S11 in FIG. 18).

  In the transmission apparatus 31, the buffer capacity monitoring unit 33 acquires the current buffer storage capacity (S12 in FIG. 18).

  In the transmission apparatus 31, the throughput measurement unit 35 acquires a measurement value of the transmission throughput (S13 in FIG. 18).

  In the transmission apparatus 31, the video bit rate calculation unit 34 calculates the video bit rate from the current buffer storage capacity and the underflow arrival time (UFT) (S14 in FIG. 18).

The calculation method is
Video bit rate = current buffer storage capacity / underflow arrival time (UFT)
It is. The transmission throughput measurement time is sufficiently shorter than the underflow arrival time (UFT).

  The transmission device 31 compares and determines the transmission throughput measured in S13 of FIG. 18 and the video bit rate calculated in S14 of FIG. 18 at the comparison / determination unit 8, and determines the video bit rate for converting the larger value. (S15 in FIG. 18).

  The transmission device 31 notifies the video bit rate determined in S15 of FIG. 18 from the bit rate conversion request notification unit 28 to the transmission device 41 (S16 of FIG. 18).

  The transmission device 41 receives the bit rate conversion request 27 transmitted by the transmission device 31 (S21 in FIG. 18).

  The transmission device 41 converts the video bit rate according to the video bit rate described in the bit rate conversion request notification 27 (S22 in FIG. 18).

  FIG. 19 is a graph showing the relationship between the accumulation amount of the reception buffer 32 of the transmission apparatus 31, the elapsed time, and the video bit rate according to Embodiment 4 of the present invention. The horizontal axis indicates the elapsed time, and the vertical axis indicates the reception buffer accumulation amount. In the present invention, the video bit rate can be lowered stepwise by executing the operation flow of FIG. 18 at the threshold values of the rate conversion execution points 1 to 3. In FIG. 19, the video bit rate is lowered step by step, and the reception buffer accumulation amount is lowered step by step, and underflow of the reception buffer 32 is prevented.

  FIG. 20 is an operation flow that is always executed in real time in the reception buffer 32 of the transmission apparatus 31 according to the fourth embodiment of the present invention without providing a plurality of threshold values (for example, rate conversion execution points 1 to 3). . The operations from S12 to S16 in FIG. 20 are the same as the operations from S12 to S16 in FIG.

(Embodiment 5)
The fifth embodiment will be described with reference to FIGS.

  As in the fourth embodiment, the fifth embodiment is a method for preventing underflow of the reception buffer of the transmission device on the video reception side, and uses the buffer storage capacity of the reception buffer.

  The difference from the fourth embodiment is that the transmission device (with a rate conversion function) 41 and the AV server 11 are integrated, and the transmission device 31 and the display device 13 are also integrated on the video reception side. It is.

  FIG. 21 shows an example of a network connection configuration in the fifth embodiment of the present invention.

  The transmission device mounted AV server 52 of the present invention and the transmission device mounted display device 51 of the present invention are connected wirelessly. Examples of the transmission apparatus-mounted AV server 52 include a wireless transmission function-equipped personal computer and a wireless transmission function-equipped hard disk recorder. Examples of the transmission device-equipped display device 51 include a plasma display with a wireless transmission function and a liquid crystal display with a wireless transmission function.

  FIG. 22 is a functional block diagram showing an example of the configuration of the transmission device-mounted display device 51. 22, the same components as those in FIG. 16 are denoted by the same reference numerals, and description thereof is omitted.

  The display unit 53 has a function of displaying video content. For example, a display etc. are mentioned.

  FIG. 23 is a functional block diagram showing an example of the configuration of the transmission apparatus mounted AV server 52. In FIG. 23, the same components as those in FIG.

  The video content storage device 23 has a function of storing video content. For example, a hard disk recorder capable of storing video content, a VHS recorder, a DVD recorder, a Blu-ray (registered trademark) recorder, and the like can be given.

  The details of the operation of the fifth embodiment are the same as those of the fourth embodiment, and follow the operation steps of FIG. 18 or FIG.

  In the fourth embodiment and the fifth embodiment of the present invention, the video bit rate is changed at the three threshold values of the rate conversion execution points 1 to 3, but it is not limited to these three points. The threshold value of the rate conversion execution point may be any number such as 1 to N.

  In the fourth embodiment and the fifth embodiment of the present invention, the video bit rate is changed at the three threshold values of the rate conversion execution points 1 to 3, but it is not limited to these three points. The video bit rate may be converted and controlled in real time without providing a threshold.

  In the fourth and fifth embodiments of the present invention, the reception buffer is a reception buffer in the wireless communication section, but the present invention is not limited to this, and the system reception buffer for the display device that reproduces video is used. Alternatively, an application reception buffer may be used.

  In Embodiments 4 and 5 of the present invention, when a burst error occurs in the wireless transmission interval, the video bit rate is adaptively converted. However, the method is limited to this wireless transmission interval. The video bit rate may be adaptively converted when a burst error occurs in a wired transmission section such as a PLC network.

  In the fourth and fifth embodiments of the present invention, the throughput measurement is measured by the transmission device on the reception side, but the present invention is not limited to this, and transmission success per unit time is performed by the transmission device on the transmission side. The throughput may be measured from the number of packets, and the throughput value may be notified to the transmission apparatus on the receiving side.

  In the fourth embodiment and the fifth embodiment of the present invention, the video bit rate conversion method for the video signal as the media signal has been described. However, the media signal is not limited to this video signal, and the audio signal is an audio signal. Other media signals such as a bit rate may be used.

  In the fourth and fifth embodiments of the present invention, when the burst error occurs, the accumulation amount of the reception buffer decreases and the video bit rate is adaptively converted. It is not limited to burst errors that occur, but due to the occurrence of random errors that cause discrete packet errors, or the deterioration of transmission path conditions, the amount of data stored in the reception buffer decreases, and the video bit rate is adaptive It may be converted to.

  In the configuration of the apparatus according to the fourth and fifth embodiments of the present invention, the throughput measurement unit 35 and the comparison / determination unit 8 are unnecessary, and the video bit rate calculation unit 34 uses the current buffer storage capacity and the underflow arrival time ( The video bit rate value calculated based on (UFT) may be directly input to the bit rate conversion request notification 28. In this case, the comparison of the measurement throughput and the calculated video bit rate is not performed, and the video bit rate is converted using the calculated video bit rate value.

  In the fourth and fifth embodiments of the present invention, the case where the media signal encoding rate (video bit rate) decreases as shown in FIG. 19 is described. However, the present invention is not limited to this. The present invention may be applied when the buffer storage capacity of the reception buffer increases and the encoding rate (video bit rate) increases.

  In the fourth and fifth embodiments of the present invention, the case where the encoding rate (video bit rate) of the media signal is reduced stepwise as shown in FIG. 19 is described. However, the present invention is not limited to this. If the buffer storage capacity of the reception buffer is not reduced, the encoding rate (video bit rate) is reduced stepwise by the methods of Embodiments 4 and 5 of the present invention, and vice versa. When the buffer storage capacity increases, the encoding rate (video bit rate) is increased to the maximum (returned) step by step when the buffer storage capacity exceeds a threshold (for example, rate conversion execution point 1). ) Control may be used.

  In the operations of Embodiments 4 and 5 of the present invention, the order of the operation flow from S11 to S16 in FIG. 18 is not limited to this order, and S11 → S13 → S12 → S14 → The order of the operation flow may be S15 → S16 or S11 → S12 → S14 → S13 → S15 → S16.

  In the operations of Embodiments 4 and 5 of the present invention, the order of the operation flow from S12 to S16 in FIG. 20 is not limited to this order, and S12 → S14 → S13 → S15. → The order of the operation flow in S16 may be used.

  Note that the configurations of Embodiments 4 and 5 of the present invention may record all or part of the functions on a program recording medium and execute them on a computer.

  The configurations of the fourth and fifth embodiments of the present invention may be realized by an LSI (Large Scale Integration) which is typically an integrated circuit. These may be individually made into one chip, or may be made into one chip so as to include all or part of the structure. An integrated circuit may be referred to as an IC, a system LSI, a super LSI, an ultra LSI, or the like depending on the degree of integration. Further, the method of the integrated circuit is not limited to the LSI, and may be realized using a dedicated circuit or a general-purpose processor. Further, a Field Programmable Gate Array (FPGA) or a reconfigurable processor that can reconfigure the connection and setting of circuit cells inside the LSI may be used. Further, if integrated circuit technology comes out to replace current semiconductor technology as a result of the advancement of semiconductor technology or a derivative other technology, it is naturally also possible to carry out function block integration using this technology. For example, biotechnological applications can be considered.

  A coding rate control method and a transmission device for controlling a coding rate according to the present invention include a wireless video transmission, a wireless voice (VoIP) transmission, a PLC video transmission, a PLC using a video bit rate conversion function or an audio bit rate conversion function. It can be used for voice (VoIP) transmission.

Relationship diagram of transmission buffer accumulation amount, video bit rate, and transmission throughput in Embodiments 1 to 3 of the present invention Relationship diagram between transmission throughput (bps) and video bit rate (bps) in the first to third embodiments of the present invention Functional block diagram showing the configuration of the transmission device on the video transmission side in the first embodiment of the present invention The figure which shows the network connection structure in Embodiment 1 of this invention. The figure which shows the flow of an operation | movement process of the transmission apparatus of the video transmission side in Embodiment 1 to Embodiment 2 of this invention. Relationship diagram between transmission buffer accumulation amount, video bit rate, and elapsed time of transmission device on video transmission side in Embodiment 1 to Embodiment 3 of the present invention Relationship diagram between transmission throughput (bps) and video bit rate (bps) in the first to third embodiments of the present invention The figure which shows the flow of an operation | movement process of the transmission apparatus of the video transmission side in Embodiment 1 to Embodiment 2 of this invention. The figure which shows the network connection structure in Embodiment 2 of this invention. Functional block diagram showing the configuration of the transmission device on the video transmission side in Embodiment 2 of the present invention The figure which shows the network connection structure in Embodiment 3 of this invention. Functional block diagram showing the configuration of the transmission device on the video transmission side in Embodiment 3 of the present invention The figure which shows the flow of an operation | movement process of the transmission apparatus of the video transmission side in Embodiment 3 of this invention. The figure which shows the flow of an operation | movement process of the transmission apparatus of the video transmission side in Embodiment 3 of this invention. The figure which shows the network connection structure in Embodiment 4 of this invention. Functional block diagram showing the configuration of the transmission device on the video receiving side in Embodiment 4 of the present invention Functional block diagram showing the configuration of the transmission device on the video transmission side in Embodiment 4 of the present invention The figure which shows the flow of an operation | movement process of the transmission apparatus of the video transmission side in Embodiment 4 to Embodiment 5 of this invention, and the transmission apparatus of a video reception side. FIG. 5 is a relationship diagram between the reception buffer storage amount, the video bit rate, and the elapsed time of the transmission device on the video receiving side in the fourth to fifth embodiments of the present invention. The figure which shows the flow of an operation | movement process of the transmission apparatus of the video receiving side in Embodiment 4 to Embodiment 5 of this invention. The figure which shows the network connection structure in Embodiment 5 of this invention. Functional block diagram showing the configuration of the transmission device on the video receiving side in the fifth embodiment of the present invention Functional block diagram showing the configuration of the transmission device on the video transmission side in the fifth embodiment of the present invention Diagram showing transmit buffer overflow due to burst error Relationship diagram between video distribution device and video playback device in the previous example Relationship between transmission throughput (bps) and video bit rate (bps) in the previous example

Explanation of symbols

1 Video transmission side transmission device (with rate conversion function)
2 wireless transmission / reception unit 3 wired transmission / reception unit 4 bit rate conversion unit 5 throughput measurement unit 6 remaining buffer capacity monitoring unit 7 video bit rate calculation unit 8 comparison determination unit 9 wireless transmission buffer 11 AV server 12 transmission device 13 on video reception side 13 display device 21 AV server with transmission device (with rate conversion function)
22 Transmission Device Mounted Display Device 23 Video Content Storage Unit 25 Video Transmission Side Transmission Device 26 AV Server (with Rate Conversion Function)
27 Bit rate conversion request 28 Bit rate conversion request notification unit 31 Transmission device on video reception side 32 Reception buffer 33 Buffer capacity monitoring unit 34 Video bit rate calculation unit 35 Throughput measurement unit 41 Transmission device on video transmission side (equipped with rate conversion function)
42 Bit rate conversion request analysis unit 51 AV server with transmission device (with rate conversion function)
52 Transmission Device Mounted Display Device 53 Display Unit 501 Transmission Buffer 601 Movie Distribution Device 602 Movie Playback Device 603 Moving Image Data Transmission Unit 604 Bit Rate Switching Unit 605 Bandwidth Measurement / Notification Unit

Claims (24)

In a network system for transmitting a media signal via a network, a method for controlling a coding rate of the media signal according to a transmission path state of the network,
An encoding rate control method including a step of causing a media signal encoding rate to decrease step by step at a rate higher than an effective transmission rate when an effective transmission rate is reduced due to deterioration of a transmission path state. In a network system for transmitting a media signal via a network, a method for controlling a coding rate of the media signal according to a transmission path state of the network,
Monitoring the remaining buffer capacity from the transmit buffer;
When the remaining buffer capacity reaches a certain threshold, calculating the bit rate of the media signal from the remaining buffer capacity and the arrival time until overflow;
A coding rate control method comprising: converting a coding rate to the calculated bit rate of the media signal. In a network system for transmitting a media signal via a network, a method for controlling a coding rate of the media signal according to a transmission path state of the network,
Monitoring the remaining buffer capacity from the transmit buffer;
When the remaining buffer capacity reaches a certain threshold, calculating the bit rate of the media signal from the remaining buffer capacity and the arrival time until overflow;
Measuring a throughput which is an effective transmission rate;
A coding rate control method comprising: comparing and determining the calculated bit rate of the media signal and the measured throughput; and converting the coding rate to a larger value in the comparison and determining step. In a network system composed of a media signal server device, a transmission device, and a display device, a method for controlling the encoding rate of a media signal according to the transmission path state of the network,
Monitoring the remaining buffer capacity from the transmission buffer by the transmission device;
Calculating a bit rate of a media signal from the remaining buffer capacity and an arrival time until overflow when the transmission apparatus reaches a certain threshold value;
Measuring a throughput at which the transmission apparatus is an effective transmission rate;
A step of comparing and determining the bit rate of the media signal calculated by the transmission apparatus and the measured throughput, and a medium signal server for the transmission apparatus to convert the encoding rate to a larger value in the comparison and determination step. An encoding rate control method comprising: notifying a device of a rate conversion request; and converting the encoding rate when the media signal server receives the rate conversion request. The media signal bit rate calculating means comprises:
Media signal bit rate (bps) = remaining buffer capacity (bit) / overflow arrival time (sec)
The coding rate control method according to any one of claims 2 to 4, which is calculated by: In a network system composed of a media signal server device, a transmission device, and a display device, a method for controlling the encoding rate of a media signal according to the transmission path state of the network,
The transmission device monitoring a buffer storage capacity from a reception buffer;
When the buffer storage capacity of the transmission device reaches a certain threshold, calculating the bit rate of the media signal from the buffer storage capacity and the arrival time until underflow;
In order to convert the encoding rate to the bit rate of the media signal calculated by the transmission device, a step of notifying the media signal server device of a rate conversion request; and when the media signal server receives the rate conversion request, encoding A coding rate control method comprising: converting the rate. In a network system composed of a media signal server device, a transmission device, and a display device, a method for controlling the encoding rate of a media signal according to the transmission path state of the network,
The transmission device monitoring a buffer storage capacity from a reception buffer;
When the transmission apparatus reaches a certain threshold value for buffer storage capacity, calculating the bit rate of the media signal from the buffer storage capacity and the arrival time until underflow;
Measuring a throughput at which the transmission apparatus is an effective transmission rate;
A step of comparing and determining the bit rate of the media signal calculated by the transmission apparatus and the measured throughput, and a medium signal server for the transmission apparatus to convert the encoding rate to a larger value in the comparison and determination step. An encoding rate control method comprising: notifying a device of a rate conversion request; and converting the encoding rate when the media signal server receives the rate conversion request. The media signal bit rate calculating means comprises:
Media signal bit rate (bps) = buffer storage capacity (bit) / underflow arrival time (sec)
The coding rate control method according to any one of claims 6 to 7, which is calculated by: The media signal may be MPEG-2 TS data or MPEG-4 AVC / H. The encoding rate control method according to any one of claims 1 to 8, which is H.264 data. The encoding rate control method according to any one of claims 1 to 8, wherein the media signal is audio data. 9. The encoding rate control method according to claim 1, wherein the transmission path state of the network is a transmission path state of a wireless network, and the wireless network is compliant with the IEEE 802.11 standard. In a network system that transmits a media signal via a network, a transmission device that controls the encoding rate of the media signal according to the transmission path state of the network and transmits the media signal to the network,
A transmission apparatus comprising means for gradually decreasing and following a media signal encoding rate at a rate higher than an effective transmission rate when an effective transmission rate is reduced due to deterioration of a transmission path state. In a network system that transmits a media signal via a network, a transmission device that controls the encoding rate of the media signal according to the transmission path state of the network and transmits the media signal to the network,
A remaining buffer capacity monitoring means for monitoring the remaining buffer capacity of the transmission buffer; a media signal bit rate calculating means for calculating a bit rate of the media signal from the remaining buffer capacity and an arrival time until the overflow; and the calculated media signal bit rate. And a bit rate conversion means for converting the coding rate in the media signal transmission side transmission apparatus. In a network system that transmits a media signal via a network, a transmission device that controls the encoding rate of the media signal according to the transmission path state of the network and transmits the media signal to the network,
The remaining buffer capacity monitoring means for monitoring the remaining buffer capacity of the transmission buffer, the media signal bit rate calculating means for calculating the bit rate of the media signal from the remaining buffer capacity and the arrival time until the overflow, and the throughput which is the effective transmission rate. A medium comprising: a throughput measuring means for measuring; a comparison determining means for comparing and determining the calculated media signal bit rate and the measured throughput; and a bit rate converting means for converting the encoding rate to a larger value in the comparison and determining means. Transmission device on the signal transmission side. In a network system composed of a media signal server device, a transmission device, and a display device, a transmission device that controls the encoding rate of the media signal according to the transmission path state of the network and transmits the media signal to the network. There,
The remaining buffer capacity monitoring means for monitoring the remaining buffer capacity of the transmission buffer, the media signal bit rate calculating means for calculating the bit rate of the media signal from the remaining buffer capacity and the arrival time until the overflow, and the throughput which is the effective transmission rate. In order to convert the coding rate into a larger value by the throughput measuring means to measure, the comparison determining means for comparing and determining the calculated media signal bit rate and the measured throughput, the media signal server apparatus A transmission device on the media signal transmission side comprising means for notifying. The media signal bit rate calculating means comprises:
Media signal bit rate (bps) = remaining buffer capacity (bit) / overflow arrival time (sec)
The transmission apparatus according to claim 13, which is calculated by: In a network system composed of a media signal server device, a transmission device, and a display device, a transmission device that controls the encoding rate of the media signal according to the transmission path state of the network and receives the media signal from the network. There,
A buffer storage capacity monitoring means for monitoring the buffer storage capacity of the reception buffer; a media signal bit rate calculation means for calculating a bit rate of the media signal from the buffer storage capacity and an arrival time until underflow; and the calculated media signal bit rate. A transmission device on the media signal receiving side comprising means for notifying the media signal server device to convert the coding rate. In a network system composed of a media signal server device, a transmission device, and a display device, a transmission device that controls the encoding rate of the media signal according to the transmission path state of the network and receives the media signal from the network. There,
Buffer storage capacity monitoring means for monitoring the buffer storage capacity of the reception buffer, media signal bit rate calculation means for calculating the bit rate of the media signal from the buffer storage capacity and the arrival time until underflow, and measuring the throughput that is the effective transmission rate A throughput measuring unit that compares the calculated media signal bit rate with the measured throughput, and the comparison determining unit notifies the media signal server device to convert the encoding rate to a larger value. A transmission device on the media signal receiving side. The media signal bit rate calculating means comprises:
Media signal bit rate (bps) = buffer storage capacity (bit) / underflow arrival time (sec)
The transmission apparatus according to claim 17, which is calculated by: The media signal may be MPEG-2 TS data or MPEG-4 AVC / H. The transmission apparatus according to any one of claims 12 to 19, which is H.264 data. The transmission apparatus according to claim 12, wherein the media signal is audio data. The transmission apparatus according to any one of claims 12 to 19, wherein the transmission path state of the network is a transmission path state of a wireless network, and the transmission apparatus is a wireless transmission apparatus conforming to the IEEE 802.11 standard. 23. A program storage medium for causing a computer to execute all or a part of the functions of the transmission apparatus according to claim 1. 23. An integrated circuit in which all or part of the functions of the transmission apparatus according to claim 1 are integrated.

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