JP2004072720A - Media transmission method, transmitting apparatus and receiving apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve high-quality media data transmission in the environment that an available band is considerably fluctuated by suppressing updating frequency of an encoding rate. <P>SOLUTION: When a transmission rate Rs is updated and the updated transmission rate Rs is settled within fluctuation width (Rc<Rs<U×Rc and U>1) defined by a present encoding rate Rc, without updating the present encoding rate Rc, an FEC (forward error-correction) data sending rate Rf is updated (Rf=Rs-Rc). When an Rc updating timer set to three sec is time-out, for example, on the other hand, the encoding rate Rc is updated by using a minimum value Rs-min of the transmission rate up to the moment (Rc=V×Rs-min and 0<V<1). Even when the transmission rate Rs is so fluctuated out of the fluctuation width, the encoding rate Rc is similarly updated. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a media transmission method for transmitting audio / video data from a camera or a microphone, that is, media data with high quality, and a transmission device and a reception device thereof.
[0002]
[Prior art]
There are various connection forms on an IP (Internet Protocol) network such as an intranet and the Internet, and the available bandwidth varies greatly from several Kbps to several hundred Mbps depending on the connection form. In addition, the available bandwidth varies with time due to the influence of other flows (transmission data). In order to perform media data transmission in such a network, transmission rate control for adjusting a transmission rate according to an available transmission band is required.
[0003]
As a protocol for transmitting media data in real time over the Internet, RTP (Realtime Transport Protocol) / RTCP (RTP Control Protocol) is known (see Non-Patent Document 1). According to the RTP / RTCP, information on the packet loss rate, propagation delay time, jitter, and the like is fed back from the receiving terminal to the transmitting terminal, and the transmission rate of media data is determined based on the feedback information. The transmission interval (notification interval) of feedback information from the receiving terminal was a fixed value, for example, 5 seconds.
[0004]
As one of the transmission rate control methods using feedback information, TFRC (TCP Friendly Rate Control) is known (see Non-Patent Document 2). According to this TFRC, by performing control such that the transmission rate is increased until a packet loss occurs and the transmission rate is decreased when a packet loss occurs, a smooth transmission rate update suitable for media data transmission can be performed. Achieved. The update interval of the transmission rate is 1 × RTT (Round Trip Time: round trip propagation delay time), for example, several tens to several hundreds ms.
[0005]
On the other hand, an RFC 2733 system which is a technology for adding an error correction capability to RTP is also known (see Non-Patent Document 3). According to the RFC 2733 system, FEC data, which is redundant data for forward error correction (FEC), is added to data to be transmitted.
[0006]
[Non-patent document 1]
H. Schulzrinne et al. , "RTP: A Transport Protocol for Real-Time Applications", RFC 1889, Internet Engineering Taskforce, Jan. 1996
[Non-patent document 2]
M. Handley et al. , "TCP Friendly Rate Control (TFRC): Protocol Specification", RFC 3448, Internet Engineering Taskforce, Jan. 2003
[Non-Patent Document 3]
J. Rosenberg et al. , "An RTP Payload Format for Generic Forward Error Correction", RFC 2733, Internet Engineering Taskforce, Dec. 1999
[0007]
[Problems to be solved by the invention]
When transmitting encoded data based on media data, if the transmission rate is updated at intervals of several tens to several hundreds of ms according to the TFRC and the encoding rate is updated every time the transmission rate is updated, the encoding rate becomes Changes frequently. Therefore, for example, the image quality of the video to be transmitted frequently changes, and the subjective image quality is reduced.
[0008]
Also, shortening the interval at which the feedback information is sent from the receiving terminal to the transmitting terminal has the advantage that the available transmission band can be quickly followed and the transmission band can be used efficiently, but the frequency of updating the transmission rate at the transmitting terminal is improved. And the quality of the media data changes frequently, and media transmission with stable quality cannot be performed. Further, the fairness of the throughput with other flows is reduced. Conversely, if the notification interval of the feedback information is lengthened, the frequency of updating the transmission rate decreases, and the transmission rate stabilizes. However, it is impossible to quickly follow the fluctuation of the transmission band, and the transmission band cannot be used efficiently. Also, when the notification interval is long, if the available transmission band becomes narrow, packets will be lost in bursts, and the transmission quality of media data will be extremely deteriorated.
[0009]
Further, conventionally, since the packet size of data is constant, when the transmission rate is reduced, the number of packets to be transmitted is reduced. The packet loss rate L is usually
L = 1− (number of data packets arriving at the receiving terminal during period T) / (number of data packets transmitted by the transmitting terminal during period T)
Is calculated. The period T is usually a time interval from transmission of the previous feedback information to transmission of the current feedback information. From this equation, it can be seen that if the number of packets transmitted by the transmitting terminal decreases, the packet loss of one packet greatly changes the packet loss rate. For example, if the transmission rate becomes extremely low and only one packet can be transmitted during the period T, the packet loss rate becomes 0% if the packet is not lost, and the packet loss rate becomes 0%. In this case, it becomes 100%. In such a situation, it becomes impossible to accurately grasp the congestion state of the network because the packet loss rate cannot be observed in detail.
[0010]
Further, in a system represented by TFRC, which focuses on fairness with TCP, a denominator of a calculation formula for determining a transmission rate includes RTT. The RTT is a time required for a packet to make a round trip between a transmitting terminal and a receiving terminal, and can take a value of 1 ms or less if the distance between the transmitting terminal and the receiving terminal is short. In such a situation, the measurement result of the RTT may indicate a fluctuation in processing delay of an operating system that performs a process of transmitting a packet from a transmitting terminal, or a fluctuation of a delay in a transfer process of a router or the like that performs a process of transmitting a packet. Is affected by delay fluctuations that are not related to the congestion state, and as a result, the transmission rate greatly fluctuates.
[0011]
An object of the present invention is to realize high-quality media data transmission in an environment where the available bandwidth fluctuates greatly.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the present invention suppresses frequent updating of the coding rate, adjusts a notification interval of feedback information, changes a packet size, and adds an offset to RTT. It was done.
[0013]
More specifically, the present invention updates the transmission rate according to the transmission state of the network and updates the encoding rate less frequently than the transmission rate of the transmission rate in the transmission of the encoded data based on the media data. It was decided.
For example, when a timer for which a timeout period longer than the transmission rate update interval is set times out, or when the transmission rate is updated to a value outside a predetermined range, a code according to the minimum value of the transmission rate within a certain time is used. Update rate. When adding redundant data for error correction to the encoded data, the difference between the transmission rate and the encoding rate may be assigned to the transmission rate of the redundant data.
[0014]
Further, in the present invention, in transmission of media data, feedback information indicating a transmission state of a network is notified from a receiving terminal at variable intervals according to the transmission state of the network, and media data is transmitted in accordance with the notified feedback information. Is updated. For example, when the packet loss rate is high, the notification interval of the feedback information is shortened, and when the packet loss rate is low, the notification interval of the feedback information is lengthened. However, it is preferable to limit the notification interval of the feedback information so as not to fall below a predetermined minimum interval.
[0015]
Further, in the present invention, in the transmission of media data, when it is determined that a predetermined number of packets cannot be transmitted within a packet loss observation period due to a reduced transmission rate, the data packet size is changed to a smaller value. It is what it was. In order to accurately grasp the congestion state of the network, the number of data packets transmitted by the transmitting terminal within a certain period should be equal to or more than a certain number even if the transmission rate decreases. A method of setting the data packet size small in advance and increasing the number of packets to be transmitted is conceivable. However, since a header is added to the packet, there is a problem that as the number of packets increases, the overhead of the header increases. Therefore, when the transmission rate is high, the packet size is set to be large, and when the transmission rate is lowered, adaptive processing such as reducing the packet size and increasing the accuracy of observing the packet loss rate is performed. As a result, the packet loss rate can be observed in detail, and an accurate transmission rate can be determined.
[0016]
Further, in the present invention, when the RTT is smaller than a predetermined value, an offset is added to the RTT. As a result, when the value of RTT is too small, it is possible to prevent the transmission rate from being greatly affected by delay fluctuations not related to network congestion.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of a media transmission method according to the present invention and a transmission device and a reception device thereof will be described with reference to the drawings.
[0018]
1 and 2 show a configuration of a media transmission system for transmitting encoded data based on media data. FIG. 1 shows an example of the internal configuration of a media transmission device (transmission terminal) 100, and FIG. 2 shows an example of the internal configuration of a media reception device (reception terminal) 200. The transmitting terminal 100 and the receiving terminal 200 are connected to each other via a network 150. The network 150 may be any of a wired network and a wireless network, and may be a network in which a wired network and a wireless network are interconnected. For example, RTP / RTCP is adopted as a transmission protocol between the transmitting terminal 100 and the receiving terminal 200.
[0019]
1 includes an audio / video input unit 101, an encoding unit 102, an FEC generation unit 103, a transmission unit 104, a transmission rate determination unit 105, an encoding rate and FEC data transmission rate determination unit. 106, a packet size determination unit 108, and an RTT calculation unit 109. The audio / video input unit 101 is a unit such as a camera or a microphone for inputting audio / video data (media data) to be encoded. The encoding unit 102 is means for generating encoded data from media data according to a designated encoding rate Rc. For example, a standardized compression / encoding method such as MPEG (Moving Picture Coding Experts Group) 1/2/4 or AMR (Audio / Modem Riser) may be adopted. Further, the encoding unit 102 has a function of outputting data with the packet size determined by the packet size determination unit 108. The FEC generation unit 103 is means for generating FEC data, which is redundant data for error correction, from encoded data according to a specified FEC data transmission rate Rf. The transmission unit 104 transmits the FEC data to the network 150 together with the encoded data, and controls the reception terminal 200 to obtain feedback information (packet loss rate, propagation delay time, jitter, etc.) indicating the transmission state of the network 150. It is a means for transmitting and receiving information. The transmission rate determination unit 105 is a unit for updating the transmission rate Rs based on the feedback information and the RTT calculated by the RTT calculation unit 109, and transmitting the packet loss rate to the FEC generation unit 103. For example, TFRC is adopted as an algorithm for determining the transmission rate Rs. The coding rate and FEC data transmission rate determining unit 106 updates the coding rate Rc at a frequency less than the frequency of updating the transmission rate Rs using the Rc update timer 107, and calculates the difference between the transmission rate Rs and the coding rate Rc. Is assigned to the FEC data transmission rate Rf. The packet size determination unit 108 is a unit for determining a packet size from the transmission rate Rs notified from the transmission rate determination unit 105 and notifying the coding unit 102 of the result. The RTT calculation unit 109 is a means for receiving feedback information from the transmission unit 104 and calculating a round-trip propagation delay time (RTT) used for calculating the transmission rate Rs from the feedback information.
[0020]
2 includes a transmission unit 201, a packet loss recovery unit 202, a decoding unit 203, a reproduction unit 204, a feedback information generation unit 205, and a notification interval control unit 206. The transmission unit 201 receives encoded data and FEC data transmitted from the transmission terminal 100 via the network 150, and transmits and receives control information so as to generate feedback information indicating the transmission state of the network 150. Means. The packet loss recovery unit 202 is means for restoring encoded data in a packet lost in the network 150 using FEC data. The decoding unit 203 is means for obtaining media data by decoding encoded data. The reproduction unit 204 is a unit such as a display and a speaker for reproducing the decoding result. The feedback information generation unit 205 is a unit for generating feedback information indicating a transmission state of the network 150. The generated feedback information is notified to the transmitting terminal 100 by the transmission unit 201 via the network 150. The notification interval control unit 206 is means for controlling the notification interval Tf of feedback information according to the transmission state of the network 150.
[0021]
FIG. 3 shows an initial operation of the coding rate and FEC data transmission rate determining unit 106 in FIG. When the transmitting terminal 100 is started, first, the values of the constants U and V are acquired. The constant U is a value (U> 1) for defining a small fluctuation range of the transmission rate Rs, and the constant V is a value (0 <V) for preventing the coding rate Rc from exceeding the transmission rate Rs. <1). Next, a timeout time To (longer than 1 × RTT, for example, 3 seconds) of the Rc update timer 107 and an initial value of the transmission rate Rs are obtained. Next, the initial value of the coding rate Rc is set to V × Rs, and the initial value of the FEC data transmission rate Rf is set to Rs−Rc. Then, the maximum transmission rate Rs_max is set to a variable Rs_min, and the Rc update timer 107 is started to enter a WAIT (standby) state. Rs_min is a variable for obtaining the minimum value of the transmission rate Rs within a certain time.
[0022]
FIG. 4 shows an interruption operation of the coding rate and FEC data transmission rate determination unit 106 in FIG. The determination unit 106 is interrupted and exits the WAIT state when the transmission rate determination unit 105 updates the transmission rate Rs and when the Rc update timer 107 times out. It is assumed that the transmission rate Rs is updated by the transmission rate determining unit 105 according to the TFRC scheme every time feedback information arrives from the receiving terminal 200.
[0023]
When the updated transmission rate Rs is notified to the coding rate and FEC data transmission rate determining unit 106 (step 301), the notified transmission rate Rs changes in the fluctuation range (Rc <Rc) defined by the current coding rate Rc. It is checked whether or not Rs <U × Rc) (step 302). If the transmission rate Rs falls within the fluctuation range, the FEC data transmission rate Rf is updated according to the notified transmission rate Rs without updating the current encoding rate Rc (Rf = Rs-Rc: step 303). Further, if the notified transmission rate Rs is the minimum transmission rate from the start of the Rc update timer 107 to the present, the transmission rate is stored in a variable Rs_min (step 304), and the state returns to the WAIT state.
[0024]
On the other hand, when the timeout of the Rc update timer 107 occurs (step 305), the coding rate Rc is updated using the value of the variable Rs_min at that time (Rc = V × Rs_min), and the current transmission rate Rs Then, the FEC data transmission rate Rf is updated according to the updated coding rate Rc (Rf = Rs-Rc), the Rc update timer 107 is restarted, and the maximum transmission rate Rs_max is set again in the variable Rs_min (step 306). , And returns to the WAIT state.
[0025]
If the transmission rate Rs is greatly changed so as to deviate from the fluctuation range (Rc <Rs <U × Rc), the notified transmission rate Rs is set to a variable Rs_min (step 307), and the coding rate Rc is set. The operation of step 306 such as updating of the above is performed, and the state returns to the WAIT state.
[0026]
With the above algorithm, the update frequency of the coding rate Rc is suppressed, and an appropriate FEC data transmission rate Rf is obtained.
[0027]
Next, an operation example of the FEC generation unit 103 in FIG. 1 will be described. To generate the FEC data, for example, an XOR (exclusive OR) operation of RFC 2733 is used. For simplicity, FEC data is generated on the assumption of fixed error resilience so that, for example, loss of two consecutive packets can be recovered. However, the error correction capability may be changed by detecting how many consecutive packets cause a loss. If the generated FEC data amount is smaller than the FEC data transmission rate Rf determined by the algorithm of FIGS. 3 and 4, all the FEC data is transmitted, and if it is larger, the transmitted FEC data amount is adjusted. If the amount of FEC data to be transmitted is too large, the FEC data amount may be reduced by lowering the error correction capability. In addition to the XOR operation, an error correction method such as parity or Reed-Solomon can also be used.
[0028]
A plurality of error correction schemes may be dynamically switched according to the FEC data transmission rate Rf or the packet loss rate. For example, when the packet loss rate is high, strong error resilience combining Reed-Solomon and interleaving is selected, and when the packet loss rate is low, weak error resilience such as parity is selected.
[0029]
When the FEC data transmission rate Rf is higher than the threshold value D2 (fixed value) for a certain period, a parity method with a small amount of error correction processing but low error resilience is used.
Conversely, when the FEC data transmission rate Rf is equal to or less than the threshold value D2 for a certain period, the Reed-Solomon method having a large error correction operation amount but a high error tolerance is used. By doing so, it is possible to reduce the processing load on the receiving terminal 200 by the parity method when the transmission amount of FEC data is large, and to maintain high error resilience by the Reed-Solomon method when the transmission amount of FEC data is small. it can. In addition, by lowering the processing load of the receiving terminal 200 by the parity method, it is possible to receive more video data from the transmitting terminal 100, and to reduce the processing delay so that media data can be reproduced with a low delay. There are advantages.
[0030]
Further, the FEC generation unit 103 may select data to which error resilience is to be given or determine the number of data according to the packet loss rate. When the packet loss rate is high, error resilience is selectively given to data important for decoding, such as an intra frame or a video header for video data and a voiced portion for audio data. .
[0031]
To explain this in detail, when the packet loss rate is low in MPEG2 video encoded data, FEC data is added to the entire video encoded data (method X). On the other hand, when the packet loss rate is high, FEC data is added only to I (Intra) and P (Predictive) frames, and FEC data is not added to B (Bidirectionally predictive) frames (method Y). ). Since the amounts of FEC data are the same in both systems X and Y, for system I and P frames, system X has a lower error tolerance than system Y.
[0032]
By switching schemes X and Y in accordance with the packet loss rate in this manner, the number of frames that can be reproduced by receiving terminal 200 can be increased as compared to a case where schemes X and Y are used alone. For example, when the packet loss rate is low, a lost packet can be recovered even with a weak error correction capability, and therefore the number of reproduced frames is larger in the method X in which error resilience is given to the entire encoded video data. On the other hand, when the packet loss rate increases, the number of reproduced frames of I and P frames decreases in the method X, so that the P and B frames referring to these frames cannot be reproduced, and the number of reproduced frames sharply decreases. On the other hand, in the method Y, since strong error resilience is given to the I and P frames, even if the packet loss rate is high, the referenced frames (I and P frames) are not lost, and the number of reproduced frames is small. Is increased.
[0033]
In the above description, the I, P, and B frames are targeted. However, hierarchical coding may be used, and the base layer may be used instead of the I and P frames, and the enhancement layer may be used instead of the B frame.
[0034]
FIG. 5 shows main operations of the feedback information generation unit 205 and the notification interval control unit 206 in FIG. The feedback information generation unit 205 measures the packet loss rate in cooperation with the transmission unit 201 (Step 401). When the packet loss rate is higher than the threshold value L1 (fixed value), the notification interval control unit 206 sets the notification interval Tf of the feedback information to a fixed value smaller than the current notification interval within a range not less than the minimum value Tfmin. It is shortened by Tc1 (step 402). As a result, the transmission rate Rs can quickly follow the available transmission band, and the occurrence of packet loss can be reduced. When the packet loss rate is lower than the threshold L2 (a fixed value smaller than L1), the notification interval control unit 206 increases the notification interval Tf of feedback information by a fixed value Tc2 from the current notification interval (step 403).
As a result, frequent switching of the transmission rate Rs can be suppressed, and the fairness with other flows can be improved.
[0035]
FIG. 6 shows a variation example of the transmission rate Rs and the coding rate Rc in media data transmission by the transmitting / receiving terminals 100 and 200 in FIGS. 1 and 2. According to FIG. 6, it can be seen that even in a situation where the transmission rate Rs is frequently updated, the operation of the coding rate and FEC data transmission rate determination unit 106 suppresses the update frequency of the coding rate Rc. In addition, when the packet loss rate is low, the operation of the notification interval control unit 206 also suppresses unnecessary updating of the transmission rate Rs.
[0036]
FIG. 7 shows the operation of the packet size determination unit 108 in FIG. According to FIG. 7, by reducing the data packet size when the transmission rate Rs decreases, the packet loss rate can be observed in detail.
[0037]
First, the packet size determining unit 108 receives the transmission rate Rs determined by the transmission rate determining unit 105 (Step 701). Thereafter, S is set as a predetermined normal packet size, and the number N of packets that can be transmitted at the transmission rate Rs in the observation period T is calculated as follows.
N = Rs × T / S
It is determined whether or not the value of the packet number N is smaller than a predetermined threshold value Nmin (step 702). If it is determined that N is not smaller than Nmin, the normal packet size S is adopted (step 703). If it is determined that N is smaller than Nmin, the packet size S ′ to be adopted is
S ′ = Rs × T / Nmin
(Step 704). Then, the packet size determined in step 703 or step 704 is notified to encoding section 102 (step 705), and the process ends.
[0038]
As described with reference to FIG. 5, in the embodiments of FIGS. 1 and 2, the notification interval Tf of the feedback information changes, and accordingly, the observation period T changes accordingly. However, if the minimum value Tfmin of the observation period is used, at least Nmin packets can be transmitted.
[0039]
FIG. 8 shows the operation of the RTT calculation unit 109 in FIG. According to FIG. 8, by adding an offset to the RTT, when the RTT is small, it is possible to suppress the fluctuation of the transmission rate Rs caused by the fluctuation of the delay that is not related to the congestion state of the network 150.
[0040]
First, the RTT calculation unit 109 receives feedback information from the receiving terminal 200 (Step 801), and acquires a measured round trip propagation delay time RTTt from the feedback information (Step 802). Subsequently, it is determined whether or not RTTt is smaller than a predetermined threshold value RTTmin (step 803). If RTTt is not smaller than RTTmin, RTTt is adopted as the round trip propagation delay time RTTcalc used for calculating the transmission rate Rs (step 804). When RTTt is smaller than RTTmin,
RTTcalc = RTTt + ofs × (RTTmin−RTTt) / RTTmin
, A round trip propagation delay time RTTcalc used for calculation is obtained (step 805). Here, ofs is a predetermined constant. Then, the RTTcalc determined in step 804 or step 805 is notified to the transmission rate determination unit 105 (step 806), and the process ends.
[0041]
FIG. 9 shows the relationship between the above RTTt and RTTcalc. In FIG. 9, the horizontal axis is RTTt, and the vertical axis is RTTcalc. The relationship between RTTt and RTTcalc obtained by the above algorithm is indicated by a thick solid line. The broken line indicates the case where RTTcalc = RTTt, that is, the case where the measured RTT is used for calculation as it is. As shown in FIG. 9, when RTTt is smaller than RTTmin, a positive addition offset is adopted. Therefore, even when RTTt is small, RTTcalc does not become too small.
[0042]
The increase in propagation delay due to congestion is several hundred ms or more, and the processing delay of the device is on the order of several ms. Therefore, by setting the RTTmin and ofs to the order of several tens of ms or less, the offset addition does not affect the propagation delay time when congestion occurs.
[0043]
The transmission protocol between the transmitting terminal 100 and the receiving terminal 200 may be a unique protocol other than IP. The connection form is not limited to the one-to-one type, but may be a one-to-N broadcast type (multicast, broadcast) or an N-to-M mesh type. The media data may be transmitted singly or may be transmitted simultaneously in parallel. The present invention is not limited to the standardized coding method, and an original coding method may be used.
[0044]
【The invention's effect】
As described above, according to the present invention, it is possible to suppress frequent updates of the coding rate, adjust the notification interval of feedback information, change the packet size, and add an offset to RTT. Therefore, it is possible to realize high-quality media data transmission in an environment where the available bandwidth fluctuates greatly.
Therefore, the present invention can be applied to various applications such as VoIP (Voice Over Internet Protocol) used for Internet telephone, TV telephone, and monitoring / broadcasting using a network.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating an example of an internal configuration of a media transmission device (transmission terminal) according to the present invention.
FIG. 2 is a block diagram showing an example of an internal configuration of a media receiving device (receiving terminal) according to the present invention.
FIG. 3 is a flowchart showing an initial operation of a coding rate and FEC data transmission rate determining unit in FIG. 1;
FIG. 4 is a flowchart illustrating an interrupt operation of the determination unit.
FIG. 5 is a flowchart illustrating main operations of a feedback information generation unit and a notification interval control unit in FIG. 2;
FIG. 6 is a time chart illustrating an example of a change in a transmission rate and a coding rate in media data transmission by the apparatuses in FIGS. 1 and 2;
FIG. 7 is a flowchart illustrating an operation of a packet size determining unit in FIG. 1;
FIG. 8 is a flowchart illustrating the operation of an RTT calculation unit in FIG. 1;
FIG. 9 is a diagram for explaining RTT offset addition realized by the operation of FIG. 8;
[Explanation of symbols]
100 transmission terminal (media transmission device)
101 Audio / video input unit
102 encoding unit
103 FEC generation unit
104 Transmission unit
105 Transmission rate determination unit
106 Coding Rate and FEC Data Transmission Rate Determination Unit
107 Rc update timer
108 Packet Size Determination Unit
109 RTT calculator
150 Network
200 receiving terminal (media receiving device)
201 Transmission unit
202 Packet loss recovery unit
203 decoding unit
204 playback unit
205 Feedback information generator
206 Notification interval control unit
Rc coding rate
Rf FEC data transmission rate
Rs transmission rate
RTTcalc RTT used to calculate the transmission rate
RTTt RTT measured
Tf Feedback information notification interval

Claims (19)

A media transmission method for transmitting encoded data based on media data via a network,
A first step of updating a transmission rate according to a transmission state of the network;
A second step of updating the coding rate at a frequency less than the frequency of updating the transmission rate. The media transmission method according to claim 1,
The media transmission method according to claim 2, wherein the second step includes a step of updating the encoding rate when a timer for which a timeout time longer than the update interval of the transmission rate is set times out. The media transmission method according to claim 1,
The media transmission method according to claim 2, wherein the second step includes a step of updating the coding rate when the transmission rate is updated to a value outside a predetermined range. The media transmission method according to claim 1,
The media transmission method according to claim 2, wherein the second step includes updating the coding rate according to a minimum value of the transmission rate within a certain time. The media transmission method according to claim 1,
A third step of allocating a difference between the transmission rate and the coding rate to a transmission rate of redundant data for error correction, and adding the redundant data to the coded data for transmission. Media transmission method. The media transmission method according to claim 5,
The media transmission method according to claim 3, wherein the third step includes a step of changing an error correction method according to a transmission rate of the redundant data. The media transmission method according to claim 5,
The media transmission method according to claim 3, wherein the third step includes a step of changing an error correction method according to a packet loss rate of the network. The media transmission method according to claim 7,
In the third step, when the packet loss rate of the network is low, error immunity is given to all encoded data, and when the packet loss rate of the network is high, only the encoded data of high importance is added. A method for transmitting media, comprising the step of providing error resilience. The media transmission method according to claim 1,
The method according to claim 1, wherein the first step includes a step of notifying, from a receiving terminal, feedback information indicating a transmission state of the network. The media transmission method according to claim 9,
A media transmission method, further comprising a step of variably controlling a notification interval of the feedback information according to a transmission state of the network. A media transmission method for transmitting media data over a network, comprising:
A first step of notifying feedback information indicating the transmission state of the network from a receiving terminal at variable intervals according to the transmission state of the network;
A second step of updating a transmission rate of the media data according to the notified feedback information. The media transmission method according to claim 11,
The first step is a step of shortening the notification interval of the feedback information when the packet loss rate of the network is high, and increasing the notification interval of the feedback information when the packet loss rate of the network is low. A media transmission method, comprising: The media transmission method according to claim 12,
The method according to claim 1, further comprising a step of restricting a notification interval of the feedback information so as not to fall below a predetermined minimum interval. A media transmission device for transmitting encoded data based on media data to a network,
Means for generating the encoded data from the media data;
Means for generating redundant data for error correction from the encoded data,
Means for updating the transmission rate according to the transmission state of the network,
Means for updating the coding rate less frequently than the frequency of updating the transmission rate,
Means for assigning a difference between the transmission rate and the encoding rate to a transmission rate of the redundant data,
Means for adding the redundant data to the encoded data and transmitting the encoded data. A media receiving device for receiving media data from a network,
Means for notifying feedback information indicating a transmission state of the network, such that the transmission rate of the media data is updated,
Means for controlling a notification interval of the feedback information according to a transmission state of the network. A media transmission method for transmitting encoded data based on media data via a network,
Updating a transmission rate according to the transmission state of the network,
Calculating the number of packets that can be transmitted within the observation period based on the updated transmission rate, the length of the observation period of packet loss in the network, and the normal packet size of the encoded data; ,
A step of comparing the calculated number of packets with a predetermined threshold, and when the calculated number of packets is smaller than the threshold, the packet size of the encoded data is changed to the normal size. Setting the packet size smaller than the packet size. A media transmission device for transmitting encoded data based on media data to a network,
Means for generating the encoded data from the media data;
Means for updating the transmission rate according to the transmission state of the network,
Based on the updated transmission rate, the length of the packet loss observation period in the network, and the normal packet size of the encoded data, calculate the number of packets that can be transmitted in the observation period. Means,
Means for comparing the calculated number of packets with a predetermined threshold,
When the calculated number of packets is smaller than the threshold, means for setting the packet size of the encoded data to be smaller than the normal packet size,
Means for transmitting the encoded data. A media transmission method for transmitting encoded data based on media data via a network,
The transmitting terminal measures a round-trip propagation delay time between the transmitting terminal and the receiving terminal,
Comparing the measured round-trip propagation delay time with a predetermined threshold,
When the measured round-trip propagation delay time is smaller than the threshold, adding an offset value to the measured round-trip propagation delay time,
Determining a transmission rate based on the round trip propagation delay time to which the offset value has been added. A media transmission device for transmitting encoded data based on media data to a network,
Means for generating the encoded data from the media data;
Means for measuring round-trip propagation delay time on the network;
Means for comparing the measured round-trip propagation delay time with a predetermined threshold,
Means for adding an offset value to the measured round-trip propagation delay time, if the measured round-trip propagation delay time is smaller than the threshold,
Means for determining a transmission rate based on the round trip propagation delay time to which the offset value has been added,
Means for transmitting the encoded data at the determined transmission rate.

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