KR100648659B1 - Rate control method and device for streaming video - Google Patents

Abstract

A streaming video rate control method and apparatus are presented. The streaming video rate control method of the present invention relates to a method of controlling a video rate for transmitting streaming video data received from a video server to a mobile terminal through a mobile communication network, and a forward delay time from the video flow controller to the mobile terminal. Predicting a reverse delay time from the mobile terminal to the video flow controller; Predicting a playback rate at the mobile terminal, the rate at which the streaming video data is played; Obtaining a bandwidth of a network located between the video flow controller and the mobile terminal; Calculating a playback queue size in a playback buffer of the mobile terminal; And calculating the video transmission rate using the playback rate, the network bandwidth, and the playback queue size. According to the present invention, a transmission rate of streaming video can be calculated, which enables efficient use of network bandwidth and minimizes queue delay and loss of video flow in the network.

Description

Rate control method and device for streaming video}             

1 is a network diagram for transmitting streaming video data to a mobile terminal according to an embodiment of the present invention.

FIG. 2 is an example of modeling a transmission path of streaming video from a gateway shown in FIG. 1 to a terminal.

3 is a block diagram of a video flow controller according to an embodiment of the present invention.

4 is a block diagram of a mobile terminal according to an embodiment of the present invention.

5 is a flowchart illustrating a method of controlling a rate of streaming video data according to an embodiment of the present invention.

The present invention relates to a method and apparatus for transmitting streaming video data to a mobile terminal through a mobile communication network, and more particularly, to a method and apparatus for controlling a rate of streaming video data that can improve streaming video quality of service (QoS). will be. Streaming technology is a technology that reproduces voice or video in real time on the Internet.

When streaming video data is transmitted through a mobile communication network, the data rate should be determined in consideration of various variables such as dynamically available bandwidth. In particular, the two main factors affecting the quality of streaming video are bottleneck bandwidth in the network and playback buffer at the receiving end. Thus, how best to use these two resources affects the quality of streaming video, or QoS.

An object of the present invention is to provide a method and apparatus for controlling a rate of streaming video data, which can improve streaming video quality by efficiently using network bandwidth and minimizing queue delay and loss of video flow in a network. have.

In order to achieve the above object, according to an aspect of the present invention, in the video flow controller for controlling a video rate for transmitting streaming video data received from a video server to a mobile terminal through a mobile communication network, Estimating a forward delay time to the mobile terminal and a reverse delay time from the mobile terminal to the video flow controller; Predicting a playback rate at the mobile terminal, the rate at which the streaming video data is played; Obtaining a bandwidth of a network located between the video flow controller and the mobile terminal; Calculating a playback queue size in a playback buffer of the mobile terminal; A method of controlling a video rate of streaming video data including calculating the video rate by using the playback rate, the network bandwidth, and the size of the playback queue is provided.

Advantageously, estimating a forward delay time from said video flow controller to said mobile terminal and a reverse delay time from said mobile terminal to said video flow controller comprises: forwarding data including controller transmission time information to said mobile terminal. Transmitting to; Receiving reverse data including terminal transmission time information transmitted from the mobile terminal in response to the data including the controller transmission time information; And calculating the forward delay time and the reverse delay time by using the controller transmission time information and the terminal transmission time information.

In order to achieve the above object, according to another aspect of the present invention, an apparatus for controlling a video rate for transmitting streaming video data received from a video server to a mobile terminal through a mobile communication network, video flow controller A delay estimator for estimating a forward delay time from the mobile terminal to the video flow controller from the mobile terminal; A playback rate predictor for predicting a playback rate which is a speed at which the streaming video data is played in the mobile terminal; A bandwidth calculator configured to obtain a bandwidth of a network located between the video flow controller and the mobile terminal; A playback queue size calculator configured to calculate a playback queue size in a playback buffer of the mobile terminal; And a target rate calculator configured to calculate the video rate using the playback rate, bandwidth, and playback queue size.

이고,

은 상기 플레이백 큐 크기,

은 기준 시점으로부터 상기 역방향 지연 시간 이전의 플레이백 큐 크기, a_pm은 m 타임 슬롯에서의 전송률, P_m 은 m 타임 슬롯에서의 플레이백 레이트, d_fn 은 상기 순방향 지연 시간, d_b 는 상기 역방향 지연 시간이며, 상기 기준 시점은 n 타임 슬롯이다. Preferably, the playback queue size calculator calculates the playback queue size by using Equation 1, where Equation 1 is

ego,

Is the playback queue size,

Is the playback queue size from the reference point before the backward delay time, a _pm is the transmission rate in m time slots, P _m is the playback rate in m time slots, d _fn is the forward delay time, and d _b is the backward direction Delay time, and the reference time point is n time slots.

이고, a_n 은 상기 비디오 전송률,

은 상기 플레이백 레이트, B^* 는 미리 설정된 이상적 큐 크기, 상기 x는 소정 계수로서 0과 1사이의 실수,

은 상기 네트워크의 대역폭, d_1n은 상기 비디오 흐름 제어기로부터 네트워크의 병목 지점까지의 지연 시간이다.Also preferably, the target data rate calculator may calculate the video data rate using Equation 2, wherein Equation 2 is

A _n is the video rate,

Is the playback rate, B ^* is a preset ideal cue size, x is a predetermined coefficient, real number between 0 and 1,

Is the bandwidth of the network, d _1n is the delay time from the video flow controller to the bottleneck of the network.

Hereinafter, a configuration of a method and apparatus for accessing an Internet service using a character string according to the present invention will be described in detail with reference to the accompanying drawings. Hereinafter, the same or corresponding components regardless of reference numerals will be described with reference to the accompanying drawings. Denotes the same reference numerals and duplicate description thereof will be omitted.

1 is a network diagram for transmitting streaming video data to a mobile terminal according to an embodiment of the present invention.

Referring to this, a network for transmitting streaming video data to a mobile terminal may include a mobile terminal 100, a base station 110, a wireless data network 120, a network matching device (PDSN) 130, a gateway ( 140 and video server 150.

The mobile terminal 100 is a terminal capable of wireless Internet service, and includes a wireless web browser (not shown) to receive and play streaming video data provided from a video server.

The base station 110 is a terminal device of a mobile communication network that is wirelessly connected to the mobile terminal 100. The wireless data network 120 may include a base station controller (not shown) and an exchange (not shown).

The network matching device 130 is located between the wireless data network 120 and the internet network 160 to perform a matching function between the two networks, that is, matching between the mobile communication protocol and the Internet protocol. The wireless data network 120 is a mobile service provider network.

The gateway 140 serves as a relay between the mobile terminal and the wireless Internet content and includes a video flow controller of the present invention.

Video server 150 is a server that provides video content, particularly streaming video content.

In the network configuration shown in FIG. 1, the gateway 140 is located between the wireless data network 120 and the wired operator internet network 160. The video flow controller according to an embodiment of the present invention is a gateway device 140. It is configured to be included within. The video flow controller inside the gateway 140 monitors the video flow entering the mobile operator network and adjusts the actual rate to be as much as possible with the target rate calculated by the video flow controller. If necessary, the excessive packet inflow in the gateway 140 may be appropriately discarded to match the actual packet rate and the target rate introduced into the mobile communication provider network. For video data, for example, low priority frames such as B or P frames are discarded first. However, the method of discarding a frame or packet is a problem different from the present invention and is outside the scope of the present invention. The present invention relates to a method for calculating an optimum desired video rate.

The two main factors affecting the quality of streaming video are the network bottleneck bandwidth and the playback buffer at the receiving terminal. Therefore, the question is how to best use these two resources.

In the present invention, the video rate control problem is formulated as rate-based feedback control. In the present invention, the video flows into the mobile communication network to minimize the queue delay and loss of the video flow in the network so that the available network bandwidth can be efficiently used, and the size of the playback queue on the receiving side approaches the target value. Control the transmission rate of the data, that is, the transmission data.

In order to control the flow of streaming video, it is desirable to model the transmission path of streaming video as two cues connected in series as shown in FIG. FIG. 2 is an example of modeling a transmission path of streaming video from the gateway 140 illustrated in FIG. 1 to the terminal 100.

The streaming video data is transmitted from the video flow controller 210 or the gateway 140 including the same to the terminal 100 and then reproduced in the terminal 100.

The first queue 230 is in the bottleneck link of the network and the second queue 250 is in the playback buffer of the receiving side, i.e., the receiving terminal. The size of the network bottleneck queue 230 is Qn, and the size of the playback queue 250 is Bn.

The delay time between the video flow controller 210 and the network bottleneck queue 230, that is, the time taken for the data transmitted from the video flow controller 210 to reach the network bottleneck queue 230 is referred to as d _1n , and the network bottleneck The delay time from the queue 230 to the playback queue 250 of the receiving terminal is referred to as d _2n .

Accordingly, the forward delay time, d _fn , which is the time it takes for data transmitted from the video flow controller 210 to reach the playback queue 240 of the receiving terminal, that is, the receiving terminal, is the sum of d _1n and d _2n . . The reverse delay time, which is the time taken for the data transmitted from the terminal to reach the video flow controller 210 or the gateway 140 including the video flow controller, is referred to as d _bn .

In the present invention, a discrete time-slotted control method is used. At the beginning of every time slot, the target video flow rate to the network is adjusted to the new value. All rates are preferably measured in bits per time slot. Therefore, the variable a _n is the number of bits of the video flow sent over the network during time slot n. The network bandwidth available for that video flow during time slot n is the minimum bandwidth given within the network during time slot n. This is defined as Cn. The minimum bandwidth will be determined by the bottleneck link among the network links. The wireless link section between the base station and the terminal will be the bottleneck link among the network links of the entire mobile communication network. Therefore, the minimum bandwidth is likely to be the bandwidth of the radio link.

 Similarly, the network bottleneck queue size and playback queue size in bits at the beginning of time slot n are defined as Qn and Bn, respectively.

The playback queue size refers to the size of the queue held in the playback buffer of the receiving terminal. The number of bits output from the playback buffer during time slot n is defined as Pn. Therefore, Pn is a playback rate which is a speed at which streaming data is played on the terminal. The playback cue size should be controlled as close as possible to the ideal cue size, B ^* . The B ^* value should be chosen to be large enough to queue enough packets at the receiving end to avoid buffer underflow, i.e. no complete frame available to the playback buffer.

If the playback queue size is small, the bottleneck in the network bandwidth may cause the playback buffer to be exhausted when not enough packets arrive in time to fill the playback buffer. Then enough packets are not available in the buffer to make up the complete video frame before the deadline. In this case, a partially configured error video frame will be displayed to the user or the previous video frame will be displayed to the user according to the frame display technique used at the receiving end.

On the other hand, the B ^* value should be chosen small enough to avoid buffer overflows. In overflow, the playback queue size Bn approaches the buffer size. Thus, incoming packets will be discarded until enough space is available after the packets in front of the queue are gone to display the next video frame.

Keeping the playback cue size Bn at the ideal cue size, B ^* , is important for video quality. It is preferable to set B ^* to half of the playback cue size, Bn.

When d _1n = d _2n = d _bn = 0, that is, there is no delay, the feedback control law of the following equation 1 is optimal in terms of time.

Where P _n is the above-described playback rate, B ^* is a predetermined value as the ideal playback queue size described above, Cn is the above-mentioned network bandwidth, Qn is the above-described network bottleneck queue size, and Q ^* is the ideal network bottleneck queue size As a preset value. And the subscript n means n time slots.

Optimally in terms of time, the rule of Equation 1 is the fastest way to get the playback queue size and network queue size to their ideal values after sudden changes in bandwidth or playback queue size, respectively. However, since it is not easy to predict the network queue size, a suboptimal law of setting Q ^* to 0 can be used. If Q ^* is set to 0, Equation 1 may be expressed as Equation 2 below.

Here, x is a real number between 0 and 1 as a predetermined coefficient but close to 1 (preferably 0.8 to 0.9). To keep the rate always below the available network bandwidth (Cn) so that Qn can be kept small enough to be negligible compared to Cn, x is close to 1 but less than 1 (preferably 0.8 to 0.9). Is selected.

The video rate control method (RCSV) of streaming video data of the present invention extends the control law of Equation 2 to a case where an arbitrary delay occurs. The wait delay in the network bottleneck, i.e., the bottleneck queue size Qn, is considered negligible so that packets transmitted in the n time slots as a reference point will arrive at the playback buffer at time n + d _fn at the rate of a _n . Here, d _fn = d _1n + d _2n .

Therefore, Equation 2 is modified as in Equation 3 below.

, 미래의 플레이백 큐 크기, 즉 n+d_fn 시점의 플레이백 큐 크기인

, 미래 가용한 네트워크 대역폭, 즉 n+d_1n 시점의 네트워크 대역폭

를 예측해야 한다는 것을 의미한다. Equation 3 shows that in order to obtain a target transfer rate a _n in n time slots, the video flow controller is a future playback rate, that is, a playback rate at n + d _fn time points.

, Play back the queue size of the future, that is, n + d _fn of the playback queue size at the time

, Future available network bandwidth, i.e. network bandwidth at n + d _1n

That means you have to predict.

To this end, the video flow controller of the present invention continuously predicts the forward delay time d _fn and the reverse delay time d _bn . Prediction of the forward delay time d _fn and the reverse delay time d _bn is made by periodically exchanging control packets containing time stamps between the video flow controller and the receiving terminal.

These control packets can be inserted into the video stream itself as in Real-time Transport Protocol (RTP) / RTP Control Protocol (RTCP) or exchanged as separate control packets between the video flow controller and the terminal as in UDP or Transmission Control Protocol (TCP). do. The time stamp preferably includes transmission time information. That is, the time stamp transmitted from the video flow controller 210 to the terminal 100 includes the transmission time information from the video flow controller 210, so that the forward delay time can be calculated. In addition, the time stamp transmitted from the terminal 100 to the video flow controller 210 includes the transmission time information of the terminal, thereby calculating the reverse delay time.

This timestamp exchange produces prediction sequences, {d _fn } and {d _bn }, for the forward and reverse delay times. These prediction sequences, {d _fn } and {d _bn }, are preferably flattened using a moving average scheme. For convenience of explanation, the sum of the forward delay time and the reverse delay time (d _fn + d _bn ) is expressed as Dn.

은 별도의 대역폭 모니터링 모듈에 의해 예측되는 것으로 가정한다. 그러나 실제로, 대역폭 모니터링이 패킷-트레인 기반 프로빙 프로토콜(packet-train based probing protocol)을 이용하여 이루어진다면, 프로브 패킷은 제어 패킷과 결합하여 순방향 지연 시간(d_fn) 과 역방향 지연 시간(d_bn)을 예측하는데 사용될 수 있다.Among the future variables required by Equation 3, the playback queue size at n + d _fn

Is assumed to be predicted by a separate bandwidth monitoring module. In practice, however, if bandwidth monitoring is performed using a packet-train based probing protocol, the probe packet is combined with the control packet to obtain a forward delay time (d _fn ) and a reverse delay time (d _bn ). Can be used to predict.

을 예측할 수 있도록 하기 위하여, 단말기(100)는 매 타임 슬롯의 시작점에서 자신의 플레이백 큐 크기를 비디오 흐름 제어기(210)로 피드백한다. 그러나, n 타임 슬롯에서 비디오 흐름 제어기(210)가 수신한 가장 최근의 플레이백 큐 크기는 n-d_b 시점의 플레이백 큐 크기인

에 불과하다. 여기서, d_b 는 n 타임 슬롯 동안 비디오 흐름 제어기(210)에 도착하는 패킷들에 대한 단말기에서 비디오 흐름 제어기(210)까지의 역방향 지연 시간이다.In video flow controller 210, the playback queue size at n + d _fn

In order to be able to predict, the terminal 100 feeds back its playback queue size to the video flow controller 210 at the beginning of every time slot. However, the most recent playback queue size received by video flow controller 210 in n time slots is the playback queue size at time n _d .

Is nothing. Here, d _b is the reverse delay time from the terminal to the video flow controller 210 for packets arriving at the video flow controller 210 for n time slots.

은 다음의 수학식 4를 이용하여

에 n-d_b 타임 슬롯부터 n+d_f -1 까지의 플레이백 큐 크기를 더함으로써 유도될 수 있다.But,

Using the following equation (4)

Can be derived by adding the playback queue size from nd _b time slot to n + d _f −1.

Here, a _pm is a data rate flowing into the playback queue during m time slots, and may be expressed as in Equation 5 below. The playback rate, Pm, in m time slots can be predicted using the known past packet size of each frame transmitted from video flow controller 210 or gateway 140 comprising it. In addition, when predicting the playback rate Pm in m time slots, it is preferable to use a frame rate together.

이 사용될 수 있다.Where d _f is the forward delay time from the video flow controller 210 to the terminal for packets arriving at the terminal during m time slots, and d ₂ is the forward delay time from the network bottleneck queue to the terminal for the same packets. to be. Instead of a _{pm in} Equation 5, the predicted value obtained by using Equation 6

This can be used.

을 사용하는 것이 꽤 적절하다.If the network bottleneck queue size, Qn, is kept at a sufficiently small value, then the prediction value obtained by using Equation 6 instead of a _{pm in} Equation 5

It is pretty appropriate to use

3 is a block diagram of a video flow controller 210 according to an embodiment of the present invention. With reference to this, the function and role of the above-described video flow controller 210 will be described by dividing it into detailed components as follows.

The video flow controller 210 includes a controller 212, a delay predictor 214, a playback rate predictor 216, a playback queue size calculator 218, and a target rate calculator 220.

Delay predicting unit 214 is the forward delay time (df, d1, d2) from the video flow controller 210 to the mobile terminal 100 and the reverse delay time from the mobile terminal 100 to the video flow controller 210 (d _b ) is predicted. To this end, as described above, a packet including a time stamp is exchanged with the terminal.

The playback rate predictor 216 predicts a playback rate, which is a speed at which streaming video data is played in the mobile terminal. Specifically, the playback rate is predicted at a predetermined time point (preferably, after the forward delay time from the reference time point) so that the target transfer rate can be calculated using Equation (3). The playback rate may be calculated using the frame rate and the packet size for each frame, as described above.

The playback queue size calculator 218 calculates a playback queue size in the playback buffer of the mobile terminal. Specifically, the playback queue size is calculated at a predetermined time point (preferably, after the forward delay time from the reference time point) so that the target transfer rate can be calculated using Equation (3). The playback queue size is calculated using equation (4).

The target rate calculator 220 calculates a video rate by substituting the playback rate, the network bandwidth, and the size of the playback queue into Equation 3. Although not shown in FIG. 3, a bandwidth calculator that calculates a network bandwidth may be further provided. However, in order to calculate the bandwidth, it is preferable that a network bandwidth monitoring module is provided at a predetermined point in the network so that the network bandwidth monitored by the bandwidth monitoring module is transmitted to the video flow controller 210.

The controller 212 controls the operation of the delay predictor 214, the playback rate predictor 216, the playback queue size calculator 218, and the target rate calculator 220, that is, inside the video flow controller 210. Responsible for the overall control of the.

4 is a block diagram of a mobile terminal 100 according to an embodiment of the present invention. With reference to this, the function and role of the above-described terminal 100 will be described by dividing it into detailed components.

The terminal 100 includes a controller 412, a display unit 414, a playback buffer 416, a data processor 418, and a data transceiver 420.

The data transceiver 420 transmits and receives a streaming video packet and a control packet through a mobile communication network. The data processing unit 418 processes the streaming video packet received through the data transmission / reception unit 420 to reproduce, or transmits a control packet received through the data transmission / reception unit 420 or a control packet to be transmitted through the data transmission / reception unit 420. It plays a role. The streaming video packet received through the data transmission / reception unit 420 is temporarily stored in the playback buffer 416, and outputs and reproduces data input to the playback buffer 416. The reproduced data is displayed via the display unit 414.

The controller 412 controls the operations of the display 414, the playback buffer 416, the data processor 418, and the data transceiver 420.

5 is a flowchart illustrating a method of controlling a rate of streaming video data according to an embodiment of the present invention. The method for controlling the rate of streaming video data according to an embodiment of the present invention is performed by the video flow controller 210 which is a rate control device.

Referring to FIG. 5, first, variables necessary for calculating a target transmission rate are initialized (S510). In the transmission rate control method of streaming video data according to an embodiment of the present invention, the transmission rate a _n is calculated using Equation 3 described above, and therefore, the playback rate P _f and the playback queue size B with n = 0 are calculated. _f Initializes the network bandwidth C _d1 .

Next, a forward delay time from the video flow controller to the mobile terminal and a reverse delay time from the mobile terminal to the video flow controller are predicted (S520). To this end, when the video flow controller transmits forward data including the controller transmission time information to the mobile terminal, the terminal transmits reverse data including the terminal transmission time information in response to the data including the controller transmission time information. As such, the forward delay time and the reverse delay time are calculated using the time stamps exchanged between the video flow controller and the terminal.

In addition, a playback rate, which is a speed at which streaming video data is played in the mobile terminal, is predicted (S530). The playback rate is preferably calculated using the frame rate transmitted from the video flow controller and the packet size per frame for a given time slot.

The bandwidth of the network located between the video flow controller and the mobile terminal is obtained (S540). The bandwidth of the network is preferably monitored by a network bandwidth monitoring module located on the network and transmitted to the video flow controller. As described above, the network bandwidth is preferably determined by the minimum bandwidth of the total bandwidths of all the links existing on the path through which the streaming video data is transmitted. The link with the minimum bandwidth as such is the bottleneck link. If the set of streaming video flows sharing the bottleneck link is 'S', the network bandwidth available for one streaming video flow can be calculated by dividing the bandwidth of the bottleneck link by 'S'. The bottleneck link in the network shown in FIG. 1 is likely to be a radio link section 170.

The playback queue size in the playback buffer of the mobile terminal is calculated. The playback queue size is calculated using equation (4).

The target rate is calculated using the playback rate, network bandwidth, and playback queue size obtained by the above steps (S560). At this time, the target transmission rate is calculated using Equation 3.

The rate of data to be transmitted is adjusted according to the calculated target transmission rate (S570). However, as described above, it is within the scope of the present invention to optimally calculate the target rate, and the method of adjusting the rate of the packet according to the calculated target rate is not within the scope of the present invention.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

As described above, according to the present invention, the transmission rate of the streaming video can be calculated so that the network bandwidth can be efficiently used and the queue delay and loss of the video flow in the network can be minimized. Therefore, if the stream video is transmitted at such a rate, the quality of the streaming video can be improved.

Claims (14)

A method for controlling a video rate for transmitting streaming video data received from a video server to a mobile terminal through a mobile communication network, Estimating a forward delay time from the video flow controller to the mobile terminal and a reverse delay time from the mobile terminal to the video flow controller; Predicting a playback rate at the mobile terminal, the rate at which the streaming video data is played; Obtaining a bandwidth of a network located between the video flow controller and the mobile terminal; Calculating a playback queue size in a playback buffer of the mobile terminal; And Calculating the video rate using the playback rate, the network bandwidth and the playback queue size Video rate control method of streaming video data comprising a. 2. The method of claim 1, wherein estimating a forward delay time from the video flow controller to the mobile terminal and a reverse delay time from the mobile terminal to the video flow controller Transmitting forward data including controller transmission time information to the mobile terminal; Receiving reverse data including terminal transmission time information transmitted from the mobile terminal in response to the data including the controller transmission time information; And Calculating the forward delay time and the reverse delay time using the controller transmission time information and the terminal transmission time information. The video rate control method of streaming video data comprising a. The method of claim 2, wherein the forward data including the controller transmission time information and the reverse data including the terminal transmission time information The video data rate control method of streaming video data, characterized in that the transmission in the general data packet. The method of claim 2, wherein the forward data including the controller transmission time information and the reverse data including the terminal transmission time information The video rate control method of streaming video data, characterized in that the transmission in a separate control packet. The method of claim 1, wherein the playback rate is The video rate control method of the streaming video data, characterized in that calculated using the frame rate and the packet size transmitted by the video flow controller during a predetermined time slot. 6. The method of claim 5, wherein obtaining the bandwidth of the network Receiving the network bandwidth measured by a network bandwidth monitoring module located on a network. 7. The method of claim 6, wherein calculating the playback queue size Receiving a playback queue size of a corresponding time slot from the terminal before the reverse delay time; Calculating a difference between the video rate and the playback rate for every time slot from before the reverse delay time; And Calculating the playback queue size using the playback queue size of the corresponding time slot before the reverse delay time and the difference between the video transmission rate and the playback rate for every time slot from before the reverse delay time. The video rate control method of streaming video data comprising a. 8. The method of claim 7, wherein calculating the video rate Obtaining a first difference value that is a difference between the playback queue size and a predetermined ideal queue size; Obtaining a second difference value that is a difference value between the playback rate and the queue size difference value; Obtaining a value obtained by multiplying a bandwidth of the network by a predetermined coefficient, wherein the predetermined coefficient is a real number between 0 and 1; Selecting a smaller value from a value obtained by multiplying the second difference value and a bandwidth of the network by a predetermined coefficient; And Setting the video rate as a larger value between the selected value and zero (0). The video rate control method of streaming video data comprising a. The method of claim 1, wherein the playback queue size is Using Equation 1, Equation 1 is

ego,

Is the playback queue size,

Is the playback queue size from the reference point before the backward delay time, a _pm is the transmission rate in m time slots, P _m is the playback rate in m time slots, d _fn is the forward delay time, and d _b is the backward direction Delay time, And the reference time point is n time slots. 10. The method of claim 9, wherein the video rate is It is calculated using Equation 2, Equation 2 is

ego, an is the video rate,

Is the playback rate, B ^* is a preset ideal cue size, x is a predetermined coefficient, real number between 0 and 1,

Is a bandwidth of the network, d _1n is a delay time from the video flow controller to a bottleneck of the network. A program of instructions, which can be executed by the one or more servers, is tangibly implemented and read by the one or more servers to perform the method of controlling the video rate of streaming video data according to any one of claims 1 to 9. Record carrier that records possible programs. An apparatus for controlling a video rate for transmitting streaming video data received from a video server to a mobile terminal through a mobile communication network, A delay predictor for predicting a forward delay time from a video flow controller to the mobile terminal and a reverse delay time from the mobile terminal to the video flow controller; A playback rate predictor for predicting a playback rate at which the streaming video data is played in the mobile terminal; A bandwidth calculator configured to obtain a bandwidth of a network located between the video flow controller and the mobile terminal; A playback queue size calculator configured to calculate a playback queue size in a playback buffer of the mobile terminal; And A target rate calculator for calculating the video rate using the playback rate, bandwidth, and playback queue size Device for controlling the video rate of streaming video data comprising a. The apparatus of claim 12, wherein the playback queue size calculator Using the equation 1 to calculate the playback queue size, Equation 1 is

ego,

Is the playback queue size,

Is the playback queue size from the reference point before the backward delay time, a _pm is the transmission rate in m time slots, P _m is the playback rate in m time slots, d _fn is the forward delay time, and d _b is the backward direction Delay time, And the reference time point is n time slots. The method of claim 12, The target rate calculation unit calculates the video rate using Equation 2, Equation 2 is

ego, a _n is the video rate,

Is the playback rate, B ^* is a preset ideal cue size, x is a predetermined coefficient, real number between 0 and 1,

Is a bandwidth of the network, d _1n is a delay time from the video flow controller to a bottleneck of the network.

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