CN104159109A - Bit rate control method and system based on VBR video encoding - Google Patents

Abstract

The invention is applicable to the field of streaming media technology, provides a bit rate control method and system based on VBR video encoding. The method comprises the steps of recording encoding information for each previously encoded frame; initializing encoding parameters of a current frame according to the encoding information and an average bit rate of video encoding; setting a maximum bit rate for the current frame based on a distortion optimization algorithm; encoding the current frame in a multi-path manner based on the encoding parameters and the maximum bit rate; estimating an encoding bit rate generated by a current path encoding of the current frame, and determining whether the encoding bit rate exceeds the maximum bit rate; and if so, conducting a next path encoding after the encoding parameters is adjusted until the encoding bit rate of the current frame does not exceed the maximum bit rate. In this way, requirements in terms of bit rate control and video quality can be effectively balanced, control of the maximum bit rate can allow an internal timing sequence of a player to be smoother, and smooth playing of a video program is facilitated.

Description

Bit rate control method based on VBR Video coding and system

Technical field

The present invention relates to stream media technology field, relate in particular to a kind of bit rate control method and system based on VBR (Variable Bit Rate, dynamic code rate) Video coding.

Background technology

Video compression coding is intended to the image sequence in video traffic to convert to the form that is easy to storage, is easy to transmission (distribution), is easy to present.At fixed video, present under the prerequisite of quality, compression ratio is one of important performance characteristic of weighing video encoder, because compression ratio is higher, the memory space that the video file of encoder output takies is less.But compression ratio is not unique measurement index.Along with emerging in an endless stream of the every application based on video compression technology, the design of video encoder need to take into account increasing factor, to meet the needs of various actual application environment that becomes increasingly abundant.

Rate Control is one of the key technology that need to consider when design video coding algorithm.By cataloged procedure being carried out to code check (being bit rate), control, can retrain video code flow at each instantaneous code check constantly.Raising along with the network bandwidth, network video distribution becomes possibility with presenting, but network is as a kind of public media, need to tackle the various requests of a large number of users simultaneously, therefore, does Internet Service Provider need to consider such problem urgently: how to realize the efficient utilization of Internet resources? for solving this realistic problem, not only need the network architecture to be optimized, also need the every data service on network to operation to carry out more effective management.Take network video-on-demand as example, in order to tackle the same time from thousands of users' order request, allow each user can enjoy the Video service of corresponding quality, except disposing abundant communication line and routing node, also need to limit the instantaneous code check of each order video stream.If the instantaneous code check of video flowing is not limited, its increase of leaving, in the situation that network data bearing capacity is given, will inevitably occur that the data of some video paragraph cannot be delivered to the situation of terminal in time so.When terminal has to because there is no data suspend broadcasting, user experiences and must be had a strong impact on.

The mode of Rate Control is divided into two kinds: VBR (Variable Bit Rate, dynamic code rate) and CBR (Constant Bit Rate, constant code rate).It is stricter that CBR compares VBR to the requirement of Rate Control, because CBR requires instantaneous code check to keep constant, and VBR allows instantaneous code check to float within the specific limits.For identical average bit rate, adopt VBR conventionally can obtain the better video quality than CBR.For a long time, rare due to network bandwidth resources, CBR is main Rate Control mode always.Yet along with the development of network transmission technology, the network bandwidth improves constantly, Internet Transmission cost constantly reduces, and network Video Applications is also graduallyed relax control the requirement of Video coding and restriction, and VBR is just replacing CBR becomes main Rate Control mode.On the one hand, 2013, China Telecom has issued < < IPTV business video/audio encoding and decoding standard V3.0 > > (being called for short IPTV3.0), this standard has been introduced VBR Video coding first in the IPTV of China Telecom business, and the maximum instantaneous code check of this class Video coding has been done to restriction.On the other hand, HLS (Http Live Streaming), the agreements such as MPEG-DASH just progressively become main network flow-medium agreement, in this quasi-protocol, video file be take section and is passed through HTTP (HyperText Transfer Protocol as unit, Hypertext Transport Protocol) agreement is passed to terminal, a section comprises the video content in 10 seconds conventionally, for a kind of like this video distribution mode, obviously do not need to adopt Rate Control mode harsh as CBR, in fact, existing many based on HLS (HTTP Live Streaming, hypertext live TV stream), in the operation system of MPEG-DASH, the Rate Control mode that VBR is generally adopted.When the codec designing based on VBR, need to adopt the mentality of designing different from CBR.Because both have different requirements to Rate Control.Although VBR allows code check to float, be still necessary the unsteady scope of code check to do strict restriction, because Internet resources are limited, and terminal plays requires good fluency.Strict restriction by code check domain of walker, can reduce network design complexity, improves the utilance of network bandwidth resources, can ensure that terminal can continue to play glibly simultaneously.

In summary, obviously there is inconvenience and defect in prior art in actual use, so be necessary to be improved.

Summary of the invention

For above-mentioned defect, the object of the present invention is to provide a kind of bit rate control method and system based on VBR Video coding, it can take into account the requirement of Rate Control and video quality two aspects effectively, maximal rate is limited and can make the inside sequential of player more level and smooth, be conducive to the smooth playing of video frequency program.

To achieve these goals, the invention provides a kind of bit rate control method based on VBR Video coding, comprise that step has:

Coded message recording step, record completed the coded message of each frame of coding in the past;

Coding parameter initialization step, according to the average bit rate of described coded message and Video coding, the coding parameter of initialization present frame;

Maximal rate setting steps, arranges the maximal rate of described present frame according to rate-distortion optimization algorithm;

Coding step, encodes to described present frame according to described coding parameter and described maximal rate, and described coding carries out with multi-channel approach;

Code check estimation steps, estimate described present frame the encoder bit rate producing when last road coding, judge whether described encoder bit rate will be over described maximal rate;

Coding parameter set-up procedure, if described encoder bit rate will be over described maximal rate, carries out next road coding after adjusting described coding parameter, until the encoder bit rate of described present frame is no more than described maximal rate.

According to bit rate control method of the present invention, the video file that described bit rate control method is encoded out meets the IPTV business video/audio encoding and decoding standard V3.0 of China Telecom.

According to bit rate control method of the present invention, the step of the coding parameter of described initialization present frame comprises:

According to the coding parameter of first order modeling initialization present frame.

According to bit rate control method of the present invention, described maximal rate setting steps comprises:

By each frame is set to maximum number bits, realize the control to described maximal rate, the described maximal rate of each frame is not less than average bit rate.

According to bit rate control method of the present invention, the described maximal rate of described present frame adopts following formula to represent:

$\frac{1}{K}{\mathrm{\&Sigma;}}_{k=\mathrm{tk}}^{k=(t+1)k}{R}_k\&le;H,t\&GreaterEqual;1$

Wherein, R _krepresent the size after k frame coding, k frame is present frame, and K represents the statistical interval of code check, every a code check of K frame statistics, the maximal rate of H for limiting.

According to bit rate control method of the present invention, the described maximal rate of described present frame adopts following formula to represent:

$H_k=\mathrm{KH}-{\mathrm{\&Sigma;}}_{i=1}^{i=n-1}{R}_{k-i}-(k-n)\stackrel{\&OverBar;}{R}$

Wherein, R _krepresent the size after k frame coding, k frame is present frame, and K represents the statistical interval of code check, every a code check of K frame statistics, and the maximal rate of H for limiting, average bit rate for Video coding.

According to bit rate control method of the present invention, described in described coded message recording step, coded message comprises R _k, D _k, Q _k, R _krepresent the encoder bit rate after k frame coding, D _krepresent the distortion of k frame, Q _krepresent the coding parameter of k frame;

Described coding parameter initialization step further comprises:

According to { (R _i, D _i, Q _i) _1≤i≤k-1and the average bit rate of Video coding the coding parameter Q of initialization k frame _k.

According to bit rate control method of the present invention, described coded message recording step further comprises:

Record had previously completed the coded message of each frame of coding, and the k frame of note input is X _k, the reconstructed frame that the coded-bit decoding of k frame is obtained is and

$D_k=\frac{1}{\mathrm{MN}}{\mathrm{\&Sigma;}}_{i=1}^M{\mathrm{\&Sigma;}}_{j=1}^N{|X_k(i,j)-{\hat{X}}_k(i,j)|}^2,j){|}^2$

Wherein, M * N is X _kdimension, X _{k (i, j)}represent X _k(i, j) individual element;

Described coding parameter initialization step further comprises:

According to { (R _i, D _i, Q _i) _1≤i≤k-1and the average bit rate of Video coding the coding parameter Q of initialization k frame _k, average bit rate computing formula as follows:

$\stackrel{\&OverBar;}{R}=E{\left[\frac{1}{k}{\mathrm{\&Sigma;}}_{k=\mathrm{tK}}^{k=(t+1)K}{R}_k\right]}^K{R}_k],$

Wherein, E[●] represent mathematic expectaion, according to first order modeling, set coding parameter Q _k, $Q_k\&Proportional;\frac{{\mathrm{\&Sigma;}}_{i<k}{R}_i{Q}_i}{\stackrel{\&OverBar;}{R}};$

Described maximal rate setting steps further comprises:

According to { (R _i, D _i, Q _i) _1≤i≤k-1and the average bit rate of Video coding the maximal rate H of the encoder bit rate of k frame is set _k;

If k=tk+n, wherein, 1≤n≤K,

$H_k=\mathrm{KH}-{\mathrm{\&Sigma;}}_{i=1}^{i=n-1}{R}_{k-i}-(K-n)\stackrel{\&OverBar;}{R},$

Wherein, K is the interval of code check statistics, H _kthe maximal rate limiting, R _k-ifor the encoder bit rate of encoded k-i frame, average bit rate for expectation;

Described coding step further comprises:

According to coding parameter Q _kwith maximal rate H _kk frame is carried out taking turns coding, and described coding carries out with multi-channel approach;

Described code check estimation steps further comprises:

Cataloged procedure to k frame is monitored, the bit estimation encoder bit rate R used according to k frame coded portion _k, judgement encoder bit rate R _kwhether will be over described maximal rate H _k;

Coding parameter set-up procedure further comprises:

If described encoder bit rate R _kwill be over described maximal rate H _k, interrupt current this road coding, upgrade Q _k← Q _k+ δ, and adjust described coding parameter Q _knext road coding of rear startup, until the encoder bit rate R of described present frame _kbe no more than described maximal rate H _k.

The present invention also provides a kind of Rate Control system based on VBR Video coding, includes:

Coded message logging modle, for record the coded message of each frame that completes coding in the past;

Coding parameter initialization module, for according to the average bit rate of described coded message and Video coding, the coding parameter of initialization present frame;

Maximal rate arranges module, for the maximal rate of described present frame is set according to rate-distortion optimization algorithm;

Coding module, for described present frame being encoded according to described coding parameter and described maximal rate, described coding carries out with multi-channel approach;

Code check estimation block, for estimate described present frame the encoder bit rate producing when last road coding, judge whether described encoder bit rate will be over described maximal rate;

Coding parameter adjusting module, if will be over described maximal rate for described encoder bit rate, carries out next road coding after adjusting described coding parameter, until the encoder bit rate of described present frame is no more than described maximal rate.

According to Rate Control system of the present invention, the video file that described Rate Control system coding goes out meets the IPTV business video/audio encoding and decoding standard V3.0 of China Telecom.

According to Rate Control system of the present invention, described coding parameter initialization module is used for according to the coding parameter of first order modeling initialization present frame.

According to Rate Control system of the present invention, described maximal rate arranges module for realizing the control to described maximal rate by each frame is set to maximum number bits, and the described maximal rate of each frame is not less than average bit rate.

According to Rate Control system of the present invention, the described maximal rate of described present frame adopts following formula to represent:

$\frac{1}{K}{\mathrm{\&Sigma;}}_{k=\mathrm{tk}}^{k=(t+1)k}{R}_k\&le;H,t\&GreaterEqual;1$

Wherein, R _krepresent the size after k frame coding, k frame is present frame, and K represents the statistical interval of code check, every a code check of K frame statistics, the maximal rate of H for limiting.

According to Rate Control system of the present invention, the described maximal rate of described present frame adopts following formula to represent:

$H_k=\mathrm{KH}-{\mathrm{\&Sigma;}}_{i=1}^{i=n-1}{R}_{k-i}-(k-n)\stackrel{\&OverBar;}{R}$

Wherein, R _krepresent the size after k frame coding, k frame is present frame, and K represents the statistical interval of code check, every a code check of K frame statistics, and the maximal rate of H for limiting, average bit rate for Video coding.

According to Rate Control system of the present invention, described coded message comprises R _k, D _k, Q _k, R _krepresent the encoder bit rate after k frame coding, D _krepresent the distortion of k frame, Q _krepresent the coding parameter of k frame;

Described coding parameter initialization module is for basis { (R _i, D _i, Q _i) _1≤i≤k-1and the average bit rate of Video coding the coding parameter Q of initialization k frame _k.

According to Rate Control system of the present invention, described coded message logging modle is for recording the coded message that has previously completed each frame of coding, and the k frame of note input is X _k, the reconstructed frame that the coded-bit decoding of k frame is obtained is and

$D_k=\frac{1}{\mathrm{MN}}{\mathrm{\&Sigma;}}_{i=1}^M{\mathrm{\&Sigma;}}_{j=1}^N{|X_k(i,j)-{\hat{X}}_k(i,j)|}^2,j){|}^2$

Wherein, M * N is X _kdimension, X _{k (i, j)}represent X _k(i, j) individual element;

Described coding parameter initialization module is for basis { (R _i, D _i, Q _i) _1≤i≤k-1and the average bit rate of Video coding the coding parameter Q of initialization k frame _k, average bit rate computing formula as follows:

$\stackrel{\&OverBar;}{R}=E{\left[\frac{1}{k}{\mathrm{\&Sigma;}}_{k=\mathrm{tK}}^{k=(t+1)K}{R}_k\right]}^K{R}_k],$

Wherein, E[●] represent mathematic expectaion, according to first order modeling, set coding parameter Q _k, $Q_k\&Proportional;\frac{{\mathrm{\&Sigma;}}_{i<k}{R}_i{Q}_i}{\stackrel{\&OverBar;}{R}};$

Described maximal rate arranges module for basis { (R _i, D _i, Q _i) _1≤i≤k-1and the average bit rate of Video coding the maximal rate H of the encoder bit rate of k frame is set _k;

If k=tk+n, wherein, 1≤n≤K,

$H_k=\mathrm{KH}-{\mathrm{\&Sigma;}}_{i=1}^{i=n-1}{R}_{k-i}-(K-n)\stackrel{\&OverBar;}{R},$

Wherein, K is the interval of code check statistics, H _kthe maximal rate limiting, R _k-ifor the encoder bit rate of encoded k-i frame, average bit rate for expectation;

Described coding module is used for according to coding parameter Q _kwith maximal rate H _kk frame is carried out taking turns coding, and described coding carries out with multi-channel approach;

Described code check estimation block, for the cataloged procedure of k frame is monitored, is estimated encoder bit rate R according to the bit that k frame coded portion is used _k, judgement encoder bit rate R _kwhether will be over described maximal rate H _k;

If described coding parameter adjusting module is for described encoder bit rate R _kwill be over described maximal rate H _k, interrupt current this road coding, upgrade Q _k← Q _k+ δ, and adjust described coding parameter Q _knext road coding of rear startup, until the encoder bit rate R of described present frame _kbe no more than described maximal rate H _k.

The invention provides the Rate Control technical scheme based on VBR Video coding, according to the coding parameter of encoding history information initialization present frame, adopt rate-distortion optimization algorithm to set the maximal rate of present frame, according to described coding parameter and maximal rate, present frame is encoded, and coding carries out with multi-channel approach, the encoder bit rate when the coding generation of last road of estimation present frame, if described encoder bit rate will be over maximal rate, after tone coded parameter, carry out next road coding, until the encoder bit rate of present frame is no more than maximal rate.Whereby, terminal plays of the present invention can not cushion, and has effectively taken into account the requirement of Rate Control and video quality two aspects, and maximal rate is limited and can make the inside sequential of player more level and smooth, is conducive to the smooth playing of video frequency program.The present invention can generate the video file that meets IPTV3.0 standard, can be used for the limited streaming media service of the network bandwidth, also can be used for comprising all internet stream media business of OTT.

Accompanying drawing explanation

Fig. 1 is the structural representation that the present invention is based on the Rate Control system of VBR Video coding;

Fig. 2 is the flow chart that the present invention is based on the bit rate control method of VBR Video coding;

Fig. 3 is the code check distribution map of first embodiment of the invention;

Fig. 4 is the code check distribution map of second embodiment of the invention;

Fig. 5 is the code check distribution map of third embodiment of the invention.

Embodiment

In order to make object of the present invention, technical scheme and advantage clearer, below in conjunction with drawings and Examples, the present invention is further elaborated.Should be appreciated that specific embodiment described herein, only in order to explain the present invention, is not intended to limit the present invention.

Fig. 1 is the structural representation that the present invention is based on the Rate Control system of VBR Video coding, described Rate Control system 100 includes coded message logging modle 10, coding parameter initialization module 20, maximal rate module 30, coding module 40, code check estimation block 50 and coding parameter adjusting module 60 is set, wherein:

Coded message logging modle 10, for record the coded message of each frame that completes coding in the past.Preferably, described coded message comprises R _k, D _k, Q _k, R wherein _krepresent the encoder bit rate after k frame (being present frame) coding, D _krepresent the distortion of k frame, Q _krepresent the coding parameter (average quantisation parameter) of k frame.

Coding parameter initialization module 20, for according to the average bit rate of described coded message and Video coding, the coding parameter of initialization present frame.Preferably, described coding parameter initialization module 20 is for according to the coding parameter of first order modeling initialization present frame.Preferably, coding parameter initialization module 20 is for basis { (R _i, D _i, Q _i) _1≤i≤K-1and the average bit rate of Video coding the coding parameter Q of initialization k frame _k.

Maximal rate arranges module 30, for the maximal rate of present frame is set according to rate-distortion optimization algorithm.Preferably, maximal rate arranges module 30 for realizing the control to maximal rate by each frame is set to maximum number bits, and the maximal rate of each frame is not less than average bit rate.

The video file that described Rate Control system 100 is encoded out meets the < < IPTV business video/audio encoding and decoding standard V3.0 > > of China Telecom.According to < < IPTV business video/audio encoding and decoding standard V3.0 > >, the available inequality group below of the maximal rate of video code flow restriction represents:

$\frac{1}{K}{\mathrm{\&Sigma;}}_{k=\mathrm{tk}}^{k=(t+1)k}{R}_k\&le;H,t\&GreaterEqual;1---\left(1\right)$

Wherein, R _krepresent the size after k frame coding, k frame is present frame, and K represents the statistical interval of code check, every a code check of K frame statistics, the maximal rate of H for limiting.

By each frame is set to maximum encoder bit rate, realize the restriction to the maximal rate of video code flow, guarantee formula (1) establishment.

Coding module 40, for according to coding parameter and maximal rate, present frame being encoded, coding carries out with multi-channel approach.

Code check estimation block 50, for estimate present frame the encoder bit rate producing when last road coding, judge whether encoder bit rate will be over maximal rate.

Coding parameter adjusting module 60, if will, over maximal rate, carry out next road coding, until the encoder bit rate of present frame is no more than maximal rate for encoder bit rate after tone coded parameter.

To the coding of each frame, can carry out one or more, until the size after present frame coding is no more than default maximal rate.

Preferably, the maximal rate of present frame adopts following formula to represent:

$H_k=\mathrm{KH}-{\mathrm{\&Sigma;}}_{i=1}^{i=n-1}{R}_{k-i}-(k-n)\stackrel{\&OverBar;}{R}$

Wherein, R _krepresent the size after k frame coding, k frame is present frame, and K represents the statistical interval of code check, every a code check of K frame statistics, and the maximal rate of H for limiting, average bit rate for Video coding.

Described coded message logging modle 10, for recording the coded message that has previously completed each frame of coding, the k frame of note input is X _k, the reconstructed frame that the coded-bit decoding of k frame is obtained is and

$D_k=\frac{1}{\mathrm{MN}}{\mathrm{\&Sigma;}}_{i=1}^M{\mathrm{\&Sigma;}}_{j=1}^N{|X_k(i,j)-{\hat{X}}_k(i,j)|}^2,j){|}^2$

Wherein, M * N is X _kdimension, X _{k (i, j)}represent X _k(i, j) individual element.

Described coding parameter initialization module 20, for basis { (R _i, D _i, Q _i) _1≤i≤k-1and the average bit rate of Video coding the coding parameter Q of initialization k frame _k, average bit rate computing formula as follows:

$\stackrel{\&OverBar;}{R}=E{\left[\frac{1}{k}{\mathrm{\&Sigma;}}_{k=\mathrm{tK}}^{k=(t+1)K}{R}_k\right]}^K{R}_k],$

Wherein, E[●] represent mathematic expectaion, according to first order modeling, set coding parameter Q _k, $Q_k\&Proportional;\frac{{\mathrm{\&Sigma;}}_{i<k}{R}_i{Q}_i}{\stackrel{\&OverBar;}{R}}.$

Described maximal rate arranges module 30, for basis { (R _i, D _i, Q _i) _1≤i≤k-1and the average bit rate of Video coding the maximal rate H of the encoder bit rate of k frame is set _k.

If k=tk+n, wherein, 1≤n≤K,

$H_k=\mathrm{KH}-{\mathrm{\&Sigma;}}_{i=1}^{i=n-1}{R}_{k-i}-(K-n)\stackrel{\&OverBar;}{R},$

Wherein, K is the interval of code check statistics, H _kthe maximal rate limiting, R _k-1for the encoder bit rate of encoded k-i frame, average bit rate for expectation.

Described coding mould 40, for according to coding parameter Q _kwith maximal rate H _kk frame is carried out taking turns coding, and coding carries out with multi-channel approach.

Described code check estimation block 50, for the cataloged procedure of k frame is monitored, the bit estimation encoder bit rate R used according to k frame coded portion _k, judgement encoder bit rate R _kwhether will be over maximal rate H _k.

Described coding parameter is adjusted mould 60, if for encoder bit rate R _kwill be over maximal rate H _k, interrupt current this road coding, upgrade Q _k← Q _k+ δ, and tone coded parameter Q _knext road coding of rear startup, until the encoder bit rate R of present frame _kbe no more than maximal rate H _k.

The present invention is directed to up-to-date IPTV3.0 standard, proposed a kind of rate control algorithm based on VBR, to realize the restriction to the maximal rate of VBR video flowing.The present invention can be used for producing the video file that meets IPTV3.0 standard, also can be used for various internet stream media application, for example, and the streaming media service based on HLS, MPEG-DASH.Other do not have the VBR encoder of maximal rate restriction relatively, and the encoder that the present invention proposes has more advantage.Suppose, with a HLS server, a video file is made to slicing treatment, each is cut into slices duration T second, and the average bit rate of video is R bps, and maximal rate is H bps.The mean size of section is RT bit, and each section the most very much not can surpass HT bit.Due in HLS agreement, video data be take to cut into slices as unit and is delivered to terminal, and the network bandwidth is normally limited, therefore, if section size too large, the transmission delay of section will be long, once and this section is not delivered to terminal in time, terminal just must be suspended and play, thereby user is experienced and had a negative impact.Therefore, slice size is limited to the continuous broadcasting that is conducive to realize terminal.In addition, if the known maximal rate of terminal is H bps, available this parameter Estimation go out to be processed each and is cut into slices the required time, these Processing tasks comprise: download, decipher, decode, the processing time of each section can change within the specific limits, therefore, maximal rate is limited and can make the inside sequential of player more level and smooth, be conducive to the smooth playing of video frequency program.

Fig. 2 is the flow chart that the present invention is based on the bit rate control method of VBR Video coding, and described method can realize by Rate Control system 100 as shown in Figure 1, comprises that step has:

Step S201, coded message recording step, record completed the coded message of each frame of coding in the past.Coded message comprises R _k, D _k, Q _k, R _krepresent the encoder bit rate after k frame coding, D _krepresent the distortion of k frame, Q _krepresent the coding parameter of k frame.

Step S202, coding parameter initialization step, according to the average bit rate of coded message and Video coding, the coding parameter of initialization present frame.Preferably, according to the coding parameter of first order modeling initialization present frame.Preferably according to { (R _i, D _i, Q _i) _1≤i≤k-1and the average bit rate of Video coding the coding parameter Q of initialization k frame _k.

Step S203, maximal rate setting steps, arranges the maximal rate of present frame according to rate-distortion optimization algorithm.Preferably, by each frame is set to maximum number bits, realize the control to maximal rate, the maximal rate of each frame is not less than average bit rate.Be more preferably, the maximal rate of present frame adopts following formula to represent:

$\frac{1}{K}{\mathrm{\&Sigma;}}_{k=\mathrm{tk}}^{k=(t+1)k}{R}_k\&le;H,t\&GreaterEqual;1$

Wherein, R _krepresent the size after k frame coding, k frame is present frame, and K represents the statistical interval of code check, every a code check of K frame statistics, the maximal rate of H for limiting.

Step S204, coding step, encodes to present frame according to coding parameter and maximal rate, and coding carries out with multi-channel approach.

Step S205, code check estimation steps, the encoder bit rate producing when last road coding of estimation present frame, judges that encoder bit rate whether will be over maximal rate, if perform step S206, otherwise process ends.

Step S206, coding parameter set-up procedure, if encoder bit rate will, over maximal rate, carry out next road coding, until the encoder bit rate of present frame is no more than maximal rate after tone coded parameter.

The video file that described bit rate control method is encoded out meets the IPTV business video/audio encoding and decoding standard V3.0 of China Telecom.Coding method provided by the invention limits the instantaneous code check of video code flow effectively, and when the network bandwidth is not less than certain critical value, terminal plays can not cushion.The present invention has taken into account the requirement of Rate Control and video quality two aspects effectively, and the in the situation that of restriction maximal rate, the quality of the video of generation does not obviously decline, and can meet the requirement of current all kinds of video traffic to aspects such as video code rate and quality.

Be more preferably, the maximal rate of present frame adopts following formula to represent:

$H_k=\mathrm{KH}-{\mathrm{\&Sigma;}}_{i=1}^{i=n-1}{R}_{k-i}-(k-n)\stackrel{\&OverBar;}{R}$

Wherein, R _krepresent the size after k frame coding, k frame is present frame, and K represents the statistical interval of code check, every a code check of K frame statistics, and the maximal rate of H for limiting, average bit rate for Video coding.

More particularly, Streaming Media dicing method of the present invention comprises 6 steps:

Step 1, yuv data enters after encoder, and encoder record had previously completed the information of each frame of coding.The k frame of note input coding device is X _k, the reconstructed frame that the coded-bit decoding of k frame is obtained is need in this step record: R _ksize after the-the k frame coding.D _kthe distortion of the-the k frame.

$D_k=\frac{1}{\mathrm{MN}}{\mathrm{\&Sigma;}}_{i=1}^M{\mathrm{\&Sigma;}}_{j=1}^N{|X_k(i,j)-{\hat{X}}_k(i,j)|}^2,j){|}^2,$

Wherein, M * N is X _kdimension, X _{k (i, j)}represent X _k(i, j) individual element.

Q _kthe coding parameter of the-the k frame (average quantisation parameter).

Step 2, encoder is according to { (R _i, D _i, Q _i) _1≤i≤k-1and the average bit rate of Video coding the coding parameter Q of initialization k frame _k, average bit rate computing formula as follows:

$\stackrel{\&OverBar;}{R}=E{\left[\frac{1}{k}{\mathrm{\&Sigma;}}_{k=\mathrm{tK}}^{k=(t+1)K}{R}_k\right]}^K{R}_k],$

E[●] represent mathematic expectaion.Encoder is set Q according to first order modeling _k,

Step 3, encoder is according to { (R _i, D _i, Q _i) _1≤i≤k-1and the average bit rate of Video coding the maximal rate H of the encoder bit rate of k frame is set _k.If k=tk+n, wherein, 1≤n≤K,

$H_k=\mathrm{KH}-{\mathrm{\&Sigma;}}_{i=1}^{i=n-1}{R}_{k-i}-(K-n)\stackrel{\&OverBar;}{R},---\left(2\right)$

Wherein, K is the interval of code check statistics, H _kthe maximal rate limiting, R _k-ifor the encoder bit rate of encoded k-i frame, average bit rate for expectation.

Provable:

● by adopting formula (2) to set H _kcan guarantee that code check is no more than maximum limit, formula (1) is permanent sets up;

● the Data Rate Distribution requirement of formula (2) coincidence rate distortion optimization.

If H _kif excessive, subsequent frame may be forced to reduce quality because available code check is not enough, if H _kif too small, can the coding quality of k frame be produced and be had a strong impact on.Formula (2) has been taken into account the requirement of code check and quality two aspects preferably.

Step 4, encoder is according to coding parameter Q _kwith maximal rate H _kk frame is carried out taking turns coding (Ye Cheng mono-road coding), and coding carries out with multi-channel approach.If the encoder bit rate obtaining surpasses H _k, Q _k← Q _k+ δ, carries out next round coding, until encoder bit rate is no more than H _k.

Step 5, monitors the cataloged procedure of k frame, the bit estimation encoder bit rate R used according to k frame coded portion _k, judgement encoder bit rate R _kwhether will be over maximal rate H _k.

Step 6, if encoder bit rate R _kwill be over maximal rate H _k, interrupt current this road coding, upgrade Q _k← Q _k+ δ, and tone coded parameter Q _knext road coding of rear startup, until the encoder bit rate R of present frame _kbe no more than maximal rate H _k.

Below provide the several propositions relevant to formula (2).

Proposition 1: if H _kby formula (2), provided, formula (1) is permanent sets up, i.e. maximal rate restriction is guaranteed.

Proof: by formula (2), $R_k\&le;H_k=\mathrm{KH}-{\mathrm{\&Sigma;}}_{i=1}^{i=n-1}{R}_{k-i},$ ?

$\mathrm{KH}\&GreaterEqual;{\mathrm{\&Sigma;}}_{i=0}^{i=n-1}{R}_{k-i}=R_k+R_{k-1}+\&CenterDot;\&CenterDot;\&CenterDot;+R_{k-n+1},\&ForAll;k,---\left(3\right)$

Wherein, meet n=k-tK, t is integer, 1≤n≤K, and the in the situation that of given k, n is unique.By formula (3), ,

$\frac{1}{K}{\mathrm{\&Sigma;}}_{k=\mathrm{tK}}^{k=(t+1)k}{R}_k=\frac{1}{K}(R_{\mathrm{tK}+K}+R_{\mathrm{tK}+K-1}+\&CenterDot;\&CenterDot;\&CenterDot;+R_{\mathrm{tK}})\&le;H.---\left(4\right)$

Proposition 2: if the H being provided by formula (3) _kmeet

Proof: establish k=tK+1, by formula (2),

Suppose for k=tk+n, k-1 ..., k-n+1=tK+1, conclusion is set up, for k+1,

$\left\{\begin{array}{c}{H}_{k+1}=\mathrm{KH}-{\mathrm{\&Sigma;}}_{i=1}^{i=n}{R}_{k+1-i}-(K-n-1)\stackrel{\&OverBar;}{R}\\ =\mathrm{KH}-{\mathrm{\&Sigma;}}_{i=1}^{i=n-1}{R}_{k-i}-R_k-(K-n)\stackrel{\&OverBar;}{R}+\stackrel{\&OverBar;}{R}\\ =H_k-R_k+\stackrel{\&OverBar;}{R}\left(4\right)\\ \&GreaterEqual;\stackrel{\&OverBar;}{R}.\end{array}\right.$

The constraint H of conclusion 2 to each frame _kdone preliminary description, shown the reasonability of formula (2), formula (2) can guarantee that the maximal rate restriction of each frame can be lower than the average bit rate of whole video.

Proposition 3: establish X ₁, X ₂..., X _kfor the K two field picture that front and back join, suppose: 1) quantified precision is enough high; 2) entropy coding is desirable;

3) X _k=f _k(X _k-1)+N _k, f _k() is compressing mapping, and N _kbe independent of X _k-1[attention], N _kindependent same distribution stochastic variable, consist of, variance is

1) it is for referencial use that k frame adopts k-1 frame in cataloged procedure, i.e. X _kcorresponding residual error is $\mathrm{\&Delta;}{X}_k=f_k\left(X_{k-1}\right){-f}_k\left({\hat{X}}_{k-1}\right)+N_k,$ $f_k\left(X_{k-1}\right)-f_k\left({\hat{X}}_{k-1}\right)$ Independent same distribution stochastic variable, consist of, variance is α _kd _k, wherein, α _k< 1, d _kit is the distortion of k frame.

Right , R _k>=R _k-1and if only if σ _k>=σ _k-1, wherein, R _kit is the code check of k frame.

Proof: by supposing,

$d_k=\mathrm{\&epsiv;}({\mathrm{\&alpha;}}_{k-1}{d}_{k-1}+{\mathrm{\&sigma;}}_k^2)e^{-{2R}_k},k=\mathrm{1,2}\&CenterDot;\&CenterDot;\&CenterDot;,K.---\left(5\right)$

? $d_k=\mathrm{\&epsiv;}{\mathrm{\&Sigma;}}_{l=1}^{l=K}\left(\left({\mathrm{\&Pi;}}_{j=l}^{i=k-1}{\mathrm{\&alpha;}}_j\right){\mathrm{\&sigma;}}_l{e}^{-2{\mathrm{\&Sigma;}}_{j=l}^{j=K}{R}_j}\right).---\left(6\right)$

To X ₁, X ₂..., X _kthe rate-distortion optimization problem of coding can be expressed as:

${\min }_{R_1,R_2,\&CenterDot;\&CenterDot;\&CenterDot;,R_K}{\mathrm{\&Sigma;}}_{k=1}^{k=K}{d}_k+\mathrm{\&lambda;}{\mathrm{\&Sigma;}}_{k=1}^{k=K}{R}_k---\left(7\right)$

Wherein, λ > 0.Without loss of generality, establish ε=1, by (6) substitution (7), and by hypothesis 1), can obtain $d_k={\mathrm{\&sigma;}}_{k+1}^2{e}^{-2R_{k+1}}.---\left(8\right)$

In conjunction with (5), (8), ${\mathrm{\&sigma;}}_k^2{e}^{-2R_k}={\mathrm{\&sigma;}}_{k+1}^2{e}^{-2R_{k+1}}.$ Therefore, R _k>=R _k+1and if only if σ _k>=σ _k+1.(9)

Proposition 3 shows the variation R of adjacent two frame code checks _k-R _k+1logarithm with complexity ratio be proportionate, if complexity changes C doubly, the absolute value of code check changes logC, and the amplitude that code check changes is less than the degree that complexity changes, therefore given average bit rate the code check R of each frame _kmeeting exists near floating.Therefore,, when distributing code check, need at least be equal to mean value for follow-up uncoded each frame reserves code check, remaining code check is as the coding upper limit H of present frame _kif the coding of present frame is not used up H _k, surplus part will be assigned to next frame.This tactful mathematical algorithm is formula (2).

In order better to describe the present invention, three specific embodiments are described below:

Embodiment 1 input film source is record class film, parameter declaration:

Fig. 3 has provided the code check distribution map after patent working, and average bit rate is 2.496Mbps, and maximal rate is 3.5Mbps, transcoding consuming time 20 minutes and 51 seconds.

Embodiment 2 input film sources are NBA Basketball Match, parameter declaration:

Fig. 4 has provided the code check distribution map after patent working, and average bit rate is 2.502Mbps, and maximal rate is 3.499Mbps, transcoding consuming time 21 minutes and 5 seconds.

Embodiment 3 input film sources are action class film, parameter declaration:

Fig. 5 has provided the code check distribution map after patent working, and average bit rate is 2.016Mbps, and maximal rate is 2.999Mbps, transcoding consuming time 10 minutes and 35 seconds.Mean P SNR is 45dB.

Above-described embodiment is implemented hardware platform used: 4 core CPU ( core ^tMi5-2500), 3.3GHz, internal memory 8GB.Experimental result shows that the present invention can do effectively to control to maximal rate, and can take into account preferably video quality.

In sum, the invention provides the Rate Control technical scheme based on VBR Video coding, according to the coding parameter of encoding history information initialization present frame, adopt rate-distortion optimization algorithm to set the maximal rate of present frame, according to described coding parameter and maximal rate, present frame is encoded, and coding carries out with multi-channel approach, the encoder bit rate when the coding generation of last road of estimation present frame, if described encoder bit rate will be over maximal rate, after tone coded parameter, carry out next road coding, until the encoder bit rate of present frame is no more than maximal rate.Whereby, terminal plays of the present invention can not cushion, and has effectively taken into account the requirement of Rate Control and video quality two aspects, and maximal rate is limited and can make the inside sequential of player more level and smooth, is conducive to the smooth playing of video frequency program.The present invention can generate the video file that meets IPTV3.0 standard, can be used for the limited streaming media service of the network bandwidth, also can be used for comprising all internet stream media business of OTT.

Certainly; the present invention also can have other various embodiments; in the situation that not deviating from spirit of the present invention and essence thereof; those of ordinary skill in the art are when making according to the present invention various corresponding changes and distortion, but these corresponding changes and distortion all should belong to the protection range of the appended claim of the present invention.

Claims (16)

1. the bit rate control method based on VBR Video coding, is characterized in that, comprises that step has:

Coded message recording step, record completed the coded message of each frame of coding in the past;

Coding parameter initialization step, according to the average bit rate of described coded message and Video coding, the coding parameter of initialization present frame;

Maximal rate setting steps, arranges the maximal rate of described present frame according to rate-distortion optimization algorithm;

Coding step, encodes to described present frame according to described coding parameter and described maximal rate, and described coding carries out with multi-channel approach;

Code check estimation steps, estimate described present frame the encoder bit rate producing when last road coding, judge whether described encoder bit rate will be over described maximal rate;

Coding parameter set-up procedure, if described encoder bit rate will be over described maximal rate, carries out next road coding after adjusting described coding parameter, until the encoder bit rate of described present frame is no more than described maximal rate.

2. bit rate control method according to claim 1, is characterized in that, the video file that described bit rate control method is encoded out meets the IPTV business video/audio encoding and decoding standard V3.0 of China Telecom.

3. bit rate control method according to claim 1, is characterized in that, the step of the coding parameter of described initialization present frame comprises:

According to the coding parameter of first order modeling initialization present frame.

4. bit rate control method according to claim 1, is characterized in that, described maximal rate setting steps comprises:

By each frame is set to maximum number bits, realize the control to described maximal rate, the described maximal rate of each frame is not less than average bit rate.

5. bit rate control method according to claim 1, is characterized in that, the described maximal rate of described present frame adopts following formula to represent:

$\frac{1}{K}{\mathrm{\&Sigma;}}_{k=\mathrm{tk}}^{k=(t+1)k}{R}_k\&le;H,t\&GreaterEqual;1$

Wherein, R _krepresent the size after k frame coding, k frame is present frame, and K represents the statistical interval of code check, every a code check of K frame statistics, the maximal rate of H for limiting.

6. according to the bit rate control method described in claim 1～5 any one, it is characterized in that, the described maximal rate of described present frame adopts following formula to represent:

$H_k=\mathrm{KH}-{\mathrm{\&Sigma;}}_{i=1}^{i=n-1}{R}_{k-i}-(k-n)\stackrel{\&OverBar;}{R}$

Wherein, R _krepresent the size after k frame coding, k frame is present frame, and K represents the statistical interval of code check, every a code check of K frame statistics, and the maximal rate of H for limiting, average bit rate for Video coding.

7. bit rate control method according to claim 6, is characterized in that, described in described coded message recording step, coded message comprises R _k, D _k, Q _k, R _krepresent the encoder bit rate after k frame coding, D _krepresent the distortion of k frame, Q _krepresent the coding parameter of k frame;

Described coding parameter initialization step further comprises:

According to { (R _i, D _i, Q _i) _1≤i≤k-1and the average bit rate of Video coding the coding parameter Q of initialization k frame _k.

8. bit rate control method according to claim 7, is characterized in that, described coded message recording step further comprises:

Record had previously completed the coded message of each frame of coding, and the k frame of note input is X _k, the reconstructed frame that the coded-bit decoding of k frame is obtained is and

$D_k=\frac{1}{\mathrm{MN}}{\mathrm{\&Sigma;}}_{i=1}^M{\mathrm{\&Sigma;}}_{j=1}^N{|X_k(i,j)-{\hat{X}}_k(i,j)|}^2,j){|}^2$

Wherein, M * N is X _kdimension, X _{k (i, j)}represent X _k(i, j) individual element;

Described coding parameter initialization step further comprises:

According to { (R _i, D _i, Q _i) _1≤i≤k-1and the average bit rate of Video coding the coding parameter Q of initialization k frame _k, average bit rate computing formula as follows:

$\stackrel{\&OverBar;}{R}=E{\left[\frac{1}{k}{\mathrm{\&Sigma;}}_{k=\mathrm{tK}}^{k=(t+1)K}{R}_k\right]}^K{R}_k],$

Wherein, E[●] represent mathematic expectaion, according to first order modeling, set coding parameter Q _k, $Q_k\&Proportional;\frac{{\mathrm{\&Sigma;}}_{i<k}{R}_i{Q}_i}{\stackrel{\&OverBar;}{R}};$

Described maximal rate setting steps further comprises:

According to { (R _i, D _i, Q _i) _1≤i≤k-1and the average bit rate of Video coding the maximal rate H of the encoder bit rate of k frame is set _k;

If k=tk+n, wherein, 1≤n≤K,

$H_k=\mathrm{KH}-{\mathrm{\&Sigma;}}_{i=1}^{i=n-1}{R}_{k-i}-(K-n)\stackrel{\&OverBar;}{R},$

Wherein, K is the interval of code check statistics, H _kthe maximal rate limiting, R _k-ifor the encoder bit rate of encoded k-i frame, average bit rate for expectation;

Described coding step further comprises:

According to coding parameter Q _kwith maximal rate H _kk frame is carried out taking turns coding, and described coding carries out with multi-channel approach;

Described code check estimation steps further comprises:

Cataloged procedure to k frame is monitored, the bit estimation encoder bit rate R used according to k frame coded portion _k, judgement encoder bit rate R _kwhether will be over described maximal rate H _k;

Coding parameter set-up procedure further comprises:

If described encoder bit rate R _kwill be over described maximal rate H _k, interrupt current this road coding, upgrade Q _k← Q _k+ δ, and adjust described coding parameter Q _knext road coding of rear startup, until the encoder bit rate R of described present frame _kbe no more than described maximal rate H _k.

9. the Rate Control system based on VBR Video coding, is characterized in that, includes:

Coded message logging modle, for record the coded message of each frame that completes coding in the past;

Coding parameter initialization module, for according to the average bit rate of described coded message and Video coding, the coding parameter of initialization present frame;

Maximal rate arranges module, for the maximal rate of described present frame is set according to rate-distortion optimization algorithm;

Coding module, for described present frame being encoded according to described coding parameter and described maximal rate, described coding carries out with multi-channel approach;

Code check estimation block, for estimate described present frame the encoder bit rate producing when last road coding, judge whether described encoder bit rate will be over described maximal rate;

Coding parameter adjusting module, if will be over described maximal rate for described encoder bit rate, carries out next road coding after adjusting described coding parameter, until the encoder bit rate of described present frame is no more than described maximal rate.

10. Rate Control system according to claim 9, is characterized in that, the video file that described Rate Control system coding goes out meets the IPTV business video/audio encoding and decoding standard V3.0 of China Telecom.

11. Rate Control systems according to claim 9, is characterized in that, described coding parameter initialization module is used for according to the coding parameter of first order modeling initialization present frame.

12. Rate Control systems according to claim 9, is characterized in that, described maximal rate arranges module for realizing the control to described maximal rate by each frame is set to maximum number bits, and the described maximal rate of each frame is not less than average bit rate.

13. Rate Control systems according to claim 9, is characterized in that, the described maximal rate of described present frame adopts following formula to represent:

$\frac{1}{K}{\mathrm{\&Sigma;}}_{k=\mathrm{tk}}^{k=(t+1)k}{R}_k\&le;H,t\&GreaterEqual;1$

Wherein, R _krepresent the size after k frame coding, k frame is present frame, and K represents the statistical interval of code check, every a code check of K frame statistics, the maximal rate of H for limiting.

14. according to the Rate Control system described in claim 9～13 any one, it is characterized in that, the described maximal rate of described present frame adopts following formula to represent:

$H_k=\mathrm{KH}-{\mathrm{\&Sigma;}}_{i=1}^{i=n-1}{R}_{k-i}-(k-n)\stackrel{\&OverBar;}{R}$

Wherein, R _krepresent the size after k frame coding, k frame is present frame, and K represents the statistical interval of code check, every a code check of K frame statistics, and the maximal rate of H for limiting, average bit rate for Video coding.

15. Rate Control systems according to claim 14, is characterized in that, described coded message comprises R _k, D _k, Q _k, R _krepresent the encoder bit rate after k frame coding, D _krepresent the distortion of k frame, Q _krepresent the coding parameter of k frame;

Described coding parameter initialization module is for basis { (R _i, D _i, Q _i) _1≤i≤k-1and the average bit rate of Video coding the coding parameter Q of initialization k frame _k.

16. Rate Control systems according to claim 15, is characterized in that, described coded message logging modle is for recording the coded message that has previously completed each frame of coding, and the k frame of note input is X _k, the reconstructed frame that the coded-bit decoding of k frame is obtained is and

$D_k=\frac{1}{\mathrm{MN}}{\mathrm{\&Sigma;}}_{i=1}^M{\mathrm{\&Sigma;}}_{j=1}^N{|X_k(i,j)-{\hat{X}}_k(i,j)|}^2,j){|}^2$

Wherein, M * N is X _kdimension, X _{k (i, j)}represent X _k(i, j) individual element;

Described coding parameter initialization module is for basis { (R _i, D _i, Q _i) _1≤i≤k-1and the average bit rate of Video coding the coding parameter Q of initialization k frame _k, average bit rate computing formula as follows:

$\stackrel{\&OverBar;}{R}=E{\left[\frac{1}{k}{\mathrm{\&Sigma;}}_{k=\mathrm{tK}}^{k=(t+1)K}{R}_k\right]}^K{R}_k],$

Wherein, E[●] represent mathematic expectaion, according to first order modeling, set coding parameter Q _k, $Q_k\&Proportional;\frac{{\mathrm{\&Sigma;}}_{i<k}{R}_i{Q}_i}{\stackrel{\&OverBar;}{R}};$

Described maximal rate arranges module for basis { (R _i, D _i, Q _i) _1≤i≤k-1and the average bit rate of Video coding the maximal rate H of the encoder bit rate of k frame is set _k;

If k=tk+n, wherein, 1≤n≤K,

$H_k=\mathrm{KH}-{\mathrm{\&Sigma;}}_{i=1}^{i=n-1}{R}_{k-i}-(K-n)\stackrel{\&OverBar;}{R},$

Wherein, K is the interval of code check statistics, H _kthe maximal rate limiting, R _k-ifor the encoder bit rate of encoded k-i frame, average bit rate for expectation;

Described coding module is used for according to coding parameter Q _kwith maximal rate H _kk frame is carried out taking turns coding, and described coding carries out with multi-channel approach;

Described code check estimation block, for the cataloged procedure of k frame is monitored, is estimated encoder bit rate R according to the bit that k frame coded portion is used _k, judgement encoder bit rate R _kwhether will be over described maximal rate H _k;

If described coding parameter adjusting module is for described encoder bit rate R _kwill be over described maximal rate H _k, interrupt current this road coding, upgrade Q _k← Q _k+ δ, and adjust described coding parameter Q _knext road coding of rear startup, until the encoder bit rate R of described present frame _kbe no more than described maximal rate H _k.