Scalable Video Bit Rate Control Algorithm Research

With the fast growing of today’s communication and network technology and videocoding technology, the transmission of video bit stream is nolonger restricted to fixednetwork bandwidth. The diversity of terminal under different applications has also putforward different requirements on video coding technology, which says not onlysimply in improving the compression ratio but also in improving the adaptability todifferent terminal and network environment. In this case, the ITU-T and ISO/IEC jointVideo team proposes a video coding standard based on h.264/AVC video codingstandard which is called the Scalable Video Coding Extensions of H.264(ScalableVideo Coding: SVC). SVC provides scalability in temporal, spatial and quality, andscalability of a combination of these three fields. Besides, in SVC, a video sequencecan code into one base layer and several enhancement layers. So according to differentterminal and network bandwidth, the most suitable layers are chosen and beingdecoded.First, introduce the features of temporal, spatial, quality scalability and the corecoding tools in SVC briefly. Furturemore, discuss the rate control algorithms and itsprogress, and emphasis on presenting the rate control algorithm of H.264.Second, describe and analysis the Hierarchical B coding structure, which is one ofthe tools to realize temporal scalability, and propose a rate control algorithm forhierarchical B coding structure. On the account of the constant coding quality, allocatebits evenly between GOPs (Group of Picture). On the account of the contribution ofcoding frames, propose an adaptive bit allocation on frame level based on codingcomplexity. The test results not only reveal that the error between the actual bit rateand the target bit rate is not beyond2%, but also testify that in the whole codingprocess, the quality of the coding frames is relatively stable.In addition, for spatial scalability, propose a bit allocation algorithm on both sides.One is a weight-based approach in macro, which allocates bits to a specific frame. Theother one is an approch based on the MAD (Mean Absolute Difference) ratio of coded frames in micro, which use to adjust bit allocations. Aiming at the scalable videocoding of the temporal and spatial combination, propose a temporal and spatialretractable joint rate control algorithm. Test results show that iterate once of codingprocess could realize bit rate control of coded bit stream on a temporal and spatialscalability of combination. Compared with FixedQPEncoder tool, which provide byJSVM, the coding efficiency of proposed algorithm is greatly improved.Finally, propose an adaptive layer control algorithm on the SVC video transport andplayback system. The purpose of this algorithm is to ensure video playbackcontinuously in time varying network environment. The realization of the algorithm isbased on the transmission rate of program stream and the size of the cache data. Viathe real time monitoring of the cache storage condition, it choose the most suitablelayer for playing. Improve the utilization rate of the network bandwidth.