Research Of Efficient Low Bit-Rate Video Coding Algorithm

With the development of the3G network and Computer technology, the wirelesscommunication technology has entered an unprecedented active period. As animportant information carrier, video has always played an increasingly important rolein wireless communications. Wireless communication technology is flexible andconvenient for erection, thus being suitable for mobile communications. But itslimited transmission bandwidth brings a great challenge to the real-time masstransmission of video information. Therefore, how to improve the video compressionefficiency while keeping higher reconstruction quality is one of the importantproblems to be further studied. In this dissertation, combining the wavelet transformtheory and human visual system, the efficient video coding algorithm is investigatedbased on the distribution characteristics of wavelet coefficients. The major researchwork includes the following two parts:(1) The research of low bit-rate static image coding algorithm. In order to obtainbetter reconstruction quality at high compression ratio, an efficient imagecompression algorithm is proposed via adaptive down-sampling and interpolation inwavelet domain. At the encoding end, the image is first transformed into waveletdomain, and the high frequency subbands are down-sampled adaptively according totheir characteristics. Then the down-sampled image is coded by the wavelettree-based Wavelet Difference Reduction (WDR) algorithm. At the decoding end, thedecoded high frequency subbands are enlarged by using an edge direction basedinterpolation method, and the reconstructed image is post processed by a strong edgebased adaptive filter to eliminate the ringing effect. The experimental results showthat compared with the spatial down-sampling based coding algorithm, the proposedalgorithm possesses higher decoding quality of images at low bit-rate, thus effectivelyalleviating the image blurring and ringing effect.(2) The research of efficient video compression algorithm. The videocompression algorithm mainly consists of the intra-frame coding module and theinter-frame coding module. In the intra-frame coding module, the first I frame in eachvideo sequence group is compressed by the efficient static image encoding algorithmmentioned above, thus providing an ideal reference frame for the reconstruction offrames remained in a video sequence group. In the inter-frame coding module, motionestimation and compensation for the adjacent video frames are first performed. Andthen fixed length coding is used for the vector information obtained after the motionestimation. Finally, the residual information generated by motion compensation iscoded by using the double WDR algorithm based on the position difference reduction.The experimental results show that the video compression algorithm has better codingperformance, and it can effectively keep the texture and detail information of theimage while possessing high coding efficiency.