Research On Stereo Video Communication Based On Unequal Error Protection Scheme Of LDPC Code

Stereo video, which can provide viewers with the benefits of added realism and improvedscene understanding, will be widely used in the fields of 3D TV, immersive video conference,telecommunication, remote control etc. Stereo video communication is one of the main tasks in astereo video application system. However, the large amount of stereo video data and the error pronecharacteristic of limit bandwidth channel are two major obstacles for a stereo video communicationsystem. This thesis concerns on the problems of stereo video communication in the limit bandwidthadditive white gaussian noise (AWGN) channels. In order to increase the communicationperformance, heighten the reconstruction effect of stereo video at the receiver, some keytechnology was used.For source encoding, a weighted joint inter prediction mode based on H.264 was proposed.For channel encoding, a class of structured irregular low-density parity-check (LDPC) code withhigh performance and low complexity was put forward, and an improved BP decoding algorithmwas given. Based on the characteristic of stereo video stream, unequal error protection (UEP) basedon joint source-channel coding (JSCC) was used according to the importance to reconstruction.Simulation results show that the proposed algorithm improves the stereo video coding performance,enhances the error correction ability of channel coding, and decreases the complexity of BPdecoding, increases the PSNR and subjective effect of the reconstructed image.Firstly, an H.264 based stereo video coding scheme was put forward. It uses the advancedpredictive method of H.264 to eliminate the spatial, temporal and inter-view co-relation in stereovideo. Variable size block is employed in disparity prediction and was integrated withmulti-prediction mode of H.264 protocol. To improve coding performance, according to thecharacteristic of motion prediction and disparity prediction, a weighted joint prediction mode wasproposed. It not only compares the motion prediction and disparity prediction, but also comparesthe motion prediction, disparity prediction and the weighted joint prediction. Then, the predictionmode which leads the least prediction distortion is chosen as inter prediction mode. Experimentalresults show that the proposed coding scheme improves the stereo video coding performance.Secondly, to deal with the error prone characteristic of coded video stream in unreliablechannels, a class of structured irregular LDPC codes with high performance and low complexitywas proposed in this paper, First, a global matrix M with a triangular plus dual-diagonal form basedon improved extended irregular repeat-accumulate (IeIRA) method was designed. Then each '1' in the global matrix M was replaced by a identity permutation matrix and each '0' was replaced by anull matrix to generate the parity check matrix H. Test results show that the proposed method canachieve very good performance, extremely low error floor with linear encoding complexity byselecting proper cyclic shift coefficient of each identity permutation matrix.Then, in order to solve the high complexity, low decoding efficiency problem of beliefpropagation (BP) decoding algorithm, a low complexity BP decoding scheme was put forward. Inthe proposed decoding scheme, a differentiate rule based on lawless check number and pseudoposterior probability was used to evaluate every bit's reliability before each step of iteration. Thebits with high reliability need not to be updated in the next iteration. Simulation results show thatthe proposed BP decoding algorithm can reduce the computational load, increase the decodingefficiency with only a little performance decrease.At last, in order to improve error resilient ability and transmission efficiency for stereo videocommunication over limit bandwidth error prone channels, a JSCC scheme based on UEP was putforward. According to the characteristic of coded stereo video, the stereo video stream was dividedinto two parts with different level of significance. Then, different level protection was used todifferent significant video stream. High degree bit nodes within an irregular LDPC code have morepowerful error-correcting ability than that of low degree ones and can provide UEP. So in this paper,two kinds of UEP scheme were put forward, one used the different correction ability of differentdegree bit nodes in one LDPC code, the other used irregular LDPC code with different rates.Simulation results show that the proposed JSCC scheme improves the reconstructed image PSNRand subjective visual quality.