Study On Methods Of Joint Source Channel Coding

Joint source channel coding combines source coding with channel coding which are carried out separately in traditional coding methods according to the characters of the input video sequences and the transmission channel to implement joint source channel coding ,and make sure the overall performance of the system can be as good as possible. As the joint source channel coding synthetically considers the source coding together with the channel coding, it can effectively reduces the distortion of the entire system and achieves better reconstructed quality.Firstly, theories of source coding and channel coding are introduced briefly in this paper makes. After that, the basic principles and common methods of joint source channel coding are summarized.Then, the joint source channel coding scheme based on unequal error protection is discussed in detail. Importance of different parts in a bit stream after source coding is different, so we can use different channel protection schemes on different parts of the bit stream. As a result, a coding scheme based on the macro block importance model is given. This scheme analyzes the importance of the macro blocks and protects them with Turbo codes of different rates. Experimental results show that this scheme can achieve better video reconstructed performance compared with other schemes.Finally, the joint source channel coding scheme based on rate-distortion model is discussed in detail. According to H.264 encoder's rate-distortion characteristics, a rate-distortion model is introduced based on a large number of experiments in this paper. Combining the rate-distortion model with the error resistant characters of the Turbo codes, this paper analyzes the end to end distortion and shows a joint source channel coding scheme based on the rate-distortion model. This scheme allocates the bandwidth of the source coding and the channel coding according to the present channel conditions to minimize the end to end distortion. Experimental results show that this scheme makes good use of the total bandwidth and can optimize the reconstructed quality of the video sequence compared with the fixed coding schemes.