| H.264 is a new video coding standard. It's developed by united video group JVT which consists of Video Coding Experts Group(VCEG) of ITU-T and Movable Image Coding Experts Group(MPEG)of ISO/IEC. It uses many new coding techniques and can improve coding efficiency obviously.In recent years, with the rapid development of communication technology, as well as individual users on the new communications needs of the business growing, multimedia communications to be especially rapid development of video communications. However, due to tremendous volume of data and video information in the transmission must be carried out before compression to reduce the amount of information transmission channel. After the video compression coding information in the course of transmission is highly susceptible to channel conditions and other factors from the impact of error. Therefore, the adoption of effective anti-BER video coding technology to ensure reliable transmission of information is very necessary.Isolation Theory traditional assumptions source coding and channel coding complexity can be unlimited increase in coding design neglected some of the practical design of the design principle of the separation of the efficiency of the system may be lower, and this has stimulated a more effective joint source and channel coding methods of exploration and research. Joint Source-channel coding based on the state channel, weigh source coding and channel coding rate rate on the impact of distortion in the source and channel coding and distribution of redundancy, through a joint strategy in both coding appropriate allocation of resources, so as to achieve the best end-to-end results to achieve the best overall performance.This paper puts forward an unequal error protection plan. The strategy mainly researches on how to partition the information created from source coder, and uses the corresponding unequal error protection to make the important date bits be seized of more error renew ability, the aim is to obtain the best whole performance. The paper proposes that according to effect of the different parts of the code stream created from H.264 coder to the video, we can use the different error protection according to different bits. Those bits that are important to renew video use higher channel protection (use more intendance bits to protect information code stream), otherwise those bits that are not very important to renew video use lower channel protection (not very important means that if those bits are destroyed, it will not bring very severe influence or can renew those content with some compensate method). In DP mode, macro-block dates in a slice are separated into A,B,C three parts to transmit respectively. A date includes the most important information in decoding video; B date is more important than C dates; C date is the lowest important. Besides the three dates have these connections: B and C date are independent, but the decoding of those date must depend on A date. According to this partition mode, coder can use unequal error protection to different date selectively in order to guarantee the most important information can be received if the channel is not good. With the FEC protection towards H.264 code stream, we use FEC1 code that has the more ability to correct the error and redundancy to protect the most important dates, including SPS,PPS and A date, and use FEC2 code that has the less ability to correct the error and redundancy to protect the less important dates, including B and C date. With this unequal error protection, we guarantee the most important information correct renew under high error condition in order to obtain the better decoding effect.The experimental results show that the video transmission in the course of error ranging from protection mechanisms implemented, although an increase of redundancy, but it could be improved to a certain extent, the transmission system performance, improve video streaming channel in the worst anti-environment BER capacity. Stationary random error channel and restore the image PSNR-Y maximum value increased 8.73 dB at least 4.49 dB increase, objective quality improvement is obvious, and UEP Without UEP system than the performance gain access channel error probability with the increase increase. Gauss channel and restore the image PSNR-Y maximum value increased 9.36 dB, at least 2.71 dB increase. Restoration of images from the subjective feeling, the adoption of error ranging from the protection of the restoration of the subjective image quality has been greatly enhanced. The results can be seen through the introduction of the coding strategy UEP, although an increase of redundancy, but significantly improved the quality of the decoding of the video.After researches on unequal error protection scheme, the paper put forward a joint source channel coding strategy further aim at wireless channel's characteristic that its bandwidth is limited and error is high. The thought is that channel coding must acclimatize itself to channel's state, matching H.264 source coder's QP,the packet's length to FEC code's rate. When the channel is not good, match coarse QP to less FEC code's rate. If increasing the value of QP, the code's rate is reduced, saving the source's bits; these bits can be used to reinforce the ability of FEC. The other way round, when the channel is good, match exquisite QP to higher FEC code's rate, used to transmit high quality video. Combining the match strategy with unequal error protection, we can achieve better balance with reliability and validity.The experiments results indicate that under high error environment using joint source channel coding can wipe off error effectively and also has better system performance than not using joint mechanism. Under high error environment, the PSNR Y at decoder receives improvement at high range. This can guarantee the video information reliable transmission and also can utilize the channel's limited bandwidth source effectively.In short, the joint source-channel video transmission technology in the protection of information, is an effective method, especially in bad channel conditions of decreased slowly, and with obvious superior system performance. Can guarantee reliable transmission of video information can be effective use of limited channel bandwidth resources. With limited redundancy to achieve an effective error protection, access to the consumption of redundancy and error a better balance between protections. |
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