Research On Soft Video Broadcast For Low Channel Bandwidth Receivers

With the development of the information technology the emergence of various convenient mobile terminals, wireless video broadcast has becoming one of the essential parts of our daily lives. The wireless video broadcast is more and more popular because more and more people prefer to watch sport games and real time news whenever and wherever possible. The main challenge for conventional digital video broadcasting(DVB) standard is it difficult to fully utilize each receiver’s channel characteristics and provide the best video quality for each receiver under his channel condition Some researchers proposed scalable video coding(SVC) to improve this situation. However, SVC still cannot avoid the stair effect completely. Recently, a novel wireless video broadcast framework called Soft Cast has been proposed. Soft Cast transmits video signal in the analog channel directly without quantization, entropy coding and channel coding. Soft Cast gets significant gain over the conventional digital video broadcasting and scalable video coding. However, Soft Cast depends on a special situation that the channel bandwidth matches the number of coefficients to transmit per second. The newly proposed Layer Cast method can effectively solve the problem which the channel bandwidth is larger than the video requirement and improves the coding efficiency at the same time, while what Soft Cast can do is just repeat transmission coefficient. Layer Cast is a kind of soft video broadcasting framework using hierarchical coset codi ng based on Soft Cast technology. However, there is no efficient soft video broadcast scheme for the case that the channel bandwidth is smaller than the video requirement. In view of this situation, we propose soft video broadcast for low channel bandwidth receivers.Inspired by Layer Cast, this paper proposes a coefficient combine and coefficient separation method on the basis of 3D-Soft Cast. It is mainly used to solve the channel bandwidth is smaller than the number of coefficients to transmit per second. When the channel bandwidth is smaller than the number of coefficients to transmit per second, we will combine part of the coefficients. At the decoder, we will separate those coefficients. Although it will decrease the precision of the part of the DCT coefficients, it can avoid a large number of DCT coefficients missing. Therefore, we can transfer more information to the decoder and obtain a better video quality, and make the Soft Cast adapt to the low channel bandwidth receivers and effectively improve the coding efficiency of Soft Cast in the case of narrow channel bandwidth. So this can make Soft Cast not only suitable for different channel SNR, but also can be applied to different channel bandwidth. The main techniques presented in this paper are coefficient combine and coefficient separation method based on the quantification as well as the new energy allocation methods for different band. The experimental results show that we proposed scheme soft video broadcast for low channel bandwidth receivers outperforms 0.1-0.5d B than the 3D-Soft Cast not only under the fixed bandwidth but also under the variable bandwidth.