SNR scalable transcoding for video over wireless channels

We propose a novel scheme integrating transcoding, SNR scalability and error protection channel coding for video transmission over wireless channels. The target application for such error-resilient transcoding is to provide robust access to the pre-encoded high quality video server from mobile wireless terminals. The high bit rate of pre-encoded video sequence is reduced through transcoding to fit greatly the limited bandwidth of wireless links. The proposed transcoding is able to reduce both size of the video frames and the bit rate of the pre-encoded video. We also design the transcoder such that the transcoding output bitstream has the desired SNR scalability in order to guarantee a basic quality of video transmission under the hostile wireless transmission environment. With SNR scalable bitstream output, we are able to incorporate unequal error protection through channel coding for the base layer and the enhancement layers, respectively. Different rate of CRC/RCPC is adopted so as to simplify the implementation of a single channel decoder at the receiver. Experimental results show that the proposed integrated scheme of SNR scalable transcoding can guarantee the basic decoded visual quality under random and bursty error channel conditions and outperform the conventional single layer transcoding without channel coding.