A joint optimization method of coding and transmission for conversational HD video service

Abstract

Multipath transmission is considered to be a promising approach for supporting data delivery of conversational high-definition (HD) video service as it is able to aggregate more transmission resources, increase the reliability of data transmission, and thereby improve the user experience of service. However, most research achievements of multipath video transmission have mainly concentrated on the efficiency of video delivery while less attention has been paid to the dynamic video bit rate adjustment which is also important to improving the quality of such video service. To take full advantage of multipath video transmission, this paper presents a joint optimization method for conversational HD video service, taking into account the linkage between video coding and transmission. In the aspect of the video coding, a region rate based perceptual coding scheme is applied by the combination usage of the characteristics of such video service, which aims to adapt the output bit rate to match the dynamic network conditions. The scheme allocates different coding frequency or rate for different regions in a video frame according to their perceptual importance dynamically, and then skips some unimportant regions and encodes the key regions. Moreover, a multipath load distribution method is adopted to optimize the transmission process which schedules the coded frames over multiple paths by employing the capacity-limited water filling (CLWF) algorithm, to meet the stringent delay requirements of conversational HD video service. Furthermore, the transmission quality of each path is assessed and the coding parameters are adjusted periodically according to the data transmission status and feedback messages. Experiments are carried out with a simulation in OMNeT++ and the results demonstrate that the proposed method performs much better than the existing schemes in terms of data transmission and playback quality.