H.264/AVC-to-SVC temporal video transcoder for video broadcasting in wireless networks

摘要

Over the last few decades multimedia usage has changed dramatically, with networks and terminals of diverse bandwidths and capabilities coexisting. To ensure a good quality of experience, this diverse environment requires adaptability of the video stream. If video streams were compressed using Scalable Video Coding (SVC) schemes, they would be able to adapt to these heterogeneous networks and a wide range of terminals. However, since the majority of multimedia contents are compressed using H.264/AVC, they cannot benefit from this scalability. This paper makes some proposals for improving a temporal H.264/AVC-to-SVC video transcoder so that it can convert an H.264/AVC bitstream without scalability to scalable bitstreams with temporal scalability. The idea behind the proposed transcoder is to accelerate interprediction, focusing on reducing the coding complexity of the mode decision and motion estimation tasks of the encoder stage by using information available after the H.264/AVC decoding stage. To accelerate the mode decision task, a decision tree for narrowing down the Macroblock (MB) types to be checked by the SVC encoder has been developed. On the other hand, to accelerate the motion estimation task, a reduced area is created dynamically for every MB and sub-MB. Moreover, time savings increase considerably when both proposals are adjusted to work together, as opposed to doing so in an isolated way. The results show that when our joint proposal is applied, the complexity is reduced by 98 % while maintaining coding efficiency.