Toward fast Wyner-Ziv video decoding on multicore processors

Abstract

The Wyner-Ziv video coding paradigm provides a framework where most of the complexity is moved from the encoder to the decoder. In this way, Wyner-Ziv coding efficiently supports multimedia services for mobile devices which have to capture, encode and send video. However, the complexity of the decoder is quite high and it should be reduced. This work presents several parallel Wyner-Ziv decoding algorithms aimed at reducing this high complexity. Considering the fact that technological advances provide us new hardware which supports parallel data processing, these algorithms efficiently distribute the burden of the complexity over the number of cores which are available in the architecture. Particularly four parallel approaches have been proposed and analyzed. In the first parallel approach, the each bitplane of a frame could be decoded in a parallel way by a different core, achieving a time reduction of 33.21 % in average, although it depends on the number of bitplanes used. The second approach proposes a spatial distribution of each frame, avoiding dependences between bitplanes and then obtaining a time reduction of 67 % in average. The third approach executes each GOP in a parallel way, avoiding all synchronization dependences and achieving 71 % of time reduction in average, although the maximum performance is reached when the key frame buffer is full. Finally, the last approach distributes the burden of complexity over two levels, namely GOP and frame, in order to obtain the advantages of both: a negligible rate distortion penalty based on the GOP approach, and a low delay introduced by the spatial distribution approach. By using this parallel approach, the decoding time is reduced up to 76 %. In addition, by using parallel decoding, 60 % of the energy consumption is saved. The proposed methods are scalable for any multicore processor architecture and adaptable for different Wyner-Ziv decoding schemes.