A scalable parallel H.264 decoder on the cell broadband engine architecture

Abstract

The H.264 video codec provides exceptional video compression while imposing dramatic increases in computational complexity over previous standards. While exploiting parallelism in H.264 is notoriously difficult, successful parallel implementations promise substantial performance gains, particularly as High Definition (HD) content penetrates a widening variety of applications. We present a highly scalable parallelization scheme implemented on IBM's multicore Cell Broadband Engine (CBE) and based on FFmpeg's open source H.264 video decoder. We address resource limitations and complex data dependencies to achieve nearly ideal decoding speedup for the parallelizable portion of the encoded stream. Our decoder achieves better performance than previous implementations, and is deeply scalable for large format video. We discuss architecture and codec specific performance optimizations, code overlays, data structures, memory access scheduling, and vectorization.