Task-based parallel H.264 video encoding for explicit communication architectures

Future multi-core processors will necessitate exploitation of fine-grain, architecture-independent parallelism from applications to utilize many cores with relatively small local memories. We use c264, an end-to-end H.264 video encoder for the Cell processor based on x264, to show that exploiting fine-grain parallelism remains challenging and requires significant advancement in runtime support. Our implementation of c264 achieves speedup between 4.7× and 8.6× on six synergistic processing elements (SPEs), compared to the serial version running on the power processing element (PPE). We find that the programming effort associated with efficient parallelization of c264 at fine granularity is highly non-trivial. Hand optimizations may improve performance significantly but are limited eventually by the code restructuring they require. We assess the complexity of exploiting fine-grain parallelism in realistic applications, by identifying optimizations of c264 and the effort they require.