Parallelization of Kvazaar HEVC intra encoder for multi-core processors

This paper introduces key parallelization strategies of our Kvazaar HEVC intra encoder for multicore processors. The schemes implemented in Kvazaar are 1) tiles; 2) Wavefront Parallel Processing (WPP); and 3) picture-level parallel processing. Kvazaar is the only practical open-source HEVC encoder that supports all these schemes. In addition, its rate-distortion-complexity characteristics are superior to other public implementations in all-intra (AI) coding. Our experiments with high-quality encoder presets show that a C implementation of Kvazaar is 19% faster than the corresponding implementation of x265 for the same coding efficiency with 8 threads and 38% faster with 16 threads. With the high-speed presets, Kvazaar improves coding efficiency by 4.5% while being twice as fast as x265. The high-speed preset of Kvazaar obtains almost the same coding efficiency as the high-quality preset of f265 while being 24 times faster when 16 threads are used.