Wavefront Parallel Processing for AV1 Encoder

Abstract

The emerging AV1 coding standard brings even higher computational complexity than current coding standards, but does not support traditional Wavefront Parallel Processing (WPP) approach due to the lacking of syntax support. In this paper we introduced a novel framework to implement WPP for AV1 encoder that is compatible with current decoder without additional bitstream syntax support, where mode selection is processed in wavefront parallel before entropy encoding and entropy contexts for rate-distortion optimization are predicted. Based on this framework, context prediction algorithms that use same data dependency model as previous works in H.264 and HEVC are implemented. Furthermore, we proposed an optimal context prediction algorithm specifically for AV1. Experimental results showed that our framework with proposed optimal algorithm yields good parallelism and scalability (over 10x speed-up with 16 threads for 4k sequences) with little coding performance loss (less than 0.2% bitrate increasing).