Efficient Multi-Rate Video Encoding for HEVC-Based Adaptive HTTP Streaming

Adaptive HTTP streaming requires a video to be encoded at multiple representations, that is, different qualities. Encoding these multiple representations is a computationally complex process, especially when using the recent High Efficiency Video Coding (HEVC) standard. In this paper, we consider a multi-rate HEVC encoder and identify four types of encoding information that can be reused from a high-quality reference encoding to speed up lower quality-dependent encodings. We show that the encoding decisions from the reference cannot be directly reused, as this would harm the overall rate-distortion (RD) performance. Thus, we propose methods to use the encoding information to constrain the RD optimization of the dependent encodings so that the encoding complexity is reduced while the RD performance is kept high. We additionally show that the proposed methods can be combined, leading to an efficient multi-rate encoder that exhibits high RD performance and substantial complexity reduction. Results show that the encoding time for 12 representations at different spatial resolutions and signal qualities can be reduced on average by 38%, while the average bitrate increases by less than 1%.