Per-clip adaptive Lagrangian multiplier optimisation with low-resolution proxies

TL;DR

This paper introduces a method to significantly reduce video encoding computational costs by using low-resolution proxies and older codecs to optimize rate control parameters efficiently.

Contribution

It proposes a novel approach to optimize Lagrangian multipliers using low-resolution proxies, including older codecs, to cut encoding time and computational load.

Findings

22x reduction in computational load using 144p proxies

Effective rate control optimization with low-resolution features

Potential for further improvements in rate-distortion curve optimization

Abstract

This work focuses on reducing the computational cost of repeated video encodes by using a lower resolution clip as a proxy. Features extracted from the low resolution clip are used to learn an optimal lagrange multiplier for rate control on the original resolution clip. In addition to reducing the computational cost and encode time by using lower resolution clips, we also investigate the use of older, but faster codecs such as H.264 to create proxies. This work shows that the computational load is reduced by 22 times using 144p proxies. Our tests are based on the YouTube UGC dataset, hence our results are based on a practical instance of the adaptive bitrate encoding problem. Further improvements are possible, by optimising the placement and sparsity of operating points required for the rate distortion curves.