Towards much better SVT-AV1 quality-cycles tradeoffs for VOD applications

Abstract

Software video encoders that have been developed based on the AVC, HEVC, VP9, and AV1 video coding standards have provided improved compression efficiency but at the cost of large increases in encoding complexity. As a result, there is currently no software video encoder that provides competitive quality-cycles tradeoffs extending from the AV1 highquality range to the AVC low-complexity range. This paper describes methods to further improve the SVT-AV1 overall quality-cycles tradeoffs for high-latency VOD applications.The paper first presents the latest SVT-AV1 encoder evaluation results generated using the conventional convex-hullbased evaluation approach. To better account for all the content being considered in the evaluation, the combined convex hull approach is then introduced and corresponding results outlined. A more practical version of the latter approach, referred to as the restricted discrete approach, is then presented. In this approach, only few discrete quality levels that are of relevance to typical adaptive streaming applications are considered. This restriction makes the evaluation data more relevant to real adaptive streaming applications and reduces the storage requirements for the encodings generated at the identified optimal encoder settings. A fast version of the latter approach is then presented, where the generation of the optimal encoder parameters is performed using a fast encoder, and the final encodings needed in the evaluation are generated using the desired encoder based on the identified optimal encoder parameters. These optimizations result in a complexity reduction by up to a factor of 10 for at most 1.5% loss in BD-rate.

Enhancing SVT-AV1 with LCEVC to improve quality-cycles trade-offs and enhance sustainability of VOD transcoding

“…Over the past year, SVT-AV1 development has focused on both extending the compression efficiency vs complexity trade-offs with a focus on VOD applications and adding support for low-delay applications. A number of improvements in SVT-AV1 have been introduced since the evaluation work reported in [1]. The main changes included the following:…”

“…To illustrate the above issue, we compared the relative efficiency of SVT-AV1 (preset 11) vs. x264 (preset faster, which according to [1] had a comparable encode time of SVT-AV1 M11) at 1080p and 540p resolutions. At 1080p resolutions, SVT-AV1 outperforms x264 across the tested range, converging only at very high data rates.…”

“…This section presents the evaluation results of the LCEVC enhancements to SVT-AV1, x264 and x265 encoders using the combined (continuous, unrestricted) DO approach discussed in paragraphs 3.2 in [1]. Rather than simply averaging BD-rates across shots, we started from the combined approach to focus the evaluation on a scenario that better reflects expected gains in practical applications.…”

“…The first part of the paper targets the evaluation of LCEVC when used to improve the quality-cycles trade-offs of SVT-AV1, x264 and x265 in VOD use cases. The latest versions of the SVT-AV1, x264, and x265 encoders were tested within an LCEVC framework using different variants of the convex-hull Dynamic Optimizer (DO)-based evaluation methodologies [1] [2] [3]. The LCEVC-enhanced encoders are first evaluated using the combined DO approach and are compared against the native versions of the same encoders.…”

“…The core idea of LCEVC is to use any video coding standard (such as AV1) as a base encoder at a lower resolution, and then reduce artifacts and reconstruct a full resolution output by combining the decoded low-resolution output with up to two low-complexity reconstruction enhancement sub-layers of the residual data. This paper starts by applying LCEVC to SVT-AV1 [5], as well as x264 [6] and x265 [7], while using two of the approaches presented in [1] to evaluate the resulting compression efficiency vs cycles trade-offs. The paper then discusses the benefits of LCEVC towards higher playback speed and lower battery power consumption when using AV1 software decoding.Results show that, with fast-encoding parameter selection using the discrete convex hull methodology, LCEVC improves the quality-cycles trade-offs for all the tested codecs and across the full complexity range.…”