ref: 31228b3595d17e8323aede7bb364bd731c192820
parent: e09e99aa14f10956ea3846982c5c815a18d5863e
author: Paul Wilkins <paulwilkins@google.com>
date: Wed Jun 20 13:21:49 EDT 2018
Improved coding on slide show content. This patch adds in detection of slide show content and allows for coding of long GF only groups up to a length of 240 frames rather than coding a large number of shorter ARF groups that gradually lower the Q. In test samples this patch gave rise to a substantial improvement in overall psnr and a drop in data rate. In some cases the average psnr fell, however, with the boost and minQ values set as they are. This is to be expected because average psnr is dominated by the best frames in the sequence and previously a relatively poor key frame could be followed by progressively better alt refs. For example a key frame at q7.5 but subsequent alt refs improving it to lossless. For slides displayed for several seconds, savings of >= 20% (or commensurate quality gains) are likely. This patch allows for long GF groups in static sections before and after complex transitions (e.g. fades) with one or more normal ARF groups during the transition. However, it enforces a single "normal" length GF group after the transition before any extended group is allowed. The reason for this is that the ARF that spans the transition my not have a very high quality and hence may not be a good GF for the long static section that follows. Change-Id: I66cc404c3b85e87dae9829b49d9d631cbf04e037