tree 338731db5854a07ff7687b41d5e190bb646b7b36
parent 9284af62c37d62117c007d100e0442f144220ab8
author Urvang Joshi <urvang@google.com> 1542756534 -0800
committer Urvang Joshi <urvang@google.com> 1542847127 +0000

Rate-control bugfix for golden frame in CQ mode.

Earlier, here is what was happening for the golden frame in CQ mode:
- The active_best_quality was set to 'rc->arf_q'
- But in some cases, 'rc->arf_q' was never really set (e.g. when
cpi->new_bwdref_update_rule == 0), and so it still had the initial value 0.
- This meant that for easy clips / high target bitrates, golden frame
ended up choosing q = 0 (or some value close to 0), and so it was really
large.

This behavior was simply a bug. 'active_best_quality' should be set from
'rc->arf_q' only for internal ARFs with cpi->new_bwdref_update_rule == 1
(as we would have set the 'rc->arf_q' value already by then, when we
encoded the ARF frame before this internal ARF).

This patch corrects this behavior, and also adds a relevant assertion to
ensure that the behavior is tested.

In an extreme case, for example, here is how golden frame compares:

Before: 328776 bytes, PSNR = 100 (lossless)
After: 680 bytes, PSNR = 56.753

STATS_CHANGED for CQ mode

Change-Id: I47697768dda1196bd0a95eec105179b332dd9222