In bug 1258870 I changed the media code so that we dropped all late video
frames. Without this, our A/V sync was broken when the decode was struggling
to keep up, and we weren't reporting dropped frames when the decode couldn't
keep up, and so players couldn't adapt to a bitrate which the decode could keep
up on.
However, dropping all late frames broke talos tests which relied on the old
behaviour of us rendering video frames that were late. So this patch adds a
pref to cause the frame dropping code to not drop the last frame in the
queue, so there will always be something for the compositor to composit. This
means talos will once again be able to test how fast it can composit frames
that aren't supposed to be drawn.
The pref is media.ruin-av-sync.enabled.
It defaults to false.
MozReview-Commit-ID: J3VvpzoDRmI
--HG--
extra : rebase_source : ee24f37f201ef266e0894ca2c5afda498629ec0a
This is a partial reversal of bug 1230338. We can't distinguish frames that are never composited because the media element is hidden from the frames genuinely dropped due to machine slowness. So until we can distinguish them, let's not report them as dropped.
MozReview-Commit-ID: ERV8Luaxp3F
