With the mpv backend on Android, every subtitle change cost two dropped
video frames on a Fire TV Cube (36 per minute with PGS SDH subtitles, 15
with srt, #2240) and accounts for the residual drops on the Shield in #2202,
whose sessions also had subtitles on. The diagnostic build showed the drops
in pairs: a frame handed over on time, then the video thread waking 90-100
ms late. vo_mediacodec rasterized subtitles and blitted them into the OSD
Surface on that thread, and locking the Surface waits CPU-side for the
compositor - dequeue plus the release fence, one or two vsyncs, 42-83 ms at
23.976 Hz. Kodi, VLC 4 and ExoPlayer all keep subtitle output off the
presentation thread.
Move the native pin to edde746/mpv-build@88c1b135e7: the whole OSD stage
runs on its own thread, fed with the video pts at every flip, so the video
thread never waits on the compositor or on libass. Subtitles latch on the
same vsync as the video in the common case and one later when the lock has
to wait. Shield on vo=mediacodec with ASS subtitles: no video-thread stage
over 10 ms and 0 drops across five 150 s runs, subtitles verified on
screen; DTS-HD MA 4K unchanged at 0 drops. The pin keeps the #2202
diagnostics and adds VO stage timing to them. Apple, Linux and Windows
assets are unchanged.
edde746
986e769ac0