Re: kern/54230: mpv drops video frames with `--ao=oss' (probably after isaki-audio2 merge)

[Tetsuya Isaki <isaki%pastel-flower.jp@localhost>]

> 	Probably since isaki-audio2 merge mpv started to drop several frames
> 	making video playback hard to follow.

Thank you for your detailed report!

It is not a new problem.
Please specify --autosync=30 for mpv.  It's suggested by mpv manpage.
Our audio driver + libossaudio layer have not implemented "a perfect
audio delay measurement" mechanism that mpv says(or requires).

On 8.99.37 (before merge) with hw.hdafg0.latency=128 (default),
 mpv                -> Dropped: 740
 mpv --autosync=30  -> Dropped: 3..4

On 8.99.37 with hw.hdafg0.latency=16,
 mpv                -> Dropped: 0      [1]
 mpv --autosync=30  -> Dropped: 0
 
On 8.99.41 (after merge) with hw.audio0.blk_ms=40 (default),
 mpv                -> Dropped: 1906   [2]
 mpv --autosync=30  -> Dropped: 0..1

On 8.99.41 with hw.audio0.blk_ms=10,
 mpv                -> Dropped: 0
 mpv --autosync=30  -> Dropped: 0

Your report compared case [1] and [2].  But this table shows
the different facts.

(And there is one more note.  The previous audio driver and audio2
have different relationship between blocksize and latency.  So you
don't compare them simply.)

Thanks,
---
Tetsuya Isaki <isaki%pastel-flower.jp@localhost / isaki%NetBSD.org@localhost>