[mythtv] frame dropping with ticket #5900 (AC3-enc) + #6279 (soft-volume)

[Mark Kendall]

2009/7/20 Markus Schulz <msc at antzsystem.de>:
> hello,
>
> i've much trouble with heavy judder cause of frame dropping.

Can you clarify what you mean here? Are you seeing frame drops
generally or is this just 'judder' following a skip/seek/etc as the
player settles down again.

> I'm using trunk with vdpau (2xadvanced) with a 9400GT (latest stable
> nvidia-cs) with mostly SD.

Which driver are you using?

> At first i think the videoout_vdpau should return true on
> hasHWAcceleration() to prevent additional juddering (see void
> NuppelVideoPlayer::AVSync(void) function):
>

<snip>

> This changes the Frame drops to skipping A/V wait (less of judder).
>
> But i don't understand why i still got a lot of:
> 2009-07-19 18:31:03.311 NVP(1): Video is 3.22685 frames behind audio
> (too slow), skipping A/V wait.
> 2009-07-19 18:31:05.891 NVP(1): Video is 3.20082 frames behind audio
> (too slow), skipping A/V wait.
> 2009-07-19 18:31:05.911 NVP(1): Video is 3.1756 frames behind audio (too
> slow), skipping A/V wait.
> 'video_output' mean = '40207,36', std. dev. = '25365,55', fps = '24,87'
> 2009-07-19 18:31:07.060 NVP(1): Video is 3.02257 frames behind audio
> (too slow), skipping A/V wait.
> 2009-07-19 18:31:07.064 NVP(1): Video is 3.17943 frames behind audio
> (too slow), skipping A/V wait.
> 2009-07-19 18:31:07.070 NVP(1): Video is 3.0658 frames behind audio (too
> slow), skipping A/V wait.
> 2009-07-19 18:31:09.553 NVP(1): Video is 3.2014 frames behind audio (too
> slow), skipping A/V wait.
> 2009-07-19 18:31:09.556 NVP(1): Video is 3.26355 frames behind audio
> (too slow), skipping A/V wait.
> 2009-07-19 18:31:09.570 NVP(1): Video is 3.07265 frames behind audio
> (too slow), skipping A/V wait.
> 'video_output' mean = '39984,38', std. dev. = '22128,54', fps = '25,01'

As noted in NuppelVideoPlayer::AVSync, hasHWAcceleration doesn't
return true for vdpau because VDPAU doesn't actually skip the av wait.
VDPAU always waits for the next vertical retrace when showing a frame
- hence I'm not surprised that after your patch the video is always
behind the audio, as it never gets a chance to catchup.

> i can reproduce the problem with the following setup:
> - softvolume enabled (mixer = software)
> - internal volume completely disabled
> - internal volume enabled with alsa:default as mixer (useless cause of
> ac3-enc and passthru)
>
> and all interlaced stuff or HD-1080p stuff. Progressive avi with 25FPS
> shows no frame drops.
>
>
> the problem arrived with ffmpeg sync (approx. cause i've build no
> version after ~20650 and before ffmpeg sync).
>
> Can someone help me to analyze this problem? Which change can introduce
> such a behavior?

r20773 might be relevant, depening on which revision you're using and
your settings.

rgds

Mark