[MPlayer-users] mplayer alsa behavior playing video vs audio.

[Reimar Döffinger]

On 02.05.2014, at 17:30, Andy Furniss <adf.lists at gmail.com> wrote:
> This is just out of curiosity really, not an mplayer bug.
> 
> I've just got a new GPU and there is am audio over HDMI bug (already reported by xbmc users).
> 
> The thing is I can't reproduce it when playing video with s/w decode.
> 
> The bug is garbled sound - mplayer does produce with -
> 
> audio file
> video file -vc null (but not -vo null)
> video file uvd decode.
> 
> The outputs and alsa hw params look the same for working and not working cases.
> 
> So, the question is what is the difference from mplayers point of view when playing to alsa
> 
> mplayer -ao alsa:device=hw=1.3 a wav file
> mplayer -ao alsa:device=hw=1.3 a video with -vc null
> 
> and
> 
> mplayer -ao alsa:device=hw=1.3 a video
> 
> any thoughts, eg. does the timing come from somewhere else?

When playing audio-only, MPlayer will query the driver for how much time it has data buffered and sleep for (more or less) that amount of time to avoid unnecessary power consumption.
When video is enabled, it has to always wake up for new frames.
However the results with UVD make no sense for that explanation, in fact it makes it more sound like e.g. a reclocking issue.
Did you try running e.g. glxgears or some other 3D program while playing an audio-only file?