[alsa-devel] snd-hda-intel+dmix: Disabling power save doesn't work
a.nielsen at shikadi.net
Tue May 8 12:19:56 CEST 2012
>> This works as expected when stopping playback, but if I only *pause* playback
>> then the signal drops almost exactly one second later, no matter what
>> "powersave" is set to. So of course then resuming playback means I lose a
>> couple of seconds of audio while the amplifier re-syncs to the SPDIF signal.
> Check the powersave option value when this happens. The system such as
> power-utils script may change the parameter by itself.
Thanks for the quick reply! I checked this and there was no change. Before,
during and after playback, the module options haven't changed.
>> It doesn't happen if I use hw:0,1 as the output device (the SPDIF signal keeps
>> going, even when paused) but as soon as I change the output device to dmix
>> then the signal drops whenever the audio is paused.
> It's weird becauase the pause function isn't implemented in dmix at
> all. Thus it's application's own behavior how to pause the stream.
> Usually the application stops the stream like a normal stop then
> restarts from the position manually.
Upon more experimentation I have noticed that the SPDIF signal also drops out
during silent sections of audio. If there's a 100% quiet part of a film or
movie I'm watching with mplayer or another program, during the silent sections
the signal drops out and I again miss a few seconds when they start speaking
I now realise this has been happening for a long time, as I created a .wav
file containing 60 seconds of very quiet white noise a few years ago. I play
this in a loop in the background whenever I want to prevent the powersave from
kicking in in the silent parts when I'm watching a movie.
It seems that this happens regardless of the output device - hw:0,1 or dmix
both drop out during silent sections. I have double-checked during pausing
though, and as before hw:0,1 keeps going during a pause while dmix drops out.
Is dmix closing its output PCM stream when all input streams are paused or
silent? I'm not sure what else would cause this behaviour.
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