[alsa-devel] Disable conversions
perex at perex.cz
Wed Nov 21 16:16:21 CET 2007
On Wed, 21 Nov 2007, Takashi Iwai wrote:
> At Wed, 21 Nov 2007 12:40:54 +0100,
> I wrote:
> > At Tue, 20 Nov 2007 01:51:51 +0100,
> > Lennart Poettering wrote:
> > >
> > > 4) If I open an audio device with "plughw:" i can disable the software
> > > resampling that takes place via
> > > "snd_pcm_hw_params_get_rate_resample()". However, there is no
> > > equivalent for disabling the channel number adjustment or the
> > > sample format conversion. This would be very useful in PA however,
> > > since this would allow me to use only the parts of plughw I am
> > > interested in (softvol), and disable all the rest (resampling,
> > > conversion, channel remixing).
> > Hmm.. It's a bit difficult to implement in a clean way.
> > For example, what would be the reason to disable softvol? It's
> > basically irrelevant with the PCM parameters. It's added just because
> > of lack of hardware volume controls.
> > One idea I have is to make an API like
> > snd_pcm_alias_plugin(src, dst);
> > For example,
> > snd_pcm_alias_plugin("softvol", "passthru");
I don't like this idea nor implementation much. It will be much better to
design a run-time communication with plugins to change configuration
parameters / behaviour (something like ioctl on opened pcm handle).
Jaroslav Kysela <perex at perex.cz>
Linux Kernel Sound Maintainer
More information about the Alsa-devel