[alsa-devel] Disable conversions

Takashi Iwai tiwai at suse.de
Wed Nov 21 12:40:54 CET 2007

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");

would take passthru plugin instead of softvol plugin.
(Suppose passthru plugin as a simply pass-through plugin to its


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