[LAU] ALSA: Using a plugin only for capture

Fons Adriaensen fons at linuxaudio.org
Tue Dec 6 23:46:20 UTC 2011


On Tue, Dec 06, 2011 at 06:27:23PM -0500, Paul Davis wrote:
> On Tue, Dec 6, 2011 at 5:43 PM, Fons Adriaensen <fons at linuxaudio.org> wrote:
> 
> > So, are you telling us that ALSA inserts the plugin in both
> > the capture and playback paths ? That would be absolutely
> > braindead.
> 
> doesn't work that way at all.
> 
> the app opens "plughw:ladspa" (for example) for playback. presto: the
> ladspa plugin is applied to the playback stream.
> the app opens "hw:0" (for example) for capture. no plugin processing
> on the capture stream.
> the app opens "plughw:ladspa" (for example) for capture. presto: the
> ladspa plugin is applied to the capture stream.

And what if the app opens the device for capture and playback ?

Isn't the whole 'plug' system meant to be transparent to apps,
so an app can just use 'default' and get whatever the user
configured to be 'default' ?
 
> remember that there is no such thing as a duplex ALSA stream (similar
> to several other audio device APIs).

Very well, but the .asoundrc syntax seems to be in terms of
duplex devices. How would you configure a plugin in 'default's
capture stream only ? 

Ciao,

-- 
FA

Vor uns liegt ein weites Tal, die Sonne scheint - ein Glitzerstrahl.



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