'Twas brillig, and Takashi Iwai at 04/04/11 11:57 did gyre and gimble:

At Sun, 03 Apr 2011 13:22:34 +0100, Colin Guthrie wrote:

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Hi,

If the user opens the "default" device in alsa, is there a way to find out if that "device" is actually a plugin?

i.e. is it possible to tell if you have opened the pulseaudio plugin via alsa?

There are various hacky ways (e.g. checking hints etc.) but that relies on downstream packaging which certainly isn't fool proof.

There is no clean way, AFAIK. A new API would be needed. For example, something like: snd_pcm_contains_type(pcm, SND_PCM_TYPE_EXTPLUG);

But checking whether PA-plugin is used is difficult with the API above because pulse plugin has no unique PCM type but it's a sub-plugin of extplug plugin...

Yeah I didn't think there was an easy way.

I guess just "strongly recommending" the distros use a hint when they redirect the "default" makes sense.

I do this: aplay aplaymidi [colin@jimmy build-master (master)]$ aplay -L null Discard all samples (playback) or generate zero samples (capture) pulse PulseAudio Sound Server default Default ALSA Output (currently PulseAudio Sound Server)

....

SO that the "default" hint contains the word "PulseAudio" which apps could check. It's obviously not fool proof, but if this is only for "hinting" purposes at the app level anyway, then it's maybe good enough.

(FWIW, it's for a situation where hinting to the user that they are going via ALSA, when an optional but more specific pulse output is supported by the app and may be more appropriate).

Thanks for the info.

Col