[pulseaudio-discuss] A few questions

keith preston keithpre at gmail.com
Wed Jun 27 06:43:42 PDT 2007

On 6/26/07, Justin Tulloss <jmtulloss at gmail.com> wrote:
> Hello,
> I'm just getting into PulseAudio and I'm looking forward to using it for
> some challenging projects. I do have a few questions however:
> 1. Is good floating point performance necessary? I saw that some of your
> algorithms do rely on floating point, but I didn't get far enough into it to
> see whether it was necessary for basic PCM routing.

No, it isn't neccesarily.    I been working with pulseaudio in an embedded
enviroment for a while.   There are two current floating point weaknesses.
These are software volume and resampling.     However I had made a patch to
use a newer fixed point speex resampler.   It got to the list for a little
while.   I'll resubmit once the speex stuff is done and stable.

2. How do direct plugin sources/sinks work? For example, the gstreamer
> plugin communicates directly with pulse. Therefore it doesn't show up as a
> source in the manager. Is there a way to get a handle to that source? For
> instance, if I had 2 sinks (A and B) and I wanted to say that all alsa sound
> (from the alsa plugin) should go to sink A where all gstreamer audio should
> go to sink B, how would I do that? That's a contrived example, but I am
> looking for that kind of flexibility.

This is very easy.   There is a API to get current sources and sinks.
Each source can tell what sink it wants to go to.    (ie. gst-launch
audiotestsrc | pulsesink device=secondaudiodevice)

3. Is anybody actively working on a D-Bus control for this? Seems like it
> would be easy enough.

I believe there has already been work to integrate dbus with pulse's
mainloop and there seems to be some code that does this.    I haven't found
it necessary to use because the native protocol works well. (although I use
dbus for everything else.)

4. How do you define policy for HAL events? I don't see an obvious way of
> saying "now that this sink is connected, all audio goes to it and the old
> sink will be turned off"

Sorry, This is the only question I don't know....

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