[pulseaudio-discuss] Screen casting with PulseAudio

[Michał Sawicz]

Dnia 2011-10-18, wto o godzinie 14:19 +0200, Rémi Denis-Courmont pisze:
--8<--
> Video applications need to provide a choice of video sources (webcams,
> desktop capture...). For this, there is no video mixer applications. In
> terms of usability, I would expect to choose the audio source at the same
> time as the video source.
As you said - there is no video mixer application. Yet.

> The "volume control" tool would have two problems:
> - It only works after the record stream is started, so that the source
> output exists. For recording purpose, you'd want to select the source
> before you start the recording.
Not true. If you select the fallback recording stream before you start
recording, that's what VLC will get as the source. Also, if you select a
source for VLC, it will "stick" thanks to module-*-restore, so after
setting it once, you'll get that until you change it again. Or other
things happen, like external headsets connected and stuff. There was a
lengthy post about routing (and its future) from Colin Guthrie, but I
can't find it now... Interwebs, help, please?

> - It has poor usability. The user would have to configure the application,
> including all parameters except the audio source and amplification. For
> those, it would have to open a separate application.
Depends on the definition of usability. Having different dialogs in
every single application dealing with audio source selection might be
poor usability to some.

> So I think it's fair for recording/streaming applications to act as their
> own "volume control tool". Of course, they should play good citizens with
> the other volume control tool(s) in the system, and in particular not
> actively fight changes initiated by the PulseAudio daemon or another
> PulseAudio client.
So what's preventing you from listing all possible input sources in VLC?

> And in fact, the same applies partly to output (playback/streaming). Any
> reasonable media player has a volume control, and possibly a balance and an
> output devices choice list. So long as it lets PulseAudio set the initial
> values and does not prevent other tools from moving or tuning the sink
> input, I must say I don't see a problem.
Show me one modern media player that has output devices choice list. Or
video conferencing, where it would make even more sense (hint: neither
Skype nor Empathy allow you to select sinks/sources). Volume control in
e.g. banshee is just a proxy to PA.

That's just how it was designed, and on purpose. I can imagine a common
(just as printing is now <but wasn't not so long ago> - you generally
always should get a printing dialog you know well) dialog for advanced
applications to choose sinks and sources for a particular app / role on
demand. But I'm not sure that's necessary and I haven't seen anyone step
up and write it.

Another thing I could imagine is a media role (are those even
implemented for sources?) of "desktop-recorder" or similar, that will
choose the monitor of the active sink for you. That's as far as I'd go,
TBH, to handling this case.

Cheers,
-- 
Michał (Saviq) Sawicz <michal at sawicz.net>
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