[pulseaudio-discuss] Questions about multiple channel volume control

Gerald Hofer hofer at sgi.com
Wed Nov 11 21:04:34 PST 2009


I have a particular problem with Pulseaudio (0.9.19 on Opensuse 11.2)  
that I don't seem to be able to solve with the current user interface.

I am using a Firefox plugin to check on Nagios servers. In case of 
faults this plugin produces a short warning sound every time it finds a 
fault during the periodic check (every 5 minutes). Pulse audio now 
finally allows me (in theory) to set a volume level independent from 
other audio sources. The problem is that the stream (and it is a 
seperate stream, not a system sound) only shows up for the very brief 
period it plays (maybe a second or so) in pavucontrol. So in reality it 
is almost impossible to change the audio level on this stream.
But I managed to change the volume level to zero, but it was almost 
impossible to set it back to a higher level. I had to changed the sound 
file to something longer to have enough time to do it...

 From the application level I feel it is the absolute correct behavior. 
The stream has to be really open for 1 second, and it is certainly 
possible that this application does not want to play a sound for several 
days or weeks. So keeping something open on the application would not be 
the correct behavior either.

I was scanning through bugs and other comments and it looks like there 
is really no way to access and change the stored volume levels for 
separate applications when there are not playing (please tell me if it 
is possible somehow).

I found  ticket #159 http://pulseaudio.org/ticket/159 that explains 
exactly my problem, but clearly that "solution" to the problem is not 
adequate here. I would be also not happy to mix that application up with 
"system sounds". For me that is a different category again.

 From an earlier discussion Lennart said:

PA actually hasn't forgotten. We store the volume/device of a stream
in our stream database. This database is actually readable from
clients. (In fact pavucontrol reads/modifies it for the event sound
slider). It is solely an UI issue to implement what you ask for --
although I still doubt that it makes much sense for anything that is
not an event sounds.

So for me this would be perfect counter example. I want to change the 
volume for that application _before_ it will play the next time. [For 
example because I know that my wife hates this tone and I have to tune 
it down in advance :-), or I am in a noisy environment and I don't want 
to miss the next warning]. Maybe this can be solved with changes to the 
application (but I doubt that a plugin in Firefox has any access to 
that) - but I really think that pulseaudio would be the right place. [I 
am still dreaming from the big mixer, where I can randomly plug things 
together in hierarchies]

The user interface that was suggested in ticket #159 is what would work 
for me. A way to switch on all the applications that have played in the 
past, probably sorted by time and a way to change the parameters.

It would also help me to switch an application from headset to speakers 
_before_ I start it. (Skype anyone?)


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