[pulseaudio-discuss] questions about no sound, 0 us buffer latency, linphone or others in general

[Peter Gervai]

Hello,

I have been fighting with PA and various SIP desktop clients (and the
view is rather
disappointing); it's not your topic anyway.

However I have been fighting with Linphone with close to no success. I
am pretty sure that
they initialise their streams with buggy values but still the result
may be a bit of PA's fault.

The effect: I set PA as linphone's output. This results perfect
capture (mic is working fine) but
no sound output: total silence. Even for the ringtone test.

Watching pavucontrol I see that the channel (sink) is opened and that
it doesn't seem to have
any data to output. Accidentally, however, I pressed the button with
"Built-in Audio Analog Stereo"
and selected the other sink, which is combined for the same, and
immediately the sound started to be
hearable.

After a long session of wild-guessing whats' what in PA I guess I have
found at least something
analogous with the problem: when the sound is silent paman (pa
manager) says that the
latency is 92777 us which equals to buffer: 0 us + sink: 92777 us.
This "buffer: 0 µs" didn't look quite
promising, and indeed when I have changed sink in pavucontrol (from
normal to combine or vice versa)
the buffer latency pops up to 30000 us or around and the sound starts.

My guess is - based on the plenthora of PA problems on the net - that
the channel was opened with
some nonsense latency requirement which make PA silent, but why does
it start to work after switching
sinks? Maybe PA was sanitising internal stuff?

Anyway. First, it would be nice to be able to tell the linphone guys
what they should fix. I'm not
knowledgeable enough in PA for that.

Second, maybe this "user error" could be prevented by forcing sane
values on channels, or log an
INFORMATIVE warning or something along this line? (I guess that this
is not a "bug" of PA, but maybe
it is.)

Thanks for your input in advance,
Peter


ps: I'd appreciate a cc on me. I may not follow the list closely. But
please reply to the list as well to make it possible to google the
solution.