No sound with pulseaudio

[Pavel]

No sound after select 'PulseAudio' in Multimedia settings. But volume indicator shows playback and capture streams (not muted), for example when I click button for ringtone test or receive incoming call. All other programs (skype, audio players) works well. ALSA works via pulseaudio plugin, but sometimes the sound quality drops.
Ubuntu 14.10 with KDE.
`pactl list` in attachment.

diff linphonerc-pulse linphonerc-alsa:
219,221c219,221
< playback_dev_id=PulseAudio: default
< ringer_dev_id=PulseAudio: default
< capture_dev_id=PulseAudio: default
---
> playback_dev_id=ALSA: default device
> ringer_dev_id=ALSA: default device
> capture_dev_id=ALSA: default device

apt-cache policy linphone
linphone:
  Installed: 3.6.1-2.4build1
  Candidate: 3.6.1-2.4build1
  Version table:
 *** 3.6.1-2.4build1 0
        500 http://archive.ubuntu.com/ubuntu/ utopic/universe amd64 Packages
        100 /var/lib/dpkg/status

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Ference (fgbrose)]

I am running linphone on linuxmint 17 with cinnamon desktop. The description applies exactly to my setup.

[McArthor Lee (macarthorzhuce)]

i use linphone on xubuntu 14.04.2 x86.
i find some odd behavious of linphone with pulseaudio:
1. right after boot to desktop, if you start linphone and dial, no audio in nor out.
2. right after boot to desktop, if you open pavucontrol first and keep it open, and then start linphone, linphone works fine with pulseaudio.
3. right after boot to desktop, if you open pavucontrol and then close it, linphone does not work.
so, what extra work does pavucontrol do???

[McArthor Lee (macarthorzhuce)]

in my environment, i found the root cause:
in mediastreamer2/src/audiofilter/alsa.c, linphone calls snd_pcm_hw_params_set_channels() with channel = 1. but my audio card driver does not support mono. i've tested with aplay a mono wave file and get no sound either.
how to set linphone to use stereo call?