No HDMI sound after Skype installation. Ubuntu mate 16.10

[yann49]

Hi,
I installed Ubuntu Mate 16.10 days ago. No problem. The HDMI sound was fine without anything to set up.
It was a good surprise as with Debian8 I had to set the parameter to HDMI after each boot.

2 days ago I installed Skype using synaptic. It seemed to be OK. Skype started but no sound.
The only possible parameter for the output in Skype is "PulseAudio server (local)".
In Pulse Audio shows HDMI/DisplayPort (plugged in) à 100% (0dB) but is mute

To check if my problem comes from hardware I made the following tests:
- a Youtube video in Firefox : no sound but video OK
- a Youtube video in Chromium : no sound but video OK
- a song in VLC: first no sound, but after changing the preference set up audio in VLC to HDMI the sound is now OK
- in Ubuntu Sound preferences parameter : change to HDMI than speakers test : OK

Than I disconnect the HDMI cable to plug a analog cable : sound is OK in all software

In summary the HDMI sound is OK in VLC and "Sound preferences parameter" but no sound in all others softwares.

Before Skype installation HDMI sound was OK.

Does someone knows how to come bring back HDMI sound ?
Thank you for your help

[yann49]

Hi,
Nobody have an idea ?