Tvheadend

UPDATE:
I've tried to install the package "pulseaudio" (i'm on ubuntu 16.04) then rebooted. now it works.
for what I can see default alsamixer now show "pulseaudio" as a very simple audio card wiyh "master" and "capture", before I see the alc887-vd realtek chip diciture and numerous control...
probably the htsp plugin require pulseaudio.

I'm running a tvheadend server (HTS Tvheadend 4.0.8~jessie) with two dvb-t adpter, on a dedicated machine (raspberry) since a bit of months without relevant problem (all goes well).
At desktop pc, I abitually see the content via htsp vlc plugin (compiled/installed with the guide in these forums).

Problem in short:
My new desktop machine (tvheadend run as server on an other machine) , an intel i5-6400t (skylake), has problem playing stream in vlc with htsp plugin.
Initially seems works but after a bit of seconds it freezes, then restart, then freezes: Impossible to watch. Has anyone a tips to solve problem?

1. Trying to go in the web interface of tvheadend server (ip:9981 in browser) and clicking to play tv channel, thus using an http stream, it works (both vlc or gplayer). Video and audio haven't issues.
2. I've noticed that problems during play (htsp plugin) generate numerous warns in vlc messages window (same in vlc -vv log), pasted here below, and that if I disable the audio track apparently it seems goes (video doesn't freeze anymore) waiting a bit, all warns about picture delay are stopped. I've tried also to re-enable audio track and sometimes, for several minutes, it has no problem (after it loop in freeze, play)

Investigation and information:
HW video accelleration
I've investigated if the video hw accelleration was enabled, and for what I've understood, after installing some packages, now it should be (http://ubuntuforums.org/showthread.php?t=2328993 her you can see all info about sw, so, kernel, driver video). Now I see in vlc-vv log also a explicit sentence for this:

[00007f3d10003e08] avcodec decoder: Using Intel i965 driver for Intel(R) Skylake - 1.7.0 for hardware decoding.

Audio:
audio is onboard, "realtek alc887 codec" says my motherboard manual. I've not understood if it's part of the intel chipset(B150), or separate, but probably yes because all devices I see in vlc appear to be "hda intel pch ....".
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core audio output warning: buffer too late (-326212 us): dropped
[0000000001688718] core audio output warning: buffer too late (-278329 us): dropped
[0000000001688718] core audio output warning: buffer too late (-254401 us): dropped
[0000000001688718] core audio output warning: buffer too late (-230450 us): dropped
[00007f3d00032538] core video output warning: picture is too late to be displayed (missing 188 ms)
[0000000001688718] core audio output warning: buffer too late (-206511 us): dropped
[0000000001688718] core audio output warning: buffer too late (-182638 us): dropped
[0000000001688718] core audio output warning: buffer too late (-158694 us): dropped
[0000000001688718] core audio output warning: buffer too late (-134721 us): dropped
[0000000001688718] core audio output warning: buffer too late (-110741 us): dropped
[0000000001688718] core audio output warning: buffer too late (-86760 us): dropped
[0000000001688718] core audio output warning: buffer too late (-62780 us): dropped
[0000000001688718] core audio output debug: playback too late (40381): flushing buffers
[00007f3d00032538] core video output warning: picture is too late to be displayed (missing 154 ms)
[00007f3d00032538] core video output warning: picture is too late to be displayed (missing 116 ms)
[00007f3d00032538] core video output warning: picture is too late to be displayed (missing 79 ms)
[00007f3d00032538] core video output warning: picture is too late to be displaye