[mythtv-users] HDMI audio issues on Intel NUC

[Matt W]

Hi -- I'm running a frontend on an Intel NUC D34010WYK. The backend is
another box, running the same version of Debian and MythTV, connected
over gigabit wired network.  I am using the current release version:

mythtv at myth-nuc:~/frontend.logs$ mythfrontend --version

Please attach all output as a file in bug reports.
MythTV Version : e4f65c8
MythTV Branch : tag: v0.27.4
Network Protocol : 77
Library API : 0.27.20140719-1
QT Version : 4.8.6

Options compiled in:
 linux profile use_hidesyms using_alsa using_oss using_backend
using_bindings_php using_dvb using_frontend using_hdhomerun
using_ceton using_hdpvr using_ivtv using_joystick_menu using_libxml2
using_lirc using_mheg using_opengl using_opengl_video using_qtwebkit
using_qtscript using_qtdbus using_taglib using_v4l2 using_x11
using_xrandr using_profiletype using_mythlogserver using_bindings_php
using_mythtranscode using_opengl using_vaapi using_ffmpeg_threads
using_mheg using_libxml2

OS is Debian Jessie/8:  3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt11-1

using the VAAPI normal profile (needed SNA acceleration set), the
video looks good and does 1080 content well.

Audio is another matter. It will work for some content but gets
intermittent on LiveTV playback and some recorded shows. I get "ALSA:
WriteAudio: buffer underrun" and plenty of "ALSA: Try to manually
increase audio buffer with: echo 576 | sudo tee
/proc/asound/card0/pcm3p/sub0/prealloc" (no matter what number I push
into the prealloc).

Upmixing is turned off, but sometimes it seems to help in playback
when changed manually in the playback 'auto detect' button.  But then
not long after, the audio will go out and the log will show buffer
underruns.

Can someone recommend some troubleshooting methods here?  My usual net
search skills have yielded nothing concrete. Any help is appreciated!
thanks
-Matt