[mythtv-users] HDMI audio issues on Intel NUC

[Tim Draper]

---- On Wed, 08 Jul 2015 08:24:39 +0100 Matt W  wrote ---- 
>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 

this is my general build notes, but have you tried configuring as follows:
install pavucontrol via repos and then run 'pavucontrol' in gui > configure to 'Digital Surround 5.1 (HDMI) output' (this output name may change, but correct for my Celeron NUC). Next, goto MythTV frontend > setup > audio > set to Alsa:pulse and 5.1 output

see if that helps - i doubt it as the problem is intermittent but might help to get you moved over to pulse. I cant remember the reason for 'Alsa:Pulse' model, but my system works best with this.

I also have to toggle HDMI audio output via xrandr on resume - 5.1 audio channels gets screwed up until you re-initialize the link. the script was take from the kodi project for the Celeron NUC specifically for messed up audio.

The XAUTHORITY path looks like it's for the logged in user - in my case a dedicated mythbuntu FE which uses 'myth' as the auto-login user.

touch /etc/pm/sleep.d/98-audio.sh
chmod +x /etc/pm/sleep.d/98-audio.sh
nano /etc/pm/sleep.d/98-audio.sh
	#!/bin/bash
	export XAUTHORITY=/home/myth/.Xauthority
	export DISPLAY=:0.0
	case "$1" in
	   hibernate|suspend)
	     xrandr --output HDMI1 --off --set "audio" "off";
		 ;;
	   thaw|resume)
	     xrandr --output HDMI1 --auto --set "audio" "on";
	     ;;
	esac