[mythtv-users] 5.1 analog sound configuration

Justin Smith justin at smithpolglase.com
Sun Sep 25 09:22:49 UTC 2011


I don't know how to configure myth sound to work as I want - can
someone give me some pointers?

My setup: Mythbuntu 11.04 with 0.24-fixes (regularly updated). No pulseaudio.

Audio hardware: onboard (analog + spdif) and Xonar D2X sound card
(analog + spdif)
Graphics: Zotac Nvidia GT430 with HDMI out.
Receiver: accepts PCM (2 channel only), AC3 and DTS. No HDMI I/O.

Output of aplay -L: http://pastebin.com/ba26YtyY

System usage: For general TV viewing, we use the TV sound. We only
switch on the receiver for some movies and listening to music.

What I would like is either (depending on what is actually possible):

1. 2-channel audio over HDMI to the TV and (concurrently) PCM/AC3/DTS
(i.e. 5.1 passthru) over spdif (either onboard or D2X) to the
- This is apparently not possible as MythTV cannot output to both
"analog" (PCM) and AC3/DTS concurrently - if I understand the
discussion in http://www.mythtv.org/pipermail/mythtv-users/2011-January/307676.html
(among others) correctly.

2. 2-channel audio over HDMI to the TV and (concurrently) 5.1 analog
audio (3.5mm jacks) from D2X to the receiver. With upmixing for stereo
to 5.1 for stereo sources.
- This should be possible, right? If not, then how about...

3. 2-channel analog from onboard 3.5mm jacks audio to the TV and
(concurrently) 5.1 analog audio (3.5mm jacks) from D2X to the
receiver. With upmixing for all non-5.1 sources to 5.1.

Can anyone help with Myth audio config and any required alsa config?

A related problem: Our local free-to-air HD channel (DVB-T)  often
broadcasts has 5 channel audio. However, I can't work out how to
configure myth to output analog 5.1 sound (3.5mm jacks) from the D2X
for this TV channel. When I use the following:

Audio output device: ALSA:surround51:CARD=D2X,DEV=0
Speaker config: 5.1
Upconvert stereo to 5.1 surround: ticked
Upmix quality: Best
Advanced audio config: None

I get no sound because it appears myth is not upmixing the 5 channels
to 5.1 channels. See the frontend log (with audio logging):

Any ideas how to fix this?


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