I just updated my MythBuntu 11.10 to 12.04.3. Now, when I try to play 5.1 content (ripped DVD), my TV (and receiver) plays a "chattering" sound. I check my receiver and the digital dolby light isn't on--it's in PCM mode. So, either the audio is getting sent as AC-3, but the TV and receiver think it's PCM or the AC-3 audio got converted to multichannel PCM and they can't handle it.

My setup: hdmi cable from htpc to TV. TV has an s/pdif output to my receiver. I know TV sends AC-3 audio out correctly because I see digital dolby light come on when I view a digital TV channel and PCM come on when I view an old analog channel.

I can connect s/pdif from my htpc to my receiver and the digital dolby light comes on and it can decode the audio just fine. It's just not sending it right over hdmi.

Now for some hints to the issue: I noticed in MythTV audio setup when I select alsa:hdmi.... the description only lists 2 channel PCM audio capability. speaker-test -Dhdmi:PCH -c6 errors about a bad channel count (only -c2 works). Finally, I tried vlc and it does the same chattering sound. These all make me think this isn't a MythTV issue, it's something lower than that.

I think the best way to troubleshoot this is to start at the drivers and check each layer, one at a time all the way to alsa. I just don't know what the layers are and how to do it. So, I need to find some audio troubleshooting guide to assist me. Or, if one doesn't exist, I'd appreciate some steps.

Thanks much,

Jim