[mythtv-users] HDMI sound works for AC3 2-channel, but not 6-channel

[Steven Ihde]

Just upgraded from mythtv 0.23.1 to 0.24.2 yesterday.  Now audio for most programs does not play back (it is silent).

I'm using the IEC958 output on the sound card to plug into the digital sound input on the video card which mixes it into the HDMI stream.  The HDMI cable is connected to directly to my TV.  This worked fine with all source material before.  Now it only works with AC3 2-channel source material.  Whenever I see this in the mythfrontend log:

2012-04-01 21:51:07.358 AO: Opening audio device 'iec958:CARD=CMI8768,DEV=0' ch 2(2) sr 48000 sf signed 16 bit reenc 0

The sound plays back fine.  Whenever I see this:

2012-04-01 21:51:17.267 AO: Opening audio device 'iec958:CARD=CMI8768,DEV=0' ch 2(6) sr 48000 sf signed 32 bit reenc 0

I get silence.  Note "ch 2(2)" vs. "ch 2(6)".  The 2(2) message is preceded in the log by "codec AC3 has 2 channels", while the 2(6) message is preceded by "codec AC3 has 6 channels".  Looking back through the mythfrontend logs from before the upgrade, it always said "ch 2(2)", even when there was a 6-channel stream (and there was no mention of 16 vs 32 bit).

Anybody have an idea what could be wrong?  

I should probably mention that I also upgraded the box from Debian Etch to Squeeze at the same time (yes, I was a little behind the times... was leaving well enough alone) so the alsa lib version probably changed as well (kernel version is the same though, 2.6.32, since I was running a backported kernel with Etch).

Thanks,

Steve