[mythtv-users] AC3 Passthrough issues

Michael T. Dean mtdean at thirdcontact.com
Mon Mar 13 02:10:35 UTC 2006

On 03/12/2006 08:33 PM, Matt wrote:
>   I've been searching around, and I can't quite find someone having
> the same issue I'm having.  I've got alsa with SPDIF passthrough. 
> It's been working great for analog shows,

Note that you cannot have "passthrough" with analog.  Passthrough is 
used to pass an AC-3/DTS stream directly through Myth to the receiver.  
For analog TV, Myth outputs PCM data, instead, because there is no 
AC-3/DTS stream to pass through.

>  and I just installed my
> digital cards this weekend.  I recorded an HD broadcast today, Nascar,
> and when I started to play it, all I heard was the cars.  I didn't
> hear announcers, sound effects... nothing besides "VROOOOM".  So... I
> figured... interesting.
> I went into the menu and saw that the first audio channel said AC3
> 5.1.  So, I figured "This is only playing a few of the channels". 
> However, it happens on all the HD stations.  I've tried many of the
> suggestions I found for passthrough, but none of them worked.  I'd
> either get no sound, or the same sound.
> The interesting thing is, that when I played analog, my receiver would
> show "PCM 48K" and play just fine.  When I played the digital, nothing
> showed up on the receiver screen and it just played the sounds.  When
> commercials came up, you could hear a little more, but you could tell
> much was missing.
> Any clues?
> Here's my .asoundrc file:
> ## Uncomment the following to use mixed digital by default
>   slave.pcm "dmix-digital"

Don't use dmix.  Change your default to "digital" (uncomment the 
"digital-hw" line and comment the "dmix-digital" line).


More information about the mythtv-users mailing list