[mythtv-users] Digital Audio Problems - Noisey, stuttering, skipping

Brad DerManouelian myth at dermanouelian.com
Mon Jan 19 22:41:02 UTC 2009


On Jan 19, 2009, at 2:25 PM, Eric Sharkey wrote:

> On Mon, Jan 19, 2009 at 5:08 PM, Mike Smith <easygreenus at yahoo.com>  
> wrote:
>> Audio Output Device - Alsa:Default
>> Passthru Output Device - Default
>> Max Audio Channels 5.1
>> Checked "Enable AC3 to SPDIF Passthrough"
>> Checked "Enable DTS to SPDIF Passthrough"
>> Checked "Use Internal Volume Controls"
>> Mixer Device - Alsa:Default
>> Mixer Controls - Master
>
> This has been coming up a lot lately.
>
> It sounds crazy, but you need to change Max Audio Channels to Stereo,
> and set the passthrough device to iec958.  If you do those two things,
> it should work.  (It did for me.)

It's not as crazy if you read up on s/pdif. It originally used XLR  
connectors which are 3-pin connectors so it only supports 2 physical  
channels. 5.1 (or whatever mult-channel) data is passed along those  
two channels using biphase mark code, but it's the job of the decoder  
on the receiver to take the 2-channel information and send the correct  
stuff to the correct speakers. Don't ask me any more about what that  
all means, though. My partner's a recording engineer so I don't have  
to deal with it. :)

-Brad



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