[mythtv-users] SPDIF audio problem in MythMusic only...

[Stuart Johnston]

Rick Stone wrote:
> I set up my first Myth box last weekend.  Eventually -- and with a lot 
> of help from the mailing list archives -- got everything set up, but 
> when playing music via MythMusic I noticed a bit of audio distortion.  
> At that time I was using the 1/8" analog outputs directly from my MB.  
> All audio played fine through the other modules (watching TV and playing 
> videos via xine), but went listening to music (no matter whether it was 
> mp3, flac, ogg or aac) it was slightly distorted.  I decided to try the 
> s/pdif output from my MB directly into my receiver.  Everything worked 
> great immediately except, of course, when I played music, which is now 
> sufferring from what sounds like a sampling rate mismatch.  There's just 
> a slight bit of digital distortion (sounds like downsampling) no matter 
> what I play, but only through MythMusic.

Your receiver is going to be expecting the signal on its digital input 
to be at 48k.  If your mp3s are not recorded at 48k they will need to be 
resampled before getting to the receiver.  The easiest way to do it is 
with Alsa.  I have seen lots of different explanations on how to 
configure it and it may depend on your sound chip.  Here's what I ended 
up with in my .asoundrc:

####
pcm.fixed {
    type plug slave {
         pcm "spdif"
         rate 48000
    }
}

pcm.!default {
   type plug
   slave.pcm "spdif"
}
####

And then in the MythMusic configuration, you put ALSA:fixed for the 
audio device.