[mythtv-users] S/PDIF + ALSA + Shuttle SB61G2

Zachary Bedell zaclist at adirondack.net
Mon Aug 2 11:55:32 EDT 2004

Hash: SHA1

On Jul 28, 2004, at 11:44 PM, Bryan Halter wrote:
> I'm trying to configure MythTV to use the S/PDIF out on my Shuttle
> SB61G2 and all I get when I set ALSA:spdif as the output is a bunch of
> snaps crackles and pops.  Can someone please help?

I've got that same machine and had nothing but problems with the sound 
output on it.  The sound quality was simply awful.  I finally gave up 
and put in an SBLive card.

The one thing that prevented me from getting any sound out of it is 
that the card is capable of 48k sample rate only.  I ended up have to 
add this to my ~/.mplayer/config file:

I also had to hack mythmusic to force resampling to 48k all the time.  
The problem was that the ALSA driver reported to Myth that the card 
could handle other rates (like 44.1k which is what 99% of my music is 
sampled at), but in fact the card couldn't handle it.  There's one line 
in mythmusic where myth asks the sound driver for a handle to a sound 
decoder at a particular rate.  The sound driver returns what rate it's 
actually setup for, and myth compares that to what it requested (I 
think...  This was a while ago.)  My hack involved forcing myth to 
always ask for a 48k decoder regardless of what the music file was 
encoded at.  Myth would then notice that 48k was different than the 
file's rate and the normal sample rate conversion code would kick in.

It worked, but the quality was pretty poor.

I don't actually use Myth as a DVR.  (got a D-Tivo, and not willing to 
sacrifice pure digital-to-drive.  If only I could find a DTV tuner PCI 
card =)  I have a feeling that a similar hack may be necessary to force 
MythTV to output sound to this card.

Good luck with the thing in any case.  I got a pair of these for 
super-cheap, so I'm not too aggravated.  If I'd actually paid any 
quantity of money for this thing, I'd be pretty unhappy...

Best regards,
Zac Bedell

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