[mythtv-users] Chaintech 7NIF2 Sound Problems

Dalen Kruse blacklion at blacklion.org
Mon Mar 29 13:01:33 EST 2004

I was having the same problems with that board.  What I found out (someone
correct me if I'm wrong) is that the on-board sound does not support
full-duplex.  If your experience is like mine, it sounds great when
playing a sound file through XMMS or watching TV with XawTV, but horrible
when watching TV with Myth.

There are three solutions to this problem.

1. Make this machine a dedicated backend that only does the recording. 
That way you don't need full-duplex sound.  The downside is that you'll
need another machine for a dedicated frontend.  Most expensive option.

2. Dump the bttv card and buy yourself a PVR-250 or -350.  The sound is
encoded directly into the MPEG-2 stream, so your on-board sound doesn't
need to do the recording.  Second most expensive option.

3. You can do what I did.  Disable the on-board sound in your BIOS and
find yourself a separate full-duplex sound card.  I'm currently using a
SoundBlaster Live 5.1 PCI card and it sounds great.  Depending on where
you buy it, this card can run you $35 to $50.  If you do get a separate
sound card, MAKE SURE it will do full-duplex.  BTW, stay away from CMedia
chipsets.  The older ones (i.e. 8739) supported full duplex, but cut the
sampling rate in half so you still had terrible sound.

Hope this helps.  This was my most frustrating part of building my Myth
box.  It's running rock solid now and I'm very happy with the results.


> I know this isn't the alsa mailing list, but I know many people use this
>  board in their Myth Boxes, so I thought I'd ask.  Is anyone using the
> onboard audio for sound capture.  I have this board with a bttv card,
> and I'm getting horrible audio.  When I aplay /dev/dsp the audio is
> really crackly, and it plays at a set volume.  Changing the master
> volume doesn't affect the sound output at all.  Playing other sounds
> works  fine.  Xawtv sounds fine and the volume controls work.  It's only
>  the playing the dsp that doesn't work.
> The sound from the bttv card runs into the cdaudio jack on the MB, and
> I'm using alsa 1.03 and the latest Nforce drives on Mandrake 9.2.
> Has any one had similar problems?
> Thanks
> Ben
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