[mythtv-users] digital sound output

Scott Alfter mythtv at salfter.dyndns.org
Fri Jan 13 04:54:01 UTC 2006


On Thu, Jan 12, 2006 at 07:08:02PM -0500, Steve Adeff wrote:
> On Thursday 12 January 2006 16:21, Mike Schiller wrote:
> > I've had substantial problems configuring my motherboard's (Asus k8n-e
> > deluxe with the nvidia ck804  + rt alc850) sound output to work
> > properly.

I've run into the same problem with the same combination of chipset and
codec, only on an Abit KN8.  With an optical S/PDIF connection to my
receiver (a Kenwood VR-6060, if it matters), I get occasional dropouts.  For
SD content recorded by one of my PVR-x50s, it's a half-second to one second. 
For SD and HD content recorded from my cable box, the glitch causes the
receiver to switch out of AC3 mode and back (it's very noticeable, with
relays clicking back and forth).  You can lose two or more seconds of audio
this way.  You can replay what you missed by winding back and replaying it,
but it was a major annoyance.

> whats the problem your having? I've gotten my ALC850 working perfectly doing 
> what you want, maybe I can help.

I had audio working pretty well with the onboard audio on an FIC AU13, the
nForce2-based board I was using previously.  Reusing the .asoundrc I had on
the old system didn't work.  I eventually got PCM and AC3 audio working, but
with the glitches described above.

I brought home a USB audio adapter today.  It's a Siig US2331, identified
more prominently on the box as the "USB SoundWave Optical 5.1." It has a USB
port on one side and 2-channel analog and optical S/PDIF outputs on the
other side.  With the usb-audio driver in the current stable version of ALSA
(probably in some older versions, too), it Just Works.  I played an HD
recording of this week's E-Ring through it and had no audio glitches at all. 
I haven't tried it yet with xine or mplayer (mainly because they're not
installed on my new Mythbox yet), but if MythTV can send both decoded PCM
data and AC3 pass-through data through it, those other apps should work as
well.  It was about $40 at Fry's, and since it's USB, it doesn't need a
slot.  (The three PCI slots on this board hold a PVR-350, a PVR-250, and a
FireWire card.) With PCI slots disappearing from new motherboards in favor
of PCI Express slots that hold mostly-vaporware PCI Express add-on cards, a
USB-to-S/PDIF converter such as this might be a better fit for a MythTV box
than a PCI soundcard.

  _/_
 / v \ Scott Alfter 
(IIGS( http://alfter.us/            Top-posting!
 \_^_/ rm -rf /bin/laden            >What's the most annoying thing on Usenet?

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