Mailing List Archive: Alsa spdif out?

Alsa spdif out?

Apr 1, 2003, 2:23 AM

Post #1 of 4 (1784 views)

Has anyone gotten such a thing to work for MythTV? :) I don't want to
have to use my analog output since 1) that would require yet another
cable in a messy area and 2) there is this low-level annoying hum that
I've yet to track down.

Better yet, does anyone know if it's possible in ALSA to route sound sent
to the OSS devices to the spdif device? (Ie, open /dev/dsp, it gets sent
through digital out) Windows drivers can usually do it, and I have the
feeling with Alsa's flexibility that it's possible, but ALSA's
documentation leaves a lot to be desired.

Ian

RE: Alsa spdif out? [ In reply to ]

Edward.Wildgoose at FRMHedge

Apr 1, 2003, 3:08 AM

Post #2 of 4 (1792 views)

Permalink

> Has anyone gotten such a thing to work for MythTV?

A few days ago someone had problems with spdif, and it turned out to be because audio was sampled at 32Khz which the amp couldn't decode. The solution was to choose 44Khz as the record frequency.

Any help?

Re: Alsa spdif out? [ In reply to ]

ijw1 at pacbell

Apr 1, 2003, 6:14 PM

Post #3 of 4 (1760 views)

Permalink

On Tue, Apr 01, 2003 at 11: 08:50AM +0100, Edward Wildgoose wrote:

> > Has anyone gotten such a thing to work for MythTV?
>

> A few days ago someone had problems with spdif, and it turned out to be
> because audio was sampled at 32Khz which the amp couldn't decode. The
> solution was to choose 44Khz as the record frequency.

Nope, this problem is even a little more basic than that. The only way
I've found to play audio through the digital out (at least with the intel8x0 alsa driver I've used) has been to
either use aplay and specify spdif as the PCM device, or specify spdif in
an application that knows more about alsa (like xine). mythfrontend
doesn't seem to know about alsa (it's not linked against alsa libs), and
the only way to specify how to play sound is through a device file,
/dev/dsp by default (and in fact, when I tried to specify a different
device file, /dev/snd/pcmC0D0p just to see what happened, mythtv changed
it back to /dev/dsp). Maybe I should look at mythfrontend and see if I
can add some more alsa functionality..

Ian

Re: Alsa spdif out? [ In reply to ]

foom at fuhm

Apr 2, 2003, 3:51 PM

Post #4 of 4 (1778 views)

Permalink

On Tuesday, April 1, 2003, at 08:14 PM, Ian Westcott wrote:

> /dev/dsp by default (and in fact, when I tried to specify a different
> device file, /dev/snd/pcmC0D0p just to see what happened, mythtv
> changed
> it back to /dev/dsp). Maybe I should look at mythfrontend and see if I
> can add some more alsa functionality..

This is a bug in the UI. While it lets you type stuff in the
textfields, it completely ignores anything you type there. Try
connecting to the mysql database (e.g. mysql -u mythtv -p mythconverg)
and doing
update settings set data="/dev/snd/pcmC0D0p" where
value="AudioOutputDevice";

Then restart mythfrontend. I don't know if this will work or not but at
least it will attempt to use the device you specified.

But as for the second, I'd like native ALSA support in mythfrontend too
instead of the OSS emulation, if you really want to do that. :)

James