[mythtv-users] OSS -vs- ALSA sound

[Ian Forde]

On Wed, 2003-10-01 at 19:32, Harondel J. Sibble wrote:
> On 1 Oct 2003 at 12:35, Ian Forde wrote:
> 
> > If your sblive is a sblive 5.1, and you're using ALSA, you can use the
> It is and I am using alsa
> 
> > attached asound.state (gzipped).  Put it in /etc, do a 'alsactl
> > restore', connect the digital coax cable to your av receiver, and you're
> 
> I'll try that, does this require reloading the alsa modules after installing 
> this asound file or just the command above?

You have to have alsa built and installed first.  You also have to have
the modules loaded.  Once that's done, you can use the command above...

> So just to make sure I understand. This implements ac3 passthru so that my 
> Creative Desktop Theatre amp will use the ac3 signal to properly play the 
> audio to my 5.1 speakers.

Correct.  It also sends regular stereo PCM output (often encoded with
Dolby Prologic for some broadcast shows) through the same channel.  My
receiver can autodetect the encoding and switch to the appropriate mode.

> Is there an easy way to use this with Xine, or Ogle, or say Mythvideo (or was 
> that MythDVD, I can't remember).

Well, in Xine, you have to configure it in the setup.  In Ogle, there's
a section in the config file that you should uncomment if you want it to
work.  Let me know if you want a copy of mine and I'll post it
(compressed, of course) to the list...

> Now, what output are you refering to?  Do you mean the stereo mini 
> analog/digital jack on the card (above the mic jack at the top end of the 
> card) or the spdif connector that exists on my digital io card (or livedrive 
> bay, what have you)?

I'm speaking of the spdif connector.  In order to get AC3 out, you have
to use a digital connector, as opposed to the analog(ue) stereo minijack
connectors that can't.  But since alsa will let you route the regular
stereo data over the digital line, you get both analog and digital data
over the same 1 cable...

So in short, I have a digital coax cable (I really hate the fact that
they used the term "coax" in this sense.  Overloading component names in
A/V is not, IMHO, a good thing[tm].)  It goes from the sblive 5.1 card
(top orange connector, I believe) to my receiver.  I have my
modules.conf file configured to load alsa and do a "alsactl restore" on
loading the alsa modules.  Ogle and mplayer are configured to do ac3
passthrough.  (Mplayer does it only when appropriate though.)

One thing I haven't played with (and will probably do tomorrow during my
hangover) is test out mplayer's ability to specify different encodings
in priority (workability) order, separated by commas.  It should cut
down on my choices of different players per audio encoding type...

That's it!

	-I

-- 
                       __________________________________
                       Ian Forde, RHCE, CCSE, SCNA, SCDME
                       CYTBeN, Inc.
                       ian at duckland.org / ian at cytben.com