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Simultaneous analog/digital out with nforce4 board M2NPV-VM
http://forum.linhes.org/viewtopic.php?f=2&t=15844		 Page 1 of 1
Author:  slowbiscuit [ Wed Jul 11, 2007 11:33 am ]
Post subject:  Simultaneous analog/digital out with nforce4 board M2NPV-VM
Hi all, just finished rolling my own dual-tuner HD Myth box. Everything's working great using KnoppMyth R5F1, well after a bit of tweaking that is (ok, a lot of tweaking :)). I'm pretty happy with it now and just have one task that I'd like to finish - getting simultaneous analog/digital output from the onboard audio (Analog Device AD1986a using the Intel HD ALSA module - latest version, 1.0.14).

What I mean is that I'd like to either listen to stereo analog on my HDTV for news, documentaries, etc. but also have digital output sent to my receiver (AC3, DTS) whenever a show with 5.1 audio is playing. So, I could listen to either or both as I wish.
I've tried just about everything I can find on the net (like the custom multi-output .asoundrc on the Configuring Digital Sound mythwiki page) but can't seem to get it working. If I set the sound device to ALSA:analog instead of /dev/dsp and digital passthrough device to ALSA:spdif (or digital), I get no sound on the TV for analog shows with AC3 passthrough enabled. If I turn passthrough off, sound works fine but then no digital. If I set sound to ALSA:multi (using the custom .asoundrc), I get buffer underruns and audio/video skipping for all shows.

So best as I can tell, you can have all going to analog or all going to digital but not both. True or false?
Author:  alien [ Thu Jul 12, 2007 7:47 am ]
Post subject: 
This isn't exactly what you are looking for, but I find it works well:

Myth 0.20 allows a separate passthrough device. It will automatically switch devices depending on what format the sound track is in (this is in the audio device settings menu).

If the soundtrack is analog, it goes out the analog device to the TV speakers. If it is DTS or AC3, it is passed digitially to my receiver.

If I want to change the output device, I change the audio track. Good enough for my needs.

I was never able to get both devices working at once... I suspect that even if I were to get both working, passthrough to the digital out would pose additional problems.
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