[mythtv-users] Simultaneous AC3/DTS passthrough & stereo analog output

[Ryan Steffes]

On 10/23/07, Gary Dawes <gary.dawes at gmail.com> wrote:
> On 18/10/2007, Bob <spam at homeurl.co.uk> wrote:
>
> > I'm using an Audigy2 in one PC and an SB Live value in another (both
> > Debian etch) and I output to a 5.1 speaker system over S/PDIF coax and
> > to my headphones (via the TV) over analogue stereo.
> >
> > I have AC3 passthrough working when I call mplayer with -afm hwac3, (I
> > think DTS will work but can't find a test clip) and I can soft decode
> > and downmix the AC3 audio with -afm liba52, so that's all great, except
> > that with -afm liba52 rear left and right are mixed and I don't get
> > anything out of the LFE track.
> >
> > What I can't do is both at once which would make life easer for SWMBO.
> >
> > My google search (below) has reviled I'm not alone in wanting this
> > (including a number of threads here) but hints that it may not be
> > possible, however, my search skills are week so I thought I'd ask.
> > "ac3 passthrough" "analog (output | stereo | downmix)" (simultaneous |
> > "both at" | "same time")
> >
> > Has anyone got any suggestions on how to get this working?
> >
> > I can install more than one sound card, so if it can be done but only on
> > a second card I'm still interested in the solution
> >
> > Thanks for any help.
> >
> > PS: Though the PCs in question aren't MythTV frontends at the moment,
> > that is their destiny and since this community seems to be one of the
> > most knowledgeable with regard to linux sound issues I thought I'd ask
> here.
> >
> > PPS: I asked the same question on the debian-user list 10 days ago but
> > with no luck so sorry to those who, like me, are subscribed to both.
> > _______________________________________________
>
>
> I'm in a similar boat. I'd like to have analogue to the TV, as now for run
> of the mill programmes such as the Wifey's soaps etc, and be able to have
> AC3 piped over digital to the receiver when I'm watching a video or DVD.
>
> Like you bob, I have googled extensively. I have also followed the guides on
> knoppmythwiki and the general myth wiki, which suggest that it is possible,
> but the examples shown do not work for me. I have a gigabyte MB with a
> nforce2 chipset.
>
> If anybody has got this working, example configs so the various solutions
> can be compared would be very useful.
>
> thanks also
>
> Gary
>
>

You should be able to accomplish yours with just the built in
functionality in MythTV, although you may need to move to SVN (Is the
ability to add a separate audio device for AC3 pass through in the
release builds yet?).  In current SVN, you'd only need to set one
device for regular sound, such as ALSA:analog (if you use the asoundrc
from the wiki) and your digital device ALSA:digital for AC3 pass
through.