[pulseaudio-discuss] "passthrough" audio (eg. AC3 / DTS / WM9)

Ng Oon-Ee ngoonee at gmail.com
Mon Oct 5 17:28:44 PDT 2009

On Tue, 2009-10-06 at 10:40 +1100, Dave Moore wrote:
> 2009/10/6 Lennart Poettering <lennart at poettering.net>
>         On Mon, 05.10.09 14:30, Dave Moore (davewantsmoore at gmail.com)
>         wrote:
>         > Hi Everyone.  I'm really sorry if this has been covered
>         before, I've read
>         > back through the past 6 months list history and found
>         nothing.... and my OS
>         > (ubuntu) and application support forums/lists are not being
>         very helpful.
>         >
>         > I would like to pass digital audio completely unaltered
>         ("bit-stream") to my
>         > SPDIF output - Can this be done with pulseaudio?
>         No. Not at this time. (See other mails in this thread for what
>         is planned)
>         If you need ac3 pass-thru then you need to bypass PA. Just
>         make sure
>         you are not using the SPDIF port for PA (use g-v-c or
>         pavucontrol and
>         make sure the sound card is notconfigured for any of the
>         'digital
>         iec985' modes). 
>         Lennart 
> Wow.  Thanks for the replies everyone.  I didn't know what to expect.
> I completely understand why PA doesn't work (well?!) with
> pass-through.... so my question is now.
> If I am to keep PA installed and configured (it's now part of my Linux
> distro and would like to keep things as "vanilla" as possible).....
> what steps can I take to have PA pass unaltered data through to my
> digital out ?
> (I understand I will not have sound mixing, or multiple applications
> able to use the card at once ->  basically I would lose all the
> benefits of PA..... but in order to stick with what my distro offers,
> but also to get what I need (encoded formats passed unaltered to
> digital out)..... what can I do?)
> Many thanks.

Please bottom-post, its more readable.

As for your question, you just need to follow Lennart's instructions,
make sure pulse does not load your digital output. You'd probably have
to comment out module-hal-detect or module-udev-detect and manually load
other soundcard modules, if any.

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