[mythtv-users] surround sound.

Willy Boyd willyboyd at gmail.com
Tue Nov 14 18:14:10 UTC 2006

I'm pretty sure the "virtual" is talking about the extra fancy
processing that's done on the 2-channel analog sound that comes out
the headphone jack, to make that sound more immersive.  However the
device comes with a mini TOSLINK adapter, and as I understood it,
outputs digital audio straight from the data stream when using Optical

If that IS the case that the little mini USB dongle is actually
encoding AC3 digital audio, I really appreciate the discovery and it
gives me the info I need to take back the Micro and get a Riviera.
FWIW though, this is what I've experienced:

- I had to enable "AC3 Passthrough" in Myth to get digital audio.
Doesn't this instruct Myth to not decode the AC3 data to WAV but
instead dump the data straight to the soundcard?

- Using the AC3 passthrough option with MPlayer, allowed me to play
5.1 audio out my speakers.

- I'm pretty sure the notes I found on the ALSA driver change that
enabled this (too busy at work ATM to find the link), said something
along the lines of digital passthrough

- Isn't analog->"virtual surround" called ProLogic, and really
3-channel?  When watching DVDs, I definitely get discrete sounds out
of my back surround speakers and center channel, and my receiver
definitely think it's getting 5.1 Dolby Digital surround.  Again this
would mean the USB device is actually a DD5.1 encoder, which I guess
is definitely possible.

- I *did* have trouble finding a really "sample" file that I could
guarantee was a good test of 5.1 channels, so I used my copy of The
Matrix.  If anyone has a link to a sample file I could play with
MPlayer's AC3 passthrough (something that does discrete, sequential
sounds on all 5 speakers), I'll do that test tonight.

On 11/14/06, Rich West <Rich.West at wesmo.com> wrote:
> David Rees wrote:
> > On 11/5/06, Willy Boyd <willyboyd at gmail.com> wrote:
> >
> >> I'm really impressed with Turtle Beach.  For what it's worth, they
> >> also make the "Audio Advantage Micro", which is a USB stick about the
> >> size of a thumb drive, that has a full TOSLINK (Optical) output.  For
> >> the same price, obviously the Riviera is a much more complete and
> >> solid solution, but for those strapped for PCI slots, the USB is about
> >> as good as having onboard.  Worked outta the box for me on FC4 with
> >> nearly no setup (just changing MythTV settings, no driver business).
> >>
> >
> > Ooh, that is tempting, only $23.99 + tax/shipping on NewEgg, same
> > price as the OEM version of the Riviera but doesn't use a PCI slot
> > which I've stuffed with tuners... Anyone try both and notice any sound
> > quality difference?
> Hrmm.. that one is listed as "Virtual" 5.1 Surround Sound where as the
> Zalman ($59!) on NewEgg is listed as "5.1 Surround Sound" (no mention of
> "virtual").  From the docs, it seems like the Turtle Beach one is taking
> analog audio and converting it to 5.1...
> -Rich
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