[mythtv-users] Turtle Beach Audio Advantage Spdif help.

[Gregory Hartman]

Gregg wrote:
> I have just installed Mythdora 10.21 as a frontend, and I am trying to
> get The Turtle Beach Audioadvantage working with spdif.  When I select
> ac3 pass through I get static.  I have looked at the groups, and
> people suggest unmuting iec958 in alsamixer.  Unfortunately it does
> not give me that option it only lists PCM.  Is there a way to enable
> that option in alsa?  Should I create an .asoundrc file?  I heard
> fedora didnt need it anymore.
> 
> Here is what I get with aplay -l :
> **** List of PLAYBACK Hardware Devices ****
> card 0: default [USB Sound Device        ], device 0: USB Audio [USB Audio]
>   Subdevices: 1/1
>   Subdevice #0: subdevice #0
> 
> I do not see digital in the list.  Shouldn't there be?
> 

I'm fairly certain that this is a long-standing driver issue in ALSA.

I have the same USB device and was unable to get AC3 passthrough to
work. It looks like ALSA doesn't support AC3 playback on most USB
devices because the devices don't follow the USB audio spec:

"The USB driver currently doesn't support AC3 streams because we have
never seen any device that would implement it according to the USB Audio
specification."

https://bugtrack.alsa-project.org/alsa-bug/view.php?id=1438

https://bugtrack.alsa-project.org/alsa-bug/view.php?id=1615

During my investigation this also seemed to hold on the Windows side:
the vendor-specific driver was needed to allow AC3 passthrough.

I was able to get DTS passthrough to work, but this isn't nearly as
interesting because most of the ATSC shows are using AC3.

Apparently there has been some progress with the M-Audio Audiophile USB:

http://www.alsa-project.org/main/index.php/Changes_v1.0.14_v1.0.15_detail

But at $160 it's quite an investment.

Greg