[mythtv-users] ALSA 1.0.25 and broken AC3 passthrough?

Steven Adeff adeffs.mythtv at gmail.com
Tue Feb 7 16:49:37 UTC 2012

On Mon, Feb 6, 2012 at 7:40 AM, Jean-Yves Avenard <jyavenard at gmail.com> wrote:
> Hi there.
> Could anyone try upgrading to the recently released ALSA 1.0.25
> drivers and libraries and try playing some AC3 content (digital
> passthrough) and see if it plays okay?
> Posted on the alsa mailing list:
> Today, I installed 1.0.25 drivers and libraries...
> AC3 passthrough is completely broken.
> My hardware: NVidia GT430, hdmi output
> Device used:
> hdmi:CARD=NVidia,DEV=0,AES0=6,AES1=0x82,AES2=0x00,AES3=0x01
> on Ubuntu 10.04 LTS (but using manually built alsa)
> It makes the application hangs or behaves incorrectly. All the time
> broken, no matter which app.
> Reverting back to 1.0.24 fixes the problem
> I haven't delved much into it yet,
> MythTV (I am the audio developer) after opening the audio device in
> passthrough mode, trying to write audio on the pcm just hangs and
> result in an I/O error after a little while
> snd_pcm_writei returns an error (not immediately)
> snd_pcm_state(pcm_handle) returns 3, snd_strerror(err) returns
> "Input/output error"
> mplayer just hangs...
> nothing obvious in the logs, audio device opens okay, i can't say I
> notice much difference in opening the device, allocating fragment and
> the lot.
> Anyone else has seen this?
> Jean-Yves

I have a non-release version of 1.0.25 on two Ubuntu machines, built
from source, in order to get hdmi audio working, both use
for the audio device setting in Myth, neither have AC3 or DTS working,
I have Myth decode the audio and send as 5.1PCM to a receiver.

it has been this way for a while. I assumed an issue with 1.0.25 and
hoped it would get fixed by the time it was fully released. Since it
worked I've never updated the kernel or alsa on either machine. I was
going to though now that it is final, but now probably not, unless a
fix is known.

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