[mythtv-users] AC3 passthrough still doesn't work.

[Hamish Moffatt]

On Sat, Oct 23, 2004 at 10:46:58PM -0500, Bo Najdrovsky wrote:
> Well, I've made quite a bit of progress on my HD2000 based MythTV box, 
> but there is one last remaining nagging issue, and that's the fact that 
> the AC3 passthrough does not work in mythfrontend.  I'm able to play the 
> recorded .nuv files with mplayer, and the AC3 passthrough works fine 
> with that program when I use the command line option -ao 
> alsa:device=spdif    This fact confirmed for me that my hardware is not 
> at fault, but the bug must be in Myth.  I went and recompiled MythTV 
> 0.16 to make sure that ALSA output is enabled, restarted everything and 
> put ALSA:spdif into the audio device field in front end configuration, 
> but the results are the same as with OSS... I hear about quarter second 
> of audio, and then silence.  I'm guessing that perhaps mythfrontend 
> isn't setting up the SPDIF port correctly.  Any ideas?

Hi Bo,

One idea along the lines of setting up the SPDIF stream correctly. In Xine, 
the default device name for AC3 passthrough is

iec958:AES0=0x6,AES1=0x82,AES2=0x0,AES3=0x2

The :AESxxx parts set some bits up in the SPDIF stream which tell the
receiver that it's AC3. You might try entering all of that as your
device name in Myth (with the ALSA: prefix). I haven't tried this so I
have no idea whether it will work.

While Myth is playing, try running iecset to query the SPDIF output
parameters.


Hamish
-- 
Hamish Moffatt VK3SB <hamish at debian.org> <hamish at cloud.net.au>