[mythtv-users] ac3 passthrough problems

Kevin Mori kmori.nospam at gmail.com
Sat Sep 30 21:18:52 UTC 2006

similar system but the Asus board.  Try playing around with xine and
it's "advanced" audio settings. Mainly I had to adjust the "speaker
arrangement" setup from "Stereo 2.0" for analog and "pass through" for
digital out.  Then you can figure out what to do in Myth based on the
alsa: ALSA:spdif and the default passthrough output device, check ac3
passthrough, etc.

On Sat, 2006-09-30 at 16:57 -0400, Richard Krehbiel wrote:
> I'm building a mythtv system now (about as slowly as anyone possibly
> can), and I'm stumped on the S/PDIF problem.
> I have an MSI K9NGM2-FID - Socket AM2, nVidia GeForce 6150, and I'm
> using on-board sound with Intel HDA drivers (snd-intel-8x0).  I
> installed Fedora Core 5, current updates.  I've got a coax from my
> S/PDIF out to my Onkyo 304, and Onkyo set to consume coax.  (It works
> from an actual DVD player.) 
> I haven't done any alsa configuration.  I looked into it, but frankly
> alsa is impenetrable  (is there a good doc?  I haven't seen one) -
> plus I've read comments saying it should work out of the box.
> I've got a DVD in right now.  I'll play it: 
> mplayer -v -ao alsa -afm hwac3 -monitoraspect 16:9
> -dvd-device /dev/cdrom dvd://1
> I get a nice picture, but no sound.
> The log from mplayer says:
>         Trying to force audio codec driver family hwac3... 
>         Opening audio decoder: [hwac3] AC3/DTS pass-through S/PDIF
>         dec_audio: Allocating 8192 bytes for input buffer.
>         dec_audio: Allocating 16384 + 65536 = 81920 bytes for output
>         buffer.
>         No accelerated IMDCT transform found 
>         hwac3: switched to AC3, 448000 bps, 48000 Hz
>         AUDIO: 48000 Hz, 2 ch, ac3, 448.0 kbit/29.17% (ratio:
>         56000->192000)
>         Selected audio codec: [hwac3] afm: hwac3 (AC3 through S/PDIF)
>         ========================================================================== 
>         Building audio filter chain for 48000Hz/2ch/ac3 ->
>         0Hz/0ch/??...
>         [libaf] Adding filter dummy
>         [dummy] Was reinitialized: 48000Hz/2ch/ac3
>         [dummy] Was reinitialized: 48000Hz/2ch/ac3
>         alsa-init: requested format: 48000 Hz, 2 channels, 100 
>         alsa-init: using ALSA 1.0.11rc2
>         alsa-spdif-init: playing AC3, 2 channels
>         alsa-init: using device iec958:{CARD 0 AES0 0x02 AES1 0x82
>         AES2 0x00 AES3 0x02}
>         alsa-lib: pcm_hw.c:1217:(snd_pcm_hw_open)
>         open /dev/snd/pcmC0D1p failed: No such file or directory 
>         alsa-init: playback open error: No such file or directory
>         Could not open/initialize audio device -> no sound.
> Okay, my /dev/snd directory contains pcmC0D0c, pcmC0D0p, pcmC0D1c, and
> pcmC0D2p.  Whic is a clue - it seems I need to change a 1 to a 2
> somewhere. 
> Please, help.  ALSA's gettin' me down.
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