[mythtv-users] SPDIF passthrough

Jason Jesso jjesso1607 at gmail.com
Tue Feb 5 16:14:12 UTC 2008

I am trying to output 5.1 audio through my sound card's digital output to my 
a/v receiver for decoding.  I cannot get this to work in Mythtv.  I can play 
the H.264/AC3 MKV file, but no passthrough to my receiver.

My current settings are:

Audio output device: ALSA:cards.pcm.iec958
Passthrough output device: ALSA:iec958:{ AES0 0x02 }

- Enable AC3 to SPDIF passthrough (CHECKED)
- Enable DTS to SPDIF passthrough (CHECKED)

What could be wrong with this?

I do have success with mplayer:
mplayer -afm hwac3 -ao alsa:noblock:device=hw=0.1 whatever.mkv

BTW, all channels are unmuted.  (works with mplayer)

The following is more sound hardware info:

$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: NVidia [HDA NVidia], device 0: ALC883 Analog [ALC883 Analog]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: NVidia [HDA NVidia], device 1: ALC883 Digital [ALC883 Digital]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

$ aplay -L
    HDA NVidia, ALC883 Analog
    Default Audio Device
    HDA NVidia, ALC883 Analog
    Front speakers
    HDA NVidia, ALC883 Analog
    4.0 Surround output to Front and Rear speakers
    HDA NVidia, ALC883 Analog
    4.1 Surround output to Front, Rear and Subwoofer speakers
    HDA NVidia, ALC883 Analog
    5.0 Surround output to Front, Center and Rear speakers
    HDA NVidia, ALC883 Analog
    5.1 Surround output to Front, Center, Rear and Subwoofer speakers
    HDA NVidia, ALC883 Analog
    7.1 Surround output to Front, Center, Side, Rear and Woofer speakers
    Discard all samples (playback) or generate zero samples (capture)

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