[mythtv-users] MythMusic spdif only works with some deciders-preamps

[Allen Edwards]

On Thu, Feb 12, 2009 at 6:59 PM, Phil Wild <philwild at gmail.com> wrote:

> <snip>
> Can I first suggest you work outside of mythtv and test with aplay
>
> aplay -Dhw:X,Y soundfile
>
> Check that it plays on both devices
>
> if not, try
>
> aplay -Dplughw:X,Y soundfile
>
> Cheers
>
> Phil


Great idea!!

This is very interesting.  Here are my results.
$ aplay -Dplughw:0,1 file.wav  -- only the Technics decoder played
$ aplay -Dhw:0,1 file.wav   -- only the Technics decoder played

Now get this:
$ aplay -Dspdif file.wav     --  BOTH decoders played!!!
$ aplay -Diec958  file.wav     --  BOTH decoders played

Now, I thought that spdif was the same as the digital output which as you
can see below is card 0 device 1..

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


I have looked high and low in the alsa documentation and cannot find a
plugin named spdif but there is one called iec958.  Is this a synonym?
 Plugin: iec958 seems to take the PCM data and so something with a preamble,
perhaps adding an iec958 preamble to the raw pcm data.  Apparently one
decider requires the preamble and the other one doesn't.

But, this has implications for mythtv if people set up their hardware with
hw:0,1 and their receiver can't decode it.

I guessed at some ways of using spdif or iec958 in alsa.conf but nothing
worked.


So, anybody know what is up with this???

Allen
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