XMMS vs S/PDIF passthrough?

Christian Weisgerber naddy at mips.inka.de
Sun Feb 8 09:09:25 PST 2009

Setup: 8.0-CURRENT, snd_hda(4), S/PDIF output connected to AV receiver.

What works:
* MPlayer's AC-3/DTS passthrough for playing DVDs
* XMMS's digital audio extraction for playing audio CDs

What doesn't work: Using XMMS to play a DTS CD.  The receiver fails
to recognize the signal as DTS and interprets it as PCM 44.1 kHz
=> noise.  Ripping a track and using XMMS to play the .wav produces
the same result.

For those who don't know, a DTS CD is just like a normal audio CD,
except the audio stream isn't really the usual PCM but actually
DTS.  The CD player doesn't know or care, though, it can just pass
the stream through the S/PDIF interface.  No additional encapsulation,
rate change, or other transformation needs to be performed.

This should work _in principle_.  (It also does on OpenBSD.)  XMMS
just needs to send the bit-exact digital audio stream and the
receiver will take care of the DTS decoding.  But somehow the audio
data is munged along the way.


Christian "naddy" Weisgerber                          naddy at mips.inka.de

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