Xonar ST: How to Set SPDIF as pcm0?

[adamlau]

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$ ossinfo
Version info: OSS 4.2 (b 2006/201112160254) (0x00040100) OSS_HG
Hg revision: changeset: 942:08a6a3839e88, tag: tip, date: Sat Nov 05 03:31:20 2011 +0200, summary: Fixes for CMedia 8788
Platform: Linux/x86_64 3.1.5-1-ARCH #1 SMP PREEMPT Sat Dec 10 14:43:09 CET 2011 (BeagleSnuf)

Number of audio devices:   2
Number of audio engines:   3
Number of mixer devices:   2


Device objects
 0: osscore0 OSS core services
 1: oss_cmi878x0 Asus Xonar Essence ST (AV100) interrupts=1368 (1368)


Mixer devices
 0: CMedia CMI8788 (Mixer 0 of device object 1)
 1: AC97 Input Mixer (CMI9780) (Mixer 1 of device object 1)

Audio devices
Asus Xonar Essence ST (AV100) (MultiChannel)  /dev/oss/oss_cmi878x0/pcm0  (device index 0)
Asus Xonar Essence ST (AV100) (SPDIF)  /dev/oss/oss_cmi878x0/pcm1  (device index 1)

Nodes
  /dev/dsp -> /dev/oss/oss_cmi878x0/pcm0
  /dev/dsp_in -> /dev/oss/oss_cmi878x0/pcm0
  /dev/dsp_out -> /dev/oss/oss_cmi878x0/pcm0
  /dev/dsp_ac3 -> /dev/oss/oss_cmi878x0/pcm1
  /dev/dsp_mmap -> /dev/oss/oss_cmi878x0/pcm0
  /dev/dsp_multich -> /dev/oss/oss_cmi878x0/pcm0

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$ osstest
Sound subsystem and version: OSS 4.2 (b 2006/201112160254) (0x00040100)
Platform: Linux/x86_64 3.1.5-1-ARCH #1 SMP PREEMPT Sat Dec 10 14:43:09 CET 2011

*** Scanning sound adapter #-1 ***
/dev/oss/oss_cmi878x0/pcm0 (audio engine 0): Asus Xonar Essence ST (AV100) (MultiChannel)
- Performing audio playback test...
  <left> OK <right> OK <stereo> OK <measured srate 48000.00 Hz (0.00%)>
/dev/oss/oss_cmi878x0/pcm1 (audio engine 2): Asus Xonar Essence ST (AV100) (SPDIF)
- Performing audio playback test...
  <left> OK <right> OK <stereo> OK <measured srate 47991.00 Hz (-0.02%)>

*** All tests completed OK ***

S/PDIF is outputting through pcm1, but OSS defaults to pcm0 (analog multi/stereo) for playback (i.e. unable to use S/PDIF digital coax out). How to set default placyback device to pcm1 (digital coax)? Would I simply modify the symlinks in /usr/lib/oss/etc/legacy_devices? UPDATE: I'll give the wiki walkthrough on changing the default sound output a shot first...

[cesium]

I intended to link to that guide before seeing your update... Do let us know should it not work.

[adamlau]

Will do...When I get another DAC in towards the end of January 2012...

[adamlau]

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$ sudo ln -sf /dev/oss/oss_cmi878x0/pcm1 /dev/dsp

...and saving the /dev/dsp setting in /usr/lib/oss/etc/legacy_devices did the trick (S/PDIF is now the default output device)...

However the issue with not being able to play 24/32-bit files as referenced in ASUS Xonar ST Not Working? persists:

1. Analog (RCA) out is unable to play 24/32-bit files without severe tempo/pitch anomalies.
2. S/PDIF out downsamples 24/32-bit files to 16-bit before playback at proper tempo/pitch speeds.
3. S/PDIF out through ALSA (--disable-mixer in alsa-lib) is able to play 24/32-bit files at correct bitrates/tempo/pitch speeds.

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$ ossinfo -v9
...
Asus Xonar Essence ST (AV100) (SPDIF)  /dev/oss/oss_cmi878x0/pcm1  (device index 1)
...
Output formats (0x00001410):
AFMT_S16_LE   - 16 bit signed little endian
AFMT_AC3   - AC3 (Dolby Digital) encoded audio
AFMT_S32_LE   - 32 bit signed little endian

So the Xonar ST does not support 24-bit files. Could this be the culprit when vmix is disabled?