[alsa-devel] M-Audio Audiophile 192 (ice1724)'s broken spdif capture
jnsptrsn1 at gmail.com
Sat Jan 26 17:35:50 CET 2013
I'm trying to get spdif capture to work properly on the M-Audio Audiophile
192 (VT1724/Envy24HT). It is generally working, but I don't get a clean
I have "Multi Track Internal Clock" set to "IEC958 In" (spdif in). When I
capture via Jack, arecord or Audacity I experience the following two
1.) The captured signal ends up 6 dB(FS) to loud (200%)! Everything above
-6 dB is distorting. A 1 kHz sine test signal at -12 dB (25%) will be
captured as -6 dB (50%).
2.) The left and right channels are shifted by one sample! When I feed a 1
kHz test signal (L+R are _exactly_ the same signal), the right channel will
be offset by exactly one sample. Zooming into the waveform clearly shows
that. Analyzing the signal with a goniometer shows a (slight but obvious)
vertical eliptical shape and not the expected single vertical line.
To make sure the hardware actually works fine, I did install a Windows 7 on
the exact same machine, installed the drivers from M-Audio and did some
recording with audacity. The result is as expected: the -12 dB signal ends
up as -12 dB and the left and right channel exactly match each other. So
the hardware is willing.
I am running a Lubuntu 12.10 and I'm am able to compile and run the current
alsa-driver source with the 3.5.0-22 kernel. I played around a bit with the
alsa driver source (e.g. pci/ice1712/ice1724.c, pci/ice1712/revo.c) and I
am able to compile and load a modified driver. So far I only was able to
make the problem worse though.
I'd now like to ask for some advice on how to approach the problem. I guess
the fact that the left and right channel differ - even though they
shouldn't - might be a thing to look for. This must be happening at some
stage in the capturing. Is there a way to hook in at different places to
narrow down what causes this?
Maybe this even already rings somebody's bells?
I'll be glad to deliver more information when needed.
Thanks and regards,
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