[alsa-devel] ca0106 SPDIF Output Problems

[Ben Stanley]

Hi,

I am having some problems getting sound out of a ca0106 card using
SPDIF. I have enabled SPDIF output using alsamixer. Some programs
produce sound, and others stubbornly don't.

I need some hints about what to try next, what information I could look
at, to be able to diagnose some factor common to the failures, and
hopefully the cause.

I am familiar with part of the driver, I have already written a patch
which used to enable 44.1kHz output on an earlier Ubuntu.

Anyway, the details are all recorded below. I would appreciate it if a
patient person could have a look through and throw me some ideas.

Thanks,
Ben Stanley.


I did a git checkout yesterday and built alsa 1.0.17rc3 on Ubuntu 8.04
kernel 2.6.24-19-generic.

I used the following configure options:
./configure --with-debug=full --with-cards=ca0106
--with-moddir=/lib/modules/`uname -r`/alsa-driver-orig

(I am using the --with-moddir to avoid clobbering the distro alsa
modules. I am selecting which modules to use by editing /etc/depmod.conf
and changing the priority order, and then re-running depmod. I can
verify the result by checking /var/lib/`uname -r`/modules.dep .)

Everything builds and installs without any warnings or errors.

So, after all that, I tested three applications:
MythTV
xine
speaker-test

My sound output is via SPDIF to a Yamaha RX-V557 digital amplifier.

I only get sound out of MythTV. I get nothing out of xine (playing
flacs) or out of speaker-test. However, I do get signal out of xine
playing DVDs.

Details:
================================================================
speaker-test --device-hw:0,0 --channels=2 --rate=48000
This should work, but instead it produces no SPDIF output. The amplifier
shows no digital signals.

root at mythtv:/proc/asound/card0/pcm0p/sub0# cat hw_params 
access: RW_INTERLEAVED
format: S16_LE
subformat: STD
channels: 2
rate: 48000 (48000/1)
period_size: 4096
buffer_size: 16384

================================================================
Testing with xine playing a 44100Hz stereo S16_LE flac:
root at mythtv:/proc/asound/card0/pcm0p/sub0# cat hw_params 
access: MMAP_INTERLEAVED
format: S16_LE
subformat: STD
channels: 2
rate: 48000 (48000/1)
period_size: 1024
buffer_size: 8192

The amplifier says 'Unknown Digital', NO SOUND PRODUCED.

================================================================Testing
with xine playing 'Riverdance' DVD in DTS surround with AC3 Passthrough:
Sound output WORKS
Amplifier says 48kHz DTS
root at mythtv:/proc/asound/card0/pcm0p/sub0# cat hw_params 
access: RW_INTERLEAVED
format: S16_LE
subformat: STD
channels: 2
rate: 48000 (48000/1)
period_size: 2048
buffer_size: 16384

================================================================
Running MythTV: Configured to open ALSA:hw:0,0 directly.
root at mythtv:/proc/asound/card0/pcm0p/sub0# cat hw_params 
access: MMAP_INTERLEAVED
format: S16_LE
subformat: STD
channels: 2
rate: 48000 (48000/1)
period_size: 8192
buffer_size: 16384

The amplifier identifies this as a 48kHz PCM signal.
Sound output WORKS.
================================================================

As a general observation, this problem was present in Ubuntu 7.10, but
was 'intermittent' (I used to be able to get speaker-test and xine
playing flacs to work most of the time.) The failures now seem to be
permanent after upgrading to Ubuntu 8.04, whether latest alsa-git is
installed or not.

Now, I need some ideas for what to look for here. I can't see
differentiating factor between things that work and things that do not.
Perhaps I need to look at some registers.
I don't know what relationship the files at 
/proc/asound/CA0106/ca0106_reg*
have to the registers declared in
alsa-kmirror/pcm/ca0106/ca0106.h
but I think I understand the registers from the header file.

Ideas please?

Once I get this sorted out I can test my patch allowing 44100Hz sampling
rates to be output to SPDIF. At the moment this bug is preventing me
from testing...

Thanks,
Ben Stanley.