[Alsa-user] Listening to SPDIF input on ALC650 / via82xx

[Nicholas P. <nic...@ni...>]

I've been trying for days to listen to (or record, or get anything at
all out of) my card's SPDIF input.

I have an Asus A7V8X motherboard, which has the VIA8235 with an
ALC650.

I've learned that:

When I'm recording (with an OSS program) and I switch on "IEC958", the
recording program hangs until I continue (or else gives up after a few
moments and exits.)

My source (a standalone DVD player) is set to giving out PCM. If I
listen to its optical output (via a portable Minidisc player) I can
hear the music correctly. (The DVD player can also be told to output
the bitstream, I presume this is the 'raw' AC3 as found on the DVD.)

I have no gear to check its Coaxial output. I have tried with both a
cable directly from its coax output, AND with a Optical->Coax
converter plugged into its optical output.

So I'm pretty sure that my coax lead has valid SPDIF PCM data (if I've
understood the terminology correctly), but alas not certain---I have
no way of checking my new optical->coax converter works.

I have learned from my motherboard manual that it doesn't like AC3
input, only PCM. (To quote the manual: "The AC-3 SPDIF-In function is
not supported by ALC650, it only supports stereo SPDIF-In".)

(I'd like to use this digital input regardless, otherwise my sound
from my DVD player has to travel through many SCART cables, then into
my TV card, then out again, and into my Line-In. THEN out again, and
to my HiFi. It sounds *very* poor after all that.)

I don't have Windows to check how it works in Windows.

I don't have any Amplifier or HiFi that can take digital input.

If I do this:
    strace arecord -Dplug:spdif
It hangs at:
    open("/dev/snd/controlC0", O_RDONLY)    = 3
    close(3)                                = 0
    open("/dev/snd/controlC0", O_RDWR)      = 3
    ioctl(3, USBDEVFS_CONTROL, 0xbfffecb8)  = 0
    ioctl(3, 0x40045532, 0xbfffecb8)        = 0
    open("/dev/snd/pcmC0D0c", O_RDWR

Exactly the same with just -Dspdif

I want to be able to listen to my DVD like this:

             COAX/SPDIF                  Normal Audio cable
 DVD Player ------------> Soundcard DAC ------------------> HiFi 

Maybe passing through userspace for volume/level adjustment, and also
so I can record the sound sometimes.

Thanks for *any* help or hints !

 Nick

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