PBM: "IEC958 default PCM" no longer seems to work

[VinzC]

Hi everyone.

If I'm correct, all of a sudden sound stopped going through the SPDIF link. I have absolutely no idea what I could have done to make it so (although I have a doubt I did anything at all but, well, let's leave that door open, just in case). I did indeed do an upgrade to my system but it was days before I got into this issue.

This problem occurred on my machine, which I installed from scratch, like two months ago. I did only *one* emerge --sync and only *one* upgrade ever since. However it was a couple of days before last Saturday, the day I played UT 2K4 (you might happen to not give a single damn, I know that) and sound was fine through the SPDIF link. See? Sounds (ha ha) weird, eh?

Then suddenly on Monday evening I noticed I got sound only with mplayer (which I had configured using /etc/mplayer/mplayer.conf to play directly through the hardware digital output). Neither Exaile nor the command line play tool, for instance, did output anything anymore. It took me a while until I considered the IEC958 switch might be involved.

By the way I have *never* — on that machine — been required to use an .asoundrc file; just my mixer's "IEC958 default PCM" switch. Ha! Of course, if I set up an .asoundrc accordingly, I get sound through the SPDIF link. But that's not my question, no-no-no!

The thing is: how come can a sound parameter get screwed on its own? Am I dreaming or did I consume something without knowing? (Yeah, of course nobody but me can answer the latter... hmwell...)

Ah, yes, the only “weird” thing that happened is that mplayer once froze on Monday evening while I was ripping a DVD and testing some samples. I had to forcibly reboot the machine with the magic Ctrl+Alt+SysRq,SAK keys. Dunno if that could have screwed my alsa settings... But it's not the only one time my machine gets unresponsive but only when I play Flash videos. (Like when I forget to stop the player before I navigate to the previous page in Firefox, for instance. But that's another story and I know it's about VDPAU. I'm digressing, sorry.)

The only one thing I can tell is that now the alsa mixer setting "IEC958 default PCM" no longer seems to drive sound through the SPDIF output like it used to. Neither alsamixer nor Xfce sound mixer have an effect on this. Does anybody have an idea what could cause this issue? And how to make that bloody IEC958 selector work again?

Thanks a whole bunch in advance.

P.S.: I don't smoke (my feet sometimes do however), I don't drink. I'm all natural. Just in case you'd wonder.
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Gentoo addict: tomorrow I quit, I promise!... Just one more emerge...
1739!

[OmegaWeapon]

I come as a traveller from Debian via Google - I had a problem that sounds very similar to this - I had lovely mixed automatic output through S/PDIF, then it suddenly stopped - I had to direct programs to output through the device and it no longer mixed.

The solution was discovering iecset and the great wiki article on Digital Out - the S/PDIF interface was stuck in 'non-audio data mode', i.e. passthrough - ALSA hadn't flipped it back to 'audio data mode' after I stopped playing something that needed the passthrough (very surprised that this problem survived a reboot to become permanent?). Since I only have one S/PDIF interface I just issued 'iecset audio true', and suddenly I got automatic mixed output through S/PDIF again

I then tested the mixing by spamming aplay along with using quodlibet to play some music, and managed to kill the mixing. Luckily all I needed to do to restore sanity at this point was restart the S/PDIF interface (toggle the switch, or mute and unmute the switch in alsamixer terms) - back in control finally.

[VinzC]

Thank you so much OmegaWeapon! I had stopped caring and accepted this issue a long ago. Reading about this however gets me somewhat on the tracks. I'll probably do some testing.

Jut note that a couple of issues that I had have found a solution with recent kernels. For instance mixing is now natural with ALSA and I no longer lose the few instants of audio since kernel 3.10 (IIRC). So I might expect the recent updates somewhat have cleared this very issue but at least you've given me enough white stones for my curiosity.

Thanks a lot again.
_________________
Gentoo addict: tomorrow I quit, I promise!... Just one more emerge...
1739!

[OmegaWeapon]

No problem - I've only started using ALSA within a few months after migrating from OSSv4 - was very pleased to get S/PDIF out and mixed at that for free (requires some basic configuration in OSSv4).

For reference, Debian Testing with kernel 3.10.11-1 here.