Sometimes, Murphy make you curse the wrong software, or the wrong people, or both.
With kernel 2.6.29, the iec958 output from my soundcard (ICE1712-based) decided to stop working properly and started getting white noise out after a while. I never had enough time to properly debug it so I left it alone. Now 2.6.30 landed, and magically the output seemed to work fine. To a point; after a while playing music I could start hearing screeches, both with PulseAudio and with direct output on the soundcard.
Changing resampler settings, format setting, all the possible setting, nothing worked. I started cursing ALSA, the soundcard producer, possible bugs along the way…. then I tried one thing out of desperation:
% speaker-test -c 2 -t sine
The default for speaker tests, both from ALSA and the internal one for self-diagnostic of my A/V receiver (which is what gets the final output) use by default pink noise. The result is that you cannot identify a distortion along the way, at least not easily and not if you’re not a technician to begin with. The sine method instead uses a sinusoidal soundwave. A single-tone, continuous beep. Much nicer to find the failure point.
Indeed, this let me find a nasty screeching sound on the left channel speaker. From that, it was just a metter of getting dirty (literally) with trying the speaker on a different channel, with a different cable, and the cable with a different speaker to make sure that the problem was, indeed, the cable itself. Luckily, because if it was the speaker it wouldn’t have been as cheap, and also because I do know Murphy well enough to have cables at home, so I change the cable, and the noise disappears.
For a while at least because now it resumed again. I’m not sure what the problem is at this point, I’ll doublecheck with an analog input in case the problem is actually server side, but I’m afraid the problem is in the receiver itself, maybe the temperature got it to fry up something. Whatever the problem, it’s a nasty one.
So now I’m again without audio on Yamato (which makes maintaining PulseAudio a bit of a problem to be honest), and relying on Merrimac to play music, not the best choice I have to say.
Suggestions for a new sound system, stereo, good stereo, no (strict) need for surround or subwoofer, digital interface with computer required, are very welcome.
Update: after some more fighting with cables, receiver, ground, speakers, computers, it turns out the problem isn’t, after all, the receiver: plugged in the iMac with the optical interface it’s fine, and even the coaxial S/PDIF interface, together with the cable connected to it, are fine once connected to Enterprise (booting Fedora 11 live) and the via82xx integrated soundcard.
So the problem is either in the ICE1712 soundcard or the related driver. I don’t want to track down the issue further at this time (my time is all allotted up already) so I’ve added an USB soundcard to my wishlist and will wait a bit, using the iMac with the receiver. Further details at the end of this other post if you care!