Ever since the Ubuntu folks switched their underlying sound architecture from ALSA to PulseAudio, I’ve had some manner of issue or another. At first, it was certain applications (e.g. Audacity) not running, due to never having been coded to use Pulse instead of its default, needing hours to hack around. Then after PulseAudio sorted out its own ALSA backward compatibility, it was the server crashing every time I opened an RDP connection using RDesktop (a recent version thankfully fixed that issue).
Today, I did some manual updates for my Jaunty installation, the first I’d done in about a week. I have automatic updates disabled on my work laptop for a number of reasons. One of the packages that came down was evidently PulseAudio, because after a reboot, sound wasn’t working. Nothing was showing as out of the ordinary on dmesg (the Linux command line based system event viewer — like in Windows going to My Computer > Manage > Event Viewer > System, or under Ubuntu you can go to System > Administration > Log File Viewer), and when I installed the PulseAudio Device Chooser applet to get access to the default device configuration, it was showing my sound card was functioning perfectly and was even outputting sound properly according to its internal diagnostics. My system volume was turned up, the laptop’s mute function was not active, and as far as I could see, everything else was working just fine, so I Googled the problem, and found this.
I wasn’t having the shutdown problem described in the bug report, but I’d had problems with ALSA disabling its own PCM in the past, so I opened my volume control via the sound icon and found that the PCM slider was all the way at the bottom, and the Mute button for it was ticked. PCM is the equivalent of the “Wave” slider under the Windows volume control — it’s the slider that handles most of the sound output aside from the “master” volume control, so basically anything that’s playing and isn’t a CD in the CD-Rom would be affected by it. I increased the volume on PCM and un-muted it, and magically sound started working again.
Now that I know this can happen because of a PulseAudio upgrade, I’ll think to look at this first, the next time this happens. But ultimately, why did it have to happen? I can’t think of a reason to ever change the PCM volume in the process of an upgrade — and if you have to default it to anything because the settings get wiped, it should default to 80% or something like that, something reasonable that doesn’t give a person the impression that something got broken over the course of an upgrade.
Don’t get me wrong. PulseAudio was a necessary and in fact laudable step toward unifying the Linux sound architecture world, where it can not only mix multiple sound streams, but can output to different sound devices or all sorts of devices simultaneously, including over the network. I will one day build a media centre that we can tune into from any computer in the house (probably including my Wii using Mplayer on the Homebrew Channel). But until that day, it’d be nice if they get the little things right before uploading their new versions.
Or maybe one day I’ll get around to learning C and step in myself…