Pulseaudio – this battle maybe won but the war lingers on
Pulseaudio seems to cause many, many problems for a lot of people. Unfortunately that’s partly the nature of audio applications on Linux. Let me explain. Only one program can talk to the soundcard at once – so you can either listen to OGGs/MP3s or get IM “ping”s, but not both. Obviously this is a tad poor so software mixers (like esd and artsd) were born, they then talk to the soundcard and you talk to them. LWN has a nice [http://lwn.net/Articles/299211/ writeup].
This has been going on for a large number of years now, never seeming to be resolved. The latest upstart (pun intended) is Pulseaudio and so it bears the bulk of complaints.
Today my sound stopped working – I only saw “Dummy output” “No cards detected”. Thanks to Alan Pope for assisting debugging this, (basically killing pulseaudio then running “pulseaudio -vvvv” helped to see what the problem was). This is best described in [http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=549001 #549001] – in my case it wasn’t just the HAL->udev transition but the CONFIG_SYSFS_DEPRECATED setting that Rupert Swarbrick mentioned. It’s very unusual for deprecated settings to cause problems, but this one does (it causes issues with another program, but I forget which).
I’ve rebuilt my kernel without CONFIG_SYSFS_DEPRECATED and it’s working nicely once again. As a bonus I can try out [http://www.linux-kvm.com/content/using-ksm-kernel-samepage-merging-kvm KSM] for better virtualisation performance.