As I also noted on the launchpad bug, I've found the commit that fixes my issue:
"Avoid an underflow in the SSE mixers if BufferSize is less than 4" http://repo.or.cz/w/openal-soft.git/commit/564a1822595e287cf808ea63a03d96719e3cc7b4 Also, the issue is already fixed in 0.16.0. Can you update the package? -- To UNSUBSCRIBE, email to [email protected] with a subject of "unsubscribe". Trouble? Contact [email protected]

