Comment 7 for bug 1101907

> I don't think we have a metric for what we can and can't afford -- any suggestions?

I do not have a metric for it. The whole topic is quite difficult because we have to share the CPU with virus scanners among other things.
On on hand, more threads are good, because the OS is able to make use of all cores. On the other hand, they are bad, because once we have 100 % load, we cannot gain CPU by an other thread, it will make things worse.

For Auto DJ needs the library, so we are bound with the library thread. We may only fix the issue that fading is not smooth by moving this to the engine thread.