videoencoder: Autodetect/autoconfigure multicore/multithread use
Submitted by Jeff Fortin Tam
As initially reported in pitivi bug 573395, there are various codecs where the user has to manually set the amount of threads to use when encoding. Theora, x264 and VP8 seem to behave differently or in strange ways. I haven't tested other codecs yet.
Users should never have to set those things manually. GStreamer encoders should use the multiple cores efficiently by default, no matter what the codec.