Threaded Optimizations in 378.13 make "shotcut" stutter with workaround

Although it has been some time, I would like to point out that the issue has recently been fixed on the side of shotcut, or more precisely the MLT framework:

https://github.com/mltframework/mlt/commit/c3574674e7d72ef2c81d90fb561bdfcaa5c7101f

Thanks