The problem.

For last two days I’ve been fighting with nasty bug during rendering videos with melt framework video (mlt). For some reason video rendering took about 2-3 times slower than usual. Symptoms ware simple: first melt took 100% of all cores for few minutes doing nothing – output file didn’t grow. Than it started to build output file but only with one CPU core.  Setting threads parameter didn’t change anything.

Biggest help was that I had one computer with properly working melt and three with this error so I was able to compare exact package versions.

Solution.

Comparing  packages I have found what causes problem:

Library libml6 updated to version : 0.9.3+git20141005.22abed67-0ubuntu0~sunab~trusty1 cause whole problem.  Going back to version 0.9.0-3 solved the problem. With Ubuntu just type:

Problem occurred with every tested version I used: Ubuntu 14.04 LTS, Ubuntu 14.04.1, Xubuntu 14.04. Both 32 and 64 bit versions. Hope this helps.