To be precise with mkv the 8 threads range from 0% to 75%, while with mp4 they range from 40% to
100%. (seen with the KDE system monitor; I don't know how significant it is).
Note that using ffmpeg from the command line does not show any slowdowns (but the settings of cfr or other may be different; I don't know).
The above is helpful information that gg is going to be interested in investigating further. Why such a big difference in cpu usage? --- he will want to see if he can figure that out!
Adam Williams in the 7.1 introduced corrections regarding mkvs
(although for quicktime and not ffmpeg). Could it not be that Cin (not
only CinGG) has an internal problem, not of the engine it uses, that
can decrease efficiency?
From the comments below in filemkv.C from version 7.1 of Adam's, I do not think it is a lack in CinGG, but rather MKV. GG is going to have to look at it as it is way beyond me.
// NOT USED
// an attempt to get frame accurate seeking with MKV, which ended up
// showing MKV doesn't have the required information in the 1st place.
I