kdenlive-19.12.0 and 19.12.1 too slow to be usable

[Simon Gerraty]

Hi all.

I cc'd ports, since kdenlive depends on lots of other packages.

kdenlive-18.x was working fine on my
i9-7900X CPU @ 3.30GHz (10 core), with
NVIDIA GPU GeForce GTX 1050 Ti

I recently ran pkg upgrade -f, and now with kdenlive-19.12.0
is it completely unusable.

The display is sluggish (to put it kindly); the play head moves in big
jumps (stalls for several seconds at times), the video does not display
even close to smoothly, and the audio is out of sync. 

There is also a huge volume of debug info being spewed to tty, with what
looks like lots of errors.  Which I did not see with 18.x

Since the release notes for kdenlive 19.12.1 mentioned disabling debug,
I tried downloading the kdenlive-19.12.1 from the latest pkg build, and
that installs and runs, but I still see lots of debug noise on tty
and the performance is still too bad to allow editing of anything.

Just to confuse things further, a machine at work, which run pkg
upgrade -f at about the same time, kdenlive-19.12.0 works tollerably
despite the endless stream of debug output.

That box has Xeon(R) CPU E5-2637 v3 @ 3.50GHz (8 core) with
NVIDIA GPU Quadro K4200 (GK104GL)

Thoughts?
--sjg