In the newer versions of Kdenlive, in the moment when I drop the denoiser onto a video track, it crashes.
The last few lines of the GDB log are:

--------------------------------------------------------------------

New Thread 0x7fffd26e2710 (LWP 4312)]
[New Thread 0x7fffd2ee3710 (LWP 4313)]
[Thread 0x7fffd26e2710 (LWP 4312) exited]
[Thread 0x7fffd2ee3710 (LWP 4313) exited]
[New Thread 0x7fffd2ee3710 (LWP 4314)]
[New Thread 0x7fffd26e2710 (LWP 4315)]
/home/mc/kdenlive/20110702/bin/kdenlive: symbol lookup error: /home/mc/kdenlive/20110702/./lib/frei0r-1//hqdn3d.so: undefined symbol: LowPassMul
[Thread 0x7fffd26e2710 (LWP 4315) exited]
[Thread 0x7fffd0edf710 (LWP 4300) exited]
[Thread 0x7fffd2ee3710 (LWP 4314) exited]

Program exited with code 0177.
bt
No stack.
thread apply all bt
where full
No stack.

-----------------------------------------------------------------

LowPassMul is just a function in the denoiser plugin (hqdn3d), why would it suddenly become undefined?

The strange thing namely is that LowPassMul is an inline function!
Shouldn't the compiler just insert it at appropriate places, and not export any symbol at all?

BUMP...

Still haven't figured this out. It could be my fault, being author of the plugin... However, if I use the same filter with ffplay or melt, like this:

ffplay somevideo.avi -vf frei0r=hqdn3d

or this:

melt somevideo.avi -filter frei0r.hqdn3d

it seems to work OK!

Should I make a bug report to Kdenlive?
(The name of the filter in Kdenlive is Enhancement > Denoiser)

If I remember correctly, this crash only happens when MLT / frei0r is built using the build script. Please check bug report:

http://www.kdenlive.org/mantis/view.php?id=2289

Where I posted a modification to the build script that fixed things for me, and post feedback there...

Signed up for new account on mantis, still waiting for the confirmation mail...

OTOH, changing the build script did solve the problem.

Compiling Frei0r should be done with -O2 in any case, it brings up to 2X improvement in speed with many plugins!