I changed from Mint to Ubuntu, 17.04. Installed the latest KDEnlive from the repos 16.12.3.

My camcorder is a Canon Legria FS200 and the previous versions of KDE were fine (15.12.3) ... but this version is declaring it as an invalid clip.

I'm temporarily getting around this by using VLC to convert the file, but I'm not sure whether my problem actually lies with KDEnlive or with Ubuntu. Perhaps I'm missing a codec that Mint has? I'm not sure.

I'd be grateful for any ideas on where I should start looking for a solution.

You can run a few tests to get and idea where the problem is
Can ffplay play your file ? From a terminal:
ffplay myvideo.mpg

Try playing your video file with MLT's player. From a terminal:

melt myvideo.mpg

No, it can't play it directly...

[libopenmpt @ 0x7ff838000920] openmpt_module_create_from_memory: ERROR: error loading file
MOV005.MOD: Invalid data found when processing input

Got the ffmpeg issue sorted with another flag -f mpeg ... now to work out why KDEnlive doesn't like it.

Is the "MOD" extension a copy-paste error? I've never seen such a format, what seems confirmed if you have to force the format detection with ffmpeg.
Just renaming the file with the right extension (MPG? MOV?) will maybe solve recognition by MLT?

I ran into this with MP4's directly from my GP-clone camera. The solution was to invoke a custom project folder. Why there's a connection escapes me, but that was the cure. I didn't need to transcode or anything else.

When choosing a custom folder, use the browser option!!! At least on my system, pathway/filenames are appear to be white on white.

The MOD extension is not an error. That's the file that comes off the Canon FS200.

Here's one of the files - http://msknight.com/bbc/videos/MOV015.MOD

Thanks Remerson - I'll try that tonight.

OK - if I rename the extension of the file to mpg then it takes it. But it rejects the same file with a .mod extension, as comes off the camera.

No clue why.

It is as if kdenlive is going off the file extension and isn't actually looking inside the file to see what it actually is.