Created attachment 104919 [details]
Small video showing the effect of the different Blur types once rendered

I was using the Kdenlive version found in the Ubuntu 16.4 (I think version no was 15. something) repositories when I read about the Library tool available in later releases, I wanted to use this so I added the PPA and updated to 16.12.3.

After the upgrade I opened a project I had already been working on that used the Blur effect. Before the upgrade this rendered perfectly.

After the upgrade, I ran a test render of the project and the blur effect produced lots of weird artefacts in the video including large patches of white, yellow and depending on the Blur type, darkening of the image and negatives in part of the image.

The Blur effect is key-framed, starting at about 900 (very blurry) and then resolving to a value of 0 (no blur) over 3 seconds.

I've re-tested this several times with different video files and the all have the same result. Tested Webm and MP4 files with On2 VP8 and H.264 video codecs.

Note: if I scrub through the time line the effects display as expected, If I play the time line I see the same artefacts in the monitor that I see in the render.

I have tested other blur effects such as Box Blur, These do render as expected but they to not look as polished as the Blur effect did in the 15.?? version of Kdenlive.