Forcing frame rate to achieve slow motion effect works in timeline, but renders incorrectly

First time post, (relatively) long-time Kdenlive user. Thanks to all the developers who make it available!

I am currently working with a Kodak Playsport portable HD camera, which is capable of 60fps at 720p. I took some 60fps footage with the intent to slow it down during editing, but Kdenlive currently re-samples all clips to the project's designated frame rate (I want my finished product to be 29.97, so that's what everything gets re-sampled to). I found that you can "force" whatever frame rate you want if you right-click the clip and select Clip Properties, so I set it to the clip's native frame rate (59.94) to see what would happen. Not what I expected; the clip still played at 29.97, but it was playing slower now. I assume that "forcing" the frame rate meant it was now using all frames in the file, but still at the same speed of 29.97 frames per second, thus the video would play at half-speed. Perfect!

I had a little bit of trouble getting the clip I wanted in the clip monitor (if I clicked ahead in the progress bar, it would simply start the clip over from the beginning), but I finally got it in the project timeline and it looked fine. Then I tried to render it. What I got was the intended effect (60fps at half-speed), but it was the beginning of the clip, not the section I had selected in the monitor.

I'd like to file a bug report, but I'm not sure where it belongs. Is this a Kdenlive issue or an MLT issue? Any help would be appreciated, thanks!


Why not set the project up as 720p 60fps, then when you render it, set the 30fps you require? Then, when the video is imported, it should work correctly at 60fps

Just tried it, but it didn't render properly; the rendered video starts fine with a title clip, but the first video clip just shows a still image, before switching to another for the next video clip. I added "r=29.97" to the Render profile. That's the way to set the frame rate, correct?

Never change the render frame rate different from the project frame rate. It will screw up the timing of all your edits. This is a known limitation and not supported. However, it might be fine to do that for a simple transcode-like operation, which is what I think moorsey was suggesting.

apologies, I thought you could work it like that, never had to do it myself, so apologies if I put you in the wrong direction. You could keep everything at 60fps, so the project settings and then the render. Then, when the output is looking correct, transcode it down to 30fps, if that is what you need

I've found that converting the original video to slow motion. For example if your original is at 120fps, you convert it to 30fps which is 25% of the original. When in kdenlive you can use the motion effect 400% to make it normal speed but where you need to do the slow motion you can put it back to 100% and not get a horrid jerky output.

Here's a page that explains how to convert your video to the slow-mo video:

It doesn't take the audio over (I don't know why) but you can get that from your original video.

I hope this helps.

Hi, i fond this code :

is possible to compile this two line code and add it to transcoding - option in kdenlive ?

so then we have slowmotion in right click - very thanks for example