Chroma keying and size and position filter doesnt work together

Bug
1

Hi, Im using Shotcut 16.06 on windows 7 64 bit machine.

I need to do this:

  1. put the green screen video next to the same video (split the screen) using Size and position filter.
  2. Chroma key both (left and right) videos and show some picture instead of green background.

I captured the work flow on the following link.


I created 3 video tracks (first two with the green screen video and the third with desired background). When I use chroma key on the second video everything is OK. When I use chroma key on the first video also, the part of the left video is also cutted out (see picture 3 from the above link) but it shouldnt.
2

I can reproduce this problem, but a workaround is to move the Size & Position after/below the Chroma Key filter on both clips of V2 and V3. You can reorder the filters by drag-n-drop the list items. I will try to fix it, but it might not be for next release.

3

Oh thank you, when I changed the order of filters it works well :). By the way - when I work with this project - two videos side by side with background, playback of video is very choppy. Can I improve it somehow? I guess I can improve it by converting source video to some less compressed format than .mts. Can you recommend some format suitable for video editing? Maybe something only with keyframes?

4

I like to use dnxhd in .mov container. I find it to be a good tradeoff of speed and quality (which I consider to be lossless).

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5

Compositing is slow. Shotcut has a limited multi-core processing mode, but it is only enabled when Settings > Realtime is turned off. That will likely make audio choppy or choppier but probably improve video. Then, there is GPU processing, which helps with compositing but not Chroma Key (not implemented on GPU), and it is experimental and unsupported (do not complain or report bugs about it). The last option is to make a project specifically for a composite effect, export it as a lossless, and then use that result in a larger project where you do not want to experience the choppiness.
P.S. “lossless” can mean truly lossless (e.g. HuffYUV) or visually lossless such as DNxHD or ProRes. As Brian notes, transcoding the clips to DNxHD prior to using them in the compositing sequence may help, but only a little. I think the last option I proposed will be the most beneficial.

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