Elements in preview player are slower than in 60 FPS export

Bug
1

  • What is your operating system?

I’m seeing this on both Windows 10 x64 and macOS Sonoma 14.8.4

  • What is your Shotcut version (see Help > About Shotcut)?

Shotcut 26.2.26 (both platforms)

  • Can you repeat the problem? If so, what are the steps?

Yes; it’s been consistently happening on every project I’m working on (and all of them are in 60 FPS), I’m just reporting on it now after a while to be sure of how to ATTEMPT at describing this!

The obvious way to see this is to have a visible element (e.g. an image), apply certain filters to it; in particular, Distort and/or Vertigo (and Glitch, I think), observe and adjust how fast you’d like it to apply (the velocity parameter, if applicable), export it, and compare to what is seen in the preview player.

I apologize that this report isn’t in extensive detail, I know it’s possible to do a more thorough list of what exact filters and parameters are affected by this, it just would be fairly time consuming (checking a bunch of filters, parameters, exporting and comparing to the preview…for each one), so I wanted to at least make this post FIRST, and see if this is easily identifiable and/or fixable by the devs, but I’d be open to verifying issues with your steps.

My preview player settings has:

  • Preview Scaling → 360p
  • Preview Scaling → Use Hardware Decoder - on
  • Player → Realtime (frame dropping) - on
  • Player → Progressive - on
  • Player → Deinterlacer → One Field (fast)
  • Player → Interpolation → Bilinear (good)

Please let me know if I should pass along any other settings.

2

I think certain velocity-like parameters are being affected by preview scaling when they shouldn’t. Preview scaling is always an approximation and not accurate, in general. As a workaround, turn off preview scaling when you need to fine tune an effect after you notice the export does not match preview well enough. With that said I can fix it for the filters listed, but I doubt I will audit every parameter of every filter.

1 Like
3

Actually, upon further investigation these parameters are not affected by the preview scale, and it is not clear that I reproduce this. I hope you are not increasing the frame rate inside of Export. That would be silly. I am testing mainly with Distort.

4

I’ll see if I can find at least 1 repro process from a new project, thanks for taking a look!

AFAIK I’m not increasing it in Export, the project is selected to be 60 FPS from creation, and I just hit Export for the video, no other settings changed.