V21.04 ALPHA/UNSTABLE - Time Remap

[brian]

@DRM

6) The speed is not starting at 1.00000 now. It starts at a speed past it. With this clip it’s starting at 1.00028x:

Good catch. This is fixed now.

@DRM

7) I’ve experienced the same thing that @MusicalBox is reporting with the Smooth keyframe. The behavior of it has to be looked at because it’s too erratic to the point of being useless as it’s so unreliable. This doesn’t happen on other keyframes with curves. I’m expecting a smoother transition between two speed points but sometimes it just decides to reverse footage and go forward again and there is nothing on the curves to show that it’s doing that. To reproduce this right after adding the Time Remap filter add three keyframes that are about 4 seconds apart from each other. Do not alter the time or speed on any of them. Just add those three keyframes. Then change the second of those three keyframes to smooth. When you play it back and it gets closer to that second keyframe you will see it reverse for no reason even though no change to speed or time was applied. Here is a demo .

The reason that this occurs is because for smooth keyframes Shotcut tries to fit a line for the smooth keyframe, the two keyframes before it, and the two keyframes after it. In your demo, the “2nd keyframe after” is all the way at the end of a long clip. You can “fix” your same example by adding one more keyframe one second after the last keyframe. By doing that, you can “coerce” the line fit to be more subtle and it will not try to go backwards. I agree that this might be unexpected or counter-intuitive for users. I do not like applications where there is a “trick to it”. But it is also a lot of work to implement a new curve fit algorithm. I hope that with this additional explanation some people can experiment further and we can brainstorm ways to make it more intuitive without throwing away what we have. Give it a try, and let me know what you experience.

@DRM

8) Simply adding the Time Remap filter adds crackling sounds to the audio. This can be heard in the demo I just linked to above.

I experience this sometimes, too. It has not been a priority for me to investigate. I think it might occur more often when the clip sampling frequency does not match the playback sampling frequency (48,000). If you have some time to experiment with sampling frequencies, let me know if you find any correlation.

@DRM

9) I’m not sure what the filter trim buttons are doing now but they behave strange. If I put the playhead right in the middle of the default start and end keyframes and press the left filter trim button then I press the reset button in the time parameter, even if it looks like the start keyframe is at its default position it’s actually frozen. So it ends up that the first half is frozen.

I have a work-in-progress to improve this. Hopefully it will be available to test in a week. I will be interested in your feedback.

@DRM

10) Cutting off the start and end of a clip with I or O makes the keyframe timeline end up looking like this:

I believe this has been existing behavior for some time and can be seen when using other filters. I do not plan to address it in the next couple of months.

@DRM

11) If you take a clip with the Time Remap applied then strech the end of the clip out to make it longer the result is that the last keyframe is held there as a freeze like this:

This will be part of the work-in-progress that I have.

@DRM

12) It seems that adding Time Remap alters the colors/tint on a clip.

Fixed. thanks.

@DRM

So how about a new added option that gives the user the ability to just use Convert to Edit Friendly on only a selected section instead of converting the whole source file similar to how the Reverse feature only reverses a selected section?

I think this is a good idea in general. I do not plan to do this right away. But we should consider it for an improvement after the time remap has been released.

@DRM

how about when you pick the the Time Remap filter and the dialog comes up instead of it just telling the user that the clip is not compatible and that they have to go ahead and do every step themselves to convert the section they want, that dialog would ask the user if they want to convert the clip to use the filter.

Great idea. This is done.

@DRM

14) When the Blend option is picked in Image Mode it applies it regardless if the footage is going faster, at regular speed or slow. Can there be an option added to only apply Blend if the footage is going faster or slower than 1.00000x?

I have to admit that the blend mode is very crude. I believe that we occasionally see frames blended when the speed is 1.0000x due to rounding errors. I think that instead of adding an option, I just need to make the blend mode match people’s expectations.

• For 1.0x, there should be no blending as you suggest.
• For <1.0x, it should blend between two frames proportional to the distance between the two frames of the ideal time. For example, if the mapped time calculates to frame 1.25, then it should blend frame 1 at 75% and frame 2 at 25%.

I will keep this in mind and look for a good opportunity to improve the blending logic.

@shotcut

@Brian we will have to disable smooth keyframes on this filter. It is impossible to change the interpolation algorithm to avoid these unexpected scenarios.

I hope it doesn’t come to that. Much of the power of the time remap effect is the ability to smoothly change the speed. I think we just need to find good ways to make the keframe UI intuitive for people in these complicated scenarios. Somehow they need to know to add more keyframes to coerce the curve to fit their desires.