Reverse and change speed using time remap

[dan99]

Hi there,

I need to both reverse a clip and slow it down to exactly 0.5x speed.

I know I could use the Reverse option, but it’s a bit cumbersome to keep these extra “reversed” files around, plus I might lose some quality. So I’d like to do this using the excellent time remapping, if possible.

And, it’s easy enough to reverse a clip using time remapping - zoom keyframe values and then hold CTRL and just flip the start and end keyframes. And voila, a reversed clip!

However, slowing the clip down to exactly 0.5x after that is proving troublesome. I can sort of do it by stretching the clip to double its original length before adding the time remap filter, and then flipping the key frames and stretching them out. However this is all done by eye, and so the resulting exported video looks bad (as my original clip is 60FPS and I want to play it at 30FPS so I need an exact 0.5x slowdown).

Can anyone suggest a way to do this in an exact manner?

A reverse-and-speed-adjust filter that uses the time remapping would be nice

[brian]

Have you tried the < and > buttons next to the time parameter to set a keyframe to a create a specific speed?

You should be able to:

1. Double the length of the clip
2. Invert the first keyframe
3. Move the second keyframe to the very end of the clip
4. Choose “Set Speed Before” and enter -0.5

Time Remap Filter

The Time Remap filter is the first filter that allows altering the timing of the underlying source clip. It maps clip time to output time. [image] Limitations It can only be added onto clips with NO B-frames. If you try to add it to such a clip, it shows the Convert to Edit-friendly dialog. A proxy clip can mask the above check for B-frames and then export may be very slow or give bad results. However, it may also be a very convenient workaround for the check and dialog mentioned above if you…

[dan99]

Thank you, that seems to work! I was a bit confused about what the set speed buttons did before.

I had to double the clip length by dragging it to the left. Does it matter that my resizing is not exact? The speed will still be 0.5 throughout the clip when I use “set speed before”?

[brian]

@dan99

I had to double the clip length by dragging it to the left. Does it matter that my resizing is not exact? The speed will still be 0.5 throughout the clip when I use “set speed before”?

After you set your remapping values, you can watch the “Speed:” status in the time remap filter to see the calculated speed while you preview. The “Speed” status is the value immediately below the white line in the filter UI (above Direction). Those status values are updated for each frame and calculated based on the mapping applied since the previous frame. If the status shows -0.5x, then you know you achieved the speed you want.

[dan99]

I see, thank you!

It still would be great if one day there could be a simple “reverse” time filter that was also compatible with speed changing in the properties. But in the meantime this works, thank you.