Time-remapping won't index at 1 sec/sec

Question

Hello all, I'm working on a project where my subject was challenged with completing a task in under 15 minutes. Due to the nature of the challenge, keeping it legitimate means being able to see the entire run in one continuous cut. My subject was able to complete the challenge in 8 minutes, but there is plenty of dead air between them completing tasks.

In order to not bore viewers, I want to speed ramp between the action parts -- but I've hit a bit of a problem. I have precomposed all of my footage into one file that I am trying to remap all at once, and I leave the start and end keyframes alone. I place a keyframe where I want to start the speedup, I place a keyframe where I want the speedup to stop, and I drag the two frames closer together. That speeds up the footage properly and I don't Easy Ease or Auto Bezier the keyframes, but then I noticed a problem.

The challenge features a stopwatch on-screen, and when I first attempted this I realized that the footage and the stopwatch were both running slower than real time when not in speedup, even when the preview was properly cached and playing in real time.

I went to check the graph editor and, wouldn't you know, the line between my "out of speedramp" keyframe and my end of clip keyframe both were set to 0.98 sec/sec or even slower. If I try and select or even direct select a specific keyframe on the graph editor and move it, Ae tries to add extra curves around the set of linear keyframes and it turns my graph into a terrifying Calc 3 expression.

I believe I understand that the interpolation between keyframes means that Ae will try to smooth the motion out between points and returning to 1 sec/sec is just trying to smooth out that transition, but even when I return both points to 1 sec/sec and smooth out their bezier handles as much as possible, there's a small (albeit imperceptible) dip between the two, Ae turns the keyframes into half-ease frames, and the issue worsens as I try to add more speedups (there are about 25 in the 8 minute segment).

Is there any way around this, or do I need to split the precomp, time stretch the section that I want, and move on with my life? Please let me know if I need to attach more pictures or provide any other information, and thank you for your help 🙂

Mylenium · Accepted Answer

The "crooked" values are merely quantization artifacts when AE reverse-calculates the effective speed, which is what you are looking at. All that should matter is the actual values in the value graph. Using fractional framerates will always cause some precision issues on that part if you are not using frameblending. Your workflow also further contributes to that since by leaving this as a single long clip forces AE to round up or down to accomodate discrete frames. So in short: Unless you enable frame blending with all it's caveats like everything becoming slow as hog and stuff looking "smeary" due to the interpolation this is nothing wrong per se. That brings us back to my initial point about chopping things up again. You would be able to minimize these issues by just treating the sections where you actually need the speed change.

Mylenium

Dan Ebberts · Answer

It seems like everything should work as long as when you move a keyframe, you also move all the keyrames that come after that. That should maintain the speed of the following segments. I played around with it a little and it does seem to retain 1 sec/sec for the segments that follow (unless I'm missing something obvious).

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