how to show this video at constant speed?

[Steve Roberts]

Dave’s right — if you could board an express train that passes by the station, that would save you a lot of time.

But if you can’t reshoot, there’s no automatic way to even that out. You have to do it by hand, with time remapping (TR). Basically, in addition to the keyframes created by TR, you need to add keyframes where the train starts to slow down (maybe), where it stops, where it starts up again, and where it settles into steady speed.

You are now going to move most of those keys to the left, starting from the end of the clip. The last two travel together: do not change their relationship to each other. First, drag the last two to the left. Play the clip. Change the slope of the curve where the train starts to speed up so it starts pointing steeply upward, then settles into the same slope as the line between the last two keys. You are speeding up the footage a lot (steep slope), and gradually settling into the footage’s original speed (slope). Play the footage and tweak the handles until the speed is constant from 0 to final speed.

As for the stopped portion, now drag all three rightmost keys (together!) to the left (no vertical movement!) until the first of those (where the train starts moving) is one frame to the right of the keyframe where the train stops. Play it. If you see a jerk, drag the right keyframe up or down a bit. Note: there will be a jerk in the trees — ignore it. As long as the track is the same, you’re okay.

You get the idea. For the deceleration, the curve should start at the same slope as the beginning of the clip (constant speed) then gradually curve upwards until it gets to the first stop point.

If you have trouble at the stop, consider splitting the clip and doing TR for the deceleration half of the clip, then for the acceleration half of the clip, trimming out the stop portion.

TR skills should be in every AE artist’s toolkit. This one could be worse, since there’s only one deceleration and acceleration. Imagine if the motion were jerky. Use your eyes, and if you get stuck, just disable TR and start again.

[Sieger Duinkerken]

i’m sorry.. but you are not very helpful with your “just shoot new material”… it is no option and would not fix the problem at all, since this is all about a journey along a few train stations, where there are no express trains.

[Brian Berneker]

I wonder if there’s any way you can use, say, one of the track boards and put some rulers on the comp to set a fixed distance for a given piece to travel on a consistent number of frames. That way, you can have a TR keyframe every x frames and make sure the piece of track moves to the right ruler position for the anticipated keyframe, and move it ahead or back accordingly… Still a manual tweaking process, but at least with some semi-objective measurement…