Thank you for the useful link. The motion aspect of the Graph Editor is very straight forward, much like the graph editor in Lightwave. It is when editing time remapping keyframes in the Graph Editor where things can be somewhat unpredictable or counterintuitive. For example: a 1 minute video clip. I may want to speed up and slow down different portions of the clip while leaving other portions unchanged.
It took me a while to figure out what was going on with time remapping. In order for the net length of the video clip to remain the same, if you speed up a portion of the clip, then other portions of the clip must necessarily expand (slow down) so the overall length of the clip is the same. However this may be an unwanted byproduct.
For instance, Let's say I have a video clip of exactly 30 seconds. I want to slow down the middle 10 seconds. So I set a time keyframe at 10 seconds (keyframe 1) and a time keyframe at 20 seconds (keyframe 2). I now move keyframe 1 back to the 5 second mark, and keyframe 2 forward to the 25 second mark. That portion of the video (between 5 and 25 seconds) now plays slowly as expect. However the first and last 5 seconds of the video are now playing quickly, because as we can see in the Graph Editor, the speed of the first and last 5 seconds have been moved up, or "squashed" to accomodate the slower, middle section of the time remapped video. I hope I'm being clear.
The only way I've found to correct this is to first allot more overall time for the clip in Composition Settings, and then extend the tail (and/or the beginning) of the video clip. Then keyframe 1 must be selected with keyframe 0 (the first keyframe added by enabling Time Remapping) and moved back together, and keyframe 2 must be selected with last keyframe and moved together as well. As a result, the beginning and ending 5 seconds of the clip will now play at the proper, normal speed.
The process can get more complex, though, when time remapping a much longer clip, where numerous time remapping transitions will be occurring. Is the only solution to split up the clip, do the time remapping on the now several existing layers, and then move everything around until it looks fluid?
I may be missing something, but it seems to me that there should be some sort of "intelligent" feature added to Time Remapping that could recognize unchanged portions of a clip, and expand the time settings of the project, etc. to automatically accomodate for this.
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Some times it's difficult to wrap your head around time and time remapping. If you adjust the speed of any part of a clip then the length of the clip is going in real time is going to change. The key to working in Time remapping is to keep the relationships between keyframes straight. Let's say that you want to do just as you asked, slow down the middle of a clip while keeping the start and end running at real time. This means that the total clip length will be longer.
When you enable time remapping a keyframe is placed at the start and end of the clip. You can then extend the out point of the clip to any length you wish. If you wanted to slow down the middle 10 seconds of a clip to half speed then that 10 seconds would now take 20 seconds. This means you'll need to extend the clip by 10 seconds. If you composition is the same length as the clip, then you'll need to extend the composition by 10 seconds. That's what I do. Most of the time I extend the composition much farther so I've got some room to play.Then before I start monkeying with the time keyframes I set a new out point for the clip at the end of the comp.
I'd then add a new keyframe at 10 and 20 seconds. To keep the speed the same for the first 10 seconds, then slow down the clip while keeping the last 10 seconds in real time I"d grab the last 2 keyframes and move them out so the last keyframe was at 40 seconds. There you go, all done.
You can do this multiple times with a clip easily if you just keep track of your keyframes and change the time in blocks instead of trying to move one keyframe at a time. Grab all keyframes from where you want to make a change to the end of the clip, move them, then go to the next keyframe, grab all to the end, move, and so on until you've made all your adjustments. Once you're done, then set the out point for your clip where ever you want.
I hope this makes sense. I really ought to do a tutorial on time remapping. It's an often used but mostly misunderstood feature.
I really ought to do a tutorial on time remapping. It's an often used but mostly misunderstood feature
Please do. It'd be a useful thing to point folks towards.
Thank you for the helpful information, Rick. I understand the principle of time remapping, it's using the graph editor to control time remapping that takes some getting used to. I do projects where often the time speed-ups or slow-downs must be very subtle .. almost imperceptible. Keyframes need to most definitely be eased out and eased in. I was first trying to do this only by using the 'Edit Speed Graph' line in the graph editor. It was possible but tedious. Then I discovered that I could use 'Edit Value Graph' and that simplified things greatly. I could control bezier handles on keyframes to a fine degree. This made a huge difference already.
I think an advanced tutorial on time remapping is greatly needed.