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Time Warp – What did I do wrong?
Got a ~36 minute DV clip of driving down the highway. I want to condense it down to about 90 seconds. Setting the speed to 2400 (way past the scroll bar, but whatever) achieves this.
Problem is that I want it to look motion-blurred. Or, specifically, I don’t want each individual frame to lack visible motion blur, as they unavoidably do when we’re talking about a 60-fields-per-second clip.
Of course this means I gotta turn motion blur on. Here’s where the trouble starts. Time Warp’s motion blur is set up to produce five samples per frame. Fair enough. I went ahead and let it render the result. I was anticipating one of two things:
1: Best case scenario, Time Warp smartly gathers motion blur information by analyzing (or straight-up utilizing) the otherwise unused frames between each nth frame. They’re there for the taking.
2: Worst case scenario, Time Warp gets its nth frames (one every 24, in this case) and interpolates motion blur based SOLELY on those nth frames, discarding all the other frames utterly.
So when the render finished, what did I see? It’s really quite an interesting spectacle. I will attempt to describe: Take a NON-motion blurred clip that’s been Time Warped to a speed of 2400. Now duplicate it four times, so you have five copies of it. Now offset each copy by about 0.2 seconds, so that the second copy plays at 0.2 seconds, third at 0.4, etc. Now blend them together so they are equally transparent. Voila. You’ve got what Time Warp spat out at me. Rather than looking like a clip with motion blur, it looks like a clip with a sort of video echo effect, like a simulation of intoxication or something.
This was a difficult problem to spot before rendering because each frame was taking about five seconds, on my Core i7 running XP. Now I don’t have a solid clue why Time Warp did this, nor how to get the motion blur effect I was after.
My best guess is that Time Warp does not handle interlaced footage intelligently, and this was just a particularly catastrophic consequence. Would love to hear otherwise. Meanwhile, it looks like it’ll be time to see if I can get the AVS plugin to work again, because I have NEVER been happy with how Premiere Pro handles interlaced footage, or colorspace for that matter.
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3 Replies
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I’ve never done what you’re trying to do but if you have After Effects you might want to try it in there instead by using the time stretch and clicking the motion blur button on.
Sorry I couldn’t be more help.
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Thanks for the reply.
Far as I have read and observed, Time Warp is identical in both applications. There is an alternative time stretching effect, but Adobe themselves point out that it’s not meant for dramatic framerate modifications, and they recommend Time Warp.
The thing is.. I have seen plenty of examples of the effect I am after. Clearly, the folks who generated their time warps found the magic, arbitrary settings which gave the result they wanted (and which should have been the default), while I have had no such luck.
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In the grand tradition of solving one’s own issues, I present the solution for anyone who finds themselves Googling this one. And it comes as no surprise to me that the solution makes as little sense as the problem. Good old Adobe.
The shutter angle. Even though it displays 180 degrees by default, it most certainly does not use that setting (at least not in my case) UNTIL you switch to “manual”. If I were to make an estimation, it may have been using an angle of 2400 degrees, to match the speed I picked for the time warp. Obviously nonsensical, but it’s a good match for the roughly one full second of “motion blur” I was getting.
This is for After Effects, which I am using preferentially because when you tell it you want 59.94fps, it gives you those 59.94fps, even if it has to bob interlaced footage. Premiere Pro hasn’t gotten that right in something like a solid decade of existence.
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