Speed decreeses = Quality decreeses

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bluelife2128
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Speed decreeses = Quality decreeses

Post by bluelife2128 » Thu May 01, 2003 11:42 pm

Sorry if anyone posted a similar problem but here's query.
In Adobe Premiere, anytime I try to slow down the speed of a clip even 1 percent, it turns REALLY choppy. It doesn't get worse as I go slower. It's just , anything under 100% speed, it becomes choppy. Anybody know why that happens? what I could do to fix the problem? Please help. Very frustrating.
P.S.
Anybody know of any High quality transition tutorials ?
Thank you
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Anime2Envy
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Post by Anime2Envy » Fri May 02, 2003 12:14 am

Try this:

Right click on your clip, goto "video options / field options" and uncheck the box that says "deinterlace when speed is uder 100%"

that should do ya.

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bluelife2128
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Post by bluelife2128 » Fri May 02, 2003 12:27 am

THANK YOU SOOOO MUCH...
That was AWSOME
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TaranT
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Post by TaranT » Fri May 02, 2003 12:35 am

(Video gurus: feel free to correct me here. :) )

Think about what's happening in this example. You have a one second clip where all that happens is that a circle moves from the left side of the screen to the right side. You've got 24 frames with a circle on each one in a slightly different position.

Now slow the clip down so the circle moves from left to right in 5 seconds instead of one. You will need 24 * 5 = 120 frames...but you only have 24. Where do the other 96 come from?

Premiere and most other NLEs (the exception is maybe Vegas) take the easy way out: they just duplicate each frame until the time span is filled. In this example, the first frame will be copied four times (total of five copies), same for the second frame and so on. Each of the original frames will show for 0.20 (5/24) second instead of 0.04 (1/24) second. Which is why the slowdown looks jumpy.

(If you're using 30 fps interlaced material, then you have another problem: the frame copying screws up the 3:2 sequencing.)

A solution is to somehow create those inbetween frames accurately instead of just copying the ones you have. That's not too difficult if all you have is a circle moving across the screen. Anything more complex is virtually impossible (think of completely re-animating the clip).

Video Vegas claims to create these inbetween frames by extrapolation, but I'm skeptical of the results. I tried it with a complex clip that had several moving elements. Some of the elements were smoothed, but most were not. It may work with a very simple scene, however.

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Post by trythil » Fri May 02, 2003 12:49 am

TaranT wrote: (If you're using 30 fps interlaced material, then you have another problem: the frame copying screws up the 3:2 sequencing.)
That should be telecined 29.97fps footage. Interlaced footage does not have a 3:2 sequence to it.

Some comments: You can do your own extrapolation fairly easy if there's only a few moving elements in the scene, and if the style of your video allows it. What you can do is time-average the reframed clip, which will average N frames together. With a moving element, this provides a motion blur effect. Done correctly, it can give the illusion of smoother motion than actually exists.

A (very poor) example of what I'm talking about can be seen in "always" (wow, I've plugged my video twice today). The teardrop sequences were constructed by creating anywhere from 24 to a hundred keyframes, and then averaging those together for tweening. It's hardly the best way, but sometimes you can half-ass your way through things.

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