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Jerky motion

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Janne LaihoJerky motion
by on Apr 7, 2010 at 9:22:03 pm


I guess here's the most basic questions of all: how to achieve a smooth (i.e. not jerky) movie file out of an animation, and end up with a movie file that's small enough to publish on an intranet for streaming?

I have a project that's entirely done within AE CS4, apart from one picture file (png) that I imported. The rest is text composed within AE, some light movements and a moving camera. In the composition the camera is flying through texts hovering on top of the image.

It seems that whichever output options I use, the motion is quite jerky. I've tried various Quicktime options: 10-bit uncompressed, animation, H.264 codecs.

My comp's frame rate is 25, and so have the render settings been also.

The end result has always been a large file, with motion that is far from smooth.

I've taken a look at somebody else's work: they've produced (I don't know with which software) a H.264 Quicktime file that has large (1280 x 720) dimensions, it's quite small in size for it's lenght (25 MB, 1.15 minutes), a decent data rate (less than 4000 kbits/s) and it looks stunning, very rich in detail and ultra-smooth movement. I wonder how this can be accomplished: I'm trying to output an animation created within AE with similar settings, yet my stuff looks nowhere near as good.

I understand that I should put a few years into studying digital video to figure these types of things out, but I'm afraid I have a bit of a situation and need to get the animation finished. So apologies for really basic questions, anyway any and all help is much appreciated.

BTW, I wonder also if it's possible to change the data rate of the output file somewhere?


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Dave LaRondeRe: Jerky motion
by on Apr 7, 2010 at 10:03:27 pm

Dave's Stock Answer #3:

Don't use AE to compress files for final delivery. The various compressors are there only to make quick 'n dirty files showing a project's progress to producers, clients, the kids, etc. AE is incapable of doing multipass encoding, a crucial feature that greatly improves the image quality of H.264 and MPEG-type files in particular.

Render a high-quality file from AE, and use a different application to do the compression. Popular ones are Adobe Media Encoder, Sorenson Squeeze and Apple's Compressor, which comes bundled with Final Cut Suite. Even compressing in Quicktime Pro is better than compressing in AE.

Making good-looking compressed files is almost as much an art as it is a science. It is NOT straightforward at all. I recommend asking a few questions at the COW's Compression Techniques forum.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA

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Janne LaihoRe: Jerky motion
by on Apr 8, 2010 at 1:27:35 pm

Hi again,

To answer my own question, in case somebody else's thinking about this: it turned out that I simply didn't have the frame rate to support a fluid motion in the movement that my animation contained. I had a few quite swift camera movements across the imaginary space, and since I didn't have enough frames in between the far left and far right views, this resulted in some jerky motion that really can't be avoided without inceasing the frame rate.

A learning experience for me (not surprisingly, this was my first animation); I didn't come think of this when planning my piece. So I think going forward I'll first think about what the final medium will be before even considering animating certain things. I.e. not extremely fast camera movements across a space if a high frame rate can't be used etc.

Thanks to Dave for the insights. Definitely an art as much as a science.


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John HillRe: Jerky motion
by on May 16, 2015 at 1:01:06 am

Thanks for your post. I've been doing simple scans and have not been able to figure out why they are jerky after info out there that I can see. But you're right! When I switched from 29.97 to 59.94 and then rendered everything was smooth! Finally! Thanks again.

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