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The judder mystery!!!

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Steve MorrisThe judder mystery!!!
by on Dec 16, 2010 at 12:31:09 pm

I'm trying to create a simple movie clip of a horizontal pan in After Effects. But it seems impossible without judder/jitter - whatever it's called. I've read lots of posts on this but no-one seems to have an answer. Here's what I've done:
Imported a jpg of a stone bridge 1880 x 720
Set composition to 25 frames/s and 1280 x 720
Set anchor point to 0,0 - top left
Set position to 0,0 and created key frame
Move photo to -600,0 and set keyframe at 6 seconds
That's a movement in whole pixels!! 100 per/s or 4 per/frame
Rendered to QT movie
It looks terrible - smooth jitter, smooth jitter across the pan.
I've tried 50 frames/sec (little better) and played with frame blending, motion blur, directional blur - no better
Rendered to different compression even H.264 - no better
It could be my computer not able to keep up - but it's a reasonably new PC with pretty good spec. I'm trying to make a HD video for the web with this clip and some timelapses. If my computer can't keep up with this movie then the average computer will also struggle - so most people will see the same problem. Is it too much to ask for a smooth pan or are average computers these days just not up to it. I don't believe this is an optical illusion by the way as the pan is smooth in parts. Any help appreciated!!

Steve Morris


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Dave LaRondeRe: The judder mystery!!!
by on Dec 16, 2010 at 4:44:09 pm

Because you want to work in a low frame rate, you're going to encounter judder sometimes: the higher the frame rate, the smoother the motion. However, you can't really deliver in the wrong frame rate, so you may be stuck there.

You can try turning on motion blur, but you might just have to fool around with the speed of the move; I assume this shows up when you do a RAM Preview.

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


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Michael SzalapskiRe: The judder mystery!!!
by on Dec 16, 2010 at 4:44:38 pm

What's the data rate of the files you're rendering?

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Steve MorrisRe: The judder mystery!!!
by on Dec 16, 2010 at 6:02:32 pm

It depends - I've rendered it so many times with different options. For my latest it's a 10Mb file with a data rate of 13mbits/s. I've tried putting the format slider for QT export in all positions from low to high quality - it makes no difference. Any help appreciated!!

Steve Morris


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Michael SzalapskiRe: The judder mystery!!!
by on Dec 16, 2010 at 7:02:01 pm

I'm with Dave, does this judder show up in RAM previews or just in the render?

- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')

No trees were harmed in the creation of this message, but several thousand electrons were mildly inconvenienced.


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Steve MorrisRe: The judder mystery!!!
by on Dec 16, 2010 at 7:11:22 pm

Thanks. I can see it in the RAM preview too!

Steve Morris


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Dave LaRondeRe: The judder mystery!!!
by on Dec 16, 2010 at 7:30:09 pm

Okay, since you're a new guy, is AE RAM Previewing at the proper frame rate, i.e. real time? Reduce the comp size to 50% and the resolution to half and check again.

If the problem persists on a real time preview, you're kinda stuck between a rock and a hard place if you have to maintain that particular speed & duration for the move. Don't forget about using motion blur.

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


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Steve MorrisRe: The judder mystery!!!
by on Dec 16, 2010 at 8:02:33 pm

Hi Dave
If I put the viewing window to 50% and the resolution to half - it looks a lot better in RAM preview and plays in real time. Where do I go from here?
Cheers
Steve

Steve Morris


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Dave LaRondeRe: The judder mystery!!!
by on Dec 16, 2010 at 9:32:30 pm

[Steve Morris] "Where do I go from here?"

I dunno. If the judder problem's gone, you can render and get ready for delivery, I guess.

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


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Steve MorrisRe: The judder mystery!!!
by on Dec 17, 2010 at 10:38:43 am

Hi Dave
Thanks for trying anyway. The web is littered with people asking this same question about jitter, judder, jerky movement for horizontal pans on still images. I don't understand why there isn't a tutorial that says - to get smooth pans this is what you do!! Also the answers are always different eg try upping the frame rate or add motion blur, try frame blending, try directional blur.
I'm beginning to think that the real answer lies in the average computer these days. It just can't keep up with shuffling the whole picture (1280 x 720) 25 times a second. OK, if you've got 12GB of RAM, two drives and the latest graphics card - you maybe OK. But what's the point of generating a video for the web that only looks good on a machine like that - Joe Average won't see it smooth.
Cheers

Steve Morris


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Dave LaRondeRe: The judder mystery!!!
by on Dec 17, 2010 at 8:49:43 pm

The average computer isn't doing After Effects work, where you try to keep images at their highest quality possible while you effects and compositing, and then create media files in the highest quality possible.

The average computer is just playing files in a delivery codec like H.264. The computer that does AE work has done all the heavy lifting, and then it gives its work to a compression application, which is designed to dumb down AE's high-quality files for the average computer.

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


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Graham MacfarlaneRe: The judder mystery!!!
by on Dec 18, 2010 at 1:06:24 pm

I agree with Dave, I don't think the computer is at fault with a 13mbits/s data rate.

The apparent 25fps judder could be one or a combination of the following:

- The eye is capable of seeing the individual frames when there is very fast motion present with an insufficient frame rate. Conversely if you had an animation of a very slow moving small object you might be able to get away with a very low frame rate before any judder is noticed.
One can help alleviate judder with motion blur and of course the video data rate needs to be kept in check as Michael points out else the computer will struggle. However these solutions are never going to work as effectively as what Dave suggested - increasing the frame rate or reducing the speed of your animated motion.


- The refresh rate of your monitor. Assuming your using a flat screen, which is normally 60Hz, a 30fps video fits very nicely into this rate. A 25fps video will work but it doesn't divide as cleanly so the display of such video is not optimal. Maybe you can lower your screen refresh rate to 50fps (nice multiple of 25) or perhaps burn the 25fps video to DVD and trying it out on a PAL TV. You might find the playback is smoother however I appreciate that these display adjustments/changes may not be possible for the media's end use.

Graham Macfarlane
3D animator and VFX specialist
London UK


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zero coolRe: The judder mystery!!!
by on Sep 14, 2012 at 9:17:04 pm

Hi,

I've been having the same problem. The animation I created is a simple move of a picture from the left side of the screen to the right (simple position animation).

When playing back AE exported videos rendered at 1920x1080 (1080P, 29.97fps Dropframe, 6-10mbps, H264, Best settings) the animation looks jittery in both windows media player and quick time. It's much worse in quick time because it seems like a whole bunch of frames were dropped. Scrubbing the time bar doesn't really help either. This is weird since h264 is supposed to be really good in Quicktime for 640x480 videos.

The thing is if I play the video back on a HD plasma tv, it looks fine. The animation is perfectly clear and it doesn't look like it does on the comp. I know this doesn't help if you need to play your videos back on a computer for presentations. But if your goal is to play it back on a TV, then it should be fine.

Good luck.


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