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Edge flicker

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Ben RobinsonEdge flicker
by on Oct 6, 2010 at 8:43:00 am

Hi,

Although I've been coming here for about a year in search of wisdom for various problems I have not had cause to post one of my own before now (forgive me if I'm a bit wordy)--but I can't seem to find anything that quite matches my issue and I'm approaching a deadline. My problem is this...

I've built a fairly basic comp in CS4 at HDTV 1080 25 settings. The comp consists of a series of clips/movies reduced from full 1920 x 1080 (shot on Canon 7D) to 35% scale and set to scroll in two alternating lines at the top and bottom of the screen/comp. As they scroll, though, their edges are flickering--in fact the whole image seems to shift/split every few frames.

Someone posted a thread some time ago with a similar issue with a moving solid. It was suggested that he switch the layer image quality to Draft to correct this and apparently it worked for him. Not so for me. I have tried several test comps with just one clip moving across the screen and the same thing occurs. Am I using the wrong comp setting? Could my graphics card be out of its depth (NVIDIA GeForce 9600M GT on MacBook Pro)? The problem is not just in display--it is still there when I render/output the comp.

Any help hugely appreciated.


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Dave LaRondeRe: Edge flicker
by on Oct 6, 2010 at 3:03:11 pm

[Ben Robinson] "I've built a fairly basic comp in CS4 at HDTV 1080 25 settings. The comp consists of a series of clips/movies reduced from full 1920 x 1080 (shot on Canon 7D) to 35% scale and set to scroll in two alternating lines at the top and bottom of the screen/comp. As they scroll, though, their edges are flickering--in fact the whole image seems to shift/split every few frames."

Canon 7D's record in H.264, and H.264 is toxic to versions of AE prior to the latest one, version 10... and that includes yours. Here's what's going on:

Dave's Stock Answer #1:

If the footage you imported into AE is any kind of the following -- footage in an HDV acquisition codec, MPEG1, MPEG2, AVCHD, mp4, mts, m2t, H.261 or H.264 -- you need to convert it to a different codec.

These kinds of footage use temporal, or interframe compression. They have keyframes at regular intervals, containing complete frame information. However, the frames in between do NOT have complete information. Interframe codecs toss out duplicated information.

In order to maintain peak rendering efficiency, AE needs complete information for each and every frame. But because these kinds of footage contain only partial information, AE freaks out, resulting in a wide variety of problems.

I'm a Mac guy, so I like to convert to Quicktime movies in the Animation or PNG codecs; both are lossless. I'll use Apple's Compressor, Adobe Media Encoder or Quicktime Pro to do it.

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


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Ben RobinsonRe: Edge flicker
by on Oct 6, 2010 at 5:27:38 pm

Thanks very much for your response.

I've been using the footage primarily in FCP, but doing some additional graphics work in AE. I had issues with the sound going out of sync and read on several forums that this was a relatively common issue with the H.264 footage coming out of a 7D. I ended up re-encoding everything to ProRes 422 and that seemed to sort out the sound issue in FCP; I was still using the native H.264 files in After Effects, though. I will plug the ProRes files in there and hopefully all will be well.

Cheers


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