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Red (and only red) jagged in H.264 footage

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Corrado CarlevaroRed (and only red) jagged in H.264 footage
by on Jul 27, 2012 at 9:27:14 am

Hi,
I import a video in AE, it says "50,00 fps; Milions of Colors; H.264; 32 bit U". It is 50 fps but it's progressive. The red color is completely jagged (sort of when you scale down some interleaved footage) but the rest is perfect. In VLC player everything is fine.
Snapshot in attachment. Any idea?
Thanks

Corrado Carlevaro



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Walter SoykaRe: Red (and only red) jagged in H.264 footage
by on Jul 27, 2012 at 2:04:38 pm

H.264 may be using 4:2:0 or 4:2:2 chroma subsampling (depending on profile). That will give you really hideous stair-stepping -- especially if the original has undergone multiple generations of lossy encoding.

If it's possible to get a higher-quality original, that's the way to go. If not, you can exchange some of the stairstepping for softness by blurring the chroma (Channel Combiner for RGB -> YUV, Channel Blur for increasing Green and Blue (now U and V) blurriness, then another Channel Combiner for YUV -> RGB).

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events


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Walter SoykaRe: Red (and only red) jagged in H.264 footage
by on Jul 27, 2012 at 2:10:22 pm

[Walter Soyka] "H.264 may be using 4:2:0 or 4:2:2 chroma subsampling (depending on profile). That will give you really hideous stair-stepping"

I should clarify -- chroma subsampling will result in hideous stair-stepping on drastic diagonal color boundaries like these diagonal green/red transitions.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events


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Corrado CarlevaroRe: Red (and only red) jagged in H.264 footage
by on Jul 28, 2012 at 11:24:26 am

Thank you,(Field Order is set to Off), but if you can clarify more I have some questions.
I can get a better original, but this chroma subsampling stuff is not very clear to me: which kind of sampling should be used? 4:2:2 is not supposed to be "good"? Or those artifacts are a "side effect"?
Moreover, in AE in H.264 Video Settings window, under "Profile" I can choose between Baseline, Main and High and under "Level" from 1.0 to 5.1: what is supposed to be used?

Corrado Carlevaro


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Dave LaRondeRe: Red (and only red) jagged in H.264 footage
by on Jul 27, 2012 at 2:06:07 pm

In the Interpret Footage settings, set the Field Order to None.

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


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