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H.264 to ProRes422HQ vs Uncompressed to ProRes422HQ - No difference?

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Jason Jones
H.264 to ProRes422HQ vs Uncompressed to ProRes422HQ - No difference?
on Jan 17, 2013 at 5:50:01 am

I tested the new Canon 1D C today. I expected a vast difference in "gradeability" between the H.264-to-ProRes422HQ I'm used to from my 5D III, and taking a clean, uncompressed HDMI signal out of the 1D C, and recording on a Blackmagic shuttle drive to ProRes422HQ.

Should be a significant difference, right? There was no discernable difference whatsoever. Couldn't see it on the scopes, couldn't see it toggling back and forth using a reference wipe. This was true of both the before- and after-grading clips.

Why not?


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Robert Houllahan
Re: H.264 to ProRes422HQ vs Uncompressed to ProRes422HQ - No difference?
on Jan 17, 2013 at 6:43:24 am

Most likely because the camera hardware is doing the demosaic work and the signal is 8-bit. The limitation is probably more in the camera hardware, line skipped sampling noise and other camera issues plus the 8-bit signal than the post camera compression.

-Rob-

Robert Houllahan
Director / Colorist
Cinelab Inc.
http://www.cinelab.com

MAHC-PRO 6-Core 3X GTX285 20Tb SAS Wave Panel Panny 11UK SDI Plasma. Light-Space CMS + Hubble


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Sareesh Sudhakaran
Re: H.264 to ProRes422HQ vs Uncompressed to ProRes422HQ - No difference?
on Jan 17, 2013 at 3:38:35 pm

Because there isn't a difference usually, as long as the specs are the same. Here's my more detailed answer: http://wolfcrow.com/blog/comprehensive-guide-to-rigging-any-camera-7-extern...

http://www.wolfcrow.com - Workflow information and support for filmmakers, photographers, audiographers and videographers.


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Joakim Ziegler
Re: H.264 to ProRes422HQ vs Uncompressed to ProRes422HQ - No difference?
on Jan 19, 2013 at 11:33:04 pm

As Robert said, the signal is probably 8-bit, and most of the camera's internal image processing is applied to both the compressed video and the HDMI out. So range and similar things should be the same, I assume that's what you mean by "gradeability".

However, what you should see improving are compression artifacts. If you try to record very shaky handheld on a dSLR, or generally very chaotic images like close-ups of fast-moving water, etc., there are usually a LOT of compression artifacts and blocking, and the ProRes shouldn't show any of that.

--
Joakim Ziegler - Postproduction Supervisor


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Jason Jones
Re: H.264 to ProRes422HQ vs Uncompressed to ProRes422HQ - No difference?
on Jan 20, 2013 at 7:36:25 pm

Very helpful - thanks a bunch, Joakim!

So that's an additional test I need to make: a comparison betwen the internal H.264 codec and the external ProRes, shooting a scene where EVERYTHING in the frame changes radically. Nice.

Cheers!

J


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