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Sorenson and Avid - Levels problems

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Annaël Beauchemin
Sorenson and Avid - Levels problems
on Jul 21, 2010 at 8:25:46 pm

Hello!

I'm regularly encoding Avid MC4 generated quicktimes references using Sorenson 6. I produce MPEG2-DVD, WMV9 or H.264 (.mov and .mp4) files depending on the needs.

WMV and MPEG2 follows the Quicktimes levels fines. What I mean is that if I export using 601 levels (16-235), the resulting encoding ends up being 601 levels (16-235). Same for RGB.

With H.264, this isn't true. If I feed a 601 levels files to Sorenson Squeeze and encode it to H.264, it will crush the blacks and clip the whites. The result is a bad looking video with levels at 0-255. The result is exactly the same if I feed an RGB Quciktime reference to Sorenson.

If I reduce contrast in Sorenson using the Contrast filter to get my highlights/blacks back, contrast is reduced but I don't get my blacks/highlight corrected. It seems to me that when encoding the H.264 format, Sorenson converts 601 levels to RGB, and does it before processing any filter you apply.

How do you guys produce H.264 files from Avid?

Windows Vista 64
Sorenson 6 (MainConcept encoder)
Avid NewsCutter 8.0.5 (sam as Media Composer 4.0.5)
QT 7.6.4


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Daniel Low
Re: Sorenson and Avid - Levels problems
on Jul 21, 2010 at 9:29:05 pm

Are you suing the Quicktime or Mainconcept H.264 codec?

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Annaël Beauchemin
Re: Sorenson and Avid - Levels problems
on Jul 21, 2010 at 9:34:44 pm

MainConcept. I am aware of the QT H.264 gamma problem.


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