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Quicktime level shifts in GFX renders

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Joe Murray
Quicktime level shifts in GFX renders
on Oct 17, 2006 at 2:15:24 pm

I'm cross-posting this because it may be useful information to some of you who do not use Autodesk Combustion, the other forum where I posted it. Also it relates to use of the AJA codecs, so I believe it's relevant to this forum.

A while back, I did some tests to figure out the best workflow when exporting from Final Cut Pro for VFX work in combustion or another compositor. Now it seems something is broken in the version of Quicktime 7 I have installed on my PC (note: this may not be an issue on Mac), so when I render a 10-bit uncompressed Quicktime (AJA, Blackmagic, Apple 10 bit, Animation, or any other codec) out of combustion, the video levels of the rendered file are not the same as the original. Even if nothing is done to the layer in combustion.

So I did a ton of tests this morning, using a clip of color bars that I had exported from FCP, and rendering out a dozen or so files with various codecs. First, I checked the file I exported from FCP to make sure it matched the original color bars before taking that file into combustion. Ideally, I need either the AJA, Blackmagic or Apple Uncompressed codecs to work since these are the only ones that play realtime in my FCP sequences.

Using Quicktime 7, none of the codecs produced a file that matched the original. So I uninstalled Quicktime 7, reinstalled Quicktime 6.3, and now the files match perfectly.

If anyone is using a version of Quicktime 7 that doesn't alter video levels in rendered files, I would like to know about it.

Joe Murray


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CharlieX2
Re: Quicktime level shifts in GFX renders
on Oct 17, 2006 at 4:44:17 pm

This used to be a HUGE problem on the Mac.... something with QT assuming you didn't know what you were doing, so it would adjust the gamma for you. But it's since gone away. Hopefully someone here with PC knowledge can point you in th right direction.

I assume you don't have the problem with sequence files?



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Joe Murray
Re: Quicktime level shifts in GFX renders
on Oct 18, 2006 at 3:40:45 am

Haven't done a test with sequence files, since that's an added step to the workflow. Image sequences, if converted back to Quicktime on the PC version of Quicktime 7, would show the same problems, I'm pretty sure. And moving image sequences over a network in order to convert them to Quicktime on the Mac takes a lot longer than moving a Quicktime. It works for me to use Quicktime 6.3 instead of 7.x, so for now that's what I'll do.

Any PC users out there having the same issues? We've seen it on 2 PCs, with both combustion and After Effects.

Joe Murray


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Dean DeCarlo
Re: Quicktime level shifts in GFX renders
on Feb 5, 2007 at 6:48:17 pm


Re-activating this thread as I am on a PC using Combustion and am having this same problem with Quicktimes. In my case it seems to be limited to anything using the Aja codec (2vuy). All these clips both SD and HD seem to have the gamma shifted by about 17%. If Animation or regular uncompressed codecs are used then there doesn't to be a problem. I've searched around and can't seem to find an answer except that it said here that it was broken in quicktime 7? I believe as there seems to be other gamma problems with Quicktime. If I render a test with Sorenson 3 for instance the gamma is much different than when rendered with regular Sorenson. This is very bad. I'm surprised I haven't found more info on this as it's been a problem for a while and seems pretty consistant. Anyone know a solution to this one?

Thanks.


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Joe Murray
Re: Quicktime level shifts in GFX renders
on Feb 5, 2007 at 7:02:49 pm

I had a solution going for a while and it was to use Quicktime 6 on the PC side instead of Quicktime 7. But this causes other issues because we work with DVCProHD and DVCPro50 files sometimes and couldn't get Quicktime 6 to play those on the PC. But you might try retro-grading your PC version of Quicktime and see if that works for your situation.

Joe Murray


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Dean DeCarlo
Re: Re: Quicktime level shifts in GFX renders
on Feb 5, 2007 at 8:08:11 pm


Yeah, I don't want to have to do that. Oh well.


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