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Re: Core Video/ H.264 Color issues

Subject: Re: Core Video/ H.264 Color issues
From: "M. Robert Spryn" <email@hidden>
Date: Sun, 9 Apr 2006 20:04:13 -0400
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This can change depending on OS platform, video hardware, and drivers.
I find it hard to believe that consistent color reproduction is so
difficult to achieve.
It's non-trivial, which is why it's impossible to achieve consistent color reproduction even with stills/photos. Heck, it's still not possible to make a PNG image match CSS colors in all modern browsers.

For better or worse, the solution is TETOTOAYTM.

I hear what you are saying Charles. I don't ever expect my colors to match exactly from machine to machine.

That being said, I don't believe that the current problem with hardware acceleration changing the colors should be "just the way it is." If the amount of change caused by the hw acc (I'm tired of typing acceleration) was wildly different on different video cards and systems, then I would agree that it would be a hard problem for the quicktime engineers to account for. But for my testing the hw acc distorts the colors incorrectly, but fairly consistently, on all the machines it supports. Therefor there needs to be some adjustment made to whatever engine is doing the translating to compensate for the average discoloration.

Even if it is different for different video cards, then Apple needs to work with ATI/NVidea to make sure they read the color profiles and compensate differently depending on what video driver they are using.

I guess what I'm saying is I want my h.264 movies to look at least as good (color wise) on all machines as the same movie does encoded with Sorenson 3 or regular mp4. If that means giving me the option to disable hw acc on a per movie basis, then that's what I want. My G4 mac mini which isn't terribly fast can handle my h.264 videos without hw acc fairly easily (I'm not talking HD resolutions.)

Have any other Mac users tried setting the video track's Visual Settings | Transparency setting to Blend (100%), Premultiplied White/Black or Straight Alpha? This was a good trick for the rare case when you want to sacrifice some hardware acceleration for better color predictability, and I'd be bummed if it's Windows-only at this point.

Actually just playing with it now I finally found a crappy solution. If you go to the video track and hit invert twice (so your mask is totally black) and change the transparency mode to "composition" then it seems to disable hw acc and it corrects the colors.

Unfortunately the video then appears to play back choppy (even on my dual 2.7 G5) for reasons I can't understand. It doesn't consume anywhere near the amount of available processor (only a modest amount more than it consumes without hw acc.)

So its a work around... but not a good one. Is this because of the composition mode? Charles when you use the straight alpha mode does playback appear choppy?

Thanks again,
Robert
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