on 11/23/02 13:33, ot at email@hidden wrote:
> Ben, I may have misunderstood the MPEG-4 gamma correction. I remember you
> saying it
> would automatic set the gamma to the computers default. This would be 'lite'
> for Mac and
> 'dark' for Win. Correct?
The file is encoded with gamma=2.2, and then on decode is made brighter
or darker to match the local playback platform.
> Now you wrote this auto-correction gets us a lot closer than before. - How, if
> it sets
> to the default values of 1.8 and 2.2? Or is it creating a compromisee in the
> middle?
> Only this, I'd say, would bring us closer together. Not resetting to the
> default
> differences.
The file itself is stored with a value in the middle, yes.
> To ask more simple: Appears a movie on a Mac darker or brighter when the movie
> is an
> MPEG-4 compared to the same movie in a non-correcting codec? To get platforms
> closer
> than before I'd expect it to appear darker.
The movie should appear the same on a Mac or Windows, even though Y=128
normally appears brighter on a Mac than Windows. That's the correction.
> What if I have adjusted my monitor gamma already for this
> closer-getting-compromise and
> write a QT MPEG-4 movie which looks fine on my Mac?
Then it'd show as too dark, since it'd reduce the midrange luma,
assuming your Mac was running at 1.8.
Ben Waggoner <http://www.benwaggoner.com>
Compressed Video Consulting, Training, and Encoding
My Book: http://www.benwaggoner.com/books.htm
Cleaner Tutorial: http://www.saferseas.com/navseries/adclean.html
Compression Books: http://www.benwaggoner.com/bookshelf.htm
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