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x.264 gamma shift?

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Thatcher Kelley
x.264 gamma shift?
on Feb 28, 2009 at 1:12:10 am

So I've had the problem many have had with h.264 shifting gamma when played in quicktime and some browsers. I fixed the problem...or so I thought by using the x.264encoder. This fixed the problem in quicktime and safari (firefox was already working fine). The video looks great. But it still gives me a gamma shift when I play it in VLC and flash players.

The final presentation of my videos will be through a website via a flash video player. This flash player still gives me a gamma shift.

Does anyone know what I should do from here?

Thanks,
Thatcher


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Chris Blair
Re: x.264 gamma shift?
on Feb 28, 2009 at 5:06:55 pm

We've minimized it by using H264 export and outputting as an MP4 file. The colors look much more accurate to the original than if we use Quicktime and H264. The resulting MP4 will play in Quicktime, Flash and and Windows Media player (with the right codecs loaded).



Chris Blair
Magnetic Image, Inc.
Evansville, IN
http://www.videomi.com


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Ed Dooley
Re: x.264 gamma shift?
on Feb 28, 2009 at 6:42:43 pm

Here's a couple of posts that may help (or maybe not!).
There's also a lot of talk that by calibrating your monitor to a custom setting, it affects the gamma when exporting a file to H.264.
Some folks have said that putting your monitor back to one of the default settings before exporting (then back to your custom setting afterwards) fixes the problem. I haven't tried it.
Ed
___________________________________________________
This one is from Chris Meyer and includes debunking of some solutions:
http://provideocoalition.com/index.php/cmg_blogs/story/brightness_issues_wi...
________________________________________________
Open the QT
Go to "Window/Show Movie Properties"
Select "Video Track", then click the "Visual Settings" tab
At the bottom left, change the transparency to "Blend" then move the slider to 100
Change the transparency to "Straight Alpha"
Close the Movie Properties window, then play or scrub the QT. Your black levels should now look correct
Save over old .mov
This is for PC's. On the mac you change the transparency to "composition."
And use "Save As..." from the File menu and select "Save as a self-contained movie."
This adds the Fast Start information to the file.
____________________________________________________________
Update on x264encoder.
There is a way to make the exported file maintain a consistent appearance whether you are in a 2.2 or 1.8 gamma workspace. I'm thrilled I figured this out.

Choose x264encoder in the QTpro export pulldown.
Click Options
Click the Extra Options tab
Change the pulldown menu that says "No nclc atom" to one of the other options (I chose 6-1-6)
Make sure the "Add gamma 2.2 (legacy atom)" is NOT checked.
Hit OK and export your movie.
Now you have an h.264 encoded movie with correct gamma, and the appearance stays the same between 2.2 and 1.8 workspaces. (Confirm this by opening your display color preferences and toggling the gamma settings while your quicktime movie is open.)



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Bram Tulloch
Re: x.264 gamma shift?
on Mar 18, 2009 at 5:15:15 am

Using the "Visual settings" trick seems great, but double check that your playback doesn't become "steppy".

We thought we were onto a winner here with that work around but then noticed all the clips we had done this on didn't playback so nice anymore.



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