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jm knowles
h264 Gamma Bug Mac vs PC
on May 10, 2010 at 4:26:20 pm

I have read many of the threads involving fixes for the h264 gamma bug here and elsewhere. It seems like the best fix is opening and saving in Quicktime Pro and then changing the video transparency settings. In a PC it is setting transparency to blend and on a mac it is setting it to composition.
In my case I am creating on a mac for presentation on a pc - which of these methods should I use.
Thanks so much in advance - this forum has been a life saver with this project!



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Chris Blair
Re: h264 Gamma Bug Mac vs PC
on May 11, 2010 at 1:14:20 am

I thought the transparency/composition trick only worked using the .mov container. Could be wrong on that. I think the best solution is to avoide the Apple H264 codec and use x264 or Main Concept's if you have it as part of an encoding app.

Another trick that allegedly works on Quicktime for Windows is the following, pulled from Video Copilot's blog.

It's dubbed the "tiff trick" by users:

1) Create a small (32×32 pixels or so) tiff or bitmap – dosent matter what color, just make it 8bit and RGB
2) Open a new player and ‘Open image sequence’ and select the tiff/bitmap. set the frame rate to whatever you’re going to be working in
3) Open your desired quicktime in another player, ’select-all’ and ‘copy’ the clip
4) Back in you ‘tiff/bitmap’ movie hit ‘add to movie’ – this will add the video over the top of the tiff/bitmap on a second video layer
5) Export using your desired codec

This is supposed to match the original better than the transparency/blend/composition trick and works using the mp4 container.

I've never tried it because we typically use either Main Concept or x264 and just avoid the issue altogether. We do have a couple of TV stations that require Apple H264 for commercial uploads, and we correct the video in an initial encoding pass to uncompressed AVI before taking the AVI into Quicktime Pro for Windows to do the H264. We simply tested color bars using that process a few times and then imported those back into our editing app to check them on a hardware waveform/vectorscope in real-time until we got them correct.

The transparency/blend trick seems to be spotty in terms of actually working. Some people say it works, others say it only slightly improves the gamma shift issue.

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


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jm knowles
Re: h264 Gamma Bug Mac vs PC
on May 11, 2010 at 4:24:44 am

Thanks for the well thought out answer. This is all so mysterious (like you said sometimes something works, sometimes it doesn't).

I will admit that checking color bars is something that is not part of my workfow (and since my video work is for web and presentations it is probably less essential than broadcast.) I do need to start paying more attention to my colors though.

I had read about the Tiff fix - I will try that - it is hard to keep track of which to do where.

I would use x264 (and maybe MainConcept - this is the first I have heard about it) except for the fact that most of my clients won't have those codecs and will freak about having to install something to watch a video ("Youtube plays - why doesn't yours play?")

It sounds like you have quite a workaround for your stations that require H264. Yikes. It really should be easier than that.

Again, thanks for the pointers. I am a web designer who is slowly learning more about video other than simple edits and the export to quicktime. I appreciate the hellp.



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Chris Blair
Re: h264 Gamma Bug Mac vs PC
on May 11, 2010 at 2:02:56 pm

With H264, I don't believe you need the specific brand or flavor of codec to play the file. I believe the specs for the codec are such that if you have a media player that can play H264, most if not all the various H264 iterations will play.

I know we've had zero problems sending out H264 files using a wide variety of codecs, from x264, to Main Concept, to Apple's to Sony's coming out of Vegas.

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


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Andrew Phang
Re: h264 Gamma Bug Mac vs PC
on Jul 9, 2010 at 3:09:54 am

Hi Chris,

This gamma bug has been devouring my brain for weeks. I've tried all the voodoo recommended and found x264 to be the magic bullet. BUT... I've just completed a project with x264 which looks identical in gamma to the uncompressed version when viewed on the Mac, but looks just as washed out as Apple h264 on a PC! Have you ever come across this with x264 before?

I am using the latest build of x264 encoder component in Quicktime 7.6.6 running on OSX10.5.8. My workflow is to render out from AE CS4 to Animation Best and then into Quicktime pro for x264 encoding. What's even more bizarre is after uploading(the x264 version) to YouTube, the gamma is restored, and the clip looks good and consistent on both Mac and PC when watching off YouTube.

Thanks in advance for your time!




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