FORUMS: list search recent posts

Gamma issue in Quicktime mp4

COW Forums : Apple Final Cut Pro Legacy

<< PREVIOUS   •   FAQ   •   VIEW ALL   •   PRINT   •   NEXT >>
Neil Kidney
Gamma issue in Quicktime mp4
on Nov 22, 2011 at 2:25:32 pm

Hi,
Slightly wrong forum, but as there's no Quicktime forum, thought this is as close as it gets...

Converting a load of vids directly in Quicktime into MP4 for web playback (ipad/phone).
Getting the usual gamma issue, even when I...
- encode on a Mac
- encode on a PC
- encode in h264
- encode in mpeg4 improved
- all combinations of the above.

Going into video properties and doing the alpha trick is not an option as you can only save it afterwards as a .mov, which is not what I need.

ANY HELP OUT THERE?!



Return to posts index

Brad Wright
Re: Gamma issue in Quicktime mp4
on Nov 22, 2011 at 2:59:23 pm

Usually, compressor 4 doesn't have any problem encoding video correctly. However, some MP4 encoders run the video through RGB which will cause significant gamma shifts. You want to test your workflow to see where the change is happening.

Create a color bars pattern and a grey scale ramp. Then run it through your encoding workflow and bring it into Final Cut Pro and look at the video scopes. You can also use the video scopes is in the free trial version of Veescope Live. Look for changes in the grey scale or color pattern.

Brad Wright is software engineer, so it may be difficult to understand what he is saying. He is always happy to explain his greater detail.


Return to posts index

Neil Kidney
Re: Gamma issue in Quicktime mp4
on Nov 22, 2011 at 3:39:00 pm

Cheers Brad.
The workflow for encoding doesnt get more basic than this...
uncompressed AVI/Quicktime is imported into Quicktime, and any compression in MP4 using either h264 or MPEG4 improved (or a .mov with h.264) on any platform results in gamma shift.



Return to posts index


Brad Wright
Re: Gamma issue in Quicktime mp4
on Nov 22, 2011 at 3:49:03 pm

Which version of the Quicktime Player? Sometimes the Quicktime Player may render in RGB which will mess up the gamma. Again, I would highly recommend not using your eyes, but using video scopes to test for the shift. Different codecs display totally differently in Quicktime. The video scopes however will always tell you what is really going on in your video. I created a video about this on my website.

Brad Wright is software engineer, so it may be difficult to understand what he is saying. He is always happy to explain his greater detail.


Return to posts index

Neil Kidney
Re: Gamma issue in Quicktime mp4
on Nov 22, 2011 at 3:51:36 pm

7.6.4



Return to posts index

Brad Wright
Re: Gamma issue in Quicktime mp4
on Nov 22, 2011 at 3:57:06 pm

What codec are the AVI or Quicktime files originally created in? I would export a test pattern out video out of Final Cut Pro with the same codec. Encode it with the Quicktime Player and import it into either Final Cut or Veescope Live and read compare the waveform monitor. In a grey ramp, the waveform monitor will be bent if there is a gamma shift. If there is no gamma shift, the waveform monitor will remain a straight line.

Brad Wright is software engineer, so it may be difficult to understand what he is saying. He is always happy to explain his greater detail.


Return to posts index

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
© 2018 CreativeCOW.net All Rights Reserved
[TOP]