I am converting a .MOV file into .MP4, .OGV and .WEBM for web use. I have found that the background rendered by QuickTime and Safari is not white although the same MP4 has a white background when viewed with Windows Media Player.

The video is compressed using http://www.mirovideoconverter.com/ which uses ffmpeg (conversion parameters used are listed https://develop.participatoryculture.org/index.php/ConversionMatrix#Output_Formats)

Can anyone tell me why this is and how I would correct the output for QuickTime?

  • I wonder if your video has an Alpha channel that's creating a partially or fully transparent background. Then each player and codec is displaying that transparency different.
    – Andrew
    Sep 14, 2011 at 20:28

1 Answer 1


it is a problem with gamma settings youre using and QT has its own gamma settings, dont bother. it will display only in QT that way...

also check for alphas, but im not so sure that mp4 can support alpha channels... only qt mov with animation codec has alpha.... as i know...

  • mp4 cant support alpha channels.
    – H_7
    Oct 17, 2011 at 23:26
  • It does seem a bit of a problem that videos would not display properly in Safari and on iPads, will do some more searching, would be good to work out how to create a QuickTime version that displayed properly
    – Tom
    Oct 19, 2011 at 15:13
  • First thing to consider, Mac OS X and Windows have different gamma setups for screens, so thats a part of your shift in white. Second thing to consider is, what is encoding preset like, third, send us few screenshots from both setups so we can see the difference in white more clearly.
    – Desmond
    Oct 19, 2011 at 19:44

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