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QuickTime gamma drop when transcoding from DNxHD to H.264

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Ivan Myles
QuickTime gamma drop when transcoding from DNxHD to H.264
on Jul 17, 2013 at 5:19:58 pm

Has anyone seen a decrease in gamma when transcoding DNxHD/MOV files to H.264 using QuickTime Pro? Images are noticeably darker: grey point in the encoded video is approximately 0.88 of the intermediate files.

Here are the specifics:

- DNxHD-90-720-24-10bit/MOV with RGB and 709 color, exported at 48-bit depth setting from Premiere Pro CS6 v6.0.3
- DNxHD file opened in QuickTime Pro v7.6.9 on Win7-64
- transcoded to H.264/MP4 at Baseline Profile, 1-Pass and 2-Pass, bitrates from 2500-32768 kbps, key frame distances from 1-24 frames
- also transcoded to H.264/MOV at auto settings, multi-pass
- analyzed using RGB Parade and YC Waveform in Premiere Pro


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Eric Strand
Re: QuickTime gamma drop when transcoding from DNxHD to H.264
on Jul 17, 2013 at 9:52:43 pm

What program are you using to transcode? Apple's Compressor was known to mess with gamma when going to H.264, usually washing the image out a little bit.


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Ivan Myles
Re: QuickTime gamma drop when transcoding from DNxHD to H.264
on Jul 17, 2013 at 10:41:16 pm

Thank you for the reply. The files are being transcoded with QuickTime Pro v7.6.9.

One of the characteristics of the QT/Compressor wash-out issue is an increase in brightness within the shadow regions. In this case the video gets darker after transcoding.


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