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Avid’s DNxHD codec in Premiere
Hi.
This might be more of a question about colour space and whether it’s actually hardcoded into the file or not. Avid’s DNxHD codec has two options I’m concerned about, and they are to do with colour space. The options are 709 and RGB. Am I correct in saying that RGB is measured from 0-255 and 709 is 16-235 (a.k.a. YUV)?
Well if that’s the case, do either of these options change the video that is exported at all? Because I find that with a test video I made which had lots of bright whites, the 709 version plays back all clipped and horrible in media players such as MPC/VLC, etc. BUT, both 709 and RGB, when bought back into Premiere, look identical. Is this colour space thing acually changing the video, or simply flagging the file to a ‘correct’ colour space so that media players play it back accurately, even if that file contains illegal values?
TL;DR: Could exporting with the wrong colour settings here (709 vs. RGB) ‘damage’ your footage?
Thanks.
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3 Replies
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It’s just a flag. avid and premiere understand it . Many players don’t.
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[Lewis Costin] “Am I correct in saying that RGB is measured from 0-255 and 709 is 16-235 (a.k.a. YUV)?”
Yes, RGB exports using 0-255 and 709 uses 16-235.
[Lewis Costin] “Is this colour space thing acually changing the video, or simply flagging the file to a ‘correct’ colour space so that media players play it back accurately, even if that file contains illegal values?”
RGB vs 709 is a flag. However, illegal values outside of 0-100 IRE will be clamped/clipped upon export when using either color space. In addition, I have had experiences where 709 sometimes clamps all values outside of ~7.5-91 IRE and then remaps the resulting image to 0-100IRE.
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Lewis,
Premiere will map 0-100 IRE values to full 0-255 RGB (in some instances you can have luma values above and below because of some filters and floating point math but most codecs will clamp above and below). In other words, Premiere is designed so you don’t need to worry about the 16-235 rule for titles and so on.
With that in mind, my educated guess is to export RGB if you want a wysiwyg result when migrating to/from Avid. I’ve yet to extensively test the workflow so take it with a grain of salt.
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