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Transcoding Clipping Super White Information in Avid's DNxHD codec

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Greg Knollmeyer
Transcoding Clipping Super White Information in Avid's DNxHD codec
on Oct 13, 2011 at 9:01:59 pm

I have been experimenting with several workflows now that I'm back in Premiere after FCP's demise. I was working on a sequence comparing using original AVCHD media in PP as well as the same footage in DNxHD codec. Some people say that there is a benefit to putting all media into a single/intermediate codec if one is going to use external color correction tools. Since DNxHD is available on both mac/pc, I thought it would be a good thing to explore.

Anyway, as I was working with the footage, I noticed that my AVCHD clips retained information in the super whites as well looking a bit cleaner. I noticed that the DNxHD clips crushed the whites and seemed to have some gamma issues. I was surprised at the difference. The pictures show the waveform and clip for both the original AVCHD and DNxHD with no corrections on either clip. I tried the codec set to both 709 & RGB (settings also pictured) with the same results.

Then I tried taking it into ProRes 422 just to see how that worked. I didn't see the gamma shift; but ahd the same issue in not being able to recover whites in that 100-110 range.

This makes me think that transcoding footage should not be the first step in a workflow including advanced color correction. However, that seems to be what I read everywhere. It seems instead that transcoding for advanced color correction would be best done after primary color is done in PP. But I also wonder, am I just doing something wrong? Can someone enlighten me about why this is happening?

Thanks for any help.

Original AVCHD with scope & image
AvidCodec
Avid Settings
ProRes with scope & image


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Greg Knollmeyer
Re: Transcoding Clipping Super White Information in Avid's DNxHD codec
on Oct 19, 2011 at 10:37:02 pm

Just a follow-up. I did a little more testing with all available settings including 10 bit in the Avid codec. Still no luck with the super-whites showing up. I do notice better results with Pro-Res (no gamma issues); but still no super whites. However with ProRes, I don't have the codec options to work with. When I click on the codec options, nothing comes up as with the Avid codec.

Finally, I went into FCPX which I've been playing with. When I imported/transcoded from there, the superwhites show up and I can recover a little detail in the highlights.

So I'm beginning to wonder if there is an issue with Adobe Media Encoder's ability to work with those codecs. I am using CS4, so that may make a difference. I'm waiting/hoping that in spring, CS6 will be out and I can pay for just one upgrade.

Anyway, I'm still wondering if there is any point to transcoding to an intermediate codec when working with footage from different cameras/sources in PP and Resolve. So far, I think not; but I keep reading the reverse. Any ideas/opinions?


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Greg Knollmeyer
Re: Transcoding Clipping Super White Information in Avid's DNxHD codec
on Oct 19, 2011 at 11:25:45 pm

OK, so this may be silly typing to myself and all; but I had one more idea. I took the clip that was transcoded to pro-res in FCPX--the one that showed the super-whites in FCPX, and placed it on my timeline within Premiere Pro. No superwhites appear on the waveform, in PP and there isn't any recovery for them

This makes me think that I'm still missing some setting or basic piece of info or CS4 has some problem recognizing superwhites if the clips are not in their native format. I welcome others to the conversation...


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