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DNX-HR codec and Quicktime Issue

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Michael Buday
DNX-HR codec and Quicktime Issue
on Nov 2, 2016 at 10:46:49 pm

I've finished a show at UHD rez/23.98 using the DNX-HR codec (Avid v8.6.4 for Mac / 10.11.5 (15F34)). The timeline clips consist of a wide variety of source material, from 4K to 720P. Everything has been rendered on the timeline to DNX-HR.

My process to get o other formats is as follows:

a) Output QT file from AVID using SAME AS SOURCE (DNX-HR)
b) Take QT file from AVID and using AMC (Adobe Media Encoder, latest CC version), encode to desired format (MP4, DCP, whatever . . )

My issue is this:

The QT looks fine (though with the typical AVID black level change). But after processing thru AMC to say, MP4 - some clips in the SEQ don't encode correctly, instead they appear filling the screen with an ORANGE color.

Has anyone seen this behavior before?

- Michael Buday


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Michael Phillips
Re: DNX-HR codec and Quicktime Issue
on Nov 3, 2016 at 2:59:23 am

I stay away from anything wrapped QuickTime (.mov) as it is not the codec that causes level/gamma issues, but the wrapper. I have tried eliminating any use of QuickTime whenever possible and use OP1a exports. See my blog for reasons why:

http://24p.com/wordpress/?p=278


Michael


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Michael Buday
Re: DNX-HR codec and Quicktime Issue
on Nov 3, 2016 at 4:33:27 am

Hi Michael,

THANK YOU!! This makes a ton of sense and in my tests it worked beautifully. I only wish I inquired sooner as I've been using the AVID > QT > "Desired format" method for a very long time.

Question:

My sequence contains a TON of AMA referenced 4K material from Sony A7sii cameras. I offlined at 1080P/23.98, all media transcoded to DNX-LB. I then imported the sequence into a new UHD project setup for DNX-HQX, consolidated the timeline and imported all the AMA references to link up to the original media.

Of course, the timeline won't play 4K XAVC-S AMA media without slowing wayyyy down, so I rendered the entire sequence so I could play it to eval the uprez.

Using your AMA OP1a export, If I export to the same codec the sequence has been rendered to, does it re-render again before exporting? Or does it reference the "already" rendered material?

Thanks again - extremely helpful.

- Michael


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Michael Phillips
Re: DNX-HR codec and Quicktime Issue
on Nov 3, 2016 at 1:20:57 pm

That's a good question and one I do not know the answer to as to what exactly goes on under the hood. From a quality perspective, the DNx codecs can go many generations before showing any type of decompress/recompress artifacts. From a time perspective, it would go faster if it did not have to decompress/recompress, but in my tests it is still doing whatever faster than any other export method when you combine all the steps needed to do the other export types.


Michael


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