Outputting questions

Posted by john 
Outputting questions
September 19, 2011 04:34PM
Hi all,

I'm outputting a project as a 10 bit uncompressed quicktime (for my colorist) and ultimately he'll deliver to DigiBeta. The project was shot in DV and archival footage was captured at 10 bit uncompressed SD. What is the best way to handle the output? Should I uprez the DV footage to 10 bit SD then put the clips in a 10 bit SD timeline with the archival footage? Or is it better to create a 10 bit SD timeline and bring in the DV footage as DV footage?

Also I'm noticing that the appearance of the sequence on my laptop is pretty soft (much softer than outputs I've made for DVD). Is there a reason for this?

Thanks smiling smiley
Re: Outputting questions
September 20, 2011 02:58AM
Digibeta is nearly 10-bit uncompressed 4:2:2 SD. Its image compression is slight.
Since your archival footage is 10-bit uncompressed 4:2:2 SD, it could, depending on the footage and the scan (or transcode, as the case may be), look better than the DV material in the final Digibeta. If this isn't aesthetically awkward for you, then your ideal workflow is to have a 10-bit uncompressed 4:2:2 SD timeline and import all the material to this line. The 8-bit DV material will require rendering before final export. Transcoding from 8-bit to 10-bit isn't "uprez". It's just adding two zeroes to each 8-bit number.

There's no harm using compressor to transform the DV material to 10-bit uncompressed 4:2:2 before dropping it into the FCP 10-bit uncompressed 4:2:2. Both programs can impose unwanted gamma shifts. One only hopes they do it after the 10-bit conversion.

All this assumes that there are no framerate or field dominance issues among the materials. The colorist can deal with possible gamma mismatches among the materials once they're in one codec.

The softness you're noticing might be due to gamma.

Dennis Couzin
Berlin, Germany
Re: Outputting questions
September 20, 2011 03:21AM
There should not be a gamma shift as they are 601 sources.

Re: Outputting questions
September 20, 2011 09:24PM
strypes Wrote:
> There should not be a gamma shift as they are 601
> sources.

I just did this confirmation: a DV tone scale was transcoded to 8-bit uncompressed 4:2:2 and to 10-bit uncompressed each in two ways, using Compressor and using FCP rendering. The four files turned out exactly equivalent. (The 10-bit binaries being the 8-bit binaries with 2 zeroes added.)

This doesn't show that the original DV tone scale was preserved, but an old experiment did show this, indirectly. It also showed how QuickTime plays DV with a 10% gamma boost. Might the FCP players do this too? There can then be a perceptual problem for the editor: DV footage which looks a certain way doesn't look that way after the transcoding.

Dennis Couzin
Berlin, Germany
Re: Outputting questions
September 21, 2011 12:05AM
I won't be surprised if that bug was fixed since then, and knowing how old the qt gamma bug is, I won't be surprised if it isn't. Graeme Nattress has had issues with QT gamma shift with QT.

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