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Outputting broadcast for web - video to data issue

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Paul Willis
Outputting broadcast for web - video to data issue
on Nov 18, 2014 at 9:11:55 pm

Hi folks,

Just a quick question, if I want to take a file mastered for broadcast with video levels and prepare it for web, should I reexport it using data levels? This is what I thought I should do to map to full range for displaying on computer displays, but it comes out very contrasty and saturated, a lot more so than I would expect.

What's the usual workflow for this and is it possible that the broadcast file is just too contrasty to begin with?

Files are being imported and correctly interpreted as video levels on import, black levels look right on the scopes in Resolve and comes out looking the same if i test exporting with video levels,

Any advice appreciated.

Paul


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Joseph Owens
Re: Outputting broadcast for web - video to data issue
on Nov 18, 2014 at 10:42:57 pm

I am in the process of building an article dealing with this difference between "full range" RGB data levels and "Linear Video", so this question would be a great lead-in if only I had it at a stage to post.

The long and the short of it is that Web Video generally wants to fall in the sRGB colorspace since most OS's want to hang in that club. It is very similar to Rec709 broadcast, so the real deal is that if you are exporting a Y'CbCr Quicktime or other -- the display processing is going to want the file values to be in that HDVideo 709 or equivalent range. Because it says sRGB, doesn't necessarily mean that it is going to use the 0-255 or 0-1023 scale associated with Photoshop-type graphic values.

Its a big deal; sometimes it appears to masquerade as the so-called "gamma" bug, but it is an entirely different mechanism.

jPo

"I always pass on free advice -- its never of any use to me" Oscar Wilde.


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Margus Voll
Re: Outputting broadcast for web - video to data issue
on Nov 19, 2014 at 7:11:15 am

But there should be a small gamma jump also from 709 2.4 to srgb 2.2 ?

--

Margus

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Joseph Owens
Re: Outputting broadcast for web - video to data issue
on Nov 19, 2014 at 7:17:26 pm

Not in the league of 1.8 -->2.2/2.4.

jPo

"I always pass on free advice -- its never of any use to me" Oscar Wilde.


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Paul Willis
Re: Outputting broadcast for web - video to data issue
on Nov 22, 2014 at 11:08:34 am

Thanks, Joseph. It seems to be a tricky issue and in a lot of ways that puts my mind at rest that the source file is troublesome, although it comes out fine monitoring in 709.

I have recently been asked to supply a file for review on a laptop (terrible idea, but it gives them a vague idea about where the grade is going), is it just best to stick with 709 and ignore any comments about contrast?! I was hoping I could find a middle ground with some tweaks, but I'm unsure what to do with that. If I run it into premiere is clearly remaps to full range (according to the internal scopes) for viewing, but what's going to come out is probably video scaled again. I haven't had chance to run enough tests to be honest, I'm forcing the client to come into the suite!

I'd love to know what BBC iPlayer and other online services do. Perhaps a question for their tech team.


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