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Best chroma key capture codec

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Greg Barker
Best chroma key capture codec
on Mar 10, 2008 at 1:37:40 pm

I'm about to digitize a bunch of interviews captured using green screen and I'm wondering what the best capture codec is to use?

I have a Kona LH, capturing in FCP 6.0.2. I will capture in an HD codec (normally it would be the AJA Kona LH: 1080i 29.97 DVCPro HD setting) for keying and archiving in a HQ format but the immediate end-use will be for the web. I thought I might capture using the AJA Kona LH: 1080i 29.97 ProRes 422 because it might be better for keying but I also thought about doing a capture to a progressive codec since the client plans to use it on the web. The interviews are fairly simple, nearly static shots. My initial comp of a ProRes 422 capture came out pretty clean but before I capture all of the interviews I wanted to make sure I was making the best decision.

Any thoughts would be welcome. Thanks.

- Greg



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Jeremy Garchow
Re: Best chroma key capture codec
on Mar 10, 2008 at 2:39:26 pm

I have been doing very well with keying and ProResHQ. I have been throwing that in instead of 10bit Uncompressed. I like the results. What keying package do you use?

Jeremy




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Greg Barker
Re: Best chroma key capture codec
on Mar 10, 2008 at 2:54:25 pm

I've been using the apps I own for now, Shake for most and Motion for some.

I've been experimenting with the trial versions of ScopeBox and Conduit over the last 4 to 5 days. With ScopeBox I really like the ability to see a comp real time although I don't intend to create live comps, it's definitely nice to be able to check your lighting and other things. Unfortunately with Conduit Live demo I am limited too much to really tell how useful it will be although I like what I see in the tutorials. The regular Conduit demo I can't really tell what kind of comp I'm getting since I'm forced to work with sample source sizes of 320x240.

Sorry, I'm going to ask this rather than do a quick scan of another forum... Is the 422 HQ a variable codec in that my capture sizes would be less with little movement and based on the fact that 75% of the background is green? In that case I would bump up to the HQ codec. I'm not worried about capture size but more with the amount of space needed to archive it.

Thanks.

- Greg



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Jeremy Garchow
Re: Best chroma key capture codec
on Mar 10, 2008 at 4:02:55 pm

[Greg Barker] "Is the 422 HQ a variable codec in that my capture sizes would be less with little movement and based on the fact that 75% of the background is green? "

You know, good question. My instinct says no. According to the AJA data rate calculator, 1080i HQ will be 1.89 GBytes per minute, 114 GB per hour with 4 channels of 24bit audio. 1080i ProRes will be 1.27 GBs per minute, 76 GBs an hour. Not really that much difference in the grand scheme. I'd stick with HQ. Less compression.

Jeremy


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Greg Barker
Re: Best chroma key capture codec
on Mar 10, 2008 at 4:46:43 pm

Thanks Jeremy. I captured the first interview (at least the usable soundbytes) in 422 HQ and they averaged slightly over a GB/minute. One of the clips was exactly 1 minute in duration and it was 1.02gb. Looks like the codec may scale some, either way it looks like the way to go. I can live with a gig per minute.

Did you have an opinion as far as sticking with interlaced at 29.97 rather than transcoding to a progressive frame rate? I can always deinterlace on the back side but I was just wondering if it's better to take advantage of the hardware transcode on ingest? Thanks again.

- Greg



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Jeremy Garchow
Re: Best chroma key capture codec
on Mar 10, 2008 at 6:35:00 pm

[Greg Barker] "I can always deinterlace on the back side but I was just wondering if it's better to take advantage of the hardware transcode on ingest?"

Since you have recorded interlaced, the damage has been done, so to speak. I'd edit and post in interlace, then do a comprehensive deinterlace at the end for the web. I like Fields Kit from revisionfx, but most web compression programs will deinterlace for you as well if it will pass your personal QC.

Jeremy




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Greg Barker
Re: Best chroma key capture codec
on Mar 10, 2008 at 6:57:22 pm

Excellent, thanks for all your help.


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