keying dv footage - not vray but may be useful for someone

[panthon]

just as a side note: as far as i know the PAL version of DV has better chroma sampling than NTSC DV
I could be wrong tho'

In my experience a lot of keying-related problems arise from bad lighting. Unless you have a huge studio its very difficult to seperate the lighting of the green/blue screen and the lighting of the action. You just dont have enough space between the actors and the screen. This leads to blue/green light being reflected back on the actors.

cu mike

NTSC DV has a sampling distribution of 4:1:1, whereas PAL has a 4:2:0, being 4 the luminance, and the others Red-Y and Blue-Y. It´s said that PAL versions provide better sample distribution for chroma key purposes, but when you test it at work, you get similar crappy keys from either format.

Quoting: "Above, both 4:1:1 and 4:2:0 sampling methods have been mentioned. The former means that both of the chroma difference signals (Cr and Cb) are sampled at one quarter of the luminance sampling rate. The latter, on the other hand, uses half the luma sample rate for the colour differences, but the two differences are only sampled on alternating lines (resembling SECAM). Both give the same total data rate, but the 4:2:0 sampling gives a better apparent colour resolution for PAL.

In the NTSC world, all three DV variants use 4:1:1 sampling. In the PAL versions, DV and DVCAM revert to 4:2:0, whereas DVCPRO uses 4:1:1 globally. Here's a catch - if you dub between PAL DVCPRO and one of the other formats, you'll end up with the worst from both worlds: a 4:1:0 sampled image, where both vertical and horizontal colour resolutions are only half of the conventional broadcast quality 4:2:2 sampling."

And yeah, having a huge studio does help with pulling good keys. And tracking points would help to more spectacular shots, and motion control cranes, and professional monitors, and pretty models and and....lots of cash

[percydaman]

These are nice...

http://www.thomsongrassvalley.com/pr...cameras/viper/

[mike.edel]

NTSC DV has a sampling distribution of 4:1:1, whereas PAL has a 4:2:0, being 4 the luminance, and the others Red-Y and Blue-Y. It´s said that PAL versions provide better sample distribution for chroma key purposes, but when you test it at work, you get similar crappy keys from either format.

Quoting: "Above, both 4:1:1 and 4:2:0 sampling methods have been mentioned. The former means that both of the chroma difference signals (Cr and Cb) are sampled at one quarter of the luminance sampling rate. The latter, on the other hand, uses half the luma sample rate for the colour differences, but the two differences are only sampled on alternating lines (resembling SECAM). Both give the same total data rate, but the 4:2:0 sampling gives a better apparent colour resolution for PAL.

In the NTSC world, all three DV variants use 4:1:1 sampling. In the PAL versions, DV and DVCAM revert to 4:2:0, whereas DVCPRO uses 4:1:1 globally. Here's a catch - if you dub between PAL DVCPRO and one of the other formats, you'll end up with the worst from both worlds: a 4:1:0 sampled image, where both vertical and horizontal colour resolutions are only half of the conventional broadcast quality 4:2:2 sampling."

And yeah, having a huge studio does help with pulling good keys. And tracking points would help to more spectacular shots, and motion control cranes, and professional monitors, and pretty models and and....lots of cash

thanks for clearing this up

regarding the cash: don't we all want a higher budget sometimes?

[Nickh]

greenscreening revisited

Hi,

I'm just about to do a job which involves comping in green\blue screen people and so found this thread interesting. However I still would like to ask a couple more questions...

We did this in a job a while back and it was tricky to get a clean key. I thought it was down to the lighting, so we have done more shopping around for a good studio to shoot the footage in and have just been sent a test clip on DVCPRO.

I still can not get a good clean key from combustion, and this a reputable studio who have a very good setup. So I am wondering if it is a sampling or interlacing issue.

It was shot on Digibeta, PAL with fields, and converted to DVCPRO (we only have a DVCPRO deck here), then I captured it in to PremierePro through a Matrox RT.X to Matrox's DVCRPO avi codec.

I've tried keying this interlaced avi directly and deinterlacing in combustion, rendering that out to .tga's and keying that - which gets slightly better edges, but its still not great.

Is there a better route I could take, given our hardware setup? should I ask for it to be shot in progressive mode?

or am I just not going to be able to get a good result given the nature of DV footage? Or maybe I'm just not using combustion's keyer in the best way?

Any guidance on this would be greatly appreciated

Thanks

[joconnell]

Heya!

Digibeta is better than DV no doubt - dvcpro isn't any great shakes, it's justa bigger tape so you can get more footage - something like dv50 is far better, it's a dv format that has higher colour sampling and thus makes it easier to key. Interlacing is a pain in the arse for no end of reasons, one major one being if it all goes wrong and you have to rotoscope stuff, its nigh on impossible to get a good edge.

In your case as soon as you go to dvcpro, you're throwing away a lot of the colour detail. I'd recommend to go to another post or edit house that can capture the digi footage and play it out as a tga sequence or uncompressed quicktime and then use something like reelsmart deinterlacer to make frames from it. Alternatively rent one of those panasonic cameras and shoot with the p2 media cards so you get 4:2:2 and progressive.

At the very minimum I'd shoot progressive DV and use the dv matte pro keyer on it - $99 well spent.

[panthon]

Heya!

Digibeta is better than DV no doubt - dvcpro isn't any great shakes

I agree with joconnel. The mistake in your workflow is going from digital betacam to dvcpro, that means going from 4:2:2 color sampling to 4:1:1. Creating an uncompressed video (like quicktime or image sequences) straight from Digital Betacam would make your life easier when keying. I am not sure about the capture cos im not familiar with your card but u could be losing some info there too. Your final image in combustion is far worse than it should, so it's not surprising you're having issues.
However try the diamond keyer in combustion. Easier to setup than discreet keyer and from my experience, better results in less time.
Ideal situation: a 4:4:4 cam...too expensive.
Affordable situation and my preferred one: panasonic DVC PRO 50
progressive shooting, excellent lighting and enough distance between your blue or green walls and the actor, to avoid color contaminations and spills...
I wouldnt think ull get a perfect key anyway. Sometimes you can use the paint operator in combustion to clean some areas; it's not that slow and very efficient way to solve those little problems ....

Hope it helps...

[Nickh]

Thanks very much, both. Useful info.

I have just been testing the DVmattePro and it is definitely better, but still not good enough I think.

Hiring a DVCpro50 deck could be an option, but I would be worried that I would defeat the object by capturing it into the Matrox card to a DV avi.

So it looks like leaving the studio with (hopefully progressive) uncompressed files is my best option.

Thanks again.

[RePlay]

We are looking at getting a license for this:

http://www.seriousmagic.com/products...hats_new_in_2/


The license includes 2 licenses because most people have a workstation and a laptop. The software seems pretty decent and is very cheap.

I will be doing some HD filming very shortly and keying so I hope to show you some of my results.

[charleyc]

This has caught by eye for a while now.

http://www.reel-stream.com/index.php

http://www.reel-stream.com/andromeda.php

[Da_elf]

id just love to be able to get a real 24p hd camera with optional slow motion as well. eheh

EDIT
just found this.

http://www.sonystyle.com/is-bin/INTE...efinitionVideo

[panthon]

[quote]Sony’s HDR-HC3 camcorder is the industry's smallest and lightest HDV1080i consumer level camcorder and player[/code]

HDV interlaced is not good news. HDV format should be banned.

[Da_elf]

why oh why oh why cant i seem to find a good camera that can do high def 24p. seems most cameras only record 24p at 720 and not at 1080. which is very strange to me, wouldnt shooting at 24p mean less data than 30i. so wouldnt it be easier for it to capture 1080 24p. or is it due to the old limitations we had with video that borught about interlacing in the first place.

[joconnell]

Yup you're right - the interlacing was down to tubes not being able to update quick enough and the frame rates were due to synching with the electricity signals. you're totally right on 24p vs 30i too - at the same res 30i has more data and looks worse (in my opinion).

That panasonic AG-HVX200 will do what you want too.

[panthon]

That panasonic AG-HVX200 will do what you want too.

Gimme gimme please, i need that cam. I have a great interest in that machine, not only because it´s cheap (under 6000) but also because it can record to DVCPRO 50, HD, DV, uses a P2 workflow and on top of that is able to do slowmotion too...and it´s lightweight, slick and heavily supported by panasonic and a legion of enthusiats....i could be all day talking bout this cam...

[percydaman]

we've been looking for a nice pro-sumer hd camera. Ill check it out. Right now all we have is a viper, which is a bit overkill most of the time.