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Decklink Studio, Canon HG20, HDMI capture for green screen

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Graham JonesDecklink Studio, Canon HG20, HDMI capture for green screen
by on Jul 2, 2010 at 7:17:52 pm

Hello, (posting this on Decklink and Canon forums too)

I am trying to set up a home green screen studio on a very tight budget, to enhance my podcast work. I've already ordered a number of soft lights and a chroma key backdrop (from cowboystudio.com -- great site by the way). As for camera, I have a Canon HG20, which records 1920x1080 AVCHD, at a maximum of 25 Mbit.

I am a TV editor, and recently have had to do a pile of green screen keys for Animal Planet, which were shot at 1080i60 with Sony 35 Mbit EX cameras. They were lit well enough, but very difficult to key, because of the very compressed format and color sampling. I know the 25Mbit AVCHD from my HG20 will be much worse.

Canon confirmed that their cameras' HDMI ports properly output the uncompressed signal directly off the CCD, before applying the lossy AVCHD compression. Since I have a Decklink Studio card, I am interested in capturing this uncompressed HDMI output directly to the hard drive.

Since the HG20 can shoot 1080p30, and the Decklink Studio can capture 1080p30 to Apple Prores 422 HQ, I thought this would be a pretty nice setup for green screen, with higher 4:2:2 color sampling and much higher bit rate, and not quite as much of a hit on my hard drive as full uncompressed HD.

I will use After Effects for the keying.

My question is -- does anyone have any real experience with this? Anything I should know about? Gotchas?

I should mention that I plan to buy a second camera, but am limited to $1,000. I am thinking of staying with Canon so the cameras are easier to match. Any recommendations?

Thanks,
Gray.


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Dave LaRondeRe: Decklink Studio, Canon HG20, HDMI capture for green screen
by on Jul 2, 2010 at 7:45:36 pm

I leave it to the Canon guys to talk about Canon cameras. I don't know beans about 'em.

You might not need to use the Prores HQ; normal Prores 422 may do just fine. I'd investigate if HQ is 10-bit and 422 is 8-bit; if that's true, you're doing the right thing.

If you have the storage, You may want to forget about Prores HQ and capture using Prores 4444. It's just what it says: 4-4-4 color, which is REALLY sweet for keying, plus it supports alpha channels!

AE has to be on the same machine where FCP is installed in order to write to prores, but you probably knew that. I bet you already understand about lighting to get a good key.

The one thing I'd do differently is save pennies, nickels and dimes to get more storage. A TB is about $100 these days, and I bet you could put together a very roomy RAID for not much cash. Ask yourself if you REALLY need that extra camera more than you need storage.

I've been trying to talk my people into a similar HDMI-out chroma keying setup, but using a seldom-used Sony V1. Gary Adcock from the COW (VERY high-end camera, AJA, lighting and FCP guy) suggested it to me six months ago.

I like your idea. A lot. Good luck with it.


Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Graham JonesRe: Decklink Studio, Canon HG20, HDMI capture for green screen
by on Jul 2, 2010 at 8:50:14 pm

Hi Dave,

thanks for your response. I forgot to mention that because I do a lot of HD broadcast editing and color grading, I already have massive RAIDs at home -- two RAID arrays totaling 16 TB, on two separate quad Mac Pro machines. So storage isn't an issue. ;-)

Both Prores HQ and Prores are 10-bit 4:2:2 -- they only differ on the data rate. You're right in suggesting I should experiment with non-HQ, as what I'm really after is the 4:2:2, and the higher data rate of HQ may be just overkill.

I may be wrong, but I think the HDMI only carries 4:2:2 -- so I think Prores 4444 wouldn't be worth it. Plus, for my purposes, the 4:2:2 will do fine.

Yeah, I have the lighting under control. 4 years of film school taught me enough of that. ;-)

Thanks,
G.


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Graham JonesRe: Decklink Studio, Canon HG20, HDMI capture for green screen
by on Jul 2, 2010 at 9:23:00 pm

Oops, just realized that my Decklink Studio maxes out at 4:2:2 -- you need the Extreme for 4:4:4. So -- I guess the only question is HQ vs non-HQ.

I guess I'll just have to experiment to see whether non-HQ will do what I need.

Thanks,
G.


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Dave LaRondeRe: Decklink Studio, Canon HG20, HDMI capture for green screen
by on Jul 2, 2010 at 9:31:24 pm

Well, I just thought of something else, too: do you have Adobe OnLocation?
http://www.adobe.com/products/premiere/onlocation/

FCP's Log & Capture function can be kinda kludgy for what you want to do. OnLocation -- or another application like it -- makes recording the shots a lot easier & faster. I think these video capture gizmos even have things like waveform monitors & vectorscopes in them.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Graham JonesRe: Decklink Studio, Canon HG20, HDMI capture for green screen
by on Jul 2, 2010 at 10:01:24 pm

Hi,

unfortunately I only have CS3, which didn't come with a Mac version of OnLocation.

Do you know of any better Mac-based Decklink-compatible capture tools, that would be better than FCP?

Thanks,
Graham.


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Dave LaRondeRe: Decklink Studio, Canon HG20, HDMI capture for green screen
by on Jul 2, 2010 at 10:24:01 pm

[Graham Jones] "Do you know of any better Mac-based Decklink-compatible capture tools, that would be better than FCP? "

Rats. I can't recall the name. But I'd be willing to bet they know on the FCP forum. However, here in the Midwest US, it's after 5PM on a the Friday of a long July 4th weekend. I'd wait to ask until early next week when people will be around.



Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Graham JonesRe: Decklink Studio, Canon HG20, HDMI capture for green screen
by on Jul 2, 2010 at 11:35:18 pm

Hmmm...

I decided to do a very quick down and dirty test -- low lighting in my office to exaggerate the grain, tried capturing 1080p30, 1080p24, 1080i60 by HDMI (ProRes HQ), and recording at the same time to the camera at 24 Mbit AVCHD to import with Log and Transfer.

Notes:
- The camera appears to Final Cut as 1080i60 regardless of which internal mode the camera is set at, whether using HDMI or Log and Transfer. I notice the 24p-style motion when recorded in that mode, but not true progressive frames. Bummer. This may not be a FCP issue -- when I check the HDMI Status in the camera menus, it says 1080i60 and has no other options.

- Though the HDMI-captured image does have significantly more colour and more detail in moving areas, it also has significantly more noise. This doesn't make sense to me -- unless it is an issue of the HDMI more accurately capturing the color noise of the grain.

- Because of this, in low light the non-HDMI actually looks better.

- That said, in my broadcast color grading experience I know that even very high end pro cameras look terrible when there is gain noise in low light. I am eager to see how these tests might differ in full studio light. If I don't have to deal with the grain, I think the HDMI improvements will be worth it.

My light kit will ship in another week or two -- I'll report back when I have more tests to share.

Thanks,
G.


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Graham JonesRe: Decklink Studio, Canon HG20, HDMI capture for green screen
by on Jul 3, 2010 at 1:43:06 am

Hi,

Silly me... I just read further in the forums and realized that though the HG20 captures 30p as 1080i60, it really is sending progressive frames. So apparently you just set FCP's sequence settings to fields "none" and it is progressive.

To my eye there's very little difference between the 1080i60 and 1080p30, but we'll see once I'm dealing with higher light levels,

Thanks,
G.


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Dave LaRondeRe: Decklink Studio, Canon HG20, HDMI capture for green screen
by on Jul 3, 2010 at 3:47:56 pm

You'll see the big difference when you check motion. And yes, most HD cameras capture 30p as interlaced in 1080. They call it "progressive segmented frame".

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Jacques DavisRe: Decklink Studio, Canon HG20, HDMI capture for green screen
by on Jul 3, 2010 at 11:17:36 pm

I work with 12 canon HV20, for three years now.They are great cameras. one thing only, they are ' fragile". one day you don't know why, on one camera the zoom started to play by itself, an other day one got a 5 magenta blue cast , etc ...Great cameras, but only consumer cameras. So if you are working 5 days a week try to get some spare ones.


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Graham JonesRe: Decklink Studio, Canon HG20, HDMI capture for green screen
by on Jul 3, 2010 at 11:21:46 pm

Hi,

thanks for your input -- good to know. Luckily I use the camcorder very sparingly, only from home, and always carefully. It was only used outside the home once last year, for example.

Thanks,
G.


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Lyle HolmesRe: Decklink Studio, Canon HG20, HDMI capture for green screen
by on Dec 3, 2010 at 2:08:51 am

Hey Graham,

I've been working with a very similar green screen setup for nearly a year. Setup:

Vixia HFS11 with HDMI out to MacPro with Decklink E3D editing and keying in FCP. Good green screen; lighting is okay but not great. I'm taking audio directly into the Mac.

How are you doing since you first posted this thread?

Here's a sample of what we're producing; I'd be interested in your comments on quality:

http://celebritas.com/client/Celebritas/homepage.html

Lyle

Seattle
Interactive Video


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