Chroma Key with DVCProHD?

[Uli Plank]

Did you ever try DV Matte Pro or DV Matte Blast (realtime, for Motion 2) from http://www.dvgarage.com ?

It can work miracles on any format, not only DV, with reduced color resolution (and, BTW, regular HD-Cam is reduced as well).

Regards,

Uli

Author of “DVDs gestalten und produzieren”, a book on professional DVD-authoring in German.

[Gary Adcock]

[OneMatchFire] “if it is possible to get a good chroma key shooting DVCProHD (Varicam, etc.) or if one must shoot HDCam.”

I see no advantage or difference between Chroma-Keying with Varicam {4:2:2} vs. HDCam{3:1:1},
However I find Keying a progressive image easier than an Interlaced one however.

Just do not worked compressed. You do not want to Key any footage when it is compressed. ( so no FW)

gary adcock
Studio37
HD and Film Consultation

[Shane Dillon]

I have to produce good results from chromakeys shot on various formats and if you have the choice, shoot your chromakeys on a green background as opposed to a blue one if you are going to use the DVCProHD format.

You see the ‘blocking’ from the format much more on the blue than the green. As Gary said, avoid compression if you can, and record in via the HD-SDi. I have to be honest the HDCam is slightly better for keying as it records more pixels for a start and on tests I have performed shows more details in fine things like hair etc.

My advice is to make sure that everything is lit well as you will see the blocking in darker areas.

I tend to use Quantel to do all keying as it has the tools to get round even badly shot material.

[Onematchfire]

Hi,

Thanks a lot everybody for your tips.

In answer to a question, no we haven’t tried those. We have ultimatte and a Nitris. But that should work, right?

The thing that doesn’t make sense is that chroma keying on Betacam and Digibeta shouldn’t be better than doing a chroma key with DVCProHD right? (Or only if it goes in through HDSDI and “uncompresses” as opposed to firewire which stays compressed.

The other issue is what if this is due to the Avid DNXHD compression codec. I don’t get totally how this works, but if you went into a Nitris via FW and it compresses stuff with the Avid codec, then wouldn’t you be getting DVCProHD compression and then Avid DNXHD compression on top of that? Because Avid doesn’t work natively with that HD Codec like FCP does. So I’m wondering if the tests were horrible because everything was compressed once or twice and with HDCAM you can’t firewire (if I’m correct) so they had to bring it in uncompressed for tests.

Am I correct? Is there any reason they would get better results from Betacam than from DVCProHD? (doesn’t make since because the resolution is so much better and everything so much sharper).

THANKS!

Rachael

[David Battistella]

All of the keys will respond better if they are captured uncompressed. I am not sure about hte DVCPRO HD version of the Nitris codec but I know that avid has to put their own wrapper on the file in order for it to be seen by the nitris. So this is AVID’s version of the codec. Try the same tests capturing the varicam codec the same way you would HDCAM (via sdi input uncompressed) and I am sure you will see a difference in the results.

As gary said. Stay away from the compressed formats for keying, you will get some blocking.

I agree, shoot it green if you can.

David

[Uli Plank]

If you have the possibility in the studio to get analog HD component from the camera as your input directly into the computer system, you’ll always be better off.

But once you’ve taped, the chroma resolution is lost forever. The codec is applied when recording, so it doesn’t matter if you transfer native or uncompressed into the system, the damage is already done. This applies to DVCProHD as well as HDCam (the ordinary version, not the high-end one used by folks like George Lucas).

You’d be surprised at the quality even a Sony Z1 can deliver via analog component as compared to the heavy MPEG-2 compression.

Nevertheless, you should use an uncompressed format (or very mild compression) in your editing system for any heavy graphics or effects work to avoid further damage. I can’t judge the Avid HD codec, but on our FCP systems the uncompressed codec from Blackmagic is a very good choice.

Hope this helps,

Uli

Author of “DVDs gestalten und produzieren”, a book on professional DVD-authoring in German.

[Onematchfire]

Thanks for all the data, und vielen dank (for the Germans)!

Unfortunately it is not feasible to go tapeless and uncompressed most of the stuff because a lot of it will be greenscreen interviews in the field where it isn’t practical to bring your computer or even a bunch of drives.

Have you been able to chroma key succesfully from DVCProHD off tape before?

Isn’t it much better when you go in HDSDI as opposed to FW?

Thanks,

OneMatchFire

[Noah Kadner]

That’s the point my friend- once it’s on tape it doesn’t matter. You are compositing DVCPROHD whether you capture it digitally via Firewire or wrap a huge uncompressed blanket around it. The original uncompressed info is lost the second you record to tape. That said it is not that hard to get a good key off DVCPROHD. Just more work to tweak in post and you’ll need to nail it in production with good lighting.

Noah

[Onematchfire]

Dear Noah,

Thanks. I get it. But that makes me ask: so, if that’s the case, what is the point of having HDSDI out on a DVCProHD deck? And what’s the point of going in HDSDI at all then, why not just FW if it doesn’t matter since it’s been compressed on the tape anyhow?

Best,

OneMatchFire

[Noah Kadner]

Because not everyone has the ability to capture via Firewire- only Final Cut Pro and some flavors of Avid. Everyone else must go HDSDI into their editing systems. And yes they are essentially wasting vast amounts of space without adding back any resolution by capturing this way.

The camera itself has SDI out because you can bypass the compression _if_ you capture uncompressed before the signal hits the onboard deck but otherwise there’s nothing to be gained- as mentioned in the posts above.

Noah