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JVC-250 and HDV codec

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Jonathan Capra
JVC-250 and HDV codec
on Jul 15, 2008 at 4:15:12 am

I work in the promotions dept at a news shop that is currently still SD-only. Our Macs have AJA Kona cards, so they are HD-capable, but so far we have only used them for SD editing.

We are doing a try-out of a JVC-250 camera next month. I was looking online at some of the specs, and best I could tell it recorded only to HDV codec for HD and DV codec for SD.

Most of my knowledge on HD so far has been from what I've read. My understanding is the idea of HDV is that it squeezes HD resolution into the same datarate as DV/SD by using MPEG-2 instead of the DV codec. Is this correct?

If that's the case, I could see how they could sell consumer and prosumer cameras that only record HD to this codec, but how are they getting away selling pro cameras like the JVC-250 when it only records in MPEG-2?

Am I wrong in thinking that despite a great lens and 3 CCD's, the color resolution will be crap because the codec is recording to 4:2:0 color-space? And that this camera would be useless for any green-screen keying because of artifacting? And I would imagine our AJA Kona cards are kind of a waste in their ability to pipe 10-bit uncompressed in and out when the source would be highly compressed 8-bit video anyway?

When they go to invest in an HD camera for our dept, should I insist on some other format such as XDCAM or P2 or DVCPRO-HD?



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Johnny Clark
Re: JVC-250 and HDV codec
on Jul 15, 2008 at 5:13:42 am

Hey Jonathan,
Whew that's a load of great questions for sure. OK lets get started.

1) What you say is correct in that it records HDV (4:2:0 MPEG-2) to tape and through firewire.
2) The image is VERY good with the JVC codec (19Mb/s)
3) Keying is similar to any of the cams in this price range (sub $10k)
4) You will overall yield similar results with all the cams you listed (EX, HVX).


Since you have the kona you can capture from the uncompressed HD-SDI out of the JVC HD250 to what ever codec you like in the kona (via live feed).

In my experience the JVC codec is an adequate acquisition format, not a great post format. I usually convert to ProRes422 and go from there. If it's just a simple color correction and down-convert then it depends. The paper says one thing the image says everything.

The file size is smaller than a DVCPRO file of the same length. I don't how they did it but it rocks the house. My advice would be go into your 'try-out' with an open mind and run the hd250 through it's paces and see if it's a fit for you and the company.

Make sure you load up the DSC CDM28 and SUPERWIDE settings from Tim Dashwood:
http://dvinfo.net/conf/showthread.php?t=93052 (link in blue at the top of the page)

Johnny C


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Jonathan Capra
Re: JVC-250 and HDV codec
on Aug 16, 2008 at 3:51:31 am

Now that I've actually gotten some experience with our first bit of footage shot on the JVC-250, I can confirm my issues with MPEG-2 as an acquisition. My mind had a hard time wrapping my mind around using any interframe codec during acquisition. And what it comes down to is, in my years of shooting/editing DVCAM I never came across a single frame that looked like this:

http://www.kb2nea.org/creativecow/HDV_peggage.tif

And I don't really want to hear about how you just have to know how to light it right or pan correctly. The fact of the matter is that if I was recording that same moment with the same conditions and camerawork with our Sony DSR-720, it would have only 525 lines, yes, but it would not look like Q-bert took a crap on it. I am reverting to my original stance as HDV being a stopgap.


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