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Old January 21st, 2006, 04:36 PM   #1
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GY-HD100, component output, hdcamsr recorder and chroma key

Hello; I was reading the discussion "4:2:0 artifact?" in the network (http://www.dvinfo.net/conf/archive/i.../t-52241.html), and I saw an interesting post:

John M Burkhart said that "sony was forced to make a high-high end camera (HDCAMSR) to their high end camera range (HDCAM)".

I understand what is HDCAMSR: it is better than HDCAM (isn't it?).

So, I use a GY-HD100. Its HDV compressed shoots aren't good for chroma key becasue of the compression artifacts.

I saw that the camcorder has an uncompressed analog HD component output that bypasses the HDV-minitape compression. I read that this camcorder is experimentally used in low-cost high quality motion pictures by importing the uncompressed signal directly from the component output to an uncompressed HD recorder (with an hd-component input).

But I didn't find PORTABLE uncompressed HD recorder: only a few, but with astronomic costs.

I fond a very interesting SONY PORTABLE HD recorder: but it has the HDCAMSR format. I read that HDCAMSR is compressed too, so I rejected the idea. I think: "it is useless" buy a recorder for capture the uncompressed output signal of the camcorder, and than compressing the video anyway.

But now, after reading the post of John, I'm asking if is it worth using that HDCAMSR recorder ?

to be brief: if I capture the UNCOMPRESSED analog HD output component signal from the GY-HD100 and I channel it in the SONY HDCAMSR portable recorder, so I'll record the uncompressed HD shooting in an HDCAMSR format, shall I solve the compression-artifacts for chroma keying?

Thanks a lot.
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Old January 22nd, 2006, 02:20 PM   #2
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Croma Key Software

hi Nicola

I am afraid I have no answers to any of your questions! However, I am doing chroma key work with the hd100.

I get amazing results with this camera in normal hdv mode. This is down primarily to the keying software that I am using which is Ultra 2. You can see it at www.seriousmagic.com Worth a look!

Trevor
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Old January 22nd, 2006, 02:42 PM   #3
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HDCAMSR has minimal compression, is a 4:4:4 format and is very robust for greenscreen work. It's more than adequate for use with the HD100.
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Old January 22nd, 2006, 02:58 PM   #4
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I agree in fact its overkill. I think the term uncompressed should be tossed out of our lexicon. The hd100 is spitting out component hd1@4:2:2 via the component out. You need to spend about 100k for a camera that will output 4:4:4. HDCAM non SR would be more than adequate for anything you could output from this camera. Good luck, Jason.
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Old January 22nd, 2006, 03:10 PM   #5
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Did "Star Wars Episode II" even use SR? I think it was plain old 4:2:2 HDCAM and then Episode III was 4:4:4 HDCAM SR.
Almost every shot was greenscreen, so that might be a good indication of the effectivness of the format.

Rodriguez I think only uses F900's with standard 4:2:2 HDCAM for his movies like "Sin City" and Spy Kids 2 and 3D. His green screen keys look pretty good too, although the B&W format of Sin City helps to hide imperfections.

I agree that the term "uncompressed" that JVC uses to descibe the component analog outputs is misleading. Analog signals aren't compressed or uncompressed, they are just analog. The question is whether the D/A converter and hence analog outputs are receiving the full 4:4:4 or 4:2:2 signal scanned from the chips or a dumbed down 4:2:0 that just hasn't reached the mpeg encoder yet? I haven't seen a definitive white paper on this yet.
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Old January 22nd, 2006, 03:57 PM   #6
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Tim,

Isn't HDCAM 3:1:1? It's not even 4:2:2, or so I thought it wasn't.

- ShannonRawls.com
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Old January 22nd, 2006, 04:17 PM   #7
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4:2:2 last I heard, same as Digibeta.
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Old January 22nd, 2006, 04:26 PM   #8
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Shannon's right. HDCAM is 3:1:1 in 8-bit, I forgot about that. Each R and B sample in 3:1:1 are one-third instead of one-half of Y?
And I've now read that HDCAM SR is actually 4:2:2 but 10-bit, even though I've always assumed it was 4:4:4, but maybe that's just when it is in 2X (HQ) speed mode? I've never actually used a HDCAM SR recorder.
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Old January 22nd, 2006, 05:17 PM   #9
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Quote:
Originally Posted by Tim Dashwood
I agree that the term "uncompressed" that JVC uses to descibe the component analog outputs is misleading. Analog signals aren't compressed or uncompressed, they are just analog. The question is whether the D/A converter and hence analog outputs are receiving the full 4:4:4 or 4:2:2 signal scanned from the chips or a dumbed down 4:2:0 that just hasn't reached the mpeg encoder yet? I haven't seen a definitive white paper on this yet.
My take on the JVC "uncompressed" as well. Uncompressed meaning that it hasn't gone through the codec. David Newman of Cineform says the signal from the component out's is 422.
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Old January 22nd, 2006, 05:22 PM   #10
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Rodriguez used the F-950 for Sin City, outputting directly to a hard-drive. Alex Toader, the lead digital artist with Troublemaker is friends with my boss, and he said that it was just a bigger pain to green screen out the 3:1:1 from the 900, so they switched to the 950. On the 950, I believe that there isn't even a tape deck if I am not mistaken.
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Old January 22nd, 2006, 07:40 PM   #11
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Thanks for the correction guys, I guess I've been carrying around misinformation for a long time. Interesting that DVCPRO50 is not numerically as lossy as HDCAM, although I think the difference is pretty marginal.
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Old January 22nd, 2006, 08:05 PM   #12
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Actually, here are some possible answers:
http://www.pci-canada.com/Misc%20Pag...20SR%20FAQ.htm
and
http://hd24.com/frequently_asked_questions.htm
and then, there is an interesting white paper at
http://www.aja.com/pdfs/AJA_whitepaper_HDV.pdf
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Old January 25th, 2006, 07:30 AM   #13
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ok

thanks to all you very much.

Bye.
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Old January 25th, 2006, 10:22 AM   #14
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HDCAM is 135 Mbit/s in 3:1:1 8 bit mpeg-4 compression. After audio data and stuff it is upto 180 Mbit. Subsamples to 1440 x 1080 first off in the luma, so chorma are only 480 pixels wide.

HDCAM SR has 2 modes and one of the modes is only achievable in the portable unit. 4:2:2 10 bit @ 440 mbits/s (tape rate i think) or in 4:4:4 mode it is 880 mbits/s using a similar mpeg-4 codec as the orginal hdcam but much less compression..

These are robust and costly formats. Unless you have a client specifically requesting it, the 50K + or rental fees could be spend on a higher end camera. The tape alone for HDCAM SR is very expensive. These formats won't be very portable either. Portable decks are costly and still realitively large. If chorma keying you in a studio so a computer with uncompressed capture might be the way to go.

Chromakey will be better on the HDCAM, HDCAM SR, D5, or uncompressed formats but all are much more costly. And I'm almost 100% sure that you will need an analog component to hd-sdi converter to use hdcam or hdcam sr since I doubt these have component input on them.
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Old January 25th, 2006, 10:48 AM   #15
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I think that HDCAM SR can also record TWO 4:2:2 440 Mb/s streams for the use in 3d videography. Has anyone used that function?

Just an obscure side note.
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