A1 vs G1 for uncompresed greenscreen studio work at DVinfo.net

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Canon XH Series HDV Camcorders
Canon XH G1S / G1 (with SDI), Canon XH A1S / A1 (without SDI).


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Old May 14th, 2007, 10:47 PM   #1
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A1 vs G1 for uncompresed greenscreen studio work

So,

This is my understanding...
The XH G1 has SDI out, ect. Which is ideal for greenscreen studio situations where you would want to capture uncompressed 4:2:2 footage for the best compositing possible.
But i have also read that with the A1 it is possible to capture uncompressed 4:2:2 footage over the analog component out, by hooking the componet output into a componet to HDMI converter and passing that into a Blackmagic intensity board - all in all saving thousands of dollars... but of coursing loosing the all digital connection... (and maybe some quality?)

So my question is this; If you plan on doing a lot of greenscreen work; Is it worth an extra 4 grand for the SDI digital setup (Having to buy not only the G1 but also a thousand dollar HD-SDI capture card) when you could for almost the same price buy two XH A1's - and still be able to theoretically capture the 4:2:2 footage over analog?

These are my thoughts out loud. Id like to hear if you think this is a good or bad decision.
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Old May 14th, 2007, 11:50 PM   #2
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Tyson,

The A1 outputs only 1440x1080 via Component (1)..
The G1 outputs not only 1440x1080 via Component, but also 1920x1080 over SDI 4:2:2 (with embeded audio, something that the XL don't do). In other words, G1 gives you Square Pixels, a bit more color range and more vertical resolution...

Sticking with the G1, you should consider expending a good money on a system able to capture the signal out of the SDI.. Ex. Mac Pro + HD board like Aja or Blackmagic Design and a good internal disk array or an external solution like Xserve RAID or something similar. Something that in its entry level is going to cost you at least 6k.

Good Look.

(1): Page 97 of the Canon XH A1/G1 User Manual

Clemente Gauer
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Old May 15th, 2007, 05:07 PM   #3
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Furtuer questions about compositing w/ these cameras...

I do a lot of compositing.
Im trying to figure out the best cost to performance ratio for green screen work.

I also understand that the HVX with its DVC-Pro HD codec is good for greenscreen compositing and a lot of ppl are using it for keys.

But how many levels better would trying to key with HD-SDI uncompressed footage allow you over DVC-Pro footage? Am I correct in saying that HD-SDI uncompressed footage would key many times better than DVC-Pro HD? If its really not that big of a difference then I would just get an HVX strictly for green screen work and also an XH A1 for all other field work, and not have to invest in all that RAID Arrays for editing uncompressed and HD-SDI capture board...
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Old May 15th, 2007, 08:11 PM   #4
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Have you looked into the AJA IO-HD? You can take that uncompressed signal off of the G1 and use the special Apple ProRess 422 codec and feed that into a laptop or desktop. All you need is a Mac and is fully integrated with the FCP. The best part is the new Apple ProRes codec offers uncompressed HD quality at file sizes of SD. Its something to look into for cost/benefits.
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Old May 19th, 2007, 09:45 AM   #5
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Yes Tyson,

Panasonic's HVX is a very good choice for studio and short movies. Its codec is great for editing (not as much processor-intensive as HDV). But, using a HVX in full-day externals, the hassle about the P2 may still be a problem.

Anyway, backing up the files of a HVX is indeed a problem. You may end a shooting day with hundreds of Gigabytes easily...

I agree with Mike Gorski, the 4 days new (shipping) ProRes 422 from Apple its an excellent choice, and sticking with a G1, you may have all you data backd-up on-the-fly in DV tapes with 1440x180 for the eternity, while you output thru SDI full res 4:2:2 to the mac.. In the future, if you want, you can batch reconect the files using the "a bit lower res" tapes..

Check the white paper of ProRes:

http://images.apple.com/finalcutstud..._ProRes_WP.pdf

Greetings

Clemente Gauer

Quote:
Originally Posted by Tyson Persall View Post
I do a lot of compositing.
Im trying to figure out the best cost to performance ratio for green screen work.

I also understand that the HVX with its DVC-Pro HD codec is good for greenscreen compositing and a lot of ppl are using it for keys.

But how many levels better would trying to key with HD-SDI uncompressed footage allow you over DVC-Pro footage? Am I correct in saying that HD-SDI uncompressed footage would key many times better than DVC-Pro HD? If its really not that big of a difference then I would just get an HVX strictly for green screen work and also an XH A1 for all other field work, and not have to invest in all that RAID Arrays for editing uncompressed and HD-SDI capture board...
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Old May 19th, 2007, 02:02 PM   #6
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Any confirmation from Canon that the analog output is *actually* 1440x1080? I've captured both the analog uncompressed output of the A1 and XL-H1 uncompressed HD-SDI into an AJA Kona card, and both outputs look basically the same.

I'm pretty sure the A1's analog uncompressed output is the same as the H1 HD SDI or G1 HD SDI in that the image is pixel-shifted horizontally from a 1440x1080 chip to achieve a 1920x1080 raster. In all likelihood, if the output of the A1 analog were 1440 horizontal, my uncompressed captures wouldn't look correct in aspect ratio. But I get correct 16x9 ful raster captures, and there are subtle details I can make in terms of horizontal resolution that HDV tape playback doesn't render quite as sharply.

Tyson,

You can actually pull better keys by going the raw HD-SDI or analog to ProRes route. The A1 or G1's uncompressed output contains more luma info (which is what carries most of the green signal) than even 1080 DVCPRO HD and quite a bit more horizontal resolution, which is not to be discounted.

Last, ProRes is likely to hold up to multi-generational renders much better than DVCPRO HD, but I've seen so many good HD keys pulled in all kinds of formats, so I don't think you'd have too much of an issue either way. Heck, people pull great keys from HDV too, so as long as your post path is up to snuff, you shouldn't have any serious issues regardless of acquisition codec.
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Old May 19th, 2007, 09:42 PM   #7
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Thanks Barlow,

That was the information i was wanting someone to finally say. I was thinking to myself it would probably be fine... -that analog component capture of uncompressed footage would be not much of a noticeable difference from HD-SDI but was afraid of something i didn't know having not actually tried it myself. After all, Analog is not really a bad word.

For my Dad's birthday, I bought him a $60 HDMI monster cable for his new HDTV. After hooking it up he gave it back to me and said there was no reason for it because it didn't look any different than his current component cable connection that cost him $15. He would rather me save my money on something that matters. -And i think thats a good point. Video equipment is so expensive and guys like us doing this on our own need to be getting maximum bang for the buck. -Not nit picking pixels that no one is counting. - And certainly not spending 3 thousand extra dollars on pixels no one will notice. of course SDI is better but not worth it in this case.

In conclusion;

Sometimes you need someone else to tell you what you already know.
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Old May 20th, 2007, 03:50 AM   #8
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Quote: "So my question is this; If you plan on doing a lot of greenscreen work; Is it worth an extra 4 grand for the SDI digital setup"

I do a lot of green screen stuff for fun and if I was to choose the difference between an A1 and a G1 just to pull a good key, I would much rather spend my money on lighting, etc. and still have a couple grand left over. I am not an expert by any means and only do this for a hobby. However, I have yet to purchase any professional lighting but am quite happy with the results I get.

Digital Juice has a couple really helpful videos that might be of assistance, but you may already know all this stuff so forgive me if I am stepping in where I shouldn't.

Here is a link to the Digital Juice videos:

http://www.digitaljuice.com/djtv/sea...searchid=15053

I personally like the "Green Screens and Ham"

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Old May 20th, 2007, 10:55 AM   #9
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Quote:
Originally Posted by Tyson Persall View Post
I was thinking to myself it would probably be fine... -that analog component capture of uncompressed footage would be not much of a noticeable difference from HD-SDI but was afraid of something i didn't know having not actually tried it myself. After all, Analog is not really a bad word.
Long live analog! (saw that t-shirt of yours in the DV Texas shootout article, Chris ;) )
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Old July 4th, 2007, 03:09 AM   #10
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Hey guys, I own a Blackmagic Decklink HD Extreme (HD-SDI & Component I/O) and a very high quality component cable. I am here to say, that analog gets very messy at the end of a 50' cable, (and hypothetically that's 1/2 to 1/3 the max cable length). Even though it's full 4:2:2, there is so much bleed, it's not sharp and could be 4:2:0 for what it mattered.

It's a shame.. the 1440 (1080i) HDV 4:2:0 image is far sharper than the uncompressed analog compent 1080i signal I get. It's so mucky that I can't even tell if I'm focused properly. I didn't want to admit this.. it's cost me a fair penny to try. And I'll have to spend more to fix it.

I am going to purchase a nanoConnect convertor to get HDMI to convert to HD-SDI (which my card can handle) so I can get a far better image.. as it stands, I can't use the analog uncompressed.

So.. HDMI/HD-SDI or bust! Digital wins.
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Last edited by Robert Ducon; July 4th, 2007 at 03:58 AM.
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Old July 4th, 2007, 03:03 PM   #11
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I've never tried to capture analog with that long of a cable run. With short runs on quality analog cable, I've had good capture results that were slightly better than HDV, but I'm not surprised your 50' run didn't hold up well. I know that I would certainly want to convert to SDI if I needed longer cable runs.

IMO, XH G1 HD-SDI is well worth the added cost if you want to do a quality tethered acquisition.
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