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General HD (720 / 1080) Acquisition
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Old May 19th, 2005, 01:23 PM   #1
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720 vs 1080 for use in SD (a tad long)

Our production company does mostly commercials and music videos shot in DV with Ike DV-7W's and a Pana DVC200. We have had an XL1, XL1s and a DVX100 for hand held acquisition and ultimately got rid of them because of lack of 16:9 and resolution matching the 1/2 and 2/3 inch chip cameras. A month or so ago I once again started on the quest for a small camera that would shoot 16:9 and hold up to the larger chip cameras. I was almost set on the XL2 when the Z1 came out and then NAB happened with it's offerings by Pana and JVC. The Pana camera is too far in the future and while I'm willing to wait for the JVC here is my question.

Since we don't deliver any HD footage at this time the advantage to me seems to be the ability to downconvert and get better footage than you would get with a SD 1/3 inch camera and to be able to crop and zoom from the HD image possibly getting a different point of view or even multiple SD angles from a single HDV source. It seems like for this use 1080 has a much greater potential than 720 footage. We have been converting to 24P motion and film look in post when necessary so 24p isn't the only important issue for us. Am I missing something as far as thinking 1080 is an advantage for this type of application or is my thinking in line. I've had the SD thing figured out fairly well as far as creative and product delivery but HD seems to open up new possibilities not only for HD but also our SD business.

Thanks,

Richard Lubash
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Atlanta
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Old May 19th, 2005, 01:43 PM   #2
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It is easy enough to get some 1080i footage to play with. Heck, I will send you some. The issue between the 720p and 1080i is more than frame size. Yes, the larger frame enables me to choose from a bigger picture when I am downconverting to DV frame size.

The down side of the Sony is that it is interlaced. So you will probably end up deinterlacing it. If that is not a problem, then go for the 1080i for two reasons. It is available now and it has a larger frame size.

But if you want to shoot 24p, then maybe you should wait.
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Old May 19th, 2005, 02:45 PM   #3
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I don't think resolution comparisons on a codec level are meaningful between the Z1 and the JVC, since the JVC has 3 1280x720 progressive chips and thus no pixel-shifting or up-sampling. In the end I would expect very comparible effective resolutions out of both of 'em, giving the nod perhaps to the JVC.

The real question is if you want 60 fps motion rendition (f=fields/frames). If so, then your only option will be the 1080i cameras. If your output format is never 60i/60p, then the JVC will likely provide (at least) equal quality images to the Z1 but with true 24p and 30p respectively for zooming etc., and be a lot easier to work with in post.

You can convert the 1080i from the Z1 to 1080p30, 1080p24, 720p60, 720p30, 720p24, 480p60, 480i, 480p30, and 480p24 with some careful post production and acheive good results... though the 24p is obviously going to suffer from 60i->24p conversions.

You can convert the 720p30 and 720p24 from the JVC to 1080p30, 1080p24 (though why you would seems like a waste of clock cyles - all it will do is add interpolation artifacts), and to 480p30, 480p24 without any difficulty.

If my output format was exclusively 24p or 30p, and I had to choose between the Z1 and the JVC, the answer would probably be the JVC on spec. The resolution for progressive frames will be higher, and natively acquired. We'll have to see video from it to be certain.

-Steve
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Old May 19th, 2005, 07:55 PM   #4
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Even though I feel as though we are not getting as much resolution from the Z1 as is claimed I think this is the best prosumer camera we have ever had for SD work. For 25p/30p I feel the camera only really gives us 960x540 resolution but this is still more than any SD can give you. Even after the image from the chip block is interolated with pixel shift to get to 1440 x 1080 I still think you get great results because this happens before the compression. If you had a 960x540 video compressed and then scaled up it wouldn't look as good as having uncompressed 960x540 scaling up and then compressing. So even though in terms of detail I think you only get 960x720 you can at least get a slightly softer but clean 1440x1080 image from the Z1. Having said that I am writing a program to give almost perfect 4:4:4 RGB SD video from the Z1 in many different formats and frame rates. This is something even a high end 2/3 chip SD camera couldn't give you right now. I say almost perfect because it is interploated from the higher resolution source and when you interpolate it is never as good as if you were starting out with raw SD pixels. It is however in my opinion way better than 4:1:1, 4:2:0 and 4:2:2.

1280 x 720 is a little bit harder to do this with. in order to try to turn 4:2:0 into an interpolated 4:4:4 the image size has to be cut in half. This means the only way to get the same quality as with the 1080 source is to only have 640 x 360 SD. Going back to any SD output format will then interpolate that back up to 720x480.
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Old May 19th, 2005, 08:29 PM   #5
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Thomas, I'm getting very close to 4:4:4 from miniDV - see:

http://www.nattress.com/CbOriginal.jpg

http://www.nattress.com/CbNiceSharpen.jpg

The second image is what normal DV chroma looks like after passing through my algorithms.

Graeme
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Old May 20th, 2005, 01:27 AM   #6
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Yeah Graeme you make some amazing chroma filters. I have checked out your earlier chroma filter. I use a PC so sadly I am not able to use any of your filters which is why I have been working on my own.

I am sure though that using your filters first on HDV material and then down sampling to SD would give even better results since you would be starting with more detail.

One other area I am trying to add to my tool is a couple of theories I have been trying out to make an interpolated 10 bit SD from an 8 bit 1080 HDV source. I'm not sure how it will work yet but I am doing some tests.
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Old May 20th, 2005, 06:58 AM   #7
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Thomas, that should work great if you can get it working. I'll look forwards to seeing the results!

Graeme
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Old May 20th, 2005, 11:05 AM   #8
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Graeme, this is really cool. I went and looked at your web site and saw the D-beta material and can't wait to run some tests. Can your filters run Varicam and HDcam 4:2:2 as well, or is it just at SD res. Also, what is the render time on D-beta per frame? Thanks!

Michael Pappas



Quote:
Originally Posted by Graeme Nattress
Thomas, I'm getting very close to 4:4:4 from miniDV - see:

http://www.nattress.com/CbOriginal.jpg

http://www.nattress.com/CbNiceSharpen.jpg

The second image is what normal DV chroma looks like after passing through my algorithms.

Graeme
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Old May 20th, 2005, 01:07 PM   #9
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I've not tested the new algorithms on Varicam or HDCAM yet, but I will in due course. The new stuff is something I only came up with last week, and it's still in testing, but it's very promising. I'm finding using both the older and newer algorithms together is producing the best results.

I'll be posting up more tests when I'm done.

Graeme
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