4:4:4 12-bit Uncompressed DVX100

Juan P. Pertierra · May 16th, 2004, 05:06 PM

I wonder if this problem is also evident in the DV frame i posted? i.e. how does the camera originally deal with it? I'm thinking they just got it as close as possible...

John Cabrera · May 16th, 2004, 06:54 PM

I just took a look at it... from what I see, there's no difference between any of the three channels in the DV frame. The camera has to be doing something to compensate what's happening in the green channel. I'm gonna keep studying the raw version and the DV version to see if there are more clues as to what's happening.

John

John Cabrera · May 16th, 2004, 08:32 PM

When I place the DV still on a layer above the Raw version, they don't match up at all. The DV version is narrower on its horizontal axis than the raw version. I had to enlarge it by about 106% horizontally for the balcony posts to line up on the two.

Why is that? Could it be a clue? And what does that mean the correct pixel aspect for the RAW footage you're pulling off the chips is? I guess I assumed that it was the same as DVs .9

Am I missing something?

John

Ben Syverson · May 16th, 2004, 08:53 PM

Green flourescent posterboard is actually a near-perfect color for greenscreen.

Juan, you shouldn't have to uprez to correct the problem -- you should be able to just use interpolation to do a sub-pixel distort or scale or whatever.

I'll dig up those interpolation functions and send them over with my notes!

- ben

John Cabrera · May 16th, 2004, 09:08 PM

When I say narrower on the horizontal axis what I mean is it's more compressed horizontally than the RAW version.

John

Juan P. Pertierra · May 16th, 2004, 09:08 PM

John,

The chips in the DVX are NTSC so the image will look wide unless you apply the correct NTSC 0.9 pixel aspect ratio.

Also, I know for a fact that there are some columns and maybe horizontal lines which are cropped off by the camera for the DV footage, and what's left is resized.

However, now that i think about it, even if the only difference in the green channel is some optical FOV, we should still be able to match the pixels by doing a transformation...afaik it should be close to linear. We can take samples at extreme points in the image and then adjust, shouldn't be that much more different than a resize if it is linear.

Obin Olson · May 16th, 2004, 09:40 PM

Juan, you can also buy some green paint at Lowes, I used that to paint our cyc wall and it works very well..make sure it's the most pure green they have..

John Cabrera · May 17th, 2004, 01:01 AM

Juan,

I don't think you understand what I mean. The DV clip is 720 x 480 right?... which will appear a bit wider unless you apply the 0.9 pixel aspect ratio to it. That will reshape it to something proportionate to 640 x 480 square pixel... and thus it will look normal on a monitor... But what I'm seeing is a difference between the the DV frame you uploaded (720 x 480... which has not had the 0.9 applied and is therefore a bit wider than normal, agreed) and the RAW frame (773 x 495... which has not had the 0.9 applied either AND YET is even more "stretched" wide than the DV frame.) Why wider than the DV frame?... the DV frame is stretched wide enough... applying the 0.9 pixel aspect to DV 720x480 will correct it to the normal propotion, but if the RAW frame is even more "stretched" then it needs an even lower pixel aspect than 0.9 to correct itself. Am I crazy... does anyone else understand what I'm seeing?

John

Laurence Maher · May 17th, 2004, 07:09 AM

Does anybody know about this new Final Cut Pro HD? It claims 10 bit 4:2:2 uncompressed 1080p at 90-160 MBps via PCI transport . . . and from SOFTWARE alone (No additional hardware)?

I'm not sure I buy this. I will say that if it does what it claims, it would limit the 4:4:4 idea, but sure gives us enough for Hollywood level acquisition.

Somebody tell me what I'm missing here:

http://www.apple.com/finalcutpro

Thomas Smet · May 17th, 2004, 10:04 AM

Don't spend a lot of time trying to light the blue/green screen setup. Just point one light at it and the subject. I know it will give harsh shadows on one side but that isn't important right now. We just need to test the side the has no shadows. Besides it would be nice to test how well the mod performs with a very bad keying setup. I assume even with bad lighting a 4:4:4 signal would be much easier to key than a DV signal would. If it was a perfect screen with perfect lighting we might not be able to tell as easily how much better the mod is. Clearly it would be better but we would get the full effect by having a badly lit setup.

If you can't get to the store you could always print out a piece of paper full of a solid 255 green image. This of course would be a huge waste of ink.

Juan P. Pertierra · May 17th, 2004, 12:38 PM

John,

Ok, here's what i see. I do understand what you are saying but I am not experiencing the same problem.

The RAW frame DOES cover a wider field than what is on the DV footage. The camera crops that off but we can see that area in the RAW footage, so right away the image is dimensionally wider. However, as for 'stretching', as long as I apply the 0.9 pixel aspect ratio on the RAW footage, it looks fine. I can especially see it on some shots of resolution charts, you can judge by the circles. The circles are ellipses without the pixel aspect ratio correction, and become circles with it applied.

What has everyone else noticed?

Juan P. Pertierra · May 17th, 2004, 01:10 PM

John,

I think i found what you are talking about..in the DVComp2, the DV version covers a slightly wider field of view, and i just noticed this...however i'm pretty sure that the camera must've been moved when i pressed the record button, it's a pretty shaky setup.

I'm going to try and take another set without movement.

John Cabrera · May 17th, 2004, 08:43 PM

Juan, is part of the 773 x 495 image being cropped or masked by the camera in order to fit the 720 x 480 DV dimensions? or is the whole thing being resized? If it's being cropped as I had assumed from previous postings, then while yes it does seem that there's a different field of view in the DV (like you accidentally moved the camera), I wouldn't say the FOV is SLIGHTLY wider. In the DV you see almost an entire plank of wood more than in the raw version. If there was even more area of the DV image that was cropped than that extra plank then that setup must have been shaky indeed... you would have had to really knock the camera in order to change the FOV that much. Anyway, those two clips are too different to compare and analyze correctly. If you could capture another two that would be great. This time hit the record button first and then start the capture. And if you can, it would be great if you could take it off letterbox mode... that would help the comparison process... I want to figure out what's going on in that Green Channel and why the DV footage doesn't seem to have it.

Thanks,
John

Juan P. Pertierra · May 17th, 2004, 08:48 PM

Will do...you're right, the only way is if i hit the zoom by mistake a bit...but we all know how touchy the zoom is when it is set to manual.

I will take another outdoor set tomorrow, and hookup the joystick so I can set the letterbox off.

John Cabrera · May 17th, 2004, 09:19 PM

I went back and took a look at that test chart you posted a couple weeks ago... very interesting.

First I scaled the image horizonally to match a 0.90 pixel aspect. And yes the circles appeared more like circles... but then I compared them to a perfect circle I created using the elipse tool while holding down shift. The circles are not perfectly round, they're a bit wider than the perfect circle I made. Of course if you've been looking at the wider version for a while then the 0.9 version certainly looks more natural, but it's still not totally propotionate.

Then I just tried resizing the 773 x 495 image to 640 x 480 (which is the size that a 720 x 480 w/pixel aspect 9.0 applied scales to.) and the circles were perrrrrrrrrfect. There's no doubt that you knocked the camera on the last comparison shots, but there's also no doubt in my mind that the raw image is more stretched out than the DV images. It actually appears that what's happening is that the camera is simply reshaping the 773 x 495 image to 720 x 480 before or durring the DV compression. So there is actually no extra part of the image we're seeing... we're just getting a higher resolution image... which is still fantastic.

Thoughts? Am I missing something? Getting somehting wrong?... I'm no expert, but this is what I'm seeing.

John

May 16th, 2004, 06:54 PM	#647
John Cabrera Regular Crew Join Date: Apr 2004 Location: California Posts: 67	DV footage I just took a look at it... from what I see, there's no difference between any of the three channels in the DV frame. The camera has to be doing something to compensate what's happening in the green channel. I'm gonna keep studying the raw version and the DV version to see if there are more clues as to what's happening. John

May 16th, 2004, 08:32 PM	#648
John Cabrera Regular Crew Join Date: Apr 2004 Location: California Posts: 67	Strange When I place the DV still on a layer above the Raw version, they don't match up at all. The DV version is narrower on its horizontal axis than the raw version. I had to enlarge it by about 106% horizontally for the balcony posts to line up on the two. Why is that? Could it be a clue? And what does that mean the correct pixel aspect for the RAW footage you're pulling off the chips is? I guess I assumed that it was the same as DVs .9 Am I missing something? John

May 16th, 2004, 09:08 PM	#650
John Cabrera Regular Crew Join Date: Apr 2004 Location: California Posts: 67	DV vs RAW When I say narrower on the horizontal axis what I mean is it's more compressed horizontally than the RAW version. John

May 17th, 2004, 01:01 AM	#653
John Cabrera Regular Crew Join Date: Apr 2004 Location: California Posts: 67	0.9 pixel aspect Juan, I don't think you understand what I mean. The DV clip is 720 x 480 right?... which will appear a bit wider unless you apply the 0.9 pixel aspect ratio to it. That will reshape it to something proportionate to 640 x 480 square pixel... and thus it will look normal on a monitor... But what I'm seeing is a difference between the the DV frame you uploaded (720 x 480... which has not had the 0.9 applied and is therefore a bit wider than normal, agreed) and the RAW frame (773 x 495... which has not had the 0.9 applied either AND YET is even more "stretched" wide than the DV frame.) Why wider than the DV frame?... the DV frame is stretched wide enough... applying the 0.9 pixel aspect to DV 720x480 will correct it to the normal propotion, but if the RAW frame is even more "stretched" then it needs an even lower pixel aspect than 0.9 to correct itself. Am I crazy... does anyone else understand what I'm seeing? John

May 17th, 2004, 08:43 PM	#658
John Cabrera Regular Crew Join Date: Apr 2004 Location: California Posts: 67	DV vs Raw Juan, is part of the 773 x 495 image being cropped or masked by the camera in order to fit the 720 x 480 DV dimensions? or is the whole thing being resized? If it's being cropped as I had assumed from previous postings, then while yes it does seem that there's a different field of view in the DV (like you accidentally moved the camera), I wouldn't say the FOV is SLIGHTLY wider. In the DV you see almost an entire plank of wood more than in the raw version. If there was even more area of the DV image that was cropped than that extra plank then that setup must have been shaky indeed... you would have had to really knock the camera in order to change the FOV that much. Anyway, those two clips are too different to compare and analyze correctly. If you could capture another two that would be great. This time hit the record button first and then start the capture. And if you can, it would be great if you could take it off letterbox mode... that would help the comparison process... I want to figure out what's going on in that Green Channel and why the DV footage doesn't seem to have it. Thanks, John

May 16th, 2004, 05:06 PM	#646
Juan P. Pertierra Major Player Join Date: Jul 2003 Posts: 479	I wonder if this problem is also evident in the DV frame i posted? i.e. how does the camera originally deal with it? I'm thinking they just got it as close as possible...

May 16th, 2004, 08:53 PM	#649
Ben Syverson Major Player Join Date: Mar 2004 Location: chicago Posts: 434	Green flourescent posterboard is actually a near-perfect color for greenscreen. Juan, you shouldn't have to uprez to correct the problem -- you should be able to just use interpolation to do a sub-pixel distort or scale or whatever. I'll dig up those interpolation functions and send them over with my notes! - ben

May 16th, 2004, 09:08 PM	#651
Juan P. Pertierra Major Player Join Date: Jul 2003 Posts: 479	John, The chips in the DVX are NTSC so the image will look wide unless you apply the correct NTSC 0.9 pixel aspect ratio. Also, I know for a fact that there are some columns and maybe horizontal lines which are cropped off by the camera for the DV footage, and what's left is resized. However, now that i think about it, even if the only difference in the green channel is some optical FOV, we should still be able to match the pixels by doing a transformation...afaik it should be close to linear. We can take samples at extreme points in the image and then adjust, shouldn't be that much more different than a resize if it is linear.

May 16th, 2004, 09:40 PM	#652
Obin Olson Trustee Join Date: Jan 2003 Location: Wilmington NC Posts: 1,414	Juan, you can also buy some green paint at Lowes, I used that to paint our cyc wall and it works very well..make sure it's the most pure green they have..

May 17th, 2004, 07:09 AM	#654
Laurence Maher Join Date: May 2004 Location: denton, texas, usa Posts: 416	Does anybody know about this new Final Cut Pro HD? It claims 10 bit 4:2:2 uncompressed 1080p at 90-160 MBps via PCI transport . . . and from SOFTWARE alone (No additional hardware)? I'm not sure I buy this. I will say that if it does what it claims, it would limit the 4:4:4 idea, but sure gives us enough for Hollywood level acquisition. Somebody tell me what I'm missing here: http://www.apple.com/finalcutpro

May 17th, 2004, 10:04 AM	#655
Thomas Smet Trustee Join Date: Mar 2004 Location: Milwaukee, WI Posts: 1,719	Don't spend a lot of time trying to light the blue/green screen setup. Just point one light at it and the subject. I know it will give harsh shadows on one side but that isn't important right now. We just need to test the side the has no shadows. Besides it would be nice to test how well the mod performs with a very bad keying setup. I assume even with bad lighting a 4:4:4 signal would be much easier to key than a DV signal would. If it was a perfect screen with perfect lighting we might not be able to tell as easily how much better the mod is. Clearly it would be better but we would get the full effect by having a badly lit setup. If you can't get to the store you could always print out a piece of paper full of a solid 255 green image. This of course would be a huge waste of ink.

May 17th, 2004, 12:38 PM	#656
Juan P. Pertierra Major Player Join Date: Jul 2003 Posts: 479	John, Ok, here's what i see. I do understand what you are saying but I am not experiencing the same problem. The RAW frame DOES cover a wider field than what is on the DV footage. The camera crops that off but we can see that area in the RAW footage, so right away the image is dimensionally wider. However, as for 'stretching', as long as I apply the 0.9 pixel aspect ratio on the RAW footage, it looks fine. I can especially see it on some shots of resolution charts, you can judge by the circles. The circles are ellipses without the pixel aspect ratio correction, and become circles with it applied. What has everyone else noticed?

May 17th, 2004, 01:10 PM	#657
Juan P. Pertierra Major Player Join Date: Jul 2003 Posts: 479	John, I think i found what you are talking about..in the DVComp2, the DV version covers a slightly wider field of view, and i just noticed this...however i'm pretty sure that the camera must've been moved when i pressed the record button, it's a pretty shaky setup. I'm going to try and take another set without movement.

May 17th, 2004, 08:48 PM	#659
Juan P. Pertierra Major Player Join Date: Jul 2003 Posts: 479	Will do...you're right, the only way is if i hit the zoom by mistake a bit...but we all know how touchy the zoom is when it is set to manual. I will take another outdoor set tomorrow, and hookup the joystick so I can set the letterbox off.

May 17th, 2004, 09:19 PM	#660
John Cabrera Regular Crew Join Date: Apr 2004 Location: California Posts: 67	Juan, I figured something out I went back and took a look at that test chart you posted a couple weeks ago... very interesting. First I scaled the image horizonally to match a 0.90 pixel aspect. And yes the circles appeared more like circles... but then I compared them to a perfect circle I created using the elipse tool while holding down shift. The circles are not perfectly round, they're a bit wider than the perfect circle I made. Of course if you've been looking at the wider version for a while then the 0.9 version certainly looks more natural, but it's still not totally propotionate. Then I just tried resizing the 773 x 495 image to 640 x 480 (which is the size that a 720 x 480 w/pixel aspect 9.0 applied scales to.) and the circles were perrrrrrrrrfect. There's no doubt that you knocked the camera on the last comparison shots, but there's also no doubt in my mind that the raw image is more stretched out than the DV images. It actually appears that what's happening is that the camera is simply reshaping the 773 x 495 image to 720 x 480 before or durring the DV compression. So there is actually no extra part of the image we're seeing... we're just getting a higher resolution image... which is still fantastic. Thoughts? Am I missing something? Getting somehting wrong?... I'm no expert, but this is what I'm seeing. John