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Old Nov 30, 2008, 12:10 AM   #1
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http://www.driveway.com/s4l5r1c3l9



Please download the following zip file and let me know what you guys think. I suspect that the 720p res of this camcorder is actually just D1 resized. I noticed one day when I was watching some of my 720p footage that edges appeared jagged, rather than smooth. They reminded me of a bad resizing job done by a poorly programmed image editing program. So I decided to do some testing. I took a shot in FOUR resoultions, CIF, D1, 720p and 1080p. I compared the edges of each of them. What I noticed is that the edges in the 720p shot look pixelated proportionally to the D1 shot. This should not be. The bumpiness of the edges should be LESS noticeable in a larger res shot. If you compare the D1 shot with the 720pshot, it looks like the 720p is just the D1 resized. The pixels should be the SAME SIZE while the IMAGE gets larger, so the edge should appear SMOOTHER in the 720p than it does in the D1 shot. However it seems as though the roughness of the edge of the D1 shot is increase with the resolution of the 720p. Hope I'm not being too confusing. I took these from VirtualDub and yes some of the 1080p shot is cut off, but it's just for reference.

I'm interested in your guys' feedback and if you can reproduce this same issue. Thanks for reading my post!
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Old Dec 1, 2008, 8:55 AM   #2
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Does look bad, the stepping looks even larger detail size in 720p. This is comparing the two with pixels at the same size on screen. Even through with the picture scaled to fit screen, the 720p looks finer, it should look no different resolution at same pixel size, if even divided in interpolation. The truth is that there is other processing to smooth out fly screening and such forth in video interpolation that add to surrounding pixels. I wonder if this is going on here. But it is a bit late to think about these things.

Does that lamp have a border around the fringe, darker border?

There is probably two things going on, that make this picture not so good. Immediately I noticed a lot of compression noise in the upper left corner on the plane surface, probably needs more data-rate. What you see is interpolation error, probably related to edge enhancement, but also some cheaper sensors have a problem with how they interpolate the pixels to a lower resolution in the sensor before that camera processing units get it. I will probably have to check the picture for individual details to get an idea of real resolution, latter, too late at the moment.

Have you got an external picture of fine detail for compression.
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Old Dec 1, 2008, 9:45 AM   #3
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I don't buy the interpolation theory.
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Old Dec 1, 2008, 10:26 AM   #4
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It could be something else, but I notice on the top of the lamp there's a row of pixels below the black pixels that is lighter, that should be dark and other strange things on the diagonals that look like it. The edge is also messed up. We have seen a number of cameras with edges messed up usually in one diagonal, where interpolation cross pixels make strange artifacts come up. I have been told be industry insider the reason.
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Old Dec 1, 2008, 11:09 AM   #5
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Why would a camera that is actually capable of 1080p interpolate the 720p mode up from a lower resolution?
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Old Dec 1, 2008, 11:32 AM   #6
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rgvcam wrote:
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Why would a camera that is actually capable of 1080p interpolate the 720p mode up from a lower resolution?
Good question!!! That is what is so frustrating about this



One day I was playing back my 720p footage on my 32 inch LCD and noticed blatantly straight edges NOT showing up as straight, but with these bumps in them that were akin to a bad resize job. If you guys want I can submit more pics, in different environments and lighting. I am also hoping anyone else with an Aiptek can try the same tests. I know this is of a curved edge, but I have FIRST noticed it on an edge that was supposed to be straight. Maybe I will do just that, shoot a few more objects with clearly defined edges and post my results.
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Old Dec 1, 2008, 11:36 AM   #7
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I used my Panasonic SDR-S10's 480i and upscaled it in software to find out if the Aiptek 720p might be interpolated and the Aiptek 720p is clearly sharper... with more detail.

I'll do a test with my Aiptek's 480p mode to be certain.
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Old Dec 1, 2008, 11:52 AM   #8
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Ok, here is the second set:

http://www.driveway.com/f4r1h7j5d1

These make it look WAY more obvious. In fact, all but the 1080p have the jagged lines in what should appear to be straight smooth lines. These are some blinds I have in the kitchen taken at a side angle. Maybe it's not interpolating UP.. maybe it's resizing DOWN? In either event this "resizing" adds these jagged artifacts that interfere with the original object being shot. I used to always wonder why my 720p shots looked so "muddled". I'm stickin' with 1080p for now, it's just crystal clear. Hands down, especially compared to these other resolutions when considering these "jaggies".



Please take a look and tell me your thoughts.
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Old Dec 2, 2008, 2:25 AM   #9
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Thanks, there was too much noise and plane surfaces to examine for certain in he last shots.

The Sanyo HD1, and first Aiptek HD had the sort of diagonal strange liens I see here, and I got inside confirmation on the problems. It looks like a mix-up or poorer quality of the way it downsizes sizes through interpolation. The reduces bit rate results in blurry blobs in footage to hide macro blocking, probably less precision in the wave modeling, and more aggressive reduction in difference between neighboring pixels, which is hardsh on plane surfaces, in other words a more muddled looking picture. As I always say, that 720p60 needs at least 9mb/s to do it justice, preferably 18mb/s (which is a bit more per pixel the DXG-596/595v. But you can try comparing between cameras with greater bit rates, Samsung, Toshiba gigashot, HSHD, Kodak 6zi (is than the model). One day we might see these sorts of rates with the sort of features in mentioned in the other thread (like 3D and GPS location/direction stamping with optional locking of all controls).
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Old Dec 3, 2008, 8:47 PM   #10
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Well, I must have missed this thread the other day. But I can add some input to it. First off, I haven't looked at your video. Right now I'm using my old Apple iBook 366 Mhz, so it isn't nowhere near fast enough to play that video. But when you described it, I knew exactly what you were talking about. I've noticed my Aiptek IS-DV2 does something similar. When I first noticed it, I too got the impression it was being upscaled or "interpolated" to 640x480 from some lower resolution.

So, I did some testing. I put the camera in 320x240 mode and took some shots of the same items, and also used a different camera in 320x240 mode. Then I carefully compared the images in 640x480 to the ones in 320x240. My conclusion? Baffled. I mean, honestly, it is very confusing. There are jagged lines noticable in many objects that have high-contrast straight edges and the detail on these objects is similar in both resolutionsl Yet, other objects that have less contrast to them, I can see considerably more detain in the 640x480 mode. Which means the camera is definately taking video at 640x480. Yet, there is something in the way their compression works that causes high-contrast edges to have less detail. I suspect it is a cheaper way to do on-the-fly MPEG4 encoding.
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