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27th February 2008, 23:10 | #81 | Link |
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http://www.channeltv.co.uk/deshakers.gif
why do these distortions happen? and what do you call them also? |
28th February 2008, 00:39 | #82 | Link |
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My guess would be the effect is caused by the distortions present at the edges of the lens. The distortion becomes worse the further away from the center of the image the 'target' is.
For a steady lens, this is of course not noticeable. However, if the lens moves around, and then the image is stabilised later, the distortion becomes very obvious (as you can see). Think 'pincusion' effect with wide angle still (and video) cameras. Is is particulary bad with cheaper lens, and is even present with more expensive lens. If you really don't want it, buy a 'hollywood' movie camera lens... but be prepared to walk away 20k poorer! MM PS: One way to minimise this effect with a "cheap" lens is to zoom in to the subject. Less of the glass is used, and the area in use is closer to the center. Only problem, if the camera is shaking to begin with, zooming in is going to make it a whole lot worse! |
28th February 2008, 00:50 | #83 | Link |
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AFAIK there was a solution for AVISynth to undo the distortions of wide angle lenses...
But I don't know its name anymore... EDIT: http://forum.doom9.org/showthread.ph...rel+distortion One need to undo the distortion before deshaking. If the fish-eye look is desired one may re-apply the distortion after deshaking again.
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28th February 2008, 19:08 | #85 | Link |
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Actually, this effect doesn't come from the fact that wide angle lenses often are imperfect, but rather from the nature of wide angles.
Most wide angle lenses are usually either rectilinear or fisheye. I guess it's pretty obvious that fisheye lenses will give strange results when deshaking, but the fact is that even perfectly rectilinear lenses will look a bit weird (which that sequence above demonstrates). Here's my attempt at explaining why, in a hopefully easy to understand way... A rectilinear lens will make straight lines in the world appear straight on the image too. Now, imagine you're taking a close wide-angle picture of a chessboard. All squares will get the same size on the image even though the outer squares are further from the camera than the squares in the middle. This essentially means that objects are magnified when they are close to the edge. When you turn the camera to point at an outer square it will get smaller on the image. And deshaker doesn't like it when objects change size when you pan the camera... |
28th February 2008, 23:18 | #88 | Link |
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oh, thats a real shame, it hasnt received an update for a very long time now, i do hope u can get to it one day, i will look forward to it.
and, since speaking to the actual creator of the filter , about the borders, i assume u have watched the video sample from YUVSoft and its comparisions to yours? can your filter literally recover the missing edges in the black borders? |
29th February 2008, 00:58 | #89 | Link |
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the video of YUVSoft is a LIE!
they didn't set up deshaker properly just to present their own product as the better one.
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29th February 2008, 13:13 | #90 | Link |
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Deshaker is lovely, but how can I speed it up?
I assumed this would have been asked before, but I can't see a list of which options really speed it up or slow it down in the five pages here. Cheers, David. |
29th February 2008, 21:46 | #91 | Link | |
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Quote:
First they steal the name "deshaker", and now this. Yes, deshaker can recover missing edges (by taking video data from past and future frames). Thanks! I recommend you search for the words "fast" and "slow" here: http://www.guthspot.se/video/deshaker.htm |
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1st March 2008, 13:40 | #92 | Link | |
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Quote:
and when it uses previous frames to recover missing edges, does it literally look for wat was suppose to be there? possible to show an example? |
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3rd March 2008, 14:30 | #95 | Link | |
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Quote:
I have read it (the web page), and used it (deshaker!), but still have a "kind of" question about edges. I'm not sure how to phrase this. Obviously everything in the frame is processed with motion estimation and compensation. However, it seems that the areas out of frame are not. Here's an example of what I'm trying to say... Let's say the area at the top of the frame is first revealed in original frame 100, but was needed for compensated frames 80-99 too. During those frames, it looks like the static top of frame 100 is copied to the top of frame 80-99. Let's say the existing top of frames 80-99 is moving left to right. It looks like there's no attempt to make the part pasted from frame 100 move left to right - it just sits there. Now I know you don't actually know how it should be moving, because it's not there in those frames(!) - however, would it not be reasonable to guess that if the parts near it are moving left to right, then the part copied from frame 100 should move left to right too? It might not be spot on, but it might be closer to reality that not moving it. I guess it comes with its own complications...! Not a criticism (because deshaker is amazing) - just a question/suggestion. Cheers, David. Last edited by 2Bdecided; 3rd March 2008 at 14:32. |
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3rd March 2008, 15:43 | #96 | Link |
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deshaker 'only' applies global motion compensation to the frames. This means that only the whole frame is being moved.
This is also done with previous and future frames. But every movement that does not equal to the whole frames movement - I call it differential movement - will most likely produce some weird artifacts at the compensated borders. Of course, one could write algorithms that will do local motion compensation on the frames that are being used form border filling. but that would slow down the process even more.
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3rd March 2008, 19:18 | #97 | Link |
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Exactly. Thanks scharfis!
This usually means that the background will be moved correctly when taken from another frame, but if there are objects moving in the borders, they tend to look a little weird. And btw, I have absolutely no problem with questions/suggestions or even criticism. It's actually even slightly ok to ask things that's already on my web page. |
6th March 2008, 13:40 | #100 | Link |
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also, here is the actual video of using the Deshaker program.
it includes a before and after processing: http://www.wikiupload.com/download_page.php?id=35945 P.S. i dont know if anyone has seen such shaky camera work either. |
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