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Old 28th June 2010, 16:12   #21  |  Link
Terka
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nice summary
i understand its a big problem, im not speaking about totally removing, but at least minimizing.
if camera is moving there and back..., there must exist a place where it stops. such frames could be used for compensation.
(assume that the filming object are not warping, only translating, maybee zooming)
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Old 28th June 2010, 18:09   #22  |  Link
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Quote:
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nice summary
Thank you.

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i understand its a big problem, im not speaking about totally removing, but at least minimizing.
Well the existing script does a reasonable job of that, but it's important to understand that it's very very difficult to get rid of the problem entirely, so that you should take care to avoid letting it happen in the first place. Pan your camera slowly, don't let it vibrate. The rolling shutter effect is not very visible on moving objects, so it's fine as long as you keep your camera still or pan only slowly.

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if camera is moving there and back..., there must exist a place where it stops. such frames could be used for compensation.
Sadly, no, there is no such place. Remember that the whole problem of rolling shutter is that the camera cannot be moving
*or accelerating*. I get the feeling that you are a school student Terka (you ask many questions), if I am right then what you need will be covered in year 11 science class. If I am wrong, or for those who did not have science or physics at school: If the camera is changing direction, it is accelerating, it is not "stopped" at any time ("stopped" here meaning that it is neither moving nor accelerating).

Incidentally at 30fps and for an 86% roll, the camera would have to be still for at least 29ms (given perfect luck, 58ms to get "at least" one frame). That's actually not that short a time by video standards.

If you had a reference scene appearance though, I could see that it could be possible to warp each frame locally to approximate the correct appearance of the frames (removing any global offset, removing bad-match blocks due to moving objects and perspective transforms, allowing that columns are caught simultaneously but rows are offset in time).
That is not a bad idea, but it would be difficult to accomplish. It would only work for panning, since appearance changes in other motions and you couldn't make such a map. You would also need a reference bigger than any one frame, which may be difficult if you are panning a camera, so it could only help in specific situations. If you only want to try to keep the appearance constant between frames - well that's what the script does more-or-less.
My challenge to you Terka is to find such a scenario, and try such a solution, it would be interesting to everyone :-)

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(assume that the filming object are not warping, only translating, maybe zooming)
Actually, zooming is one of the worst problems for image matching or optical flow, even rotation is not as bad as zooming. The change in scale makes matching difficult! I would recommend keeping away from zooming if you can, it isn't impossible to deal with, but it makes results difficult.

Last edited by PitifulInsect; 28th June 2010 at 18:11.
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Old 28th June 2010, 21:15   #23  |  Link
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anybody had to actually deal with this with canon 7D? how bad is it with this specific camera? is there any difference with changing the shutter speed? (with about 600 clips taken so far i could find exactly one shot that looks problematic and it was a tilt (squash effect).)

i'am thinking of getting this specific DSLR.
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Old 29th June 2010, 08:41   #24  |  Link
Terka
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i think the shorter shutter, the smaller 'rolling effect'
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Old 29th June 2010, 10:34   #25  |  Link
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i think the shorter shutter, the smaller 'rolling effect'
I don't know about the 7D, but generally this isn't the case at all. The rolling shutter is due to the sequential readout of the sensor - it has nothing to do with shutter speed. A faster shutter speed means each pixel on the sensor is exposed for a shorter time, but the delay between the top pixel being exposed and the bottom pixel exposed remains the same, irrespective of shutter speed.

Shorter shutter speed = less blur = rolling shutter artefacts might be slightly more obvious, but that's a secondary effect.

Cheers,
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Old 29th June 2010, 13:56   #26  |  Link
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are you sure?
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Old 29th June 2010, 15:46   #27  |  Link
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are you sure?
Yes!

I own an HV20(!).

If a shorter shutter speed meant less rolling shutter, then we could avoid rolling shutter outside in daylight just by making the shutter faster (at the expense of strobing). But this doesn't work at all.

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Old 29th June 2010, 19:17   #28  |  Link
Terka
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I own an HV20 too.
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Old 30th June 2010, 20:11   #29  |  Link
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anybody had to actually deal with this with canon 7D? how bad is it with this specific camera? is there any difference with changing the shutter speed? (with about 600 clips taken so far i could find exactly one shot that looks problematic and it was a tilt (squash effect).)

i'am thinking of getting this specific DSLR.
I got the 7d a half year ago, awesome piece of technology... :)
If you don't move the camera "spasticity-style", you will hardly get visible rolling-shutter!
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Old 1st July 2010, 11:09   #30  |  Link
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I got the 7d a half year ago, awesome piece of technology...
If you don't move the camera "spasticity-style", you will hardly get visible rolling-shutter!
Sometimes camera movement is inevitable, or wanted. Can you imagine Saving Private Ryan shot with a rolling shutter! The other day I filmed on a roller coaster - I used by cheap (CCD) point-and-shoot camera in video mode, because I knew the HV20's output would be unusable. The point-and-shoot has no optical image stabiliser, but that was useful for creating realistic effect. VirtualDub deshaker worked very well on the video, but it didn't feel so much like a roller coaster then!

btw, rolling shutter can be measured - there's no need to guess or give subjective impressions.

e.g. see the suggested method in the deshaker guide...
http://www.guthspot.se/video/deshaker.htm
(search for rolling shutter)


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I own an HV20 too.
Then you must know that a shorter shutter speed doesn't help at all? (where's the "confused" smiley? )

Cheers,
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Old 1st July 2010, 15:52   #31  |  Link
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im quite new with the hv20, and didnt have some 'real issue' with its RS, i also dint change the shutter yet. ;(
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Old 1st July 2010, 16:33   #32  |  Link
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Theoretically, if you use a shutter speed of 1/framerate you don't lose any temporal information (it just gets mixed in with spatial info in a non-separable fashion). It will probably be a lot easier to reduce rolling shutter artifacts if you stay close to this limit. Although this will make high motion stuff difficult to deal with as well, the degradation introduced should look more normal.
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Old 1st July 2010, 16:49   #33  |  Link
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Theoretically, if you use a shutter speed of 1/framerate you don't lose any temporal information (it just gets mixed in with spatial info in a non-separable fashion).
If it's mixed and non-separable, it sounds lost to me! I get what you're trying to say, but I'm not convinced.

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It will probably be a lot easier to reduce rolling shutter artifacts if you stay close to this limit. Although this will make high motion stuff difficult to deal with as well, the degradation introduced should look more normal.
Not really. If you're panning past a vertical thing (e.g. a pole, a window, whatever) a slower shutter just makes that "thing" blur, i.e. it looks wider. Whereas the rolling shutter means it's not vertical! It's the same amount "not vertical" (i.e. it's the same angle) whatever the shutter speed.

On less obvious examples, the blur might help to hide the effects, but it's marginal really.

Cheers,
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Old 1st July 2010, 18:46   #34  |  Link
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If it's mixed and non-separable, it sounds lost to me! I get what you're trying to say, but I'm not convinced.
temporal and spatial data are already highly interdependent and non separable, I was just saying that the change is non-ideally reversible.

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Not really. If you're panning past a vertical thing (e.g. a pole, a window, whatever) a slower shutter just makes that "thing" blur, i.e. it looks wider. Whereas the rolling shutter means it's not vertical! It's the same amount "not vertical" (i.e. it's the same angle) whatever the shutter speed.
The primary reason a slower shutter should help is that it should allow motion compensation to work more optimally. slower shutter speeds should also greatly reduce the severity of "tearing" caused by flashing lights etc. Basically the slower shutter speed should ensure that just about everything left over should be almost entirely recoverable.
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Old 2nd July 2010, 20:51   #35  |  Link
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Many thanks cretindesalpes for the modified MVTools2 and the script. What you were able to do is exactly what I suggested here:

MVTools2 discussion of Rolling Shutter

when this idea was first brought up. I expect that it will probably help fix the problems associated with left/right camera panning. I'm not sure what happens with vertical camera movement or with camera rotation.
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Old 2nd July 2010, 21:03   #36  |  Link
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Sometimes camera movement is inevitable, or wanted. Can you imagine Saving Private Ryan shot with a rolling shutter! The other day I filmed on a roller coaster - I used by cheap (CCD) point-and-shoot camera in video mode, because I knew the HV20's output would be unusable. The point-and-shoot has no optical image stabiliser, but that was useful for creating realistic effect. VirtualDub deshaker worked very well on the video, but it didn't feel so much like a roller coaster then!
Yeah, ultra shaky run-n-gun and filming from a roller coaster or a motorbike (without one of this glide or gyro stabilizers) is what i meant with "spasticity-style". Okay, sometimes its wanted for realness effect, but in 99% of situations its not the case, and that's why I wrote you will hardly get visible rolling-shutter!
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Old 2nd August 2010, 08:40   #37  |  Link
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shot some stuff with 50mm 1.4 primes (handheld), everything set to manual, including ISO (100) and i got gazillion problems with rolling shutter.
Could there be any direct connection between ISO and the defect? (that would mean using some slower lens or some sort of ND would be nice for outside stuff, with an ISO setting of... =?)
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Old 2nd August 2010, 15:04   #38  |  Link
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No, Rolling Shutter is caused by the method of capturing in the Image Sensor. I own a HV30
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Old 18th October 2010, 00:56   #39  |  Link
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Hi everyone, sorry for bringing something that hasnt been talked for awhile, but once again Rolling Shutter has become an issue with me, one of the reasons was that I intend to buy a new Lumix GH2 that was rumoured to be 'Global Shutter' in their LiveMOS image sensoprs, unfortunately that development was haulted and focus was shifted to developing the 3D lens, however the image scanning is faster this time but the rolling sbutter artifacts will still remain, nevertheless the DSLR is fantastic and still will get it.

Because of this, i have came back here and I believe it can be fixed but we users would have to know our own equipment at the same time. I dont know exactly how this current script deals with the Rolling Shutter artifact, but I would like to add if somehow we were able to Temporally analyze the previous and future frames bearing in mind that vertical edges (that was straight is straight no-more due to the lag) will be straight again, this will be incredibly useful for those who are doing point & shoot and run n' gun filming. Probably a preprocessing mask to detect vertical edges could be something of use.

Also how does the RollAway script perform? I hear its slow as hell and would crash on HD footage, has there been any development or optimizations afterwards or recently? Also does it bear its own artifacts like the Foundry plugin by any chance?
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Old 22nd June 2012, 06:27   #40  |  Link
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Hey all, it's been a while. Recently I updated RollAway to use SVP. Here it is:

Code:
function RollAwaySVP_alpha1(clip c, float amount, int segh, int "pel", int "blk", int "ovr")
{
    Assert(c.height%segh == 0, "'segh' must be a dividend of clip height")
    ctime = amount/2.0
    segs = c.height/segh
    den = segs-1
    num = den
    mult = segs/(ctime/50)
    rad = segs/2
    test = Default(test, false)
    flip = Default(flip, false)
    pel = Default(pel, 1)
    blk = Default(blk, 16)
    ovr = Default(ovr, 2)
    thSAD = Default(thSAD, 100)
    super = c.SVSuper("{pel:"+String(pel)+"}")
    vec = SVAnalyse(super, "{block:{w:"+String(blk)+",h:"+String(blk)+",overlap:"+String(ovr)+"}}")
    
    long = SVSmoothFps(c, super, vec, "{rate:{num:"+String(mult)+",den:1},algo:2}", "www.svp-team.com", 1.0, GetMTMode(true))
    
    stack = BlankClip(long)
    
    GScript("""
        for(r=-rad,rad-1,1)
        {
            nseg = long.SelectEvery(1, -r).Crop(0, (r+rad)*segh, -0, segh)
            stack = StackVertical(stack, nseg)
        }
        
    """)
    
    return stack.SelectEvery(int(mult), 0).Crop(0, long.height, -0, -0)
}
It requires the SVP plugins, as well as Gavino's GScript (no more recursion!). It's not nearly as fast as cretindesalpes' version, but it doesn't suffer from low bit depth issues like his, and it is far more stable than my previous versions. Give it a try and let me know what you think.
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