Is there a method to get rid of the rolling shutter in post? at DVinfo.net

David Delaney · December 24th, 2007, 03:03 PM

Is there a method to get rid of the rolling shutter with the HV20? Is it individual frames?
I was reading that even the Red camera suffers from this - so is there a workaround?

Giroud Francois · December 24th, 2007, 04:17 PM

you still have to define what rolling shutter problem you need to remove....

David Delaney · December 24th, 2007, 05:54 PM

When I watch some footage from the HV20 (as well as other cameras), I notice that odd flicker/flash - where it draws portions of the screen at a time, I was just wondering if there is a post-processing way to get rid of it.

Here is the url :
http://techthoughts.org/2007/12/17/r...r-redux-again/

Although this is the RED camera, it uses a CMOS (like the HV20)

Jack Walker · December 24th, 2007, 06:33 PM

Quote:

Originally Posted by David Delaney

Although this is the RED camera, it uses a CMOS (like the HV20)

Sorry to not understand, but what is the problem I am looking at. The picture in the link looks fine. No?

Giroud Francois · December 24th, 2007, 06:56 PM

no, that is a typical rolling shutter effect.
a short flash will be recorded only partially , splitting the picture into a darker and brighter area (look carefully at the sample).
since it is supposed to happen only one one frame, you can try to restore the brightness on the faulty area.
if you are lazy, you just need to delete this frame and replace with a blend of previous and next frame.
On the other hand, i am not sure than somebody except superman would be able to see such problem into one picture among 25 per sec.

David Delaney · December 24th, 2007, 07:40 PM

Here is the video where it is really noticeable.
http://web.mac.com/fini1/iWeb/Site%2...%20Camera.html

I would think getting rid of the frame might do the trick, but it is definitely noticeable.

Giroud Francois · December 25th, 2007, 04:17 PM

yes, in your sample there is A LOT of frames, some heavily impacted.
that is particularly visible since you can early notice they seems to be caused by some flash in the background.
I do not know this camera, but there is probably a way to set exposure to a less sensitive setting.
For this sample, i do only see a tedious work of removing frames by hand and replacing with some other (blended or not)

Graeme Fullick · December 26th, 2007, 02:54 PM

Camera flashes cuase frame crash with HDV, and rolling shutter effects with CMOS imagers. I have had good success fixing these in post with white filters of 70-100% transparency. I use Avid Liquid which is an mpeg editor and it seems to repair the frame by re-rendering to the point where the problem is not noticeable at all.

Giroud Francois · December 26th, 2007, 05:40 PM

probably you can mark the faulty frames a way or another (making them all green ?) and then using a script (Avisynth, after effect) that can replace the green frames with the previous one.

David Delaney · December 26th, 2007, 07:00 PM

I hope someone that is proficient in this can make a quick fix with a script or something - it would be nice not to have to worry about this kind of thing. I have also noticed this flash when there are pans, even slower ones.

Giroud Francois · December 27th, 2007, 06:12 AM

i think it is possible to write a frame analyzer that looks for the darkest/brightest range and finds the artefact block. (the part that is brighter will have range shifted to the bright.)
since the split is always horizontal, it should be easy to find an formula.
it should be even easy to fix the picture, no replacing it.
looking for few columns of pixel across all the frame should be enough and very fast.

Ben Syverson · December 27th, 2007, 10:41 AM

I could write such a thing, but I guess I'm wondering... how often do you shoot with camera flashes going off? It seems like a pretty obscure problem.

Ian G. Thompson · December 28th, 2007, 09:14 PM

Quote:

Originally Posted by Ben Syverson

I could write such a thing, but I guess I'm wondering... how often do you shoot with camera flashes going off? It seems like a pretty obscure problem.

Well...that would be great if you could. It's not just camera flashes but lightning from thunderstorms etc.

Wes Vasher · December 29th, 2007, 06:57 AM

If you are going to be shooting a lot of flashing light you'll just want to get a camera that doesn't have a CMOS in it.

Ian G. Thompson · December 29th, 2007, 10:56 AM

Personally I don't really have a problem with the flashes. But Wes that soution is not practical especially with the 10's of thousands of folks who already own CMOS cams. But a software solution for this seems like it would be an easy fix. Matter of fact...instead of trying to get rid of he flash...just making the whole affected frame uniformley white would probably be the best solution.

In regards to panning skews (where a verticle line bends when panning fast) this also seems like a software solution should be able to fix it. I'm just guessing here...but it would sort of act like motion tracking and when the pan happens the software takes the upper scan lines and moves it ahead to keep up with the bottom scan lines (you might have o crop the picture a little in the end result...but the idea seems to make sense to me...

You can call the software..."Rollback Shutter." lol

December 24th, 2007, 03:03 PM	#1
David Delaney Trustee Join Date: Feb 2006 Location: Niagara Ontario Canada Posts: 1,121	Is there a method to get rid of the rolling shutter in post? Is there a method to get rid of the rolling shutter with the HV20? Is it individual frames? I was reading that even the Red camera suffers from this - so is there a workaround?

December 24th, 2007, 05:54 PM	#3
David Delaney Trustee Join Date: Feb 2006 Location: Niagara Ontario Canada Posts: 1,121	When I watch some footage from the HV20 (as well as other cameras), I notice that odd flicker/flash - where it draws portions of the screen at a time, I was just wondering if there is a post-processing way to get rid of it. Here is the url : http://techthoughts.org/2007/12/17/r...r-redux-again/ Although this is the RED camera, it uses a CMOS (like the HV20) Last edited by David Delaney; December 24th, 2007 at 06:25 PM.

December 26th, 2007, 02:54 PM	#8
Graeme Fullick Major Player Join Date: Mar 2005 Location: Newcastle, Australia Posts: 337	Camera flashes cuase frame crash with HDV, and rolling shutter effects with CMOS imagers. I have had good success fixing these in post with white filters of 70-100% transparency. I use Avid Liquid which is an mpeg editor and it seems to repair the frame by re-rendering to the point where the problem is not noticeable at all. __________________ Graeme

December 29th, 2007, 06:57 AM	#14
Wes Vasher Major Player Join Date: Jan 2006 Posts: 440	If you are going to be shooting a lot of flashing light you'll just want to get a camera that doesn't have a CMOS in it. __________________ Clips \| Stills

December 24th, 2007, 04:17 PM	#2
Giroud Francois Inner Circle Join Date: Feb 2004 Location: switzerland Posts: 2,133	you still have to define what rolling shutter problem you need to remove....

December 24th, 2007, 06:56 PM	#5
Giroud Francois Inner Circle Join Date: Feb 2004 Location: switzerland Posts: 2,133	no, that is a typical rolling shutter effect. a short flash will be recorded only partially , splitting the picture into a darker and brighter area (look carefully at the sample). since it is supposed to happen only one one frame, you can try to restore the brightness on the faulty area. if you are lazy, you just need to delete this frame and replace with a blend of previous and next frame. On the other hand, i am not sure than somebody except superman would be able to see such problem into one picture among 25 per sec.

December 24th, 2007, 07:40 PM	#6
David Delaney Trustee Join Date: Feb 2006 Location: Niagara Ontario Canada Posts: 1,121	Here is the video where it is really noticeable. http://web.mac.com/fini1/iWeb/Site%2...%20Camera.html I would think getting rid of the frame might do the trick, but it is definitely noticeable.

December 25th, 2007, 04:17 PM	#7
Giroud Francois Inner Circle Join Date: Feb 2004 Location: switzerland Posts: 2,133	yes, in your sample there is A LOT of frames, some heavily impacted. that is particularly visible since you can early notice they seems to be caused by some flash in the background. I do not know this camera, but there is probably a way to set exposure to a less sensitive setting. For this sample, i do only see a tedious work of removing frames by hand and replacing with some other (blended or not)

December 26th, 2007, 05:40 PM	#9
Giroud Francois Inner Circle Join Date: Feb 2004 Location: switzerland Posts: 2,133	probably you can mark the faulty frames a way or another (making them all green ?) and then using a script (Avisynth, after effect) that can replace the green frames with the previous one.

December 26th, 2007, 07:00 PM	#10
David Delaney Trustee Join Date: Feb 2006 Location: Niagara Ontario Canada Posts: 1,121	I hope someone that is proficient in this can make a quick fix with a script or something - it would be nice not to have to worry about this kind of thing. I have also noticed this flash when there are pans, even slower ones.

December 27th, 2007, 06:12 AM	#11
Giroud Francois Inner Circle Join Date: Feb 2004 Location: switzerland Posts: 2,133	i think it is possible to write a frame analyzer that looks for the darkest/brightest range and finds the artefact block. (the part that is brighter will have range shifted to the bright.) since the split is always horizontal, it should be easy to find an formula. it should be even easy to fix the picture, no replacing it. looking for few columns of pixel across all the frame should be enough and very fast.

December 27th, 2007, 10:41 AM	#12
Ben Syverson Major Player Join Date: Mar 2004 Location: chicago Posts: 434	I could write such a thing, but I guess I'm wondering... how often do you shoot with camera flashes going off? It seems like a pretty obscure problem.

December 29th, 2007, 10:56 AM	#15
Ian G. Thompson Major Player Join Date: Jan 2007 Location: Rockledge, Florida Posts: 351	Personally I don't really have a problem with the flashes. But Wes that soution is not practical especially with the 10's of thousands of folks who already own CMOS cams. But a software solution for this seems like it would be an easy fix. Matter of fact...instead of trying to get rid of he flash...just making the whole affected frame uniformley white would probably be the best solution. In regards to panning skews (where a verticle line bends when panning fast) this also seems like a software solution should be able to fix it. I'm just guessing here...but it would sort of act like motion tracking and when the pan happens the software takes the upper scan lines and moves it ahead to keep up with the bottom scan lines (you might have o crop the picture a little in the end result...but the idea seems to make sense to me... You can call the software..."Rollback Shutter." lol