How to fix camera lens induced problem spot in video export?


Windows 10
Shotcut 18.07.02

I just noticed in an exported video that there’s a consistent small spot in the lower right side of the video. Then I carefully inspected some recent videos I took and they all have this little spot in them too. I cleaned the outside of the lens very well, but the spot persists. So I have to live with for now.

My question is are there any known tricks of the trade in Shotcut for kind of hiding a spot in a video export, where the obscuring of the problem spot does not noticeably affect the rest of the video? Like maybe a blur filter to affect just a very (very) tiny portion of the video screen? Maybe some some sort of pixel of “blending” technique at the site of the problem spot?

Thanks for any ideas.

This might work for your problem spot.

Made a short video with a spot on it. Used the Mask and Size and Position filter to hide it.

You can download the video and the mlt to see if this works for you.


Problem spot.mlt (8.9 KB)

1 Like

You can search the forum here (or YouTube) for some posts that explain how to use the Mask filter to confine a filter such as Blur to a specific portion of the image. The basic approach is to use 2 video tracks and put the same clip on both tracks at the same time position. Then, apply the Mask and Blur filters to the top clip. Adjust the filters’ parameters as-needed.

Thanks so much. Sorry it took a few days to get a look at your helpful example.
So if I understand correctly, you just put the problem video on top of itself and shift it over a little bit, and then shrink it way down in size just enough to cover the problem spot with very similar material?
I guess this works for situations where there’s no very distinct variations in the visual materials around the problem spot.

Here’s what it looks like zoomed way in (ie using crop filter).
I post this here to see if I’m understanding seeing what’s going on correctly:
Problem_spot_my_crop_1.mp4 (1.1MB)

Thanks again for the idea and the example.

I put the same video on two tracks then added a mask filter to the upper track. Also added an invert color filter to the upper track to be able to position the mask to cover the spot. Once I positioned the mask to cover the spot I removed the invert color filter.

Then I added a size and position filter and moved it just enough to mask the spot.

Yes. This works if the spot is small and the visuals in the area don’t change much. You could use the size and position filter’s advanced key-frames to shift the mask around if needed.

Avidemux (a free, old, opensource editor) has a filter that can hide a spot with better results than my trick.

Okay, thanks for the ideas.

By the way, if anyone’s interested,here’s an example of the video
where the spot in the lower left corner is quite noticeable.

movie_Jul17_18_1_3_camera_problem_spot_section_1.mp4 (6MB)

I was not able to reproduce the technique mentioned above successfully.
But I’ll explore it further.

By the way,
what’s the preferred method for putting up a dropbox link here,1 or 0 at the end of the link?
1 appears to make it a direct download
0 appears to direct over to dropbox page?

Thanks for any other ideas.

Here’s your video with the spot hidden with Avidemux.

Spot hidden with Avidemux

This is the mlt that I made with your video. You need to look at how the filters are applied to make it work.

Spot hidden Shotcut.mlt (7.5 KB)

IMO either method works fine.

Very nicely done. Is that a common blur filter that comes with AviDemux?
And what were your settings there I wonder?
I’ll see what I can do with that.

Thanks so much.
Okay, I think I’m getting it now.
The video you use to do the masking is best if it’s the same video because that way the coverup of the problem spot video will be with very similar material as the problem spot video.
Then you just let a portion of the covering video through, and that’s called masking.
In this case only a tiny (very tiny) bit of the covering video is let through on top of the problem video.
Then the covering video is shifted around a little bit until it obscures the spot on the problem video.
And the spot on the covering video does not show up because that portion of the video is not being let through because of the mask filters settings.

Good to know.

Thanks again for your help with this.

Used Avidemux 2.7.1. The filter is called Mplayer delogo2 and it’s a standard filter that comes with Avidemux.


Upon close inspection of the camera spot problem area in this particular video section, I seem to notice zero artifacts with the Avidemux delogo filter method.

With the masking method, viewed very closely, I notice some tiny artifacts. Not a problem really, because only zoomed way in is it noticeable.

Both ways work.

Thanks again for the great ideas, and the details of how to get the desired results.

You’re welcome. Happy editing.:smile: