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GOP/Keyframe 0.3-0.5 stop brightness changes in shadow-midtones :(
254 12 2017-4-19 06:03:03
michaeldk
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Cyprus
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Hey all,

Purchased my drone in Cyprus - very recently produced - the 15th of April. Noticed that my shadows felt very "jittery" and not smooth. First thought it was lack of ND filter that caused it, but in the end comparing to other Mavic footage mine looked pretty useless at times. Finally managed to nail down the issue.

Every 8 frames the brightness resets to either darker or lighter than the 8 frames before, and significantly so (up to half a stop). It only does so in the shadow areas and darker midtones, and mostly in areas that are more uniform and with limited color saturation.  I called DJI and they told me that downgrading the firmware might help, as their last firmware possibly had some fault that could cause this.

Sadly the visual defect is still present and ruins a lot of my shots. I'm not a video expert, but I am a very experienced photographer by education and have around 2 decades of high end image processing/manipulation behind me. And I don't think that this issue is 'user error' .

Things I tried:
- 4k, 2.7k.
- 24/30 fps
- Sharpening to +1, 0 and -1 (for the famous waterpainting shadow issue, thought this might be related but it wasn't)
- MOV/MP4 (shouldn't matter, but hey, it's free so why not)
- Installing lens hood (modified gimbal protector), making sure prop shade was not the issue (sun from behind etc).
- Trying to remove it with 1-frame nudge and opacity to 50% (To even out brightness). Small improvement, but major decrease in sharpness. No go.



Any tips or advice would be highly appreciated. I need to use the Mavic for a documentary that I'm shooting next week (11 day trip to Spain) and can't realistically afford to not have it with me during that time frame. Thank you very much
2017-4-19 06:03:03
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Ex Machina
First Officer
Flight distance : 277874
United States
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Prop shade was the first thing I thought looking at your video, seems to go away as you complete your turn to the right.
2017-4-19 06:37:54
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michaeldk
lvl.1
Cyprus
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Ex Machina Posted at 2017-4-19 06:37
Prop shade was the first thing I thought looking at your video, seems to go away as you complete your turn to the right.

Thanks for your answer The sun was firmly from behind, and as mentioned a lens hood in place. I also have the issue when there is no sun (clouds) or when looking straight down (with/without lens hood)

Also the fact the brightness changes occur exactly at the GOP frames (every 8) indicates its a processing error, if I am not mistaken. Right?
2017-4-19 06:56:15
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Ex Machina
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michaeldk Posted at 2017-4-19 06:56
Thanks for your answer  The sun was firmly from behind, and as mentioned a lens hood in place. I also have the issue when there is no sun (clouds) or when looking straight down (with/without lens hood)

Also the fact the brightness changes occur exactly at the GOP frames (every 8) indicates its a processing error, if I am not mistaken. Right?

Do you see the same effect at the frame level after the turn?
2017-4-19 07:08:02
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michaeldk
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Cyprus
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Ex Machina Posted at 2017-4-19 07:08
Do you see the same effect at the frame level after the turn?

Yes, but because there are less dark areas in the frame the effect is much more pronounced (large areas seem to trigger it much more than smaller ones). Basically when a darker area becomes 'textured' enough the effect gets a lot less (But still visible upon close inspection).
2017-4-19 07:10:39
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michaeldk
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Cyprus
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Nobody else any opinion on this ?
2017-4-20 09:26:42
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Ex Machina
First Officer
Flight distance : 277874
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michaeldk Posted at 2017-4-19 06:56
Thanks for your answer  The sun was firmly from behind, and as mentioned a lens hood in place. I also have the issue when there is no sun (clouds) or when looking straight down (with/without lens hood)

Also the fact the brightness changes occur exactly at the GOP frames (every 8) indicates its a processing error, if I am not mistaken. Right?

Do you think your lens hood will 100% eliminate prop shade effects? I'm wondering if the GOP behavior is a red herring, or even coincidental. I guess you could test this by recording video without running the props and then checking the GOP frames.
2017-4-20 13:08:16
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michaeldk
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Cyprus
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Ex Machina Posted at 2017-4-20 13:08
Do you think your lens hood will 100% eliminate prop shade effects? I'm wondering if the GOP behavior is a red herring, or even coincidental. I guess you could test this by recording video without running the props and then checking the GOP frames.

Well, even with the sun straight from above (meaning prop shadow has no way of reaching the lens element) the effect is visible, sadly. So I'm fairly confident it's not that. I've seen prop shadow once or twice but it looked very different!
2017-4-20 13:18:24
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Sangarone
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michaeldk Posted at 2017-4-20 09:26
Nobody else any opinion on this ?

Im surprised you posted this without seeing all the recent information on other forums and on youtube... This whole issue is gaining a lot of traction and I have found 2 videos of people that seem to have fixes. I havent used it on my videos yet so I cant say for sure but I just made my NeatVideo order and am waiting for the license key to be sent.

2017-4-20 17:28:26
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Ex Machina
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Sangarone Posted at 2017-4-20 17:28
Im surprised you posted this without seeing all the recent information on other forums and on youtube... This whole issue is gaining a lot of traction and I have found 2 videos of people that seem to have fixes. I havent used it on my videos yet so I cant say for sure but I just made my NeatVideo order and am waiting for the license key to be sent.
https://www.youtube.com/watch?v=1310HP78Jh0&t=265s
https://www.youtube.com/watch?v=XluCECVG278

Wow, really interesting info -- thanks for sharing!
2017-4-20 19:48:29
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Sangarone
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Ex Machina Posted at 2017-4-20 19:48
Wow, really interesting info -- thanks for sharing!

This one is intriguing as well, Im going to test this all out this weekend.

2017-4-21 07:07:11
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michaeldk
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Cyprus
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Sangarone Posted at 2017-4-20 17:28
Im surprised you posted this without seeing all the recent information on other forums and on youtube... This whole issue is gaining a lot of traction and I have found 2 videos of people that seem to have fixes. I havent used it on my videos yet so I cant say for sure but I just made my NeatVideo order and am waiting for the license key to be sent.
https://www.youtube.com/watch?v=1310HP78Jh0&t=265s
https://www.youtube.com/watch?v=XluCECVG278

I've seen both videos but neither of them comes even close to the level of flickering that I have. What I have can't even be called flickering, it's completely unusable footage rather than just a minor imperfection in theirs. I've also seen the last video you sent me of the mushy shadow footage, and I also tried changing the sharpening setting to +1 and -1 (as I mentioned in the start post!) to see if my issue is related.

The flickering issue is a minor annoyance related to GOP frames. What I have is just completely ruined footage that can't even be used semi professionally. It's a 5x worse version of the ones you showed, so I'm certain there is some relation of course.
2017-4-21 12:21:46
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thehippoz
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michaeldk Posted at 2017-4-21 12:21
I've seen both videos but neither of them comes even close to the level of flickering that I have. What I have can't even be called flickering, it's completely unusable footage rather than just a minor imperfection in theirs. I've also seen the last video you sent me of the mushy shadow footage, and I also tried changing the sharpening setting to +1 and -1 (as I mentioned in the start post!) to see if my issue is related.

The flickering issue is a minor annoyance related to GOP frames. What I have is just completely ruined footage that can't even be used semi professionally. It's a 5x worse version of the ones you showed, so I'm certain there is some relation of course.

I just looked at my 4k footage, it looks like the first video explains a lot. It's the compression algorithm h.264 that has one clear frame every 8 then depending on the compression level, the next 7 get gradually softer. Least that's what I'm seeing. Pictures below are from the clear frame and the one before it. Frame 3 through 7 are a lot softer.

Interesting you can like in premiere, create a repeat sharpen for frames 1 through 7 gradually increasing to match 8. I don't really get all that noise at iso 100 like the fix video above, just sharp to soft every 8 frames.
8.jpg 7.jpg
2017-4-21 18:09:32
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