Hey guys,

maybe someone knows what is going on here...

Recently during a vacation I took about 3 hours of video material in 4k@30fps and all videos
which have moving cloud shadows do have this issue. The clouds are not moving smoothly, they stutter.

When I set the resolution to 2,7k@30fps everything is looking good. No stutters.

The following two sample videos are taken in 4k@30fps with the P3P:




2,7k@30fps video sample. To me it looks like it is smooth and doesn't stutter:


4k@30fps video sample. Same location and day time as the video before, this time with stuttering:


Does anyone have the same problem or knows what exactly is going on / how to solve it?

Greetings,
slain

Edit:
I uploaded the unprocessed material to my Dropbox account:
https://www.dropbox.com/s/jxgwpzff8ilxip4/3.mp4?dl=1 (84MB filesize)

Nice place ：）

DJI-Paladin Posted at 2016-6-22 12:16
Nice place ：）

This is the island of Mauritius.

Looks like your videos are playing at half speed

Interesting.

I notice nothing else is stuttering like the horizon, or especially in the 2nd video, the cars on the road.

I don't really know, I'm not an expert on these things, but I wonder if it does this on the raw source video, before processing.

Chris

Not A Speck Of  Posted at 2016-6-22 10:44
Interesting.

I notice nothing else is stuttering like the horizon, or especially in the 2nd video, ...

You're on the same line of thinking I am.   Since this is a 4K video, it is possible that the computer you are rendering your final video on cannot keep up with the data streaming of 4K and creating frame drops.

It does the same on the original video without any processing...

I tried the video material on three different PCs and a tablet. It is always the same :-(

Even if I load the video into Premiere and downscale it to 720p@20MBit/s, it is still stuttering.
It is definitely not due to player performance.

I uploaded the unprocessed material to my Dropbox account:
https://www.dropbox.com/s/jxgwpzff8ilxip4/3.mp4?dl=1 (84MB filesize)

Might I suggest you try another day with a location with sun/clouds and try different video formats and frame rates to see if it changes any? i.e. try 4K/30fps or if 2.7k/30fps or 1080p/60fps or 1080p/30fps show the same thing?  

I wonder if this was just an unfortunate occurrence on that particular day with a strange 'boot-up' of your camera.


ALSO, maybe try re-formatting your MicroSD card to ensure you have a good/clean format.

I got this problem on different days spread across two weeks. I also got this problem on two different SD cards (same model).

I will have to try out another FPS/resolution. Thanks.

So, today was good weather for testing and I tried several different settings.

What I found out is:
It is stuttering in 4k @30fps and in 24fps as well.
It stops stuttering in 2,7k, no matter if 30fps or 24fps.

I tested this with the MicroSD card, which was included in the drone bundle by DJI.

I uploaded one of the 2,7k videos I took to YouTube. To me it looks like it is smooth and doesn't stutter:

Does no one have an idea, what this could be? Why the cloud shadows are stuttering @4k, but not @2,7k?

Are there other things abnormal when you shoot videos with 4K, other than clouds?

Nope, just clouds. Everything else is moving smoothly. Cars, trees in the wind, etc....
There are two cars visible in the second YouTube video I linked in my first post. This is a good example.

Because your fps rate is 30, be sure that your shutter speed is set to 60 fps. You will need nd filters to compensate for the exposure. When I shoot at 4k I know this makes a big difference. I have a 4k compatible laptop w/ i7/6800 and Geforce 4gb and 16gb memory.

Hm? Shutter speed is not Frames per Second.
Frames per Second is how many pictures are put together for getting one second of video (like 60 frames per second).
Shutter speed is the amount of time one of those pictures is taken with (like 1/120s).

A P3P can only shoot 30fps max @4k. For getting 60fps I would have to choose 1080p as a resolution.
Also when I choose 2,7k with 30fps, it does not have the problem with stuttering.

Or am I somehow missing the point? Sorry :-/

Last try to find someone who has an idea of what is going on here :-/

slaindevil Posted at 2016-7-4 08:35
Last try to find someone who has an idea of what is going on here :-/

Which micro sd card are you using ? The card I received with my P4 was a SanDisk Extreme UHS-I U3 16GB.

I currently use a SanDisk Ultra 64 GB C10 XC1 and have not been aware of any issues regarding stuttering.

The 16GB memory that was delivered with the P3P.

slaindevil Posted at 2016-6-27 12:21
Hm? Shutter speed is not Frames per Second.
Frames per Second is how many pictures are put together  ...

If you switch to 'manual' mode then there is control over how long the 'shutter' remains open. So you can get your 30 images per second (30fps), each of these images might be 1/30th, 1/60th, 1/120th of a second in duration.

slaindevil Posted at 2016-7-4 11:36
The 16GB memory that was delivered with the P3P.

"The 16GB memory that was delivered with the P3P."

So what type is it, it's either a memory problem (not fast enough), or some kind of strobe effect due to the frame rate/shutter speed.

I got no clue what kind of SD Card DJI included in their P3P pack, but it should be capable of handling those <10MB/s, so I don't think it is a SD card problem.

I also tried a SanDisk Ultra microSDXC 64GB Class 10 and it has the same issue.

I will try setting a manual shutter of a multiple of 30fps (1/60th or 1/120th) and give an update if this solved my problem.

That is really strange effect, never seen this!

But I agree with mjlstudios, this is most likely a matter of too high shutter speed.

I assume you dont fly with ND or CP filters, therefore on a sunny day your shutter speed will be 1/400 - 1/1000 = HIGH. Rule in video is to keep shutter speed LOW, as a guide 1/ (2x FPS). This is mostly to keep movement smooth. (If you have a ceiling fan and camera with manual shutter control, you can easily see why 1/60 is much nicer than 1/600.)
try to pick up a set of ND filters - it will give you a cleaner, smoother image on sunny days.

That could explain jerky movement in general. But I have no clue why only part of the image is affected. That is really strange.

I remember having a video though, where it looked like the sky was 'detached' from the horizon and sort of moving on its own, compared to the ground. But at least that was reeeally bright sky vs. normal ground. In your video, that s not even the case.



oh, and all the PC too slow or SD card faulty is obvioulsy incorrect. Processing / data issues would result in visually destroyed image = artifacts. Your image is cleanly processed.

I am using a ND8 or ND4 filter, depending on the weather conditions to lower the shutter speed and get rid of jello effects.
The shutter speed of the videos above was somewhere around 1/200s.

slaindevil Posted at 2016-7-4 15:27
I am using a ND8 or ND4 filter, depending on the weather conditions to lower the shutter speed and g ...

to clarify - on the shot with stuttering clouds you used an ND filter?

Sebb Posted at 2016-7-4 15:28
to clarify - on the shot with stuttering clouds you used an ND filter?

I used ND filters on all three videos posted above.

On the one which is not stuttering as well as on the two videos with stuttering clouds.

Yes.

Here is video I was referring to from 2014.
notice the sky at 0:45. This was visible also on original file, before post processing.

Sebb Posted at 2016-7-4 15:48
https://www.youtube.com/watch?v=VchCwTs6y8s

Here is video I was referring to from 2014.

To me that looks a little bit like the jello effect of a GoPro.

It s an old Phantom 2 (non-vision, no gimbal..)
no not jello.. I know how that looks very well from back then
I was referring to how seperate the sky appears to shift around, while the horizon line stays more still.

Video compression was not designed to work with a transparent foreground plane moving at a different speed and/or direction than the background. I see this for both shadows of clouds and looking down through clouds at the ground. The compression algorithm can only do a single motion vector. Note that of the three shots you posted, only the one in which the background was stationary had no stuttering of the cloud shadows.

This Phantom 2V+ video I shot in January shows the problem clearly:

interesting theory, but

- the sensor receives a 2D image. There is no transparency to deal with. it doesnt know the clouds are transparent. it just sees greyer trees.
- there are also examples where it is rendered smoothly.

i dont think algorythm is to blame.
Edit: well, I take that last statement back. algorythm is actually a good candidate for causing this, but transparency doesnt apply I think.

from point of view of algorythm, the image information gets gradually more/less contrasty as clouds move across. But isnt that something that happens all the time anyway in video of landscapes, even without clouds? Why dont we see it more often then?

Edit2: ok, after some reading, I think I understand now. you are right, it makes sense. the algorythm works by taking pixels in motion from A to B without changing them, thereby saving information. But if the pixels change only slightly while moving from A to B, e.g. slightly lighter/darker due to clouds, then this is ignored by algorythm. only when arriving at B they are updated (new keyframe) and for us that causes the visible jump. In other parts of the image where pixels stay same color/saturation/etc., it appears smooth.

This is probably also directly dependent on bitrate. The lower the bitrate, the more these issues appear.

So the reason why it didnt happen in the 2.7K example most likely is
- 2.7K has higher per-pixel bitrate than 4K
- the field under the shadow has much less detail, and drone itself isnt moving = easier for algorythm anyway.

This is an interesting idea of what is going on.

On the day I took the 2,7k video above I also took a 4k@30fps video sample. Same day, time and position:

2.7K @ 45MBit = 0.44bits/pixel
4K @ 60MBit =  0.29bits/pixel  = 40% lower


Here is a clip showing bitrate vs resolution dilemma


I am considering shooting everything in 2.7K ... certainly worth making some tests..on the other hand, if anything i am really impressed with 4K image quality. just made move from P2 with Hero4b to P3P, and it s soo much nicer, especially the rectilinear 20mm lens vs 14mm fisheye mess

Yes, I will also tune down to 2,7k resolution then :-(
This way at least I can be sure, that this cloud shadow stuttering won't happen again.

With only using 2,7k I could have bought the P3A and saved some money, since there is no real advantage right now...
Maybe DJI will ramp up the bitrate for 4k with some firmware update, but I don't think this will happen.

Thanks for the help guys!

The only thing that stays in my head is, why can't we see this effect happening on many more videos out there?

ha, now it happened to me

1:05 on the water
2:30 on the sand

and obviously i didnt notice until i was home.
hm.

I am sorry, that I made you aware of this problem :-/

At least I now know that my unit isn't faulty ^^

Thanks for the video! It looks nice by the way...

Edit: Oh, what is a bloom drop test?

slaindevil Posted at 2016-7-12 09:20
I am sorry, that I made you aware of this problem :-/

At least I now know that my unit isn't faulty ...

thanks
bloomdrop = Philip Bloom made this amazing opening shot for a video in Iceland.
I tried to recreate it with Litchi app waypoints for a video i m working on. quite tricky to get it smooth, still not happy.

go to 1:40

Oh I see... Yeah, this shoot looks simply awesome... Wow! I definitely have to try that too...
Thanks for sharing!

Sebb Posted at 2016-7-12 16:26
thanks
bloomdrop = Philip Bloom made this amazing opening shot for a video in Iceland.
I tried to r ...

Great shot! Too bad its 'awesomeness' depends on the landscape. If I'd make that shot in my area, it wouldn't nearly be that epic.