Strange Video Artifacts In Low Light (DJI Mavic Air)

[Voltaic]

Hey guys! I've been a longtime lurker on these forums but this is my first post. I'll preface by saying that I've already sent an email to DJI Support but wanted to get some feedback from other users. Perhaps this is just a limitation of the tiny camera sensor in the Mavic Air and the MP4 compression the aircraft uses but I figured I would put this out there in the event anyone else is trying to shoot low light / night stuff. I've just seen some other videos online that don't seem to show this sort of artifact but given the compression that Vimeo and YouTube can put on the videos, perhaps it just gets swallowed up? Anyways, here we go.

Problem? I am seeing a strange video artifact when shooting video in low light. There's a 'pulse' to the video every two seconds or so and the areas of the shot with lower exposure seem to get a bit darker.

I am shooting in full manual video mode using D-Cine Like and 4K 24 fps but the issue is present in auto mode provided I'm in a very dark environment. I see the artifacts no matter which ISO. Prior to my shoot last evening, I had not done any lowlight tests outside of some sunset or sunrise shooting but even then, it was not necessarily dark.

And before anyone raises a concern, I am Part 107 certified and I was only flying within 30 minutes of sunset. I play by the rules lol.

Was unit in a crash? No, I've owned the Mavic Air since the beginning of May and it has a flawless flight record.

What have you tried so far? I was worried it may be the memory card so I switched to internal storage but the issue is present there as well. I've been able to recreate the issue in my office with the lights off and the blinds closed (see video link below). It does seem that when enough light enters the frame, the issue goes away so again, this could be a matter of how the camera is compressing the video.

What device are you using ( iphone , ipad, Samsung , etc)? iPhone 8 running iOS 11.41

What firmware are you running ( aircraft, remote controller)?

Mavic Air - 01.00.0400
Remote Controller - 01.00.0100

What Go app version are you using? 4.2.24

Any modification? Not sure if it counts as a modification but I do have a PolarPro UV filter on the camera. It's just a clear filter to protect the lens, so it should not cause any limitations on light getting to the camera sensor.

I also use a PolarPro phone mount for the controller so that it is top mounted instead of on the bottom. This forces me to use a different micro USB to Lightning cable but I don't see how that would have any effect on the video quality (open to suggestion if it could cause issues though!).

Did you change anything or install any apps? I'm running a fairly stock aircraft and the DJI software. I haven't been able to justify the cost of Litchi yet given I'm still kind of learning.

Do you have a video or pictures of the problem? I'll leave this live for a week or so, but here's a link on my dropbox - Dropbox - DJI Mavic Air Video Artifact.MOV

 

[Voltaic]

Well DJI already replied and they basically said it's normal. Not the end of the world and it's honestly what I expected but still a bummer.

 

[Qoncussion]

I believe what you are describing is the keyframe interval - and it is perfectly normal. On the Mavic, if memory serves, every eighth frame is a keyframe (a frame containing the full image). Not every frame in video is a full image. The seven frames that occur between keyframes are simply recording any changes, such as camera movement, or changes in the scene. This indeed would be more noticeable on a low light shot.

 

[Voltaic]

Yeah I'm pretty sure you're right but the interval is way slower than 8 frames, it's more like every 50 frames or so (I think it happens every two seconds, at first I thought maybe it was the LEDs on the front of my Mavic Air).

That said, after DJI initially replied that this was normal, they've now replied asking me for additional information so I'll post back here if I hear anything else.

I do think this is just a limitation of the hardware but as long as DJI would like to explore the issue with me, I'll provide the data