How to fix frame flicker and digital noise in drone videos
Drones are fascinating little (and not that little) flying bugs. They have opened so many opportunities for filmmakers, scientists, real estate agents, marketers and many other specialists. However, the highest demand for these high-tech fliers is definitely in video and photo content creation.
As with pretty much anything, they have their own issues. Some of the biggest concerns filmmakers have about the video quality of UAVs lie in the significant digital noise in the resulting picture, together with frame flicker, compression artifacts, repeated noise and soft spots in shadows.
The good news is that with an advanced digital noise reduction plug-in like Neat Video, all of these issues can be addressed and with the right approach you can usually achieve breathtaking results. In this article, we’ll discuss some of the limiting factors of these tiny cameras and offer some solutions to use Neat Video to improve the video quality of your spectacular drone shots.
1. Intensive digital noise in drone footage
The relatively high intensity of the digital noise in videos recorded for example by DJI Mavic Pro is just a limitation of the camera. It does not handle low light well enough, which means even low-ISO videos are quite noisy. At this stage, cameras of consumer-grade drones are simply not as capable as the regular DSLR cameras.
This one is fairly simple. Drone footage can be denoised pretty much in the same as any other video clip, with one difference.
Just open your video in your preferred video editing software (Neat Video supports Premiere Pro, Final Cut, Resolve and heaps of host applications), pick a key frame (more about key frames in Frame Flicker in Drone Video section below) and build a noise profile.
If you don't have featureless areas in the video, use another video shot in same camera mode, use one of generic profiles provided with Neat Video or use Calibration Target to prepare a test shot in same camera mode and then build a noise profile from it.
In case you have different noise levels in featureless areas and in areas full of details, tweak the noise level using Noise Level Tuning Assist. Here you want to remove all the video noise, including dots and lines. Then adjust other filter settings to your liking.
As you can see, this process is pretty much the same (except the key frame part) as with any video from a regular video camera. You just build a noise profile and adjust the filter settings in the regular way, which will reduce the noise quite well.
2. Frame flicker in drone video
The other issue drone pilots have to deal with is frame flicker. With this phenomenon, it looks like the video suddenly changes in brightness and detail every 8 th frame (sometimes every 9th, 16th frame, etc). This is because the drone’s video codec treats these groups of frames (8 at a time) together, in order to achieve better compression. However, the effect is the jarring change in brightness and jumps of details that we recognize as flicker. Sometimes it’s almost invisible, other times – very distracting.
To remove the frame flicker (1) build the noise profile using a key frame (the first frame in a group of frames usually contains the strongest noise that allows to get a sample of best preserved noise) and then (2) apply the strongest temporal processing with the largest Radius of 5 frames.
The easiest way to find a key frame is to look at the Lumetri Scopes (Luma, Luminance, etc.; names may vary from one video editing software to another) while going from one frame to another in the timeline of your video editing software. You will see a jump in luminance that takes place every 8 frames. Once you have found a key frame, open Neat Video and build a noise profile on that frame. Then adjust the Temporal Filter Radius to 5, apply the filter and check those Scopes in the video editing application again to see if the jump of luminance has been reduced now. Also check that in playback. The flicker should be reduced now.
3. Compression artifacts
Codecs employed to compress drone videos not only introduce flicker, but also introduce blocky compression artifacts into the picture. They are mostly noticeable when the picture is very rich in details.
If you find a key frame in such a clip and then move one frame forward, you will see some additional compression artifacts which appear as blurry blocks. Moving to each following frame you will see more and more of those blocks showing up. Those artifacts are introduced by the codec because it cannot squeeze all the picture information into the limited storage space that it has been allowed. So, the codec has to throw away some details. When there is not much detail in the video, codec is able to squeeze them all into the same limited storage space without introducing those artifacts.
The same method can be used here as in the case of the frame flicker: (1) build a noise profile using a key frame (to get a sample of best preserved noise) and then (2) apply the strongest temporal processing with the largest Radius of 5 frames. In addition, (3) disable Spatial Filter (unless you really need to further reduce any remaining noise).
4. Soft Spots in shadows
The other very annoying characteristic of drone video is soft and blurry spots in shadow areas. This happens when you set Sharpening to 0 and below in camera settings.
You may not realize it, but Sharpening is linked to in-camera noise reduction in most popular drones including DJI Mavic Pro, DJI Mavic Air, DJI Phantom and other drones. Negative Sharpening also enables the in-camera noise reduction function, but what it does is far from quality noise reduction. It just blurs and ruins all the details in shadows where the video noise is the most pronounced.
The worst thing about this is that once it is applied to your video there is no way to get those details back. You will get much better results using an external denoiser in post-production.
To avoid blurry spots in shadows, adjust drone’s Sharpening to +1 or more. This will make the recorded video a bit more grainy, but you will be able to clean up that noise using Neat Video denoiser (check the previous and following tips) and achieve better overall results.
Keep the whole picture in mind.
Since drone videos often contain several of the above problems at the same time, these recommendations should better be applied together to achieve the best results. So when you’re assessing your clips, take all these things into account when deciding how best to treat your video. Together, they can make a huge difference in creating a result that exceeds your expectations.