Shotcut Tutorial 4: Using filters
Learn how to use filters with your VR video content, using the free open-source VR video editing software, Shotcut.
This is a guest post by VR creator XR Stereo Video - most videos on his DeoVR channel are rendered in Shotcut. Check out his other Shotcut tutorials:
- Shotcut Tutorial 1: Beginner’s Guide to Shotcut (free VR video editor)
- Shotcut Tutorial 2: Adding text to VR videos and more
- Shotcut Tutorial 3: Exporting a thumbnail or 2D video from VR (currently reading)
- Shotcut Tutorial 4: Using filters
- Shotcut Tutorial 5: How to make high-resolution foveated 3D VR180 video
Using filters with Shotcut
Just like most complex video editors, Shotcut can alter the image both for regular and VR video using a range of filters. Here's how:
To alter a video clip, select it in the Timeline by clicking on it, then head over to the “Filters” tab/ sub-window and click on the “+” sign to select the filter.
The advantage over command-line ffmpeg is that in Shotcut, you can see the changes in real time and fine-tune each video clip.
VR filters
360:Transform
With this filter, you can rotate 2D 360 and 3D 360 videos on the vertical axis, for example, to recenter them. This is also useful if you’ve rendered your video from your 3D VR180 camera as 3D 360. This filter can rotate 2D 360 videos on the other two axes as well; support for 3D isn’t directly implemented yet in Shotcut - you would need a more complex workaround using FFmpeg.
360:Stabilize
This filter is probably the best and most complex VR filter that Shotcut has. It only supports stabilizing 2D 360 videos, but you could also stabilize 3D 360 and 3D VR180 videos by involving FFmpeg.
When this filter's “Analyze” box is ticked, the video will write to a file when the video is played back. Then untick the “Analyze” box and play it back again - the video should be stabilized. Experiment with the various settings for your personal needs.
360: Equirectangular Mask
This filter will reduce the field of view to mask out unwanted details in the periphery of the image
By default, this filter only supports 2D 360, but with a workaround also involving FFmpeg, I’ve used it to mask my shadow in 3D 360 and 3D VR180 in the Laura Cosoi videos I’ve posted. Watching the video, you can see my shadow when Laura was getting out of frame at the end.
You can also see that I had to shoot the video with the camera handheld and I have actually used the 360:Transform filter with the help of FFmpeg transformations in order to restabilize the 3D VR180 video.
Regular filters
There is a long list of filters/ tools that Shotcut has, such as:
Sharpen – the sliders are easy to use. You might want to use a Small size and experiment with the Amount
White balance – this one is also easy to use with its slider or text box
Reduce Noise: HQDN3D - a high-quality noise reduction filter.
You’ll want to stay pretty low on spatial denoising with VR video, such as 4% . The more static the video and its subjects are, the higher you can go on temporal denoising, which averages pixel color over time and the better the denoising will be, the higher the value. Use lower values if there is more movement in your clip, otherwise there will be a sort of ghosting where movement is. Use higher values if there is less movement. It is best to split the clips into segments and denoise with higher temporal values where there is less movement and lower temporal values where there is more movement.
Brightness, Contrast and Color Grading (the latter can be used for shadows, mid-tones (gamma) and highlights.
There are also brightness and contrast filters with simple sliders. When I recently wanted to brighten the shadows in the Laura Cosoi video, I thought it didn’t have shadow control. However, it does have shadows, highlights and midtones (gamma) controls, found in the “Color Grading” filter.
Chroma key - for greenscreen and black screen overlays
With this filter, you can overlay greenscreen, blackscreen or other key colors content on your videos, in a similar way to passthrough for AR in your VR headset. When the right key color is selected, it will be transparent in your overlayed video.
This filter is also often used in conjunction with the “Alpha Channel: Adjust“ filter, where you can, for example, choose the “Shrink soft” mode.
There are also hue, saturation and all sorts of other filters available in Shotcut, depending on your personal needs, so you can get the best result out of your videos.
Join the discussion at the DeoVR forum, Facebook and Reddit.
