Video Production Stack Exchange is a question and answer site for engineers, producers, editors, and enthusiasts spanning the fields of video, and media creation. It only takes a minute to sign up.
Sign up to join this community
I try to create a Picture In Picture effect where a smaller video playing in parallel on top of a background video. I dragged two videos of same size and codec into timeline and scale one of the video size to 60% from its original, keeping the background video to its original size.
After I down scale the video I notice the quality of the video deteriorate, as shown in the screenshot the text clearly gets blurry. Why this is happening and how to resolve this problem?
Why this is happening: because an interpolation method the Premiere uses for scaling kills high frequency details (ie., sharp edges, as text or some thin elements of the GUI are).
A scaling interpolation method (in our case, Lanczos method, as an Adobe employee mentions here) is an algorithm used to map an array of pixels of one size into an array of a different size. You have a 200x200 image and want it to be 400x400. What do you do? Quadruple each pixel of an original image so it will take 4 pixels in an upscaled image? Or blend the neighboring ones somehow?
There are a couple of algorithms developed, like Nearest Neighbor, Bilinear, Bicubic and Lanczos. They differ in computational complexity and in the quality of the results they produce. And the quality (here we finally come to your question) also depends of the nature of the source material. Adobe chose Lanczos because it does a decent job at scaling natural images taken by camera. If this was an image of a person, you would expect that a scaled down version will not have the individual hairs and the little marks on the skin to be seen in the same detail as they are seen on an original larger image.
Yet, you are scaling down a different kind of footage – the screen capture of a software GUI. The one you'd want to see all the sharp details even on a scaled down image. As you see, the Lanczos method does a bad job here.
And we come your second question: what algorithm would do a better job, or how to fix this?
Short answer: in Premiere, you can't. Long answer: a scaling algorithm we need is a Nearest Neighbor algorithm. This one preserves the sharp edges of the GUI just as we like it. Adobe After Effects has it (called "Draft" scaling quality). Premiere doesn't (natively). You can try your luck searching for "Nearest Neighbor scaling plugin" for Premiere.
As of Adobe Premiere Pro 2020 (14.3.1) you need to use plugins to be able to use of different interpolation algorithms for scaling footage.
For example the free 'PixelPerfect' Plugin by Autokroma adds Nearest Neighbor, Linear Interpolation and Nearest Neighbor with Anti Aliasing: https://www.autokroma.com/Vizual
Since no one else has done so yet, I'm going to attempt a super low-tech answer to your question here: when you downscale you're literally user fewer pixels to display the image so any downscaled image is going to lose some image sharpness and fine detail (due to how the software is resampling the image); to my knowledge, the only thing you can do about this in Premiere is to use a Sharpen effect on the scaled footage to reintroduce some image sharpness - don't overdo it, though.
I'm not sure what sort of resampling Premiere does but I'm guessing that you might get better results going into a program like After Effects to do your picture in picture because you can alter the sampling method that the program uses (draft, bicubic, bilinear) which might give a better result. Please, please correct me on this if I'm wrong!
The best solution here, to prevent blurriness, is to have your main workspace video in 4k despite if the main video is only 1080p. This way as you scale down the clips, it will retain most of it's pixels at least until you hit 1/4th size (1/2 high, 1/2 tall) anything further than that and you will start to get blur again but since it's 4k, the blurred pixels will be much smaller and harder to notice. By taking a 1080p video and shrinking it, you are throwing away pixels so Premier scales the video into less pixels giving you blur and losing fidelity.
