Basic resize of a video
Convert to 1080p (1920x1080)
Convert to 4K (3840x2160)
Maintain aspect ratio
https://ffmpeg.org/ffmpeg-filters.html#scale
https://write.corbpie.com/upscaling-and-downscaling-video-with-ffmpeg/
https://trac.ffmpeg.org/wiki/Scaling
https://write.corbpie.com/a-guide-to-upscaling-or-downscaling-video-with-ffmpeg/
https://superuser.com/questions/547296/resizing-videos-with-ffmpeg-avconv-to-fit-into-static-sized-player/1136305#1136305
https://en.wikipedia.org/wiki/Lanczos_resampling