This is a very complex methodology, more than a few sentences can fully explain. The most complex of them all, specifying what video scaling algorithm to use when scaling. You can read more about the encoding options here and here. Scale a video and also encode or compress it at the same time: ffmpeg -i input.mp4 -vf scale=3840:2560 -c:v libx264 -preset fast -crf 22 output.mp4 So if it was a video of 16:9 ratio then output.mp4 will be 1280×720.
This sets the width of the video as 1280 and then will automatically calculate the height keeping with the ratio of the input video. If you want to scale a video to a custom width but keep the ratio you can input -1 after the width: ffmpeg -i input.mp4 -vf scale=1280:-1 output.mp4 Make a video half its original size: ffmpeg -i input.mp4 -vf scale=iw/2:ih/2 output.mp4 Scaling by resolution with the ratio To double a videos resolution: ffmpeg -i input.mp4 -vf scale=iw*2:ih*2 output.mp4 To scale the video file by “times its self” such as twice as large or twice as small you can use variables * or / along with iw and ih to specify the input width and input height respectively. This will upscale input.mp4 to be 4k resolution. If you know the desired resolution, simply setting the specific width and height for scaling with the scale flag: ffmpeg -i input.mp4 -vf scale=3840:2560 output4k.mp4 There is no flag or parameter to do either upscaling or downscaling rather this is determined by the values set for the scale flag. Or an advanced scale with flags and encoding: ffmpeg -i input.mp4 -vf scale=2560x1440:flags=lanczos -c:v libx264 -preset slow -crf 20 output_compress_1440p.mp4 The basis of scaling a video with FFmpeg uses the scale flag after the filtergraph ( -vf), then you can either do basic video scaling such as upscaling the video to twice the original resolution: ffmpeg -i input.mp4 -vf scale=iw*2:ih*2 output.mp4
Scaling a video means to make it either larger (higher resolution) or smaller (smaller resolution). How to do video scaling using FFmpeg with examples for different types of upscaling and downscaling methods.
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