It doesn't work. I've tried -i A Christmas Carol (1999) 4K Upscale AI.mkv -preset slower -c:v libx264 -crf 17 -c:a aac -b:a 192k A Christmas Carol (1999) 4K Upscale AI.mp4
AND
ffmpeg -i A Christmas Carol (1999) 4K Upscale AI.mkv -preset slower -c:v libx264 -crf 17 -c:a aac -b:a 192k A Christmas Carol (1999) 4K Upscale AI.mp4
neither works. They say no such file or directory. Am I putting the command in wrong ?