In my input video is a 48 second range that I wish to speed up. I wish to save only that sped up portion to a new video.
Solution:
ffmpeg -y -ss 00:00:03 -t 00:00:48 -i input.mp4 -an -crf 20 -pix_fmt yuv420p -vf "scale=1080:-1, setpts=PTS/10.0" "output.mp4"