$ ffmpeg -i inVideo.mp4 -s 1920x1080 -c:v libx264 -crf 18 -acodec copy outVideo.mp4

$ ffmpeg -i input.avi -vf scale=320:240 output.avi

$ ffmpeg -i inVideo.mp4 -vf scale=320:-1 outVideo.mp4

• Scaler documentation : https://ffmpeg.org/ffmpeg-scaler.html

#
# You can specify which algorithm is used for resizing with the -sws_flags option. For example, to use bilinear instead of the default bicubic scaling:
#
$ ffmpeg -i inVideo.mp4 -vf scale=504:376 -sws_flags bilinear outVideo.mp4
#
# To set multiple flags you can combine them with a + sign. For example:
#
-sws_flags lanczos+full_chroma_inp
#
# You can also specify the options directly in the scale filter, for example:
#
-vf scale=1920x1080:flags=lanczos