Command line utility ffmpeg can be used to scale a video to a specific widht and height. Here are some examples.
Resize to given width and height
This may not preserve the aspect ratio.
$ ffmpeg -i input-file.mp4 -vf scale=300:200 output-file.mp4
Resize to given width or height
Here we specify either width or height. The other value is auto calculated to preserve aspect ratio. We put -1 for other value.
$ ffmpeg -i input-file.mp4 -vf scale=-1:200 output-file.mp4
