Using ffmpeg to compress, convert, and resize videos

To compress for web at a reasonable broadband bitrate of about 1.5Mbps video / 128kbps audio:

ffmpeg -i source.mp4 -c:v libx264 -b:v 1.5M -c:a aac -b:a 128k target.mp4

To scale down a high-resolution source video to something more reasonable for Web (qHD for cellular, HD for broadband), the -filter:v argument is used:

ffmpeg -i source.mp4 -c:v libvpx-vp9 -b:v 0.33M -c:a libopus -b:a 96k \
-filter:v scale=960x540 target.webm