Combine audio and video files with ffmpeg

➜ ffmpeg -i video.mp4 -i audio.mp4 -c:v copy -c:a aac output.mp4

I needed to combine two files (video and audio) so I can watch them together. This ffmpeg spell did the job and was surprisingly fast.

ffmpeg ## Runs ffmpeg 
-i video.mp4  # -i [path/url] is for input files
-i audio.mp4
-c:v copy # -c is for codec, with stream specifier of (v)ideo and special value `copy` that indicates no re-encoding
-c:a aac # -c is for codec, with stream specifier of (a)udio and a codec aac
output.mp4 # output file

ffmpeg docs