Convert YouTube ripped video to H.264 with FFMPEG

Youtube encodes its videos in the VP9 (video) and Opus (audio) codecs. These files won’t open in QuickTime Player but open just fine using VLC Player. But what if you want to open the files for use in Adobe Premiere? VP9/Opus is not supported in Premiere so it must first be converted. The following ffmpeg command will take care of this for you:

ffmpeg -i inputfile.mp4 -vcodec libx264 -acodec aac output_file.mp4