youtube-dl --extract-audio --audio-format mp3
[user1@localhost ~]$ youtube-dl --extract-audio --audio-format mp3 https://www.youtube.com/watch?v=nI3sH53SH2k
[youtube] nI3sH53SH2k: Downloading webpage
[youtube] nI3sH53SH2k: Downloading video info webpage
[youtube] nI3sH53SH2k: Extracting video information
[youtube] nI3sH53SH2k: Downloading MPD manifest
[download] Destination: testfile-nI3sH53SH2k.webm
[download] 100% of 129.58MiB in 00:31
[ffmpeg] Destination: testfile-nI3sH53SH2k.mp3
