[FFmpeg-user] Download audio only bytes with ffmpeg

[Feras Salim]

Hi,
I noticed a few youtube downloaders out there give the option of
downloading only the audio and skipping the video stream. I was wondering
if that is possible with ffmpeg. Given we have an url that has flv or mp4
source and is seekable, is it possible to download only the audio form it
and convert to mp3, without having to download the whole file first. I
tried the following commands but all of them resulted in using the
bandwidth to download the entire video:

ffmpeg -i "url" output.mp3
ffmpeg -i "url" -vn -c:a copy output.mp3
ffmpeg –i video.flv –vn –c:a libaac –ar 44100 –ac 2 –ab 64k audio.mp3
ffmpeg -i video.flv -ab 160k -ac 2 -ar 44100 -vn audio.mp3
ffmpeg -i “input” -vn -acodec copy output.mp3
ffmpeg -i "input" -vn out.mp3

Is doing something like that even possible?