How do I use piping with ffmpeg?

Question

My goal is to use wget to download an flv file, and pipe the output to ffmpeg to convert it to an MP3. This way the user can download the MP3 without waiting for the FLV to download to my server first. I've been playing around with it, and it seems that ffmpeg can only do piping on raw video. So I was working with something like this:

wget -O - 'videoinput.flv' | ffmpeg -y -i - -vcodec rawvideo -f yuv4mpegpipe - |  ffmpeg -y -i - -ab 128k audiooutput.mp3

Anybody have experience with this type of on-the-fly ffmpeg encoding process?

Answer 1

I haven't tested this but should be like this or very close.

wget [URL] | ffmpeg -i pipe:0 -vcodec mpeg4 -s qcif -f m4v -y output.flv

Answer 2

A potentially better option to piping from a separate HTTP client is to use ffmpeg's built-in one. At least newer versions can take a URL as an input file argument. This way FFmpeg can pull the file down itself, and for formats that have container data near the end of the file, it can (if the server supports it) grab that portion of the file first, unlike piping from curl or wget, which fetch the file sequentially. See http://ffmpeg.org/ffmpeg-all.html#http