I need someone who is an expert with using ffmpeg.
This is what I need to happen: my server downloads a video file (FLV) from an external site, ffmpeg encodes it to mp3, then the user downloads the mp3. The problem, is I need ffmpeg to encode the video as it is being downloaded to the server - and output that immediately to the user. This way the user can begin downloading the MP3 immediately without having to wait for my server to download the video file completely. I will be paying you to write the code for this process so that ffmpeg encodes the video as it is being downloaded (maybe using piping). I will then connect your code to my PHP site, so keep in mind that the ffmpeg commands will be called using exec() from PHP.
This CAN be done. There are sites that do this like mp3ify.com and getaudiofromvideo.com - take a look at those if you want to see the feature in action.