You tube to mp3 converter

I want a script similar to D I R P Y . COM - [login to view URL] capable of : 1). Converting You tube to mp3 with features shown in the screenshot. 2). Capable of utilizing multiple servers so can scale easily, the plan is to create a front-script on a dedicated-box which handles user-requests and distributes work to other scripts on slave servers so the front-script is always available serving requests fast - the slave scripts must validate/authorize input from valid domains/ip's so external scripts cant abuse our server resources.. 3). We don't need the trimming features (start and end time) ID3 tags will be sufficient. 4). The script should be able to spit out files in real-time (download is pushed to user immediately while the file is still converting) just like d i r p y did, realtime transcoders are available and I guess this can also be achieved via FFMPEG. Thanks, PM for any clarifications.