auto-merging mp3 files (overlay, not concatenation), live on web server

[Web]

hi, i need to merge the sounds of two mp3 files into one mp3 file that sounds like it's playing the two original files simultaneously, and i need to do it all automatically on a website, after a user uploads their 2 files to be merged.

ideally i'm looking for a php solution but i've found nothing in any language yet. can anyone help with this nearly impossible task?

[inimino]

It would be impractical to do this in pure PHP, but once the files are uploaded on the server, you can launch another process using a commandline utility to mix the audio and encode the result. The PHP page can then monitor the progress of the utility and offer the mixed file for download or further processing once it has completed.

[Web]

what program could i launch to do the merging task?

[inimino]

sox

[the_pm]

This sounds like something that could be accomplished in Flash. Basically a Flash process would encode both tracks and then play then simultaneously launch both clips at the same time.

To be honest, I'm not entirely sure what this would entail. Possibly Adobe Flash Media Server? http://www.adobe.com/devnet/flashmediaserver/