nginx dynamically changing config for rtmp

Question

I'm using the RTMP module to push out an rtmp stream and i'm looking for ways I can dynamically pass in variables that can be used in the push stream.

For example:

    application live {
        live on;
        record off;

        #Youtube
        push rtmp://a.rtmp.youtube.com/live2/$my_publish_key;

        #Facebook
        push rtmp://example.com/$my_publish_key_2;

    }

Are there any tricks to be able to dynamically pass in variables that could be used to complete the urls?

Ideally these would be passed as $args that could then be parsed out. Another idea would be if it's possible to set a variable in nginx from a value retrieved from a URL that could then be used.

Any ideas? Thanks!