rtmpsrv merely reports whatever the Flash client spat out. In your case, your browser/Flash combo chooses 360p. It might just be a default, or it might be choosing based on a measurement of your network speed. You might be able to toggle a menu in the flash player to get it to use a higher resolution stream. None of this is controlled by rtmpsrv, it's all up to the Flash client.
My old get_hulu script let you explicitly choose the quality that you wanted. The
get-flash-videos plugin would always grab the highest available. But these are all external to the rtmp programs.