We propose the method of application level multicast for delivering real-time streaming video over Internet, and realized with a prototype of multiparty videoconference system-Metrino. Different from conventional wisdom to use simple source-specific trees or shared overlay, we constructed a bone share tree with key nodes, and added additional minor nodes to nearest node as source-specific tree when new endpoints joined in. The whole video streaming delivery graph constructed as a Sunflower Delivery Graph (SDG). SDG can keep some level of efficiency while avoiding the tree reorganization frequently. More over, Metrino is able to deal with difference scale of end users from several to hundreds due to its scalable architecture.