We propose a streaming video system, which can be used in various system environments. This system has three features for providing real-time video delivery services in the Internet. The first is to use QoS (quality of service) control rules adapting to the system environments. The second is to improve estimation accuracy of the network conditions while a user is watching a stream. The third is to notify QoS degradation factors to the user actively. These features make it possible to provide streaming services with a high level of user satisfaction. We show an experimental system in our laboratory as an implementation example.