We propose in this paper a novel content-aware stream-level approach to authenticating multimedia data transmitted over wireless networks. The proposed approach is fundamentally different from conventional authentication methods and offers robust authentication for multimedia data in the presence of channel noise. The scheme is designed in such a way that it facilitates explicit capture and exploitation of channel condition as well as how the multimedia content is packetized and transmitted. The design allows the integration of authentication with the framework of Joint Source and Channel Coding (JSCC) to achieve adaptiveness to the content and efficient utilization of limited bandwidth. We have realized the proposed scheme through optimal resource allocation and authentication graph construction. Experiment results demonstrated the effectiveness of this novel approach.