This paper addresses the End-to-End Quality of Service (QoS) guarantees and control for multimedia content delivery over heterogeneous networks, with a particular focus on end user terminal perspective. We design and implement a multimedia terminal which contains several probes to monitor network conditions and end user perceptual characteristics. A series of QoS mapping between perceptions and adaptation are calculated with the parameters provided by these probes, facilitating content adaptation by any generic adaptation server or intermediate service. Such a design approach illustrates a next- generation multimedia end user system supporting End-to-End QoS control in multimedia content adaptation over a heterogeneous delivery chain.