End-to-end Quality of Service (QoS) provision to video-streaming applications over Mobile Ad hoc Networks (MANETs) poses a specially challenging problem because of the dynamic inherent characteristics of these networks. To cope with this, in this paper we propose a Cross-Layer (XL) network architecture design to optimize the overall performance of video- streaming services over MANETs. The idea relies on applying several optimization strategies to different network layers in a holistic way. In our proposal, a real-time XL Optimizer (XLO) collects information about the node and network states from different layers of the network's protocol stack. In order to minimize the error between received and transmitted video signals, the XLO module takes then the necessary decisions to act on different layers' parameters dynamically. Preliminary simulation results show that our proposed network design can improve the performance of video-streaming transmissions over MANETs in spite of frequent changes in network topology and node conditions.