We propose a cross-layer design framework for supporting delay-critical traffic over ad hoc wireless networks and analyze its benefits for video streaming. In this framework, link capacities and traffic flows are jointly allocated to minimize the congestion experienced by video packets. The optimal solution, calculated via time sharing among different transmission schemes, concentrates resources only on active links. Experimental results on a simulated network illustrate the advantages of cross-layer design over another method based on oblivious layers. With one path, the cross-layer approach yields a 10-fold gain in supported data rate or equivalently 8.5 dB improvement in PSNR of achievable received video quality. Using 3 paths, the gain is 3-fold in rate or 5 dB in video quality. While multipath routing is essential to high data rate in oblivious-layered design, cross-layer design achieves efficient resource utilization regardless of the number of routes.