Cognitive radio, which enables dynamic access of under-utilized licensed spectrums, is a promising technology for more efficient spectrum utilization. Since cognitive radio enables the access of larger amount of spectrum, it can be used to build wireless mesh networks with higher network capacity, and thus provide better quality of services for high bit-rate applications. In this paper, we study the multi-source video on-demand application in multiinterface cognitive wireless mesh networks. Given a video request, we find a joint multi-path routing and spectrum allocation for the session to minimize its total bandwidth cost in the network, and therefore maximize the number of sessions the network can support. We propose both distributed and centralized routing and channel allocation algorithms to solve the problem. Our algorithms not only increase the maximum number of concurrent sessions that can be supported in the network, but also improve each session's adaptivity to spectrum m...