Transmitting video streaming is challenging as it requires strict network quality of service (QoS). To enhance the performance, multipath transmission strategies are widely used to extend bandwidth for video streaming services. To apply this strategy, flow rules should be stored in OpenFlow switches along the multiple paths, which consumes a large amount of ternary content-addressable memory (TCAM). In this paper, we propose an on-demand multipath transmission approach for video streaming services using a cross-layer collaboration architecture. In the proposed method, the player buffer is monitored and a bandwidth adjusting request is sent to the SDN controller when the buffer size is below a certain threshold. The SDN controller will accordingly build multipath for the requesting streaming. To save the limited TCAM resources, a hard timeout based multipath retrieval mechanism is employed to release established multiple paths. Experimental results proved that the proposed method can effectively improve the quality of video streaming transmission, as well as reduce the TCAM cost in SDN.