Due to the limited budget and high maintenance cost, it is difficult to deploy a large amount of roadside units (such as 802.11 base stations) to cover all road sections. Through a sparse network infrastructure, vehicles experience long download delay for large-size videos. In this paper, we proposed a Video Frame Sharing Mechanism (VFSM) to improve the performance of download sessions. We also investigate how to prevent selfish nodes in VFSM. Through VFSM, users can download video frames from RSUs (Road Side Units) or share video frames with neighboring vehicles by V2V communications in a fair manner. As a result, the video downloading can be speeded up and the video quality can be substantially improved. The extensive simulation results show that the our proposed protocol is practical.