People carry their mobile devices, such as smartphones and tablets, all the time, and generate tremendous amount of mobile video traffic. Per a Cisco report, mobile video represents 51% of mobile traffic in 2012, and mobile video users demand for short waiting time when clicking on a video. Unfortunately, network conditions are diverse and changing over time and locations, which leads to fluctuating throughput and thus degraded viewing experience. To cope with this issue, opportunistic transmissions may be leveraged, which come in different forms, including (i) prefetching and (ii) delay-tolerant transfer. Prefetching tries to download videos that are likely to be watched in advance, while delay-tolerant transfer attempts to postpone downloading videos. Both of them aim to transfer videos under the best channel conditions.