# Short Summaries

### [Vantage: optimizing video upload for time-shifted viewing of social live streams](https://dl.acm.org/doi/10.1145/3341302.3342064) - **Ray et al., SIGCOMM' 19**

Social live video streaming (SLVS) applications have audiences with a wide variety of viewing delays, and thus have varying degrees of latency tolerance. However, existing approaches for handling network bandwidth variations(in mobile uplinks) are tailored for one particular viewing delay.&#x20;

The authors analyzed a real-world trace about the variability of bandwidth in mobile upload links and observed that: periods of low/high bandwidth are common and more bandwidth is gained during high periods than is lost during low periods.&#x20;

As a result, the authors proposed a method called **quality-enhancing retransmission**. Low-quality real-time frames transmitted during periods of low bandwidth can be retransmitted at a higher bitrate during a later period of high bandwidth while the live streaming session is ongoing, thus improving the video quality for delayed, time-shifted viewers. Choosing the optimal tradeoff between the drop in real-time quality(because of the retransmission) and the improvement in delayed video quality can be envisioned as a quality (SSIM) maximization problem across the time-shifted delays
