GRACE：基于数据可伸缩自编码器的抗丢失实时的视频通信
GRACE: Loss-Resilient Real-Time Video Communication Using Data-Scalable Autoencoder
摘要：
在许多实时的【形】视频应用中，我们看到越来越多的需求（特别是在长延迟和动态带宽中）允许客户端在接收到其数据包的任何（非空）子集后对每个帧进行解码，并提高每个新数据包的质量。我们称之为数据可扩展交付。不幸的是，现有技术（例如，FEC、RS和喷泉码）都有不足之处：它们需要传递最小数量的数据包来解码帧，和/或在预期数据包丢失时用冗余填充视频数据，如果没有数据包丢失，这会损害视频质量。这项工作探索了一种新的方法，灵感来自神经网络自动编码器的最新进展，使数据可扩展的交付成为可能。我们提出了格雷斯，一个具体的数据可伸缩的实时的【形】视频系统。在相同的视频编码下，当没有数据包丢失时，Grace的质量略低于没有冗余的传统编解码器，但随着每个丢失的数据包，其质量下降的幅度比现有的解决方案要小得多，允许客户端在帧延迟和视频质量之间灵活地进行权衡。Grace有两个贡献：（1）它训练新的自定义自动编码器，以平衡压缩效率和弹性，防止各种数据包丢失;（2）它使用一种新的传输方案，将自动编码器编码的帧作为可单独解码的数据包传输。我们在真实的网络痕迹和视频上测试了Grace（以及传统的丢失恢复方案和编解码器），结果表明，虽然Grace的压缩效率略低于经过大量工程设计的视频编解码器，但它显著降低了尾部视频帧延迟（在第95百分位数时降低了2 $\times$），视频质量略有降低
英文摘要：
Across many real-time video applications, we see a growing need (especially in long delays and dynamic bandwidth) to allow clients to decode each frame once any (non-empty) subset of its packets is received and improve quality with each new packet. We call it data-scalable delivery. Unfortunately, existing techniques (e.g., FEC, RS and Fountain Codes) fall short: they require either delivery of a minimum number of packets to decode frames, and/or pad video data with redundancy in anticipation of packet losses, which hurts video quality if no packets get lost. This work explores a new approach, inspired by recent advances of neural-network autoencoders, which make data-scalable delivery possible. We present Grace, a concrete data-scalable real-time video system. With the same video encoding, Grace's quality is slightly lower than traditional codec without redundancy when no packet is lost, but with each missed packet, its quality degrades much more gracefully than existing solutions, allowing clients to flexibly trade between frame delay and video quality. Grace makes two contributions: (1) it trains new custom autoencoders to balance compression efficiency and resilience against a wide range of packet losses; and (2) it uses a new transmission scheme to deliver autoencoder-coded frames as individually decodable packets. We test Grace (and traditional loss-resilient schemes and codecs) on real network traces and videos, and show that while Grace's compression efficiency is slightly worse than heavily engineered video codecs, it significantly reduces tail video frame delay (by 2$\times$ at the 95th percentile) with the marginally lowered video quality
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