Video coding is a video compression technique that compresses the original video sequence to produce a smaller archive file or reduce the transmission bandwidth under constraints on the visual quality loss. Rate control (RC) plays a critical role in video coding. It can achieve stable stream output in practical applications, especially real-time video applications such as video conferencing or game live streaming. Most RC algorithms either directly or indirectly characterise the relationship between the bit rate (R) and quantisation (Q) and then allocate bits to every coding unit so as to guarantee the global bit rate and video quality level. This paper comprehensively reviews the classic RC technologies used in international video standards of past generations, analyses the mathematical models and implementation mechanisms of various schemes, and compares the performance of recent state-of-the-art RC algorithms. Finally, we discuss future directions and new application areas for RC methods. We hope that this review can help support the development, implementation, and application of RC for new video coding standards.

翻译：视频编码是一种在视觉质量损失约束下，对原始视频序列进行压缩以生成更小存档文件或降低传输带宽的视频压缩技术。率控（Rate Control, RC）在视频编码中起着关键作用，它能够在实际应用中实现稳定的码流输出，尤其在视频会议或游戏直播等实时视频应用中至关重要。大多数率控算法直接或间接地表征比特率（R）与量化参数（Q）之间的关系，然后将比特分配至每个编码单元，从而确保全局比特率和视频质量水平。本文全面回顾了历代国际视频标准中使用的经典率控技术，分析了各类方案的数学模型与实现机制，并比较了近期最先进的率控算法性能。最后，我们探讨了率控方法的未来发展方向及新兴应用领域。希望本篇综述能为新视频编码标准中率控技术的开发、实现与应用提供支持。