缩写

• RTT - round trip time
• SR - sender report
• RR - receive report
• REMB - Receiver Estimated Maximum Bitrate

概述

• Loss-based controller:发送端，根据丢包率、RTT和REMB，计算出一个目标发送码率
• delay-based controller:接收端，根据收到包的信息，或是SR包的信息，计算出一个最大码率REMB，传回给发送端

实现

以上两种controller共同工作，实现了拥塞控制算法

都工作在发送端

• WebRTC目前采用该方法，两张算法分别计算目标码率，然后取最小值
• Delay-based control:A_hat
• Loss-based controller:As_hat

都工作在接收端

Delay-based control

• a pre-filtering
• an arrival-time filter
• an over-use detector
• a rate controller

Loss-based controller

• 从RR中获取丢包率
• 根据如下公式计算

$$[{As\text{ _ }hat \left( i \left) ={ \left{ \begin{array}{{20}{l}} {As\text{ _ }hat \left( i-1 \left) ,\text{ }\text{ }2\text{%} < p < 10\text{%}\right. \right. }\ {As\text{ _ }hat \left( i-1 \left) * \left( 1-0.5p \left) ,\text{ }\text{ }10\text{%} < p\right. \right. \right. \right. }\ {1.05As\text{ _ }hat \left( i-1 \left) ,\text{ }\text{ }p < 2\text{%}\right. \right. } \end{array}\right. }\right. \right. }]$$