Adds the adaptivePtime property to RTCRtpEncodingParameters(https://w3c.github.io/webrtc-pc/#rtcrtpencodingparameters). This new flag sets a sender in a real-time communication (RTC) system to enable/disable adaptive packet rate.
As the packet rate is a big determining factor to the overall bitrate of an audio stream, an optimal congestion control should be allowed to adapt the packet rate. The audio packet rate is analogous to the video frame rate, which also plays an important role in the video bitrate adaptation. Although adaptive packet rate may be ubiquitously beneficial, we need this API for applications to enable and disable it, since, otherwise, it may introduce interoperability problems. Some implementations have taken a fixed packet rate as an assumption, and thus may fail or perform sub-optimally with an adaptive packet rate. Therefore it is needed to add a flag for applications to enable or disable the adaptive packet rate.