1. If there is no frame for a long time before decoding, IDR frame request
The receiving end of webrtc controls the I frame request according to the time to be implemented in the packet before decoding. If there is no packet received within the specified time, an I frame request is sent.
VideoReceiveStream2::StartNextDecode
RtpVp8RefFinder::ManageFrame framing does not actively send I frame requests here, there are only three framing actions, cache, discard, and transmit video frames to the frame_buffer_queue. Decoding in the frame_buffer_queue is not enough data, only to send I frame request
2. If the NACK hole is greater than kMaxNackPackets, send an IDR frame request.
When NackModule2::AddPacketsToNack enqueues packets, judge the empty size.
