Using net.Buffers.WriteTo send multiple RTP packets to reduce system calls to improve performance

[Dylan-Ying]

Describe the feature

Description Each RTP packet sent invokes the io.Write function once, and a frame of video generates many RTP packets. From the pprof, it can be observed that RTP transmission consumes a significant amount of CPU resources.

[aler9]

Hello, thank you very much for bringing to attention the existence of net.Buffers and the fact that multiple UDP or TCP buffers can be sent with a single call. Using net.Buffers.WriteTo() instead of net.Conn.Write() can surely improve performance in case all RTP packets of a video frames are available in advance, and this happens with the following cases:

• RTMP to RTSP
• HLS to RTSP
• SRT/MPEG-TS to RTSP
• RTSP to WebRTC (since RTP packets are decoded and re-encoded with a lower MTU)

However this approach won't bring any benefit when RTP packets are received singularly and sent out as soon as possible, and this happens with:

• RTSP to RTSP
• WebRTC to RTSP

Therefore: in the future we can add to gortsplib a new method, WritePacketsRTP(pkts []*rtp.Packet), that allows to send out multiple packets at once.