For those who want to start end-to-end video transmission over the Internet with IP with low-latency, available transmission protocols are very limited, not to mention there being obstacles such as packet loss and jitter as of the public network transmission. Currently, the most commonly used protocol for Internet transmission are RTMP and SRT.
RTMP Internet transmission
RTMP is Adobe’s proprietary protocol. As a TCP-based packet retransmission mechanism and adjustable buffer capacity, RTMP is a relatively mature streaming media protocol. During RTMP video transmission, the video stream header does not contain a timestamp, instead only the timestamp of the actual video stream – and a single data packet does not contain a timestamp. Therefore, the RTMP receiver needs to send each received data packet to the decoder within a specified time interval. In order to lessen the difference in transmission time as of each packet, a larger buffer zone needs to be used. Therefore, the delay of RTMP in the video transmission process will be greater. The delay of RTMP on the market is currently around 900ms. And RTMP depends on the transfer platform. The front-end video source is transmitted through the RTMP protocol and needs to be received by the transfer platform. This is a third-party platform.
SRT Internet transmission
SRT is an open source low-latency video transmission protocol. SRT is an open source protocol developed by Haivision. SRT is a transmission protocol based on UDT, which retains the core idea and mechanism of UDT and uses AES256 encryption. During the video transmission of SRT, each data packet of the video stream contains a time stamp, which allows the receiver to reconstruct the signal characteristics and significantly reduce the buffer requirements. That is to say, the bit stream of the SRT sender and the bit stream of the receiver are highly Similarly, SRT can identify each lost packet and only retransmit the lost packet when packet loss occurs, thereby reducing latency. SRT does not require a transfer platform. SRT can achieve point-to-point transmission. No transfer platform is required between the video sending end and the receiving end. Only one end needs to have a fixed public IP address. The SRT delay test is about 500ms from end to end with the lowest as 300ms. SRT can transmit media streams with a code rate of up to 20Mbps anywhere. When the distance is too far, RTMP can only transmit streams with a code rate of 2Mbps.
SRT Internet transmission
For remote video transmission, the longer the distance, the greater the impact on end-to-end delay. The SRT speed is more than twice that of RTMP. In terms of end-to-end delay and maximum transmission code rate, SRT performance is higher than RTMP. If your project application refers to transmission through the Internet with low latency, you may try SRT protocol technology.
