RTP
The Protocol is a new protocol proposed by IETF in 1996 for real-time data transmission. The RTP protocol is composed of real-time transport protocol and real-time transport control protocol. RTP provides real-time transmission of continuous media data based on multicast or unicast networks. RTCP The Protocol is RTP. The control part of the protocol is used to monitor the quality of data transmission in real time and provide congestion control and Flow Control for the system. The RTP protocol is described in detail in rfc3550. Every
RTP packets are composed of two parts: Fixed Header and payload. The first 12 bytes of the header have a fixed meaning, while the load can be audio or video data. The fixed RTP Header Format is 1: The key parameter settings are described as follows:
(1) Mark bit (m): 1 bit. The meaning of this mark bit is generally defined by a specific media application framework (profile) to mark important events in the RTP stream.
(2) load type (PT): 7-bit, used to indicate the specific RTP load format. In rfc3551, the default values of RTP transmission load types in common audio and video formats are defined. For example, type 2 indicates that the RTP data packet carries voice data encoded using the ITU g.721 algorithm. The frequency is 8000Hz and the single channel is used.
(3) serial number: 16 bits, each sending an RTP Data packet, with the serial number plus 1. The receiver can use it to detect group loss and restore the Group order.
(4) timestamp: 32 Time stamp indicates RTP The sampling time of the first byte in the Data Group reflects the deviation between each RTP packet and the initial value of the timestamp. For the RTP sending end, the sampling time must come from a linear monotonic increasing clock.
From RTP The data packet format is not hard to see. It contains the type, format, serial number, timestamp, and whether additional data is transmitted. These provide a foundation for Real-Time Streaming Media transmission. The Transport Control Protocol RTCP provides congestion control and Traffic Control for RTP transmission. For the specific packet structure and meaning of each field, see rfc3550.
Example: RTP payload format
For H.264 video
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