Common network video camera transmission protocols

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(Generally, gateways and routers do not support multicast data packets ).

1. Transmission Protocol
Network Cameras provide many IP-based transmission protocols to ensure audio and video data as much as possible. PTZ controls the quality of data network transmission. Real-time video streams are transmitted over an IP network. They are combined with multiple protocols to adapt to various complex network transmission environments.

RTP (Realtime Transport Protocol) is a real-time transmission protocol designed specifically for Real-Time Streaming Media. The basic function of RTP is to reuse several real-time data streams into a UDP group stream.UDP streams can be sent to one host (unicast mode) or multiple target hosts (Multicast mode). Because RTP is only encapsulated as a standard UDP protocol, the router theoretically does not have any special treatment for the group, but now all advanced routing devices have RTP protocol optimization options. The timestamp mechanism of RTP not only reduces the impact of jitter, but also allows synchronization between multiple data streams, this allows you to easily add subtitles to Video Images Based on I/O events. Network Cameras often encapsulate audio and video encoding data into RTP groups.

RTCP (Realtime Transport Control Protocol) is a sister protocol of RTP that processes feedback, synchronization, and user interfaces, but does not transmit any data. Its main function is to provide feedback on latency, jitter, bandwidth, congestion, and other network features to the source end, which can be fully utilized by the encoding process. Therefore, when the network condition is good, it can increase the data rate (to achieve better quality), and when the network condition is poor, it can reduce the data rate.Encoding through continuous feedbackAlgorithmYou can make continuous adjustments to provide the best quality possible under the current conditions..

RTSP (Real Time Streaming Protocol) Real-time stream protocol. RTSP uses the push server method to send a request to the audio and video browser, the Network Camera only keeps pushing audio and video encoded data encapsulated into RTP groups to the browser end. The Network Camera can transmit streaming media with a low system overhead.

HTTP (Hypertext Transfer Protocol) Hypertext Transfer Protocol, network cameras provide Web access through HTTP, it is easy to transmit audio and video data through a complex network, but real-time audio and video support is not ideal.

User Data Protocol (UDP) is the most basic network data transmission protocol. Using the IP protocol to provide network-less connection services, UDP is often used to encapsulate real-time network audio and video data, even if a group is lost during network transmission, audio/video browsing is not affected on the client.

The TCP (Transmission Control Protocol) transmission control protocol uses the IP protocol to provide connection-oriented network services, designed to provide a reliable end-to-end byte stream on an unreliable interconnected network. The TCP protocol usually requires multiple "handshakes" between the server and the client to establish a connection,Therefore, the overhead of audio and video streams with strong real-time performance in TCP transmission is high.If the network is unstable, audio and video jitter is obvious.. The reliability is often used to transmit Network Camera management commands, such as PTZ and I/O device control commands.

2. transmission protocol combination
Network Cameras often use different combinations of RTSP, RTP, RTCP, HTTP, UDP, and TCP Protocols to transmit real-time audio and video streams. Common protocol combinations are as follows.

RTP + RTSP protocol combinationThis Protocol combination (RTP can be encapsulated using TCP and UDP protocols, and RTSP is encapsulated using TCP protocol). In a normal network environment, the client can view real-time audio and video, vendors often recommend network cameras to use this Protocol combination. Some network devices often support RTP + RTSP multicast mode.

RTP/RTSP protocol combination. RTP groups are encapsulated into RTSP groups. Some network firewalls only allow the RTSP protocol group to pass. However, the Network Camera must use the RTP protocol to provide real-time audio and video. This combination method increases the complexity of the network load and the client management system when there is no way.

RTP/RTSP/HTTP protocol combinationHTTP encapsulation is added based on RTP/RTSP data. This protocol combination is mainly used to adapt to the network environment where only HTTP protocol is allowed by the network firewall. Although network load increases, network cameras can adapt to more complex Internet environments.

UDP (TCP) ProtocolSome network cameras do not use the RTP + RTSP application layer protocol to encapsulate audio and video data to adapt to poor bandwidth conditions in China. They only use UDP or TCP Transport Layer Protocol to encapsulate audio and video streams. In this way, audio and video streams can use a small network bandwidth to transmit streaming media. This Protocol combination can also provide advanced features similar to RTP + RTSP, but it cannot be used to optimize network routing devices based on the combination of RTP + RTSP.

UDP (TCP)/HTTP protocol combination, encapsulate audio and video stream data into HTTP data groups, and then transmit the data to the client using UDP (TCP) protocol. This protocol can adapt to complex Internet environments and penetrate most network firewalls.

The combination of various transport layer protocols ensures the reliability of real-time transmission of audio and video and PTZ data. However, the computing capability of the built-in processor of the Network Camera is limited, resulting in a limited number of concurrent users. In this way, Network Cameras often use network transmission devices with multicast functions to respond to more concurrent access requirements. Some Network Camera clients have powerful functions and use the data forwarding mechanism to act as a "Virtual Network Camera" that can respond to more concurrent access users. This method is also applicable to the PTZ Network Camera. It is of great significance for the construction of large-scale digital video surveillance networks.