Things to know about IP CCTV Cameras
Protocols you should know about when dealing with IP CCTV Cameras.
- The Real Time Streaming Protocol (RTSP)
Is a network control protocol designed for use in entertainment and communications systems to control streaming media servers. The protocol is used for establishing and controlling media sessions between end points.
RTSP is the control protocol for the delivery of multimedia content across IP networks. It is based typically on TCP for reliable delivery and has a very similar operation and syntax to HTTP. RTSP is used by the client application to communicate to the server information such as the media file being requested, the type of application the client is using, the mechanism of delivery of the file (unicast or multicast, UDP or TCP), and other important control information commands such as DESCRIBE, SETUP, and PLAY. The actual multimedia content is not typically delivered over the RTSP connection(s), although it can be interleaved if required. RTSP is analogous to the remote control of the streaming protocols.
Real Time Transport Protocol (RTP)
RTP is the protocol used for the actual transport and delivery of the real-time audio and video data. As the delivery of the actual data for audio and video is typically delay sensitive, the lighter weight UDP protocol is used as the Layer 4 delivery mechanism, although TCP might also be used in environments that suffer higher packet loss. The RTP flow when delivering the content is unidirectional from the server to the client. One interesting part of the RTP operation is that the source port used by the server when sending the UDP data is always even—although it is dynamically assigned. The destination port (i.e., the UDP port on which the client is listening) is chosen by the client and communicated over the RTSP control connection.
Real Time Control Protocol (RTCP)
RTCP is a complimentary protocol to RTP and is a bidirectional UDP-based mechanism to allow the client to communicate stream-quality information back to the object server. The RTCP UDP communication always uses the next UDP source port up from that used by the RTP stream, and consequently is always odd.
- ONVIF (Open Network Video Interface Forum) is a global and open industry forum with the goal of facilitating the development and use of a global open standard for the interface of physical IP-based security products.
The surveillance industry has created an open standard protocol called ONVIF that allows cameras to communicate with each other and with network recording devices. ONVIF has different versions of compatibility that dictate which features can be integrated into the system. In some cases a camera can have basic video compatibility but lack the ability to do more advanced features, such as motion detection.
There are 4 ONVIF profiles: make sure your cameras or NVR is profile S compliant.
- for IP-based video systems
- Video & audio streaming
- Pan-tilt-zoom control & relay output
- Video configuration & multicast
- for IP-based access control
- Site info & configuration
- Door access control
- Event & alarm management
Profile G (proposed)
- for edge storage and retrieval
- Video & audio streaming
- Configure, request and control recording from conformant devices
- Receive audio & metadata stream
Profile Q (proposed)
- for plug-and-play NVR compatibility