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PTZ = pan, tilt zoom

NVR = network video recorder.

LPR = license plate recognition.

Cameras are just dumb devices. They simply display the video. You can connect directly to the camera by typing in the IP address of the camera. The cameras have different settings & functions depending on the carmera manufacturer. Most of the time though, you can at least view what's on the camera. What's interesting is that all the capabilities of the camera are not always available via the web interface. More on that later.

Take note however, that what's being displayed on the camera is in no way related to what's being recorded. These are actually two different resolutions depending on settings.

For a HIKVISION NVR (DS-7608NI-SE/8P) to record what's on the camera, it must connect to the camera. To be able to connect to the camera, it needs:

• -the camera IP address.
• -a protocol.
• -a port number.
• -a channel number.
• -a username.
• -a password.

The important part here is that as long as the NVR can communicate with the camera, it should be able to record the video.

This leads to two scenarios.

1- in the first scenario, if the NVR can communicate to the camera, everything is good as long as it has the settings above.

2- in the second scenario, some NVR's have their own IP address range and use this range on the switch built into the device. This IP range is 192.168.xxx.(1-254). So if you look at the back of the device, you will see 4 ports or 8 ports or possibly more. When a camera with DHCP is plugged into one of these ports the NVR will assign it's own IP address to the camera. For example, 192.168.254.10

If a camera has a static IP set, the NVR will NOT assign an IP address. Consequently, you must:

• -connect the camera to the local network (not the back of the NVR).
• -change the IP address to that of the internal NVR network (for example 192.168.254.12).
• -this will cause the camera to no longer be accessible.
• -manually plug the camera into the back of the NVR.

Protocol

Regardless of how you connect, the protocol must match. There are different protocols for each manutfacturer (Axis, etc) and an ONVIF protocol as a generic protocol using port 80.

Stream Types

The cameras have multiple streams and in different formats.

The record is on the MAINSTREAM (stream-1 or channel-1). Typically this stream is of higher quality and bit rate compared to a sub-stream..

The view is on the SUBSTREAM or SECONDARY STREAM (stream-2 or channel 2). This happens because stream-1 but might not be good for viewing over the wan internet. Typically the sub-stream is a lower-resolution.

MJPEG: This format uses standard JPEG still images in the video stream. These images are then displayed and updated at a rate sufficient to cr eate a stream that shows constantly updated motion.

MPEG-4: This is a video compression standard that makes good use of bandwidth, and which can provide high-quality video stre ams at less than 1 Mbit/s. MPEG-4 can be encoded in 2 ways either SIMPLE (sets the coding type to H.263 ) or ADVANCED. Usually SIMPLE is fine.

Communication Methods

To deliver live streaming video over IP networks, various combinations of transport protocols and broadcast methods are employed.

• RTP (Real-Time Transport Protocol) is a protocol that allows programs to manage the real-time transmission of video data. It uses UDP.

• RTSP (Real-Time Streaming Protocol) allows a connecting client to start an MPEG-4 stream. It serves as a control protocol, to negotiate which transport protocol to use for the stream. RTSP is thus used by a viewing client to start a unicast session, see below. It uses TCP. The default setting is port 554. If it is not enabled, MPEG-4 streams will not be available.

• UDP (User Datagram Protocol) is a communications protocol that offers limited service for exchanging data in a network that uses the Internet Protocol (IP). UDP is an alternative to the Transmission Control Protocol (TCP). The advantage of UDP is that it is not required to deliver all data and may drop network packets when there is network congestion, for example. This is suitable for live video, as there is no point in re-transmitting old information that will not be displayed anyway.

• Unicasting is communication between a single sender and a single receiver over a network. This means that the video stream goes independently to each user, and each user gets their own stream. A benefit of unicasting is that if one stream fails, it only affects one user.

Unicasting should be used for video-on-demand broadcasting, so that there is no video traffic on the network until a client connects and requests the stream. However, if more and more unicast clients connect, the server will at some point become overloaded. There is also the maximum of 20 simultaneous viewers to be considered.

• Multicast is bandwidth-conserving technology that reduces bandwidth usage by simultaneously delivering a single stream of information to multiple network recipients. This technology is used primarily on delimited networks (intranets), as each user needs an uninterrupted data flow and should not rely on network routers.

It is not possible to multicast through a router. Consequently, it is not possible to multicast over the Internet. It is possible to get around that by using RTP tunneled over RTSP. Crazy isn't it.

Accessing Video Real-Time

As single JPEG images in a browser. Enter the path, for example: http:///axis-cgi/jpg/ image.cgi?resolution=CIF

• • Windows Media Player. This requires codecs to be installed. The paths that can be used are listed below, in the order of preference.
• • Unicast via RTP: axrtpu :///mpeg4/media.amp
• • Unicast via RTSP: axrtsp:///mpeg4/media.amp
• • Unicast via RTSP, tunneled via HTTP : axrtsphttp:///mpeg4/media.amp
• • Unicast via RTSP, tunneled via HTTP S: axrtsphttps:///mpeg4/media.amp
• • Multicast: axrtpm:///mpeg4/media.amp

Resolution

• D1 = 704x480
• HD = 1920x1080p