Monday, November 20, 2017

Tendências Tecnológicas

 

IP Cameras

Oliver Vellacott, CEO of IndigoVision, gives an overview of professional IP Camera technology and outlines the challenges faced when comparing performance

IP Video technology is now firmly established as a mature technology that brings significant benefits to CCTV surveillance applications. To complement this, the growth in dedicated IP cameras has also been significant. However, unlike traditional analog cameras where performance can easily be compared, IP cameras present a different proposition.

Autenticação de Identidade

What is an IP Camera?

An IP fixed camera or dome is a single integrated unit that contains the camera itself, codec for video compression and transmitter/receiver for the network. All that is needed to connect the camera to the network is a single CAT-5 cable and local power, or just the cable if Power-over-Ethernet (POE) is implemented. IP Cameras enable simple and easy deployment of network CCTV systems.

An IP fixed camera or dome is a single integrated unit that contains the camera itself, codec for video compression and transmitter/receiver for the network. All that is needed to connect the camera to the network is a single CAT-5 cable and local power, or just the cable if Power-over-Ethernet (POE) is implemented. IP Cameras enable simple and easy deployment of network CCTV systems.

Compression Technology

Compression Standards

Video - both analog and digital - consists of a sequence of still images/frames. At 25/30 fps (depending on whether it's PAL/NTSC) the sequence is so fast that the eye cannot see the individual images and interprets it as live video. JPEG is the well known standard for compressing a single image, and MJPEG is simply a sequence of JPEG images (though there is actually no defined standard for MJPEG!). MPEG-4 is one of the so called 'motion codecs' (along with MPEG2, MPEG1, H.261, H.263) which look for matches between frames in order to: 
(a) just encode the differences and 
(b) match blocks that have moved their position from one frame to the next.

By exploiting the fact that in 25/30 fps video 90% of the scene remains the same, or has only moved its position slightly from the previous frame, MPEG-4 delivers 10-30 times better compression than MJPEG. The MPEG and H.26x standards, defined respectively by the ISO and the ITU organisations, have long followed 'parallel paths' but are coming together in the H.264 standard, which is also known as MPEG-4 Part 10.

There are two predominant compression technologies used in IP cameras, MJPEG and MPEG-4 - see sidebar. However, 99% of IP cameras currently available in the marketplace are based on MJPEG. MPEG-4 can deliver much higher video quality, but a proper implementation of MPEG-4 has until recently been too expensive to incorporate into a dedicated IP camera.

However, the cost, performance and power consumption of the camera sensor and MPEG-4 compression hardware has now reached a point where it can be packaged in a dedicated professional IP Dome. Domes are the obvious starting point for high-end IP cameras as the physical size of the enclosure makes it easier to accommodate the necessary electronics – see “Anatomy of a High End IP Dome”. The price/performance of the hardware has been further enhanced due to the investment by some IP video manufacturers in dedicated custom chips for MPEG-4 compression.

Video quality from these new domes when transmitted via a network and displayed on an analog monitor is indistinguishable from analog video directly connected to that monitor. That’s a long way from the early ‘stuttering’ performance of MJPEG IP Cameras.

There can however be major differences in the implementation of MPEG-4. It is possible to use MPEG-4 in 'I-frame only' mode, which is basically the same as MJPEG, and yet it is compliant with the MPEG-4 standard. In this case the IP camera can be labelled MPEG-4, but with video quality similar to MJPEG!

The problem with MJPEG is that it requires a huge amount of bandwidth to generate good quality video, typically 10-30 times what a good MPEG-4 implementation requires. This has impact on bandwidth and storage. The network provision has to be at least 10 times larger than it should be, and the cost of storage (often a major component of system cost) is also at least 10 times what it should be. Even though MJPEG based IP cameras are typically lower cost, the rest of the system is very expensive, resulting in an overall system cost that is higher than if a good quality compression technology is used.

Using Analog Cameras in IP Systems

The professional end of the CCTV market has to date preferred to use standard analog cameras connected to separate transmitter/receiver units to compress and transmit video over the IP network. These units have far more processing power for compression and networking tasks, and therefore enable a cost effective deployment of storage and network bandwidth.

There are several other advantages to using this approach. It is an ideal solution for the retro-fit market where existing analog CCTV cameras are linked to new networks and IP video systems. This maximizes existing investment and smoothes migration to a network CCTV solution. The range of analog cameras available is also far wider than with IP cameras. There is a camera for almost every need, and the advance in sensor performance is still continuing apace. These advances generally don't feed through into IP cameras for some time. In fact the average price of analog cameras has actually gone up in the last few years, as demand for high-quality video images has increased. The CCTV system can only ever be as good as the performance of the front end camera sensor – “garbage in, garbage out.”

An alternative to the IP camera is a stand-alone transmitter/receiver module that compresses and transmits digital video, audio and control data over the IP network from the connected analog camera Video Server - Transmissor e Receptor

That being said, IP cameras will clearly eventually take over from analog cameras as they will drive down overall system costs through lower camera costs and reduced installation/wiring – one CAT5 network cable can replace local coax, 2-way audio, PTZ control and power cabling.

However IP cameras will not be accepted by the mainstream security market until the video quality is good enough, a diverse range of cameras is available and, most importantly, the system management software is available to support them.

It’s a Software Game

With an IP camera the quality of the digital video displayed in the control room is a function of the camera sensor, compression technology and the software that is managing the IP Video system. Without capable enterprise level video management software the quality and benefits of IP Video will not be realized. These software applications provide control, administration and viewing of the live camera feeds and recorded video over the IP network. The power of IP CCTV is not in the camera, but in how the management software delivers a useable application to the end user. So how this software interacts with the IP Camera, the recording hardware and the network is vital to overall performance.

 Anatomy of a High-End IP Dome

Anatomia da Câmera Speed Dome IP Features of the new generation of high-end professional IP Domes: 
1. Sony Camera Module with built in zoom motor 
2. Custom chip for MPEG-4 video processing 
3. Pan motor 
4. Tilt motor 
5. Housing

This is a sea-change from the world of analog CCTV cameras, monitors and DVRs, where you could typically buy any product and evaluate its capabilities and performance in isolation. With IP systems the solution is not a single box. It's a collection of components which get distributed across an IP network, with the software to manage them as an absolutely essential component. So IP cameras on their own are not enough; the real value lies in the software, and that should be at the top of anyone's decision making process when selecting an IP Video solution.

One example of how IP cameras can benefit from the integrated approach is in the ability to have advanced features built-in to the camera itself such as ACF and Analytics. Activity Controlled Framerate (ACF) is designed to reduce network traffic. If no movement is detected in the camera scene then bandwidth is dramatically reduced. This feature is most effective in places where low activity occurs, such as in corridors, on fire escapes, or in buildings which are unoccupied at night. Recording in these areas becomes virtually free!

Analytics is the processing of video images to detect such events as congestion, stolen objects, cars parked too long outside a building, people moving the wrong way through security checkpoints, etc. In integrated IP systems analytics can be run in two modes: real time within the IP camera, and postprocessing, on any operator’s PC via the management software. The real time mode allows the system to automatically identify events as they occur. Post processing allows operators to run many different scenarios on recorded video, e.g. look for cars parked for more than 2 minutes. These two modes offer the best of both worlds, using analytics at the camera to identify events as they occur, and also providing advanced search tools for operators to analyze footage from a central location. Human operators are particularly poor at watching video monitors for long periods of time, but are generally very good at confirming whether or not something is an incident, once it has been flagged up automatically by the system.

In summary, in an IP security system the value is in the management software – look first at that when evaluating a system. That software however ultimately depends on the performance of the image sensor and quality of compression. IP cameras still have a generally poor reputation for security applications, but the first few professional quality IP domes, that match or exceed analog domes in quality, are starting to appear.

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