Going Mainstream

Low-bandwidth, high-definition IP cameras will accelerate the move to HD

Over the last 10 years, the CCTV industry has seen a major shift from analog to digital networking solutions for surveillance applications. In the next few years, the industry will see the adoption of high-definition IP video into mainstream consumer CCTV systems. The issues associated with high data rates and storage are being addressed with the recent launch of high-definition IP cameras with low data rates.

The three main advantages of HD IP cameras are:

General surveillance. A single HD megapixel camera can replace several standard 4 SIF cameras, thereby reducing costs. An HD megapixel camera can see more detail in the same field of view or view a wider field of view with the same level of detail.

Forensic detail. Many existing analog CCTV systems simply do not provide enough resolution or quality for forensic evidence. Megapixel cameras, on the other hand, are ideal for identifying and recording faces, vehicle license plates and objects.

Digital PTZ. HD megapixel cameras can digitally zoom quicker and with greater detail than analog cameras, while still recording the whole picture for later analysis. This provides superior performance and is more reliable than mechanical PTZ devices.

Typical applications for HD IP cameras include retail point of sale, banks, casinos, car parks, building entrances, military installations and city center monitoring.

Technology Hurdles

In order for HD megapixel cameras to be adopted for mainstream use, the current technology hurdles must be overcome:

Lenses. Megapixel cameras require a higher resolution lens than ordinary CCTV cameras to maximize the picture quality. These lenses are readily available but are expensive in CCTV mounts— although this will change with the higher volumes from mainstream adoption.

Sensors. Megapixel cameras use the same CMOS image sensors used in still digital cameras, whereas analog cameras typically use CCD sensors. This is likely to change with the adoption of sensors from the HD TV and video industry.

A higher density of pixels on a same sized sensor means there is less light falling on each pixel. Each pixel, therefore, has less sensitivity and needs more light. The "noise" in the sensor has a larger impact because it is a higher percentage of the signal, which is why first-generation HD IP cameras typically had a worse low-light characteristic than analog cameras. However, sensor technology is improving quickly, with significant research and development resources being focused in this area.

Video compression. Compression is arguably the most important factor to consider with its impact on network bandwidth and storage requirements. HD megapixel cameras are unlikely to be adopted for mainstream use until lowbandwidth camera designs are readily available. This is starting to happen with the launch of HD IP cameras with superior compression and much lower data rates.

H.264 is the latest video codec standard, which surpasses MPEG-2 and MPEG-4 video standards and offers improvements in both video quality and compression. Many of the current 1 and 2 megapixel HD cameras use MPEG-4 compression, resulting in higher video data rates. For HD to become usable in mainstream CCTV applications, H.264 compression technology needs to be deployed in the camera to provide the lowest possible data rates. However, not all implementations of the H.264 standard deliver the same quality of compression. The data rates from different manufacturers’ cameras can vary significantly, even when comparing cameras implementing H.264. Table 1 details the typical data rates for a single 1 megapixel camera monitoring a fairly static scene such as a building entrance.

The huge disparity in camera performance makes a significant difference in the cost of an HD CCTV solution. Using cameras with data rates of less then 1 MBps means that HD IP cameras can use standard networks and storage and be costeffective for everyday CCTV applications.

It is important for system designers and end users to know the data rates and storage requirements for particular HD IP cameras so performance and costs can be fully understood. However, some of the actual data rates are so high that it’s not surprising that these figures are often hidden and difficult to determine. Take a look at a typical datasheet for a 1.3 megapixel camera from a mainstream manufacturer, and the camera has a framerate of up to 30 fps. However, nowhere is there a mention of how good the compression is—i.e., what the typical data rate is and how much storage is required to record a stream from that camera.

Some manufacturers are forced into using local storage because their HD IP camera bandwidth cannot reasonably be streamed live across the network. This somewhat negates the distributed and scalable benefits of IP video. By removing the high-bandwidth problem, designers are free to choose a truly distributed architecture, placing storage wherever the best system design dictates it should be, whether that is in a central location, distributed close to the camera or in a fault-tolerant redundant configuration mixing the two.

Low-Bandwidth, HD IP Cameras

The key to the adoption of HD CCTV into mainstream surveillance is the ability to develop low-bandwidth HD IP cameras. The three main elements that make up such a camera are using a true IP camera solution, excellent implementation of H.264 and dedicated hardware architecture.

A true IP camera completely eliminates any analog signal by connecting the digital signal processor directly to the compressor chip. This ensures no additional signal noise is introduced.

H.264 Compression

There are three common compression standards used in current HD IP cameras: M-JPEG, MPEG-4 and H.264.

Video is compressed using two types of frames, such as I Frame, also known as the index or key frame, which contains the whole image, and P Frame, which only contains the information that is different from the previous frame.

M-JPEG only uses I Frames, whereas MPEG-4 and H.264 use a combination of both I and P Frames and consume considerably less bandwidth than M-JPEG. H.264 will require up to 50 percent less bandwidth than MPEG-4 to transmit the same quality image, therefore it is the chosen compression standard for the highest performance IP cameras.

The H.264 standard specifies a set of optional tools, which can be used to compress video. A compliant decoder must implement every tool, whereas a compliant encoder can choose which tools to use. This means that there can be a big difference between encoders from different suppliers—and some compress well, while others compress poorly.

H.264 Implementation

Best Compression Technology

Average Compression Technology

Typical Data Rate (MBps)

<1

5-6

 

Approx. storage required for 30days at 15 fps continuous recording (terabytes)

0.5

3

 

To determine what information is transmitted in a P Frame, the image has to be searched for motion in each frame. The quality of the compression depends on how well the search is completed on each frame. The limitation to this searching is the available processing power in the camera.

Compared to the best encoders, a poor encoder design could result in higher bandwidth for good quality video, increased bandwidth during high motion, dropped frames and blocky or blurry video.

Hardware Architecture

Due to the huge processing demands of a low-bandwidth HD IP camera using H.264, it is essential that the compression engine is implemented with dedicated hardware, such as field programmable gate arrays. With this type of design, lowbandwidth HD compression can be achieved without dropped frames.

The use of HD megapixel IP cameras for CCTV monitoring offers real benefits. However, graduating from their current use in primarily specialized applications to everyday use requires HD IP cameras with the best compression technology and low data rates.

This article originally appeared in the June 2009 issue of Security Today.

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