ADVANTAGES OF HI-RESOLUTION IP
CAMERAS IN PUBLIC SECTOR CCTV SYSTEMS
Why does a common cell phone store images in
better resolution than most public sector CCTV systems? Mobotix, manufacturer of hi-resolution IP
cameras presents the case for use of high-resolution digital surveillance systems in video
Even basic digital cameras provide more
definition than the images from CCTV camera systems that are commonly used to identify terrorists.
A simple comparison between digital and older technology clearly highlights the difference in image
detail: the simplest of digital cameras stores images of around 3 million pixels (3 Mega pixel); in
comparison the "classic" video technology is restricted to 1/30 the pixels (101,000 pixels or 0.1
Mega pixel). Even the most inexperienced amateur photographer would not buy such a low resolution
camera these days. Despite these facts this kind of security camera system is still being specified
and deployed in a large number of public safety applications.
50 YEAR OLD STANDARD BLOCKS INNOVATIVE
The poor quality of the images used in these
public safety applications is not, as one would imagine, a result of the currently available
technology, but rather the systems specified as the systems of choice. These, in turn, are based on
television technology more than 50 years old, using video cameras that deliver live images with a
maximum of 0.4 Mega pixels. Due to technical and cost constraints of theses systems, the images are
further reduced by a factor of 4:1 to just 0.1 Mega pixels, making facial recognition almost
ISSUES WITH IMAGE STORAGE IN 0.4 MEGA
So why do we not store the original image in 0.4
mega pixels? There are video systems that can store images at 0.4 mega pixels, however, these are
expensive and do not give the user sufficiently more detail. TV technology standard - the video
stream is broadcast in "half frames", and as the name suggests these have only half the detail. The
electronic fitting together, or interlacing, of these half frames when viewing or recording moving
objects, which is the most important aspect of security surveillance, causes combing distortion
(blurred edges) in the image.
CALCULATING 0.1 MEGAPIXEL FOR A CIF IMAGE
The image delivered by a video camera has 576
lines made up of 2 half frames, each with 288 lines, which are, exposed consecutively one after the
other and then transmitted. Because of the technical and financial considerations mentioned
earlier, most of the systems in use today are digitising and storing on a half frame basis. In
context with the width to height ratio, 352 horizontal pixels are digitized for each of the 288
lines resulting in a so-called CIF image with 352 x 288 = 101,000 pixels, which is equivalent to
0.1 Mega pixel.
NO IMPROVEMENT THROUGH USE OF 2CIF OR
The 2CIF image format also uses only 288 lines
but combines them with double the amount of pixels per line, giving us around 0.2 Mega pixel.
Despite the increase in pixels per line, a considerable amount of important information is still
missing from the image because every second line within each image is simply ignored, leaving us
with what is accurately described as a half frame or half image.
Made up of two interlaced consecutive half
images, a 4CIF format has indeed 704 x 576 = 0.4 Mega pixel but every second line is staggered or
deferred because the half frames are exposed at different times. As a result of this so-called
combing effect, 4CIF recording is hardly ever used in actual systems. For example, at the World Cup
stadiums only CIF, or in some cases 2CIF, half frames were recorded.
SNAPSHOTS ARE UNRELIABLE IN FACIAL
An additional problem with existing video
technology lies in the low refresh rate of recorded images during playback. Again, because of
technical and cost factors, 95% of existing systems cannot achieve more than 1-3 frames per second.
With such a low refresh rate of "snapshots", it becomes very difficult to find an image with enough
detail for facial recognition.
This low playback rate is the result of one
single computer having to digitise and store video feed from multiple cameras. The computing power
for full video is generally only sufficient for two cameras, therefore, when recording more cameras
the frame rate has to be drastically reduced.
Because of this limited processing power, MPEG4
also cannot be implemented for the recording of high-resolution video. The processing power is just
not available for multiple cameras.
LIMITING USE OF HIGHER RESOLUTION VIDEO
Why don't the traditional surveillance camera
manufacturers simply use high-resolution sensors in their video cameras? The clear, but far from
comforting answer is that the standard the systems are based on for the transmission and recording
of images is 50 years old and it is technically impossible for the video cable to process such
high-resolution images. Understandably the video surveillance industry is reluctant to change;
however, to protect the public, change is inevitable.
THE DIGITAL DIFFERENCE: IP CAMERAS
New digital technologies also present
opportunities for innovative manufacturers to offer new solutions. In the last few years there has
been an emphasis on developing Mega pixel technology and transmitting video streams via modern
computer networks, LAN, WAN, WLAN or over the Internet. In order to achieve this, a high
performance processor with extensive software package for processing, compressing, recording and
storage of the image sequences was developed and integrated into the video camera itself.
REMOTE ACCESS DURING
One of the great advantages of modern network
camera technology is the ability to manage all configurations and to access live and stored images
simultaneously while the camera is recording, remotely over the network, anytime, from anywhere in
the world. These camera installations will be linked on the existing company network or even the
Internet via a secured connection (VPN) and firewall.
In this way, any incident or suspicious
behaviour in a train station, airport or any other public place can be immediately investigated by
retrieving the images to the control centre via the network without the necessity of having someone
on site or having to stop the recording and live viewing. New or improved software for further
functionality can simply be loaded into the camera through the
COST ADVANTAGES OF NETWORK/ IP VIDEO
By using 960 instead of conventional 288 lines,
a stored image from a camera has 12 times more detail which means, for example when watching
turnstiles in a sports stadium, less cameras in total are needed to view the same amount of
turnstiles. With a standard 90-degree lens it is now possible to view an entire room in more detail
using only one camera.
The use of worldwide IT standards makes it
possible to integrate inexpensive system components: whether over copper, glass or wireless via
WLAN. A power outlet is not necessary as cameras do not require heating to prevent misting and as a
result can be supplied with power via the network cable all year round. That is why the 77 security
cameras installed in the World Cup stadium in Kaiserslautern have full functionality with only
500-Watts emergency power. An innovative storage technique developed requires considerably less
storage PCs for high resolution and streaming video. Internal buffering of the video within the
camera protects the recorded images against power failures of a few minutes duration. The automatic
regulation of frame rate based on motion detection further increases the storage capacity of the
A DIRECT COMPARISON HIGHLIGHTS THE
A comparison of a CIF image with 288 lines and a
camera image with 960 lines dramatically highlights the difference in quality and detail. Mega
pixel imaging shows 12 times more detailed resolution, so that a face taking up only 1/40th of the
image width is still clearly recognisable. With the appropriate post editing the image quality can
be further improved. In comparison, the image extracted from the CIF image is unrecognizable and
DIGITAL IS NOT ALWAYS TRUE
Many IP cameras, or network cameras are still
using the old analogue technology internally and merely transmit a digitised image via a computer
network. Although it is hard to believe, most IP camera systems are only storing CIF half
40 FLUID VIDEO STREAMS ON ONE PC
The decentralised recording process through the
camera itself, enabling the simultaneous recording of around 40 fluid high-resolution video streams
on one single PC, which is the equivalent of 4,800 CIF-images per second in the old technology. The
commonly used centralised concept cannot, because of the limited PC processing power available,
record multiple network cameras in high resolution and have a maximum performance level of 100-200
CIF images per second in total for all cameras.
SWITCHING FROM THE MPEG4 TO MXPEG FOR SECURITY
The video standard MPEG4 was developed for
compressing a single video stream (e.g. movie) and not for the compression, management and viewing
of multiple high-resolution cameras. MPEG4 transmits moving objects at lower resolution and quality
because the human eye does not take in all the detail of a moving object; therefore, it makes no
difference when watching a movie. For this very reason MPEG4 is not suitable for security systems
because in a security situation, it is these moving objects that are of great importance and must
be therefore highly detailed.
To handle the needs of security video, the video
standard MxPEG, requiring around only 2 Mbps for a high-resolution video stream and exhibiting a
shorter reaction time than MPEG4 is ideal. The MxPEG standard is currently being implemented and
supported by manufacturers and developers worldwide.
For more information, contact Raine Sadie, IAC
(Pty) Ltd, +27 (0)12 657 3600, firstname.lastname@example.org