CCTV Video Resolutions
CIF, QCIF, 2CIF, 4CIF. Sounds like a bad nursery rhyme, right? If your eyes glaze over when you hear terms like these you are not alone. In this section, we will attempt to demystify the terminology and put it into a framework that’s easy to understand and use.The table below lists some of the more commonly used resolution terms in CCTV applications. Any resolution over 1 million pixels is considered ‘megapixel’. In the case of megapixel cameras, the labels are approximate. For example, a 2 megapixel camera actually captures 1,920,000 pixels per frame. A 3 megapixel camera captures 3,145,728 pixels per frame.
| Notes | ||
|---|---|---|
| QCIF | 176 x 120 | Quarter CIF (half the height and width as CIF) |
| CIF | 352 x 240 | |
| 2CIF | 704 x 240 | 2 times CIF width |
| 4CIF | 704 x 480 | 2 times CIF width and 2 times CIF height |
| D1 | 720 x 480 | aka “Full D1” |
| 720p HD | 1280 x 720 | 720p High Definition |
| 960p HD | 1280 x 960 | 960p High Definition (Sony HD standard) |
| 1.3 MP | 1280 x 1024 | aka “1 Megapixel” or “1MP” |
| 2 MP | 1600 x 1200 | 2 Megapixel |
| 1080p HD | 1920 x 1080 | 1080p High Definition |
| 3 MP | 2048 x 1536 | 3 Megapixel |
| 5 MP | 2592 x 1944 | 5 Megapixel |
When comparing megapixel camera specifications you may notice pixel counts slightly different from the above. This is because some cameras will specify the total number of pixels captured by the sensor, and others will specify the ‘effective’ pixels. Some of the total pixels are used to contain technical housekeeping type of data, and are not contributing towards the ‘effective’ details of the image.
Definition of a BRIDGE
A WiFi Bridge can link your network to another network so that resources like Internet can be shared.
Bridging devices work together in pairs so you will need two units.
One unit is placed at each network.
When a WiFi connection is established between both bridging units then the two networks become one.
IP Wireless security camera system design is very similar to standard IP camera system design except for
the addition of wireless access points (Bridge) inserted between the home network switch and the remote
camera network switch. This allows you to place cameras up to 2.4 km (plus up to 100 metre of Ethernet cable)
away from your local area network (LAN).
For now, installing analog cameras coupled with DVRs is still the most cost-effective
approach for most security applications. However, the cost of IP cameras and components
is rapidly declining, making IP systems more and more affordable and desirable.
A typical medium quality analog dome camera sells retail for about R750 to R2200. A similar quality IP camera sells for at least twice that amount. Analog cameras are available with many different features: varifocal lenses, pan/tilt/zoom, and long distance infrared, for example. Finding just the right combination of features in a network camera for your application might be more difficult and expensive. Sometimes you may have to buy an analog camera and add a separate video server to do the job. Single-channel network video servers currently start at about R4500 retail.
IP advocates may point out that businesses often have IP networks in place and therefore no additional cabling or hardware is needed. However, each camera requires a port to plug into the switch, so more or bigger switches may need to be purchased. POE adapters might need to be added. If the existing network will not handle the load of the additional network devices, upgrades might need to be made, thereby making the installation more expensive.
Finally, bandwidth on the local area network (LAN) needs to be considered. Video uses a lot of bandwidth. The bandwidth used by each camera varies by many factors including the resolution, the compression method, and even the amount of movement in the field-of-view.
Analog camera systems transmit over coax, not the LAN, so their bandwidth is not much of an issue. The only use of the LAN in analog systems is for the DVR to broadcast video data over the network to local desktop users or to the internet. DVRs tend to broadcast video very efficiently and will only use bandwidth if people are currently viewing the cameras.
In IP camera systems on the other hand, each IP camera uses the LAN to broadcast their signal to the NVR so bandwidth can be a big issue. As a general rule, an IP camera using full CIF (352 x 288) resolution, 30 frames per second (30 fps), and MPEG4 compression will require about 720K bits per second (720Kbps). Therefore, if we put 100 IP cameras running CIF on a network, we would use about 72Mbps of bandwidth. This number will double if audio is also transmitted. However, to make bandwidth matters worse for IP – most of the newest IP cameras are coming out with ‘megapixel’ resolution. This is wonderful from the standpoint of how much clarity and field-of-view can be captured, but it comes at a huge price to bandwidth. A single 2-megapixel IP camera, running 30 fps with MPEG4 compression will use a whopping 6.5Mbps of bandwidth. It should come as no surprise then that some companies have gone so far as to create an entirely separate IP network just to run their camera system.
FYI – see above for more information about CCTV Video Resolution Standards.
High-resolution IP cameras also require a great deal of hard drive space to store the video. The single 2-megapixel camera described above would require approximately 67 Gigs of hard drive space to record one day’s worth of video.
A typical medium quality analog dome camera sells retail for about R750 to R2200. A similar quality IP camera sells for at least twice that amount. Analog cameras are available with many different features: varifocal lenses, pan/tilt/zoom, and long distance infrared, for example. Finding just the right combination of features in a network camera for your application might be more difficult and expensive. Sometimes you may have to buy an analog camera and add a separate video server to do the job. Single-channel network video servers currently start at about R4500 retail.
IP advocates may point out that businesses often have IP networks in place and therefore no additional cabling or hardware is needed. However, each camera requires a port to plug into the switch, so more or bigger switches may need to be purchased. POE adapters might need to be added. If the existing network will not handle the load of the additional network devices, upgrades might need to be made, thereby making the installation more expensive.
Finally, bandwidth on the local area network (LAN) needs to be considered. Video uses a lot of bandwidth. The bandwidth used by each camera varies by many factors including the resolution, the compression method, and even the amount of movement in the field-of-view.
Analog camera systems transmit over coax, not the LAN, so their bandwidth is not much of an issue. The only use of the LAN in analog systems is for the DVR to broadcast video data over the network to local desktop users or to the internet. DVRs tend to broadcast video very efficiently and will only use bandwidth if people are currently viewing the cameras.
In IP camera systems on the other hand, each IP camera uses the LAN to broadcast their signal to the NVR so bandwidth can be a big issue. As a general rule, an IP camera using full CIF (352 x 288) resolution, 30 frames per second (30 fps), and MPEG4 compression will require about 720K bits per second (720Kbps). Therefore, if we put 100 IP cameras running CIF on a network, we would use about 72Mbps of bandwidth. This number will double if audio is also transmitted. However, to make bandwidth matters worse for IP – most of the newest IP cameras are coming out with ‘megapixel’ resolution. This is wonderful from the standpoint of how much clarity and field-of-view can be captured, but it comes at a huge price to bandwidth. A single 2-megapixel IP camera, running 30 fps with MPEG4 compression will use a whopping 6.5Mbps of bandwidth. It should come as no surprise then that some companies have gone so far as to create an entirely separate IP network just to run their camera system.
FYI – see above for more information about CCTV Video Resolution Standards.
High-resolution IP cameras also require a great deal of hard drive space to store the video. The single 2-megapixel camera described above would require approximately 67 Gigs of hard drive space to record one day’s worth of video.
There are poor quality components and good quality components no matter which type of system is used.
That being said, network cameras do offer some technological advances in the areas of video quality
and wireless installations. Analog cameras cannot provide resolution above TV standards,
the maximum being about 0.4 megapixel. Resolution of IP cameras can be many times higher
(currently up to 5 megapixel) and they can capture a clearer image when objects are moving.
This could make a difference in high risk applications such as for casinos and law enforcement.
Wireless communication over IP networks has fewer problems with interference, and encryption
security is built into the technology.
If an IP network is already in place at the installation site, and it can handle the additional
load of the new cameras, then IP cameras will be easier to install. If additional RJ-45 jacks
are needed to plug in the network cameras, then the installer only has to run a CAT-5 cable
from the camera to the nearest switch. An inexpensive switch can be installed right at the
nearest wall jack. In contrast, each cable for analog cameras must be run all the way back to the DVR.
If upgrades need to be made to an existing IP network to handle the additional load,
obviously the installation would be more difficult.
The power for the cameras can be handled fairly easily with either technology. For IP networks, built in POE adapters make sending the power through the existing ethernet cable easy. For analog systems, use RG59 Siamese cable to combine the video and power cables into one jacket. Either way, there is no additional cabling for power. POE can run 100 metre without a repeater. RG59 can be run 300 metre without a repeater.
The power for the cameras can be handled fairly easily with either technology. For IP networks, built in POE adapters make sending the power through the existing ethernet cable easy. For analog systems, use RG59 Siamese cable to combine the video and power cables into one jacket. Either way, there is no additional cabling for power. POE can run 100 metre without a repeater. RG59 can be run 300 metre without a repeater.
Analog wireless systems do not work well.
This is because the government regulates on which frequencies analog wireless devices can run
and how strong the signal can be. Interference from other wireless devices such as cell phones
can cause the camera video to be distorted. Interference is especially problematic in buildings
with florescent lighting.
Digital IP wireless is much better. The digital transmission does not get interference from other analog wireless devices, and the 802.11x communication standard used has encryption built in. Consequently, there is no problem with unauthorized access to the video.
Digital IP wireless is much better. The digital transmission does not get interference from other analog wireless devices, and the 802.11x communication standard used has encryption built in. Consequently, there is no problem with unauthorized access to the video.
IP cameras should be considered for large installation sites that already have a high bandwidth
network installed – especially if the cameras will be spread out over a wide area,
or if wireless cameras will be used.
For large installations with many cameras, some installers still prefer a multiple DVR solution to an IP solution. Software is bundled with higher-end DVRs that allows you to view and record cameras from multiple DVRs. The multiple DVR solution also provides better failover protection. If the network goes down in an IP based system, video is lost from all the cameras. If the network goes down in an analog system, the DVRs are still recording the cameras.
An even better solution may be to use a hybrid solution which combines the use of analog and IP technology.
For large installations with many cameras, some installers still prefer a multiple DVR solution to an IP solution. Software is bundled with higher-end DVRs that allows you to view and record cameras from multiple DVRs. The multiple DVR solution also provides better failover protection. If the network goes down in an IP based system, video is lost from all the cameras. If the network goes down in an analog system, the DVRs are still recording the cameras.
An even better solution may be to use a hybrid solution which combines the use of analog and IP technology.