There are two types of closed circuit TV (CCTV) systems: digital and analog. With digital CCTV, a digital camera views the scene in front of the lens and broadcasts the video images as a digitized signal over a LAN line (Local Area Network) where it's then transmitted to a computer or server. In turn, the server manages all of this information. Depending upon the software used to manage the digital images, it can record, display or re-transmit the images to anywhere in the world.
True IP-based digital surveillance uses CCD cameras that employ signal processing with the purpose of sending packetized video streams over the LAN through a Cat 5 cable rather than a coax cable network. This system provides more intelligent data mining and information retrieval. If security is an issue, full digital surveillance offers the added advantage of data encryption opportunities to protect against image tampering; something not possible with analog recording.
The main difference between the two camera types is the way in which the video signal is delivered. Analog cameras turn the video signal into a format that can be received by a television or other receiver such as a VCR or monitor. An IP-based camera, also known as an IP network camera, digitizes the video signal using a specialized encoder that contains an onboard web server. This allows the IP camera to act as a network device, thus allowing captured video images to be viewed not only through an existing network, but also through a web browser that can be accessed through the Internet.
The advantage of a digital system over an analog is clear, and by that I mean literally - better picture quality. After all, the whole point of a Video Surveillance System is to see exactly what is happening in the moment. How many times have you heard about or seen grainy footage of a perpetrator committing a crime that was taken by a traditional CCTV system? Most often you can't make out more than a fuzzy form and the images are useless to law enforcement. In addition to quality, digital cameras also cover a larger area. For instance
While an analog camera is ideal if you want to monitor one location from a fixed position, an IP camera is more flexible and can enable more sophisticated surveillance, recording and review. IP cameras can deliver high definition or megapixel images, which give greater detail and can cover a greater range. All the more, they can be powered over a network using Power over Ethernet (PoE) that does not require a separate power supply. Some IP cameras have audio recording built in which allows recorded messages to be broadcast automatically to warn people that they are being watched. However, this functionality can be integrated into any camera's housing, and is not a specific benefit of IP. Both types of cameras can feature infrared technology to capture full-color images during the day and black-and-white images in low light or even complete darkness.
Even at the highest resolution available for CCTV, the clarity of rapidly moving objects, such as a person running or speeding car, has long been problematic in security and surveillance applications. In an analog CCTV environment, a rapidly moving object will appear blurry. This is because the video signal, even when connected to a DVR, interlaces to create the images. Interlaced images use techniques developed for analog TV monitor displays, made up of visible horizontal lines across a standard TV screen. If you happen to have shopped for a new TV lately you are probably aware that 1080i is not nearly as good as 1080P. Interlacing divides images into odd and even lines and then alternately refreshes them. The slight delay between odd and even line refreshes creates some distortion - only half the lines keep up with the moving image while the other half waits to be refreshed.
A better way to understand the differences between analog and IP-based video surveillance may be to compare the two and how they work:
Analog or CCTV+DVR
• Easy to use - operates like a VCR
• Changing and rewinding tapes - humans may interfere with effectiveness
• Image quality is poor
• Storage tapes wear out over time
• Broadcasting images live isn't an option
• Storage is bulky
• Uses analog recording, recording in low-grade picture quality and inability to search and track easily
• Adding DVR systems must be done in blocks of 16 channels
IP-based
• IP-based recording means instant transmittal of images anywhere in the world
• Can monitor multiple cameras from one remote location
• No decrease in recording quality over time or with repeated replays
• Digital picture quality far superior to analog
• IP-base recording is highly compressed for easier storage and can be transported over a variety of media
• Digital images can be encrypted for security purposes
• Updates and add-ons are relatively inexpensive through software packages and Internet computer networking
• Adjustable frame rates
• Remote or shared viewing may be done over the Internet or a wireless connection
• Standard IP video compression techniques are used
• IP surveillance cameras may be added individually or in groups according to your needs
