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CCTV SYSTEMS

RESOLUTIONS USED IN CCTV

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CCTV SYSTEMS

CCTV resolution is measured in vertical and horizontal pixel dimensions and typically limited by the capabilities of both the camera and the recorder that you are using for your CCTV surveillance installation.

CCTV systems use an analog video signal

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CCTV SYSTEMS

The resolution of CCTV equipment is usually measured by TV lines (TVL).

Vertical TV lines have a maximum of 350 TV lines in a 525-line NTSC system and is not variable.

The horizontal TV lines, which is used as the parameter of picture quality, vary depending on the quality of camera, lens, transmission and monitor.

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CCTV SYSTEMS

For standard analog cameras, resolution is measured by TVL.

For most new analog cameras the TVL range is 320 to 700, Although 320 TVL is considered low resolution.

CRT monitors are also quoted with these numbers.

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CCTV SYSTEMS

In the NTSC standard the resolution is 480 TVL combined with additional info not visible on a TV or monitor it totals 525 TVL.

INTERLACED VIDEO IN ANALOG SYSTEMS

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CCTV SYSTEMS

The images produced by the new generation of surveillance cameras are often collectively referred to as high-definition (HD) or as megapixel images.

Since the terms HD and megapixel both indicate an improved level of imaging performance compared to traditional analog video, they are often mistaken to be the same.

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CCTV SYSTEMS

HD may be considered a subset of megapixel.

HD is defined by specific resolutions at specific frame rates with a specific aspect ratio.

Any camera with a resolution of more than a million pixels is by definition a megapixel camera.

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CCTV SYSTEMS

HD refers to cameras with a standardized resolution of 720p or 1080p, the numbers 720 and 1080 refer to the horizontal resolution.

Therefore, 720p HD camera resolution provides images that are 1280 x 720 pixels (921,600 pixels - not megapixel), and 1080p HD cameras provide 1920 x 1080-pixel resolution, or 2.1 megapixels.

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CCTV SYSTEMS

The lowest resolution in the megapixel range in the security market is around 1.3 megapixels, which provides 1280 x 1024-pixel resolution (or 1.3 million pixels), to resolutions as high as 10 megapixels (3,648 x 2,752 pixels).

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CCTV SYSTEMS

The HD video format also uses an aspect ratio of 16:9 rather than 4:3, and the frame rate is standardized at 60, 50, 30 or 25 fps.

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CCTV SYSTEMS

CCTV resolution for IP (internet protocol) cameras (megapixel specific) are able to deliver a much higher resolution.

An IP megapixel camera is already digital so there is neither conversion nor compression.

Megapixel camera signals are transmitted over Cat 5e/6.

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CCTV SYSTEMS

The higher resolution provided by megapixel cameras also allows system designers to use fewer surveillance cameras to cover larger areas without losing detail, and with reduced infrastructure and cabling costs.

In addition to reducing the initial installation costs of a system, these benefits translate directly into greater return-on-investment (ROI) and lower total cost of ownership

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CCTV SYSTEMS

So the bottom line here is that analog cameras have a lower resolution than IP based megapixel cameras that are digital.

Another factor in overall resolution is the compression format or how the video images are saved.

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CCTV SYSTEMS

For television specifications (which CCTV uses) the highest resolution that can be captured and stored is 704 x 480 (NTSC for the United States).

This resolution is knows as D1 resolution which is a commonly quoted specification for DVRs.

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CCTV SYSTEMS

D1 = 704 x 480

CIF = 352 x 240 (Common Interchange Format)

2CIF = 1/2 of D1 (720 X 260 pixels)

QCIF = 176 x 120 pixels

4CIF = D1

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CCTV SYSTEMS

D1 CCTV resolution is 704 x 480 (720 X 520) pixels and is the highest resolution the CCTV system can record at.

High end digital video recorders offer this resolution and only the highest end recorders can offer D1 resolution at 30 frames per second recording.

This format uses a lot of disk space in a DVR.

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CCTV SYSTEMS

CIF (LOWEST) CCTV resolution is 352 x 240 pixels in size.

This resolution is typically used by mid level stand alone DVR recorders when recording real time video.

It is also typically used by higher end systems for remote internet viewing (as streaming D1 video for multiple cameras uses a lot of bandwidth).

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CCTV SYSTEMS

QCIF CCTV resolution is 176 x 120 pixels in size and is one quarter the size of CIF resolution.

This resolution is typically used for remote viewing from a mobile device (cell phone).

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CCTV SYSTEMS

Another commonly quoted compression format is the H.264

The developments related to H.264 video compression makes bandwidth and storage requirements of megapixel images in IP-based systems comparable to those of standard resolution images.

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CCTV SYSTEMS

H.264 is a fairly new standard for video compression, and is currently one of the most commonly used formats for the recording, compression, and distribution of high definition video.

The H.264 standard, (also known as MPEG-4 Part 10/AVC for Advanced Video Coding), is expected to become the video standard of choice in the coming years.

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CCTV SYSTEMS

Lets take a look at some specifications of a DVR.

Unitek Standalone DVR 4 CH H.264, Quadplex, 120/120 Real time D1 Recording, DDNS, Remote & Mobile Viewer, CMS

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CCTV SYSTEMS

Here is the recording chart for the Unitek DVR

DVR MODEL TYPE

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CCTV SYSTEMS

FPS

D1

H.264

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CCTV SYSTEMS

The H.264 standard compresses video to smaller formats while maintaining a great deal of detail.

The D1 standard takes that H.264 compression and plays it back at the highest standard video play back.