Compression Standards

Compression Standards

To save hard drive space and transmit faster, digital images are often compressed. The compression ratio is generally between 10-100. An uncompressed image with a resolution of 640x480 pixels occupies about 600KB (2 bytes per pixel). An image compressed by 25 times is approximately 25KB.

There are many compression standards available. Cameras using static image standards transmit a single image over the network. Cameras using video standards transmit static images mixed with updated data. In this way, unupdated data (such as backgrounds) is not transmitted in every image. The refresh rate refers to frames per second (fps).

Image quality can vary due to many different factors, with compression standards being just one of them. Comparing images from different cameras, you will find significant differences in image quality among different brands. If you want to use a camera in low light, check the images captured at 50 Lux.

Common Compression Standards

JPEG

A widely supported and popular standard for static images used in many network cameras.

Dynamic JPEG

Dynamic JPEG is a variant of JPEG. It displays static images at high frame rates. It can achieve high-quality images, but unfortunately, it contains a lot of data.

Wavelet

This standard is optimized for images with minimal data. Therefore, image quality may not be the highest. Wavelet has not been standardized and requires special software.

JPEG 2000

A new and still relatively uncommon standard based on Wavelet (not JPEG) technology.

GIF

GIF is a good standard for uncomplicated images, such as logos. It is not recommended for images captured by cameras with limited compression rates.

H.261, 263, 321, 324, etc.

A series of standards designed for video conferencing, sometimes used for network cameras. This standard offers high frame rates, but image quality is low when images contain large moving objects. Typical image resolution can reach 352x288 pixels. Due to limited resolution, newer products do not use this standard.

When using H series compression standards, moving people appear pixelated. Backgrounds that are generally less interesting may receive relatively better image quality.

MPEG 1

A video standard that may have many variants. It offers 352x240 pixels at 30 frames per second (NTSC) or 352x288 pixels at 25 frames per second (PAL). Due to limited resolution, new products are now using the MPEG2 standard.

MPEG 2

A video standard that may have many variants. It offers 720x480 pixels at 30 frames per second (NTSC) or 720x576 pixels at 25 frames per second (PAL). Because it requires significant computational power, currently only computers can decode MPEG2.

MPEG 4

A new video standard that performs better than MPEG2 but is not widely used.

Proprietary Standards

In addition to official standards, many proprietary standards have been developed and used by different companies. It is recommended to use archived and widely adopted open standards.

Which Compression Standard is the Best?

It is recommended to use JPEG, Dynamic JPEG, and MPEG2 compression standards because they are well-known, widely used, and cost-free international standards.

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