4K UHD – a resolution standard with an image size of 3840x2160 pixels at 16:9 aspect ratio. The resolution is four times higher than the commonly used Full HD (1920x1080) and nine times higher than High-Definition (1280x720).
4K means 4096 pixels of horizontal resolution. Full resolution at 4:3 ratio is 4096x3112 pixels at over 12.7 million pixels, and in the cinema quality - 4096x2160 at over 8.8 million pixels.
Fig. 1. Comparison of 4K and Full HD resolution
High resolution requires higher streaming bitrates, efficient video compression, usually H.265/HEVC for CCTV and high storage capacity. DCI standard defines 4K video as 4096x2160 or 4096x3112 pixels images recorded at 24 fps. The colour depth of each pixel is 36 bits. Image compression is JPEG 2000 to 250 Mb/s.
Fig. 2. Colour space standards introduced with 4K:
CCTV monitoring uses more and more cameras and recorders featuring 4K technology. The systems offered by the leading manufacturers, i.e. Hikvision and Dahua include not only 4K IP cameras, but also analogue cameras, e.g. HD-CVI (Dahua) or HD-TVI (Hikvision).
To save the bandwidth, instead of JPEG 2000, CCTV uses H.265/HEVC compression, and usually does not require 24 fps. The framerate can be adjusted to the available bandwidth.
A dynamic development of both the IP and the analogue technologies means lower prices of new 4K solutions and more common use of high-resolution devices.