Subrat Kumar Sahoo, Asst. Manager Technical, News 18

The successive revolutionary workout to achieve enhanced resolution of digital video broadcasting presently follows the Ultra High Definition (UHD). The Consumer Electronics Association (CEA) declared in 2012 that UHD can be used to display on a screen having aspect ratio 16:9 or wider. International Telecommunication Union (ITU) has specified the technical parameters of UHD. The key parameter behind UHD is the resolution which refers to the number of pixels that compose the picture on the television.

UHD is conventionally known as 4K. Why it is called 4K is a definite question. The resolution size of UHD is approximately four times that of its follower generation (i.e., full HD) and the term K exists due to the amount falls under the order of 103 (kilo). Full HD has a pixel size of 1920*1080 which is 2.07 megapixel, while the next-generation video UHD is having pixel size 3840*2160 which is 8.29 megapixel.

In Asia, there are some 4K television channels like UMAX, MBC UHD, UXN, and SKY UHD broadcasting UHD data. The UHD will very soon become a utility format for television broadcasting in India. The implementation of 4K content for television broadcasting has been achieved first by Direct TV via satellite to its subscriber with the help of a compatible satellite box at both ends. On the other hand, implementing in cable broadcasting is still in process.

High-efficiency video coding (HEVC) H.265 should allow streaming of content with 4K resolution with a bandwidth of 20 to 30 Mbps and HDMI 2.0 or even higher version should be used in order to achieve a better-resolution video on the screen. 4K video is especially effective on very large screens. In order to notice the best from 4K video, it is recommended that the observer should be very close to the UHD TV screen (0.75H) than in case of HDTV. To stream 4K signal, the minimum broadband speed required is 15 Mbps.

Apart from pixel density, dynamic range and color percentage are greatly enhanced when observing UHD video. The international standard aspect ratio format is 16:9 (42:32) for UHD and it is used universally. The mentioned aspect ratio represents the UHD to its best on the screen without any distortion. To achieve a true nature video, it is not enough to increase the pixel amount, color gamut, and depth of color; indeed a wider contrast range is required, which is called high dynamic range. To maintain a dynamic image definition, the frame rate needs to be increased while enlarging the pixel amount. ITU recommended holding frame rates of up to 100 to 120 Hz for UHD video.

To maximize the quality of 4K screen resolution, highest texel density should be provided by using the largest possible texture size. 4K screens resolve additional underlying details; hence maximizing texture details is the foremost key. Using anisotropic filtering adds detail to the image which is even more noticeable at 4K resolution. Scaling with SLI multi-GPU setups is even more important to ensure the smoothest experience at 4K resolution. Native 4K describes 4K UHD content, which does not require upscaling from a lower resolution source, thus producing a sharper image theoretically while Master in 4K is optimized to be upscaled.

By magnification of source textures, one gets additional magnification at 4K of fetches from other offscreen render targets. 4K resolution is obviously heavier on video memory consumption than lower resolutions. Four times the pixels will mean four times the memory used for screen-sized buffers, in addition to any extra memory consumed by higher-resolution source art or higher-resolution intermediate surfaces. While talking about UHD TV, with  significant enhancement in video quality, sound quality is also upgraded appreciably. 24 channels of audio can be adopted with 24 speakers producing a difference comparable to the UHD video resolution.

It is still considered as extra-expensive technology to adopt for television broadcasting, while 4K/UHD has rapidly become standard for screens of TVs, laptops, smartphones, camcoders, etc.





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