Meenakshi Singhvi, Deputy Director, All India Radio, Vadodara
Television has witnessed many revolutions from black-and- white to color, analog to digital, standard defi (SD) to high defi (HD), and the latest revolution is Ultra HD or 4K.
The Consumer Electronics Association defi UHD displays as having a 16:9 ratio and a minimum pixel count of 3840×2160. It offers four times the resolution of 1080p Full HD TV. Technically, 4K describes the 4096×2160 resolution, fi introduced in digital cinemas while UHD refers to the 3840×2160 resolution, but the terms 4K and Ultra HD are used interchangeably.
4K images are composed of nearly 8.3 million pixels – four times higher than just over 2 million found in a 1080p image, the full HD resolution. Increased pixel density leads to closer viewing distance, without the pixel grid becoming obvious to the viewer.
Pixel density is one benefit, which means sharper lines, smoother curve, and more details. It can also handle content delivery at 60 frames/second (f/s), which makes fast-moving scenes much smoother and clearer than 30 f/s TV.
Because the resolution is much higher, it requires more bandwidth to transmit. The HDMI 2.0 standard was developed to support 4K, and allows 2160p video to be displayed at 60 f/p. HDMI 1.4 is limited to handling a 4K signal at 30 f/p.
New video compression formats allow broadcasters and web services to stream bulky 4K video fi more easily. The International Telecommunications Union recently introduced the H.265 (or HEVC – High Effi Video Codec) standard as a successor to the H.264 standard widely used to deliver video via broadcast, Blu-ray, and web. H.265 promises to deliver quality comparable to that of H.264, despite using half the bandwidth.
Ultra-high-defi television (UHD TV)/4K also allows benefi of high dynamic range (HDR), and wide color gamut (WCG). HDR can provide a higher level of contrast between light and dark images on the screen to create a much more realistic image. This means whites will look super bright, and blacks will look very dark. Contrast is measured by the difference between the brightest whites and the darkest blacks a TV can display, and is measured in candelas per square meter (cd/m2), known as nits. The ideal low end is completely black, or 0 nits – currently possible only on OLED displays, which can turn pixels completely off. Practically, the latest HDR standards for premium 4K UHD TVs cover 0.05 to 1100 nits; however, key players are pushing for the ideal HDR that would involve a dynamic range of 0 to 10,000 nits, which would really bring 4K TVs close to what real life looks like.
Another crucial aspect of modern 4K TV content is color gamut technology, or the ability to deliver the largest possible range of rich colors. The color gamut represents all the colors that a TV can display; the bigger the color gamut, the more colors a TV can show, and the better the picture.
Currently, many 4K TVs have started to offer color ranges that conform to two particularly broad gamuts called DCI P3, which is frequently used in commercial cinematic display, and REC.2020, which is the current “Wide Color Gamut” standard for 4K UHD. However, not all 4K content fits these higher quality standards and much of the video and 4K TV display technology still on sale is REC.709, which was developed for older HD TV display technology.
Today’s UHD TVs are backward compatible. All 4K TVs include built-in 4K upconversion, also called upscaling, which takes the video signals from a Blu-ray player, satellite, or cable TV box, or game console, and makes them fi the four-times greater pixel count of the 4K screen.
Amazon and Netfl are some of the popular service providers offering 4K content. Also major satellite and cable companies are in the process of 4k UHD delivery, and major studio houses are in content creation process. This technology is defi worth considering when one next upgrades one’s television.