[Home Theater Network HDAV.com.cn] Want to really understand what 4K is? First of all, through a few key words to step by step in-depth understanding!
1, resolution:
4K is a range of resolution, that is, 4096 × 2160 pixel resolution, generally used for professional equipment, the current home equipment, such as 4K TV, 4K display, 4K projector or even 4K Blu-ray disc resolution is 3840x2160. 2K resolution is 2048x1080 pixel resolution, HDTV, HD display, projector and Blu-ray resolution are basically 1920x1080 pixel resolution.
HD 1080p can display 2,073,600 (1920×1080) effective pixels, 4K (4096x2160) can provide at least 10 million pixels of display quality, display fineness is more than 4 times 1080p. The film industry says 4K, the resolution is relatively large, and the aspect ratio is 17:9. For mainstream TV equipment manufacturers, they are more inclined to manufacture devices close to 4K (3840×2160) because the resolution ratio of this resolution standard is 16:9, which is close to the viewing ratio accepted by consumers. The true native 4K projector is 4096.
2, HDR:
The HDR full name is High-Dynamic Range, which is a high dynamic range image technology. Previously, this technology was applied to photography. It is often heard that turning on HDR during the photo process can make the original dark scene brighter and more transparent. This technology has been applied to home TV.
The range of brightness that traditional TVs can exhibit is extremely limited, far from what the human eye can perceive. The reason is that the brightness of the traditional TV in the bright part of the picture cannot be lifted, and the dark place cannot be dark. As a result, the human eye perceives the perceived layering of the picture, and a lot of details are lost. HDR super-quality display technology came into being to solve this problem.
HDR display technology representation
For HDR, the most important is contrast. The LCD TV can display a minimum brightness of 0.1 nits, the brightest is between 500 and 1000 nits, and the contrast ratio is only 5000 to 1. If the brightness is doubled to 1000 nits, it can reach 10,000 to 1.
3, color gamut:
The BT.2020 color space has been positioned by the ITU International Telecommunication Union to target an image signal gamut standard in the 4K/8K era and is one of the standards for 4K UltraHD Blu-ray. The normal Blu-ray standard uses the BT.709 color space, which covers only 35.9% of the BT.2020 color space, which is the largest color space in current display devices, covering 75.8% of the CIE 1931 color space.
The widely known wide color gamut TV in the market is actually using a wide color gamut technology that allows the color gamut to exceed the BT.709 standard to display more colors.
From the above figure, the BT.2020 color gamut brings a larger color gamut triangle, which is much larger than the Rec.709 color gamut, indicating that the system can display a richer number of colors. In addition, 4K Ultra HD uses a 10-bit or even 12-bit video system, so the gray level transition or color depth level performance is larger than the 8-bit video system used in the current HD or Full HD system. Upgrade.
At this stage, no products can reach the 2020 color gamut. The current goal of the projector is in the DCI-P3 color standard.
4, color depth:
The 4K UltraHD Blu-ray standard specifies a color depth of 10 bits, which means that it can display 1.07 billion colors (each of the RGB has 2 to 10 powers, that is, 1024 levels, and RGB three colors have 1.07 billion (1024 × 1024 × 1024). Color matching). The ordinary Blu-ray standard supports 8bit color depth, only 16.77 million colors, and the gap is wide. In other words, through the 10-bit output, the color is richer and fuller, and the level transition is smoother than the 8-bit.
For example, this is the case:
The left side is an 8-bit effect, the color transition is uneven, the color gradation is very obvious, and the 10bit effect color transition on the right is smooth, the color is rich and full, and the effect is very good.
5, HDMI 2.0:
Compared with the previous 1.4 standard, the most significant sign of HDMI 2.0 is that the data transfer speed is greatly improved from 10.2 Gbit/s to 18 Gbit/s, which provides sufficient bandwidth support for ultra-high definition video output, enough for 12-bit color. The picture is displayed at a high frame rate of 60 fps per second.
Although the current HDMI1.4 interface can support 4K video playback, due to technical reasons, it can only achieve a playback speed of 30 frames per second, that is, the refresh rate is only 30Hz.
The improved version of the new HDMI 2.0 interface has significantly improved bandwidth, up to 18Gbps, and up to 50fps or 60fps per second. Therefore, for those who have higher requirements for 4K TV, it is possible to start with a 4K TV equipped with HDMI2.0 interface, and for ordinary home users, the HDMI1.4 interface is sufficient.
6, 60P
The number of frames represents the number of pictures contained in the 1 second video. The higher the number of frames, the smoother the picture is observed by the human eye, and there is no intermittent feeling.
The normal Blu-ray standard has a frame count of 24p and the Ultra HD Blu-ray standard can support up to 60p. So as long as the content supports a high number of frames, playing Ultra HD Blu-ray discs will result in smoother picture performance.
Although it is said that for 4K resolution products, you want to output smooth 4K resolution dynamic images, and the refresh rate is not less than 24fps to meet the 4K video vision requirements. However, if you compare the BT.2020 standard, you can see that the supported frame rate has been increased to 50fps, 59.94fps, 60fps, or even 120fps. The new 4K movies have also been produced at higher frame rates, such as It is famous that Peter Jackson's "Hobbit" is a HDMI 1.4 standard that uses a frame rate of 48 fps/sec and does not support 4K signals at these frame rates. On the other hand, HDMI 1.4 can only support 8-bit color, and can not really play the 10-bit color depth display advantage of 4K video. The world premiere of the recent Hollywood commercial blockbuster "Billy Lynn's Midfield War", in which director Ang Lee first used 3D movie shooting at 4K per frame at an ultra-high frame rate of 120 frames per second, meaning 2.5 times more than "Huo. Bitman is 48fps/sec.
7, viewing distance:
The author has found some calculation methods for viewing the best distance of 4K, and the version is also more, then we calculate according to the formula of the best viewing distance of the equipment in Europe and America. Taking the most mainstream 55-inch as an example, it is necessary to see the difference between 4K and 1080P in the 0.7-meter position and 1.2-meter in the 65-inch. Obviously, this distance is too close for the user. In the homes of many users, the actual viewing distance is between 2 meters and 3 meters. In fact, this concept is also time to change.
Interested friends can calculate according to the position of their living room sofa and viewing equipment, what distance is the most suitable. Formula: Best viewing distance (cm) = screen height ÷ vertical resolution × 3400
8, content source:
Streaming media: Compared with the lack of 4K resources in China, 4K resources in foreign countries, especially in Europe and America, will be slightly richer. But for some users who are unable to overturn the wall, these so-called foreign 4K resources are also slightly tasteless.
Foreign resources:
Website: http://demo-uhd3d.com, http://, http://
TV station: Foreign countries such as Canada, the United States, Denmark, etc. have already launched TV stations that support 4K playback.
Domestic resources:
Website: http://, http://4k.znds.com, http://, in addition, some well-known portal videos such as IPTV, Tencent, etc. have also launched 4K live broadcasts. Or the source of the film for everyone to enjoy.
TV station: Some cities in China have opened 4K test channels, and have conducted trial broadcasts, such as Jiangsu Cable, Dalian Cable, and so on. In addition, Gehua Cable in Beijing has also opened a 4K ultra-clear column, providing some 4K video on demand programs to meet the needs of users watching 4K Ultra HD programs. However, in general, 4K TV programs are still very scarce, and the true 4K live TV program still needs a long way to go.
Disc: Of course, if you are obsessed with 4K, you can also choose to buy some 4K Blu-ray discs officially released by the film company. Of course, you can also have a 4K player. And the price will make many people discouraged.
Extended reading:
8K
The so-called 8K, also known as QUHD technology, has a resolution of up to 7680×4320, which is 4 times the display effect of 4K (UHD) display, and is 16 times of the current mainstream HD (FHD) resolution. We have seen from many media that most of the adjectives for 8K are bright and shocking. It can be seen that the visual impact and influence of 8K on people is still very large. Although there are already a lot of 8K TVs on the market, the problems and constraints of film source, price, storage, transmission, etc. are also difficult for ordinary consumers to follow. However, the author believes that in the near future, with the continuous advancement of technology, 8K will enter the ordinary people's home like the 4K today, and it will allow us to watch the movie at the IMAX theater.
More fresh and fun home theater information, please pay attention to home theater network http:// (WeChat: cnhifi), the country's most influential home theater audio player interactive media website.
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