Especially 4K, it is coming very fast. First, JVC brought the first 4K home theater projector with e-shift technology to enter the ordinary family at the beginning of the year. Then Sony also transplanted the professional cinema 4K technology to the home projection field, and launched the world's first original 4K based display chip. Home theater projector. After that, Sony, LG, Sharp, Samsung and other manufacturers brought their respective 4K TV products, which means that the consumer electronics display field has entered the 4K display era. Even more surprising is that the ITU-R International Telecommunication Union Radiocommunication Sector has developed the BT.2020 standard for next-generation television broadcast and video manufacturing specifications, which sets out a series of detail standards for 4K and 8K TV broadcasts, which is 4K Ultra. The comprehensive popularity of HD has laid a solid foundation.
However, what is the international standard for 4K display technology? Is 4K technology really suitable for ordinary families? What are the current domestic 4K products on the market? What is the difference between their respective technical characteristics? These are topics that are of great concern to ordinary consumers, audio-visual enthusiasts and enthusiasts. In this issue, we will conduct an in-depth discussion of each of the issues and provide a full range of 4K.
In the field of electronic video display and broadcasting, the goal of pursuing clearer images has always been achieved, mainly by increasing the display resolution, from 480p SD to 720p HD, then from 720p HD to 1080p Full HD, until the nearest 4K. With 8K Ultra HD starting to enter the civilian field, you can clearly see the development trend of the entire field. Higher resolution means more detail and levels of display, and the size of the display device needs to grow larger. For example, Sony's latest 4K LCD TV has reached 84 inches, far larger than the current mainstream 50-inch 1080p full HD flat-panel TV. For the average consumer, it is precisely because 4K technology allows us to see a larger picture, richer colors and details, so it has become a high-profile display technology.
4K shows the establishment of standards, ITU-R defines a new "Ultra-high definition" standard
In the latest ITU-R BT.2020 TV system standard, 4K and 8K are simultaneously included in Ultra-high definition (Ultra HD)
4K, also known as 2160p, represents the birth of a new display resolution. According to the latest BT.2020 Ultra-high definition ultra-high definition television system standard promulgated by the ITU-R International Telecommunication Union Radiocommunication Sector in August 2012, 4K refers to the display of 3840 (horizontal resolution) × 2160 (vertical resolution). Resolution, also known as Ultra-high definition, is four times the precision of 1920×1080. It is worth noting that 8K (7680×4320) is also included in the ultra-high definition in the BT.2020 standard. This is a very interesting phenomenon. Different from the previous standard definition, high definition and full HD, only a single physical resolution is defined as the standard. When entering the ultra high definition field, it is the situation of 4K and 8K development at the same time. This is the result of mutual compromise due to regional development differences. For example, South Korea has announced recently that it will fully promote 4K (3840×2160) ultra HD TV broadcasts next year. In Japan, it advocates the direct development of 8K (7680×4320) TV broadcasting technology to avoid the technical obstacles that may arise from the transition from 4K to 8K. For these two different Ultra HD standards, ITU-R clearly indicates that different countries and regions can develop according to their own needs, but it is recommended to gradually transition from 4K Ultra HD to 8K systems. According to the current domestic ultra-high-definition display devices brought by major consumer electronics brands, most of them are still in the 4K standard. Therefore, at this stage, 4K is still the mainstream.
The birth of 4K display standards is closely related to 8K display technology
The birth of the 4K display standard is related to the 8K ultra-high definition display system developed by NHK in Japan.
The establishment of the 4K display standard is in fact inseparable from the 8K display technology. Our understanding of ultra-high-definition display technology was first learned from the Super Hi-Vision system brought by the NHK (Japan Broadcasting Association) Science and Technology Research Laboratory in 2003, and the core display technology of this system is adopted. 8K (7680×4320) ultra high definition display resolution. In 2005, NHK was able to use the fiber-optic network to transmit 8K TV broadcast signals to 260 kilometers using DWDM dense wavelength division multiplexing technology. At the 2008 International Broadcasting and Television Expo IBC 2008, NHK TV, RAI TV, BSkyB, Sony, Samsung, Panasonic, Sharp and Toshiba jointly demonstrated the world's first public real-time ultra-HDTV system from London, England to Amsterdam, the Netherlands. In order to showcase the 8K Ultra HD system, it is entirely possible to replace the current mainstream HDTV broadcasting system. At the just-concluded London Summer Olympics, BBC Television has also implemented real-time broadcasts of ultra-high-definition television broadcasting systems in parts of the UK. The stunning images brought by Ultra HD have been well received by audiophiles and enthusiasts.
Japan advocates direct development of 8K TV broadcasting technology (Super Hi-Vision), and believes that 8K is the mainstream of ultra HD in the future.
Despite the rapid development of the 8K display system, organizations including the ITU and the EBU (European Broadcasting Union) at the time believed that it was very difficult to achieve the popularity of the 8K ultra-high-definition television broadcasting system on a global scale, after all, most of the world. The country and region do not have sufficient technology deposition to achieve the leap from full HD to 8K ultra-HD technology, so the 4K ultra-high definition display technology standard was born. More importantly, 4K Ultra HD display technology is currently used in some high-end professional theaters in the full HD range, and many movies are manufactured according to the DCI (Digital Film Advocacy Organization) related 4K standard, so from the technology From the point of view, the upgrade of civilian 1080p to 4K is relatively easy.
The ITU-R BT.2020 Ultra HD standard is more than just a definition of display resolution
ITU-R introduces a new BT.2020 recommended specification standard for ultra high definition television systems
Just as ITU-R BT.709 (or the Rec.709 standard) specifies a series of performance indicators and parameters for high-definition television broadcasting, high-definition Blu-ray disc production, and high-definition display equipment, ITU-R BT.2020 is equally standardized and defined. A series of related performance indicators and parameters, not limited to the definition of display resolution. In other words, when the video professional adjustment staff adjusts the 4K or 8K ultra-high definition display device, it is no longer in accordance with the Rec.709 standard, but in accordance with the BT.2020 standard.
The BT.2020 standard specifies the parameters of the picture characteristics. The most special place is to define the ultra-high definition display resolution of 3840×2160 and 7680×4320.
The BT.2020 standard stipulates that the display resolution of Ultra-high definition ultra-high definition images is 3840×2160 and 7680×4320, the screen display ratio is 16..9, and the supported frame scanning frequencies include 120p, 60p, 59.94p, 50p, 30p, 29.97p, 25p, 24p, 23.976p. Among them, it can be found that all images of the Ultra High Definition standard are based on progressive scanning. The interlaced scanning technology that has undergone nearly one hundred years has finally withdrawn from the historical stage in the era of Ultra HD.
Ultra HD image standard only supports progressive scan, does not support interlaced scanning
In terms of color, the BT.2020 standard has been significantly improved over the Rec.709 standard. The first is the color depth, which is raised from 8bit of Rec.709 standard to 10bit or 12bit, of which 10bit is for 4K system and 12bit is for 8K system. This improvement played a key role in enhancing the color and transition of the entire image. The change in color depth standard also causes a change in the standard for adjusting the optimal dynamic range of the picture, which we can follow according to the following criteria.
Ultra HD images will use 10bit or 12bit systems
For 10bit systems, the BT.2020 standard defines the entire range of video signals in the range of 4-1019, where 64 is the standard black level and 940 is the standard peak, so the effective video signal is 64-940. While 0-3,1020-1023 puts the clock reference signal, 4-63 is the signal below the standard black level, and 941-1019 is the signal above the standard peak.
For 12-bit systems, the BT.2020 standard defines the entire range of video signals in the range of 16-4079, of which 256 is the standard black level, 3760 is the standard peak, and the effective video signal range is 256-3760. While 0-15, 4080-4095 puts the clock reference signal, 16-255 is the signal below the standard black level, and 3761-4079 is the signal above the standard peak.
For a signal brightness, it consists of 0.2627R+ 0.6780G+ 0.0593B
In addition to the improvement of color depth, the definition of gamut triangle has also changed a lot. The area of ​​the whole triangle is much larger than the range of Rec.709 standard, which means that the ultra-high definition system can display more colors. . However, the definition of white point is still maintained in the D65 standard of Rec.709. In addition, for the brightness of a signal, it consists of 0.2627R+0.6780G+0.0593B. It should be noted that the larger the gamut triangle, the higher the performance requirements for the display device. For example, according to the actual situation of the segment home theater projector, only the models using LED or LED laser hybrid light source can achieve the above standards. The emergence of the BT.2020 standard will further advance the development of projection light source technology.
RGB color space parameters under the ITU-R BT.2020 standard
| White dot | Main color | ||||||
| X-axis coordinate | Y-axis coordinate | Red X coordinate | Red y-axis coordinate | Green X coordinate | Green y-axis coordinate | Blue X coordinate | Blue y-axis coordinate |
| 0.3127 | 0.3290 | 0.708 | 0.292 | 0.170 | 0.797 | 0.131 | 0.046 |
Above, we have carried out a detailed analysis of the BT.2020 standard. It can be found that the ultra-high definition system not only improves the resolution, but also adjusts the refresh rate, color depth, color space and gamma correction. In particular, the expansion of the color gamut triangle makes the color performance of the picture far better than the high-definition system, which is very much expected.
For DCI's 4K digital film production standards, we also need to understand
Why do we have an understanding of 4K film production standards? The most important reason is that most of the projectors using native 4K display chips at this stage do not use the 3840×2160 specification, but use the 4096x2160 specification based on the DCI digital cinema standard, including the first native 4K. Home theater projector Sony's VPL-VW1000ES. These 4K projectors are not really "native" home models, and when 4K projections continue to move into the home sector, I believe that more and more 3840 × 2160 consumer-grade models will be born.
Among the DCI digital film standards, the 4K display resolution specification is 4096×2160.
In the production of 4K digital cinema, the display ratios of two different specifications are often used, one is 4096×1716 of 2.39..1, and the other is 3996×2160 of 1.85..1. Therefore, the projection of these two 4K movies can be achieved with a 4096x2160 4K projector. In fact, since the vertical resolution of the display core is still 2160, although the horizontal resolution is large, it does not affect the image that displays the 4K broadcast standard, or the disc playback made by the relevant standard. In addition, DCI stipulates that 4K movies have a frame rate of 24f/s and support 10bit or 12bit color depth.
It is worth noting that when we adjust the 4K home theater projector, we must adjust it according to the 4K program source we are watching. If you are watching a signal source that uses the BT.2020 broadcast system standard, you need to use the BT.2020 standard for picture correction. If it is based on the DCI digital cinema standard, you need to adjust it according to the DCI standard. However, the sources of DCI standards are often only found in digital cinemas. Therefore, under normal circumstances, we are all calibrated using the BT.2020 standard.
Summary: The former 4K ultra-high definition display system has been basically improved in terms of technology, including the production of 4K program source, the development of 4K display related standards, the transmission of 4K signals, etc., and 8K is also the same as 4K, incorporating BT of ITU-R. Under the 2020 international standards, and in Japan and other countries have achieved gratifying research and development results. This means that after 4K technology, it will be followed by the era of 8K ultra-high definition display.
From the technical point of view, the essence of 4K display technology has not only improved the display resolution, but also has a big difference between the color, grayscale transition and transmission and the current full HD or HD system. This means that if users want to replace 4K flat-panel TVs and home theater projectors, to maximize their advantages, they must fully upgrade the entire audio-visual system, from signal sources, AV amplifiers to transmission cables, and in accordance with the new BT The .2020 Ultra HD standard fine-tunes the machine. This will cost a lot. Therefore, many audio-visual enthusiasts and enthusiasts will think about such a question: "Is the 4K display really suitable for ordinary families?" Below, we will analyze the advantages of the 4K ultra-high definition display system compared to the current mainstream 1080p full HD display system. .
One of the advantages of the 4K display system:
Display resolution is improved, making the picture more detailed
The biggest advantage of 4K display is the improvement of display resolution, the picture is more refined, and the display area of ​​the same size can allow users to watch at a closer distance.
There is no doubt that anyone who has seen 4K flat-panel TVs and home theater projectors will find that the picture is far better than the 1080p Full HD model. Just like this year's CIT show, Sony's booth demonstrated the SXRD display chip home theater projector VPL-VW1000ES with 4096x2160 physical resolution, and also used the original 4K Ultra HD movie clip in the signal source. Its exceptionally detailed picture shocked every audience, indicating that this is the best picture at the entire CIT show.
There are two important key factors that affect the fineness of the picture, one is the pixel of the picture, and the other is the vertical resolution of the picture. The higher the pixels of the picture, the finer the pixels on the same size picture and the smaller the lattice. And because the human eye is quite sensitive to the vertical resolution of the image, the higher the vertical resolution, the more detail and level the human eye can recognize.
Full HD has approximately 2 million pixels and a vertical resolution of 1080. The 4K picture pixels reach 4 times of full HD, about 8 million, and the vertical resolution reaches 2160, which is twice the 1080. Therefore, from the data point of view, the 4K picture accuracy is indeed above the 1080p full HD picture.
The second advantage of the 4K display system:
Color levels and detail enhancements make the picture closer to real life
The transition from standard definition to high-definition display systems is actually an upgrade in terms of resolution, and there is not much improvement in color. However, in the era of 4K ultra-high definition, in addition to the dramatic leap in resolution, the changes in color are quite noticeable. This part is reflected in the latest ITU-R BT.2020 Ultra HD broadcast standard.
This is the contrast between the BT.2020 color gamut and the Rec.709 color gamut. The area is much larger, indicating that the 4K display system can bring more color than the HD system.
In the previous section we have analyzed in detail a series of details in the BT.2020 standard, as well as the relevant parameters of the RGB color space under the standard. Based on these parameters, we can draw the corresponding gamut triangle on the CIE1931 chromaticity table, and find that its area is not only larger than the gamut triangle of the Rec.709 HD standard, even more than the gamut triangle under the DCI digital cinema. Big. It should be explained here that the semi-elliptical area on the CIE1931 chromaticity meter is the area visible to the human eye, and the triangle range under the area indicates the amount of visible light that the display device can display. The 4K Ultra HD display system can bring a larger color gamut triangle, indicating that the system can display a richer number of colors.
The latest projectors have begun to use new solid-state light sources such as LEDs and lasers to make the color gamut perform better.
Many audio and video enthusiasts may be curious. Why didn't the gamut triangle be set larger when the Rec.709 HD standard was set? This is mainly due to the fact that the HD shooting and display device itself could not achieve too much color gamut performance, especially in terms of display devices. Nowadays, with the continuous development and maturity of LED, OLED and laser light sources, the new generation of flat-panel TVs and home theater projectors already have a sufficiently wide color gamut triangle in physical properties. If we calibrate the color gamut of the screen according to the Rec.709 HD standard, in most cases it is necessary to compress the native gamut of the display device. Doing so will reduce the performance of the projector's output brightness, because the most compressed part is the brightest green. The emergence of the BT.2020 standard allows the projector's native color gamut to be fully utilized, making the color richer and the energy of the picture more abundant.
The third advantage of the 4K display system:
The 4K video system handles 10-bit, even 12-bit encoded video signals.
At this stage, the HD or Full HD system uses an 8-bit video system, while the 4K Ultra HD uses a 10-bit or 12-bit video system. Therefore, whether it is the gray level transition or the color depth level performance, it has a greater improvement than the HD system. However, it should be noted that due to the processing of more than 10 video signals, the signal source equipment of the 8-bit system under the current high-definition system will not meet the requirements. At the same time, in the process of picture adjustment, it should be noted that the standard black level and standard peak value of the 10-bit system are also different from the 8-bit system, and it is impossible to test with the previous test pattern. Video tuning technicians and audio-visual enthusiasts must pay attention to this problem. For example, a 10-bit encoded video signal has a valid range of 64-940, and a 12-bit encoded video signal has a valid range of 256-3760 instead of 8-bit 16-235.
In addition, since the entire system has to be upgraded from 8 to 10 or 12, meaning that all associated devices need to be upgraded, there is a certain degree of difficulty, which will affect the overall popularity of the 4K display system.
The fourth advantage of the 4K display system:
4K display device enhances the performance of passive 3D glasses
3D display is a very hot topic in recent years. In just a few years, almost all of the latest flat-panel TVs and home theater projectors have built-in 3D display capabilities. There are two mainstream 3D technologies, one is active shutter 3D glasses technology, and the other is passive 3D glasses technology. In view of the current market development, active shutter 3D glasses technology accounts for the vast majority of market share. The main reason is that active 3D technology can achieve full HD resolution for both left and right eyes, while passive 3D technology is theoretical. But it can't be realized. However, passive 3D glasses technology has the advantages of no flickering of the screen, no crosstalk between left and right eyes, and high comfort for wearing glasses. It is also favored by many audio and video enthusiasts.
Interestingly, Sony and LG's 4K LCD TVs, which first appeared on the market, used passive polarization 3D glasses technology. The 4K display capability enables them to display stereoscopic images of full HD resolution with both left and right eyes in passive 3D technology. The fineness of the picture is comparable to the active shutter 3D technology, and the picture distortion is lower, and the dynamic image transition is smoother. natural.
The above is the four main advantages of the 4K display system, reflecting that the 4K display system will eventually replace the current mainstream 1080p full HD system and become the mainstream. But as a whole new thing, it often causes many questions.
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