4K What exactly is the resolution?

The current mainstream computer display resolution is 1920x1080, which is often said the FHD standard, but the smartphone is beginning to 2560x1440 forward, the PC monitor clearly needs further strengthening, the next generation standard is 4K resolution, that is, UTLRA HD standard. This year, Dell, Lenovo, Asus, Samsung and other companies have launched Low-cost 4K display, the cheapest only more than 4,000 can be bought, is expected at the end of next year will be reduced to 3000 yuan, the user is also easier to accept.

4K for us is not only a resolution upgrade, its impact is far greater than the previous 1680x1050 resolution upgrade to 1920x1080, from the application experience, UI optimization and performance of the more serious challenges, but more importantly, 4K is coming, many people have no clear understanding of 4K.

Let's start from scratch today and talk about 4K resolution in the end.

Recall that the previous two years, the TV manufacturers are also in their own products can be a full HD as a selling point, but since the launch of Sony 4K TV, Full HD has become a TV field "backward" pronoun, first of all brands in the flagship product launched 4K model, and then the 4K model to popularize to mainstream products and even entry level products, Of course, there are also a variety of "4K is more than Full HD" good publicity, a time consumers see dazzling, some do not know how to feel.

In fact, a lot of consumers will choose to buy 4K TV, simply because the store salesman told him that "4K TV is good, buy a 4K TV," but what the 4K television and even the 4K television is what the problem, they are completely unaware of. This time we will talk about the 4K resolution and 4K TV, 4K display choice problem, let us understand what is 4K, now follow the trend to buy 4K products is not really meaningful.

　　What do we often say about the 4K?

To understand 4K products, first of all, we should start with the relevant standards of 4K images. The size of the image can be expressed in pixel resolution, such as 1920*1080 resolution, which means that the image is made up of 1080 pixels per row, 1920 pixels in a horizontal direction, and a vertical orientation. For the convenience of communication, the industry is often represented by the image in the horizontal direction of the pixel value of the picture size, and in order to simplify the communication process, the general use of "K" to describe the pixel value, where 1 K is the equivalent of 1024 pixels, a few K refers to the horizontal direction of the image of each line of pixels to reach or nearly 1024 times.

As a standard, 4K image refers to the horizontal direction of each line of pixels to reach or close to 4,096 images, in most cases, especially 4096*2160 resolution. Depending on the scope of use, 4K images also have a wide range of derivative resolutions, such as full Aperture 4K 4096*3112, Academy 4K 3656*2664, and UHDTV standard 3840*2160, all of which belong to the 4K image resolution category.

Today's common 4K resolution has 4096*2160 and 3840*2160 two, the former mainly used in the field of digital cinema, the latter is more used in the 4K TV or 4K display. A TV or monitor with a 3840*2160 resolution is also called a UHDTV standard product. The UHDTV standard is developed by the International Telecommunication Union, which is the ultra high Definition television, or ultra clear TV. The UHDTV resolution is exactly four times times that of FHDTV, compared to the 1920*1080 resolution's full High definition television (FHDTV, all High-definition TV), and can display finer images in the same screen size. And because the aspect ratio is also the 16:9,UHDTV standard product also can be very good compatible with the FHDTV image, is easier to be accepted by the consumer.

In strict terms, however, 4K TV is not exactly the same as an ultra-clear TV because the UHDTV standard contains 7680*4320 resolutions besides 3840*2160 resolution, which is also known as 8K resolution. So technically, 4K TV is a super clear TV, but ultra-clear TV is not limited to 4K TV. Now the focus of television or display manufacturers will be on the "4K" instead of "super clear", in addition to the former read a stronger sense of technology, one of the reasons is to want to give future "8K" products to make a difference in space.

　　How high is the refresh rate required for 4K products?

For 4K resolution, it has only horizontal pixel value and vertical pixel value of two attributes, but for the 4K TV and 4K display products, in addition to the resolution to meet the standard, the level of refresh rate can not be ignored. Refresh rate refers to the screen image of the update rate, the previous CRT monitors rely on electronic excitation screen phosphor display image, but because the same time only one pixel is lit, to display a complete image, the monitor must be in the phosphor before the end of the light to fire again.

It's just that the CRT display's phosphor-peripheral time is actually very short, so the electron must be in a very short time to restart the fluorescent powder, in order to maintain the stability of the image, and this excitation frequency is what we now often said refresh rate, if the refresh rate is not enough, CRT display screen will appear flashing, it looks very uncomfortable. In general, CRT display refresh rate is higher the better, at least to 85Hz above, the human eye will not feel the obvious flashing.

Now that TVs and monitors are already in the LCD era, the LCD works quite differently from the CRT, and it's more like a slide, just replacing the film with an LCD. LCD pixels can be seen as a separate switch, only a single refresh action can display a stable image, can be done only after the image changes to refresh the screen. Now the LCD screen will also be a constant frequency to refresh the image, even if only static images, more is in the product compatibility considerations, but also conducive to the rapid transformation of dynamic picture. Of course, compared to the "higher refresh rate," The CRT screen, LCD screen on the refresh rate is undoubtedly much lower, basically no less than 24Hz can guarantee the smooth image.

Because of the visual remnants of the human eye, we can make this pattern with a rotating led light.

So why does the LCD screen need more than 24Hz refresh rate? In fact, this is determined by the visual residue time of the human eye or the response time of the optic nerve, which is about 1/24 seconds, in other words, when the image is converted to 24 times per second, due to the visual residual effect, The image that the human eye sees is no longer a separate picture, but a coherent animation, which is the main reason for the film's principle and the video frame speed, which is mostly 24FPS. Because the LCD screen needs to be refreshed when the image changes, when playing 24FPS video per second, you need to refresh the screen at least 24 times per second to ensure that every frame of the video appears on the screen in order to ensure that the eyes see a coherent image, which is the LCD screen refresh rate requires no less than 24Hz.

For 4K resolution products are the same reason, want to output fluent 4K resolution dynamic image, screen refresh rate can not be less than 24Hz, so the current mainstream of the two 4K resolution 3840*2160 and 4096*2160, they have 24/25/30/50/ 60Hz, such as a variety of different refresh rate specifications, which are more common in the 24Hz, 30Hz and 60Hz, the first two common in the 4K TV, and the 60Hz specifications are basically only PC monitors or flagship TV products will be used. As to why such arrangements are made, we will explain them in detail in subsequent articles.

　　Which video interfaces can output 4K resolution?

Currently can output 4K resolution of the interface only HDMI and DisplayPort, where the HDMI interface to the output refresh rate of 4K resolution, you must use the support of HDMI 1.4a or higher standards of products, can output 4K resolution specifications for the highest 4096*2160@24 Hz or the 3840*2160@30hz;displayport interface needs to output 4K resolution to support the DP 1.2 standard, but its maximum output refresh rate of 60Hz 4096*2160 and 3840*2160 resolution.

The reason for this difference is that, in the final analysis, two interfaces corresponding to the data bandwidth is different, the HDMI 1.4a interface data bandwidth of 10.2Gbps, and DP 1.2 interface data bandwidth up to 21.6Gbps, is the former twice times more. HDMI interface to output 60Hz refresh rate 4K resolution, only wait until the HDMI 2.0 interface officially debut rear side can be achieved, HDMI 2.0 interface data bandwidth of 18Gbps, can fully meet the 60Hz refresh rate 4K resolution of the output demand.

It is worth saying that the current HDMI interface and DP interface is the product can be output in 4K 60Hz refresh rate of the most intuitive difference, the current environment only configured HDMI interface products can not output 60Hz refresh rate under the 4K screen, only the device configured with DP interface is this possibility. Now most mainstream 4K TV screen specification is the highest is 3840*2160@30hz, so they have only configured the HDMI interface, only a few flagship products will configure the DP interface, support output 60Hz refresh rate 4K resolution screen.

　　What hardware is required for output 4K resolution?

To output 4K resolution of the image, the hardware is also not ambiguous. Although the HD player, which claimed to be able to decode 4K video earlier, has only recently started landing on the HD player that supports output 4K resolutions, and most of them can only output 24Hz or 30Hz refresh rates. To output 4K images under the 60Hz refresh rate, the current PC is still the best choice. The hardware that determines whether the PC can output 4K resolution is the video card, currently only Kepler architecture, GCN architecture, or the stand-alone graphics that update the architecture support output 4K resolution, the set platform aspect will use Haswell architecture processor or Kaveri APU side can support.

First, let's look at how the set up platform outputs the 4K resolution, and the Intel platform must be equipped with the HD Graphics 4200/4400/4600/5000 and the iris Pro Graphics 5200, Iris Graphics 5100 Core Graphics products, The fourth generation core I3/i5/i7 series processor. These core graphics cards through the HDMI interface output 4096*2304@24hz and 3840*2160@24HZ resolution specifications, want to output 60Hz refresh rate 4K resolution, you must use the DP interface for output, the highest can be output 3840*2160@60hz specifications.

And it is noteworthy that the mobile version of the U series can only output 3840*2160@30hz resolution specifications, Y Series in the 60Hz refresh rate can only output 2560*1600 resolution, only H series is configured with the IRIS series core graphics products to output 3840* The resolution specification of the 2160@60hz. As for the previous generation Ivy Bridge can only output 2560*1600, all do not support output 4K resolution.

AMD APU to better identify some, only with GCN architecture graphics core products to support 4K resolution, the refresh rate is also the highest HDMI interface output 30HZ,DP 1.2 interface maximum output 60Hz, in other words, to the APU platform output 4K resolution, Currently, only the Kaveri APU using the socket fm2+ interface can be selected.

Incidentally, the structure is based on the APU platform PS4 and Xbox One support 4K resolution, but since they do not configure the DP 1.2 interface, so even if you can output the 4K resolution of the video signal, which is the maximum 30Hz refresh rate, Basically only video playback and static picture browsing and other places will use, 4K game or don't think.

The platform, first of all, we look at Nvidia graphics products, from the Kepler architecture of the product began to have a basic 4K resolution output capability, but earlier Fermi architecture products can do nothing, the highest output only 2560*1600 resolution. Similarly, the output 3840*2160@60hz specifications need to standard DP 1.2 interface products, in accordance with the public version of the product to GTX 650 Ti boost above only the logo with DP interface.

AMD graphics needs GCN architecture products, HDMI interface can output 4096*2160@30hz specifications, DP interface can output 4096*2160@60hz specifications. Since AMD also has a DP 1.2 interface configured on the entry-level GCN, the 4K resolution of the output 60Hz refresh rate on the AMD-only platform is less expensive.