Cell phones, almost everyone has become indispensable electronic products in life, work and study. And with the continuous development of display technology, human perception of the screen is increasingly picky, a good screen, what parameters or performance to look at?
As we all know, the screen color saturation, color gamut, resolution, pixel density, refresh rate, contrast ratio, HDR display, support for MEMC and other aspects, all affect the human eye perception, but also affect the screen can become a good screen.
Color saturation, color gamut, resolution and other aspects, we are already very familiar with, here will not repeat, the following specific elaboration of several other important parameters related to the performance of the screen.
HDR display
HDR (abbreviation for High Dynamic Range), which translates to high dynamic range images, is a term widely known in the photographic community. HDR, a group of technologies used to achieve a greater dynamic range of exposure than ordinary digital image technology, is a term widely known in the photographic community. HDR and SDR (Standard Dynamic Range) are both made from masters with a wider dynamic range, corresponding to the capabilities of the display devices of the time. HDR devices have now become increasingly available, while the amount of HDR content is also growing.
HDR10 is the most prevalent HDR standard and is the mandatory format for the Ultra HD Blu-ray specification. HDR10 sets a number of conditions for image reproduction capabilities, including 10 Bit color depth and BT.2020 color space. It also requires a display brightness of at least 1000 nits.
The HDR standard specifies a color depth of 10bit, which means that it can display 1.07 billion colors, while the ordinary Blu-ray standard SDR supports a color depth of 8bit, with only 16.77 million colors, a huge difference between the two.
Color reproduction range of BT.709 and BT.2020
SDR and HDR effect comparison
Screens with HDR display can display high dynamic range of images, which can truly restore the original light and dark effects of the scene, more comprehensive and detailed rendering of bright and dark picture details, fuller picture, smoother color transition, and can bring more stunning visual effects. Therefore, HDR display gives the screen a higher performance capability, which can better perform higher contrast between light and dark and a wider color gamut to meet the human eye’s detailed insight into the screen image.
HDR display is effective in games or movies and dramas, and HDR display can be seen as a standard for high-end cell phones. With HDR display, it means that the screen has completed the first step from ordinary to excellent.
A few representative phones that support HDR display
Netflix’s 200 HDR movies still account for only 4% of its total library, and for Amazon Prime Video, the number is less than 0.1%, so compared to the overall number of movies, HDR content still seems insignificant. is still insignificant compared to the overall number of movies. High frame rate movies (movies with a high frame rate of 48 fps or higher) are similarly rare, with only 14 of the 500,000 movies made between 1978 and 2019 statistically being high frame rate.
These figures show that even a high-definition phone that supports HDR display may not always render a satisfactory image perfectly.
Then why the phone obviously has a high resolution, high color saturation, high color gamut, high refresh rate, and can also support HDR display, but still does not meet the user’s psychological expectations? This is because it may be displaying a non-HDR format, a low frame rate movie. Because the content format lags behind the hardware performance capability of the device, this reality seriously affects the visual experience on the phone; at the same time, the rapid change of ambient light when users use the phone will also further reduce the visual experience of the phone.
So what is the solution to the annoying problem of the huge gap between cell phone display and content?
First, several facts need to be recognized.
All smartphones have refresh rates between 60-120 Hz.
However, the vast majority of video content frame rates are between 24-30 fps (well below the phone screen refresh rate), and only a very small number of movies are produced at frame rates greater than 30 fps; with the popularity of streaming services, and UGC short videos, lower frame rates (e.g. 15 fps) have emerged.
A smooth display is only possible if the screen refresh rate matches the frame rate of the displayed content, while a lower frame rate (usually lower than the display refresh rate) can lead to jitter, which is perceived as “intermittent” or discontinuous motion pictures, making the motion picture a poor visual experience. HDR video requires higher brightness and greater contrast than SDR (Standard Dynamic Range) video, and HDR video has greater black and white differences and higher contrast than SDR video, which makes the jitter more obvious.
If you watch a normal SDR movie with a phone that supports HDR display but no related solution, it usually will not achieve the effect that users expect.
Therefore, especially when watching high-speed motion video, it is very important to perfectly render a smooth display, which requires a perfect solution to accurately detect motion content and accurately display video content regardless of the content frame rate or refresh rate, eliminate face painting defects such as dithering, and self-adapt to the ever-changing effects of external ambient light.
About MEMC Technology
The phone screen that can perfectly present the motion picture is the only screen that can be excellent. So the current high-end cell phones are making efforts to smoothly present the motion picture.
For example, the latest release of One Plus 8 Pro on April 16, which is a good solution to problems such as jittering of motion picture display, is a phone that supports MEMC. Liu Zuohu, CEO of OnePlus Technology, said that MEMC can insert the classic image of minimum 24 fps up to 120 fps by independent chip + exclusive algorithm.
So what exactly is MEMC, known as MoTIon EsTImaTIon/MoTIon Compensation, which is created to achieve higher frame rates, simply by interpolating frames between two traditional frames and adding motion compensation frames by predicting the trajectory of object motion through chips and algorithms. It turns the original 24 fps or 30 fps video into 60 fps or higher, thus increasing the actual frame rate of video playback to make the content exactly match the refresh rate of the phone screen and make the motion picture appear smoother.
In addition to the OnePlus 8 Pro phone, the OPPO Find X2, OPPO Find X2 Pro, Black Shark 1, Black Shark 2 and Black Shark 3 also use MEMC technology. These phones can give a smooth picture and fine picture quality when watching movies and playing games. This is also an important factor for their popularity among electronic enthusiasts and gamers.
Before the application on cell phones, the MEMC dynamic compensation technology has been widely used in the middle and high-end TVs, but the name of each manufacturer is different. For example, Xiaomi directly named it as MEMC, while Sony named it as Motionflow, LG called it TruMotion, Samsung called it Auto Motion Plus, Hisense called it SMR, and WeiWei called it RuiLiDe. But no matter how they are called, they all effectively eliminate the problems of blurring, dragging and jittering by inserting motion compensation frames into the motion picture, which can present high-speed motion scenes clearly and smoothly, allowing users to watch motion pictures without missing any wonderful details and reducing the corresponding vertigo and discomfort.
MEMC technology has been applied to TV, but it is the first time to be applied to cell phone, so the new application will have one or another shortcomings, and the MEMC video frame insertion is not a panacea, because its principle is to “predict” the content in the middle of two frames by the machine’s algorithm. The inserted “frame” does not exist in the original content after all, so if the overall picture does not change much, the interpolation can achieve a relatively good display effect, but if the video motion is intense, or the original content changes a lot between the two frames, it may produce “ghosting”, that is The picture that does not match the actual motion track. Any electronic products want to achieve excellent display effect, but also need the processor, display, image processing algorithm and other hardware and software configuration to effectively match the joint decision, relying on MEMC alone will not achieve the perfect effect.
At present, both cell phone companies and TV manufacturers have mentioned the MEMC technology to a position of sufficient importance. Xiong Junmin, vice president of Huawei Glory Business Department, pointed out in his comment on smart screen that MEMC is a watershed for high and low-end products, and products that do not support MEMC technology in the market at present can basically be categorized as low-end. It shows the status of MEMC technology in his mind.
It is believed that with the efforts of manufacturers, the presentation of motion pictures on cell phone screens will reach the limit of what the naked eye can distinguish in the future, just like the presentation of static pictures. As listed below, the naked eye can’t see any graininess in static images.
Some of the high-resolution, high pixel density representative models
As more and more phones upgrade to higher resolution (2K or even 3K screen), higher refresh rate (120Hz) and support HDR display, MEMC frame insertion will become a necessary feature on high-end smartphones. In the future, more high-end flagship phones will join the ranks of “high frame” to display smooth and dynamic images.
