#PictureMasteringIndex(PMI)

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What is refresh rate in modern TVs

Modern television uses the latest innovative technologies. As a result, their description contains a large number of technical terms and concepts. As a consequence, many users often confuse them. In addition, the description from companies often contains a marketing component, which additionally distorts objective information.

Refresh rate and FPS

The confusion with the screen refresh rate and frame rate due to the same unit of measurement (frames per second) and the similarity of their physical values (information density per unit of time) well illustrates this problem. But they characterize different values. The screen refresh rate corresponds to the maximum number of frames played by the TV per second. In other words, a screen with a frequency of 60 Hz reproduces the image 60 times per second. In fact, the refresh rate of the LCD screen characterizes the frequency of the signals coming to the matrix with information about the color change of the pixels. That is, this value characterizes the objective ability of the device to reproduce frames. Thus, a 50 Hz screen displays the 60 FPS video with lossy. Frame frequency or Frames Per Second (FPS) or Frame Rate or Frame Frequency characterizes the number of frames replaced per second in video content, that is, the shooting technology. This concept was first used by photographer Eadweard Muybridge, who experimented with chronophotographic shooting the moving objects with several cameras. Thus, the difference between these values can be formulated as follows: FPS characterizes the number of frames per second of a video content, and the screen refresh rate determines the possibility of its playback on a particular TV screen. Of course, the optimal choice requires taking into account this aspect. Probably, an expensive display with a frequency of 100 Hz and above will be unnecessarily redundant for playing 25 FPS video content. The video at the end illustrates in detail the difference between these specs.

Modern TVs

In general, modern LED TVs use IPS matrices or their modifications. They provide good color rendering up to 99% and wide viewing angles of 178 ° vertically and horizontally. The response of the modern IPS matrix is about 5 ms. Thus, it plays a maximum of 1000 ms / 5 ms = 200 frames per second. But really, the response time can reach 7 milliseconds. Today, manufacturers install 3 types of matrixes on TVs: - matrix with a frequency of 60 fps; - matrices with a frequency of 120 fps (most common); - matrix with a frequency of 240 fps (usually in expensive models). Today video content for various standards supports: - 1080i - interlaced standard with a frame rate of 25 or 30 (29.97) fps; - 1080p - standard with progressive scanning, allowing the use of 24, 25, 30, 50 or 60 fps; - 720p - standard with progressive (line-by-line) scanning, allowing the use of 50 or 60 fps; - SD - standard digital television 50 or 60 fps; - Analog signal - 25 fps.

Frame interpolation

Refresh rate directly affects the smooth reproduction of high-dynamic scenes and the screen flickering. Accordingly, its increase improves smoothness and reduces flicker. Today, companies solve this task by hardware or by using special processing algorithms (frame interpolation).

Frame interpolation forms additional intermediate frames in video content. Today, almost all segment leaders use their own technologies. The list of indices and technologies of dynamic scenes from different companies includes: - Clear motion rate (CMR), Picture Quality Index (PQI) – Samsung;

- Picture Mastering Index (PMI) - LG; - Perfect Motion Rate (PMR) - Philips; - Motionflow XR – Sony;

- Active Motion & Resolution(AMR) - Toshiba; - Backlight scanning BLS - Panasonic; - Clear Motion Index (CMI) - Thomson; - Subfield Motion - Samsung plazma. Unfortunately, companies use different index calculation methods. Accordingly, TVs without an index of dynamic scenes reproduce an image with a frame rate of the input signal, without its correction or improvement. But today, such models are found only in the budget segment.

Indices of dynamic scenes

TVs with an index of dynamic scenes 100 improve the image by adding 1 frame between the existing two (frame interpolation). Usually, additional virtual frames are identical to the original. In this case, increasing the frequency reduces flicker. Thus, a 60 Hz matrix with an index of 100 visualizes an improvement only for video content with a frequency of less than 60. The index of dynamic scenes 200 is virtually identical to the previous, but uses an improved image processing algorithm by the processor. TVs with a 120 Hz matrix typically support a 400-600 index. They generate 2-3 additional frames between the original ones. The format of the generated frames (identical or different) depends on the processing algorithm. Given the use of identical processors for the indices 100 and 400, it can be assumed that they are identical. Additionally, models with such indices necessarily use local dimming. Theoretically, this technology provides an improvement even for UHD, but many users do not confirm this in their feedback and comments. Models with with support for 800-1200 index use expensive matrices and high-performance processors that provide frame analysis and the creation of new intermediate real frames. According to TV owners, the visualization of improved playback of high-dynamic scenes is present between models with indices 100 and 200, but disappears at indices 400 or 600. Therefore, many experts consider the indexing to be partially marketing. Of course, interpolation requires perfect processing algorithms. Otherwise, inaccurate conversion or generation of intermediate frames reduces the quality of the final image due to digital artifacts. Therefore, increasing the frequency significantly increases the requirements for processing algorithms.

Features

Unfortunately, some companies incorrectly use the concept of 200 Hz. Honest dynamic image enhancement technology uses motion interpolation, generating additional frames. Other a cheaper and less efficient technology uses Scanning Backlight technology, which reduces motion blur. Such TVs with pseudo 200 Hz mode and Scanning Backlight technology actually provide frame refreshing only with 100 Hz. In this case, the control system divides the screen into three parts horizontally and periodically on / off backlight. Next, the TV adds a dark rectangle to the image on the screen, that moves across the screen at a frequency of 100 times per second, creating the illusion of playback with 200 Hz. Periodically dimming the backlight reduces the blurring effect of a moving object, increasing the sharpness of the contours in intermediate frames. Additionally, this technology reduces power consumption. But, of course, Scanning Backlight is radically different from the real frequency of 200 Hz and has significant drawbacks. In particular, it reduces the overall brightness of the image and increases the flicker of the screen. The test mode of such images illustrates the difference between real 200 Hz and Scanning Backlight.

Although, of course, the lower cost partially compensates for this nuance.

Conclusion

Today, models of the world's leading electronics companies, including Samsung, LG and Sony, provide real 200 fps with the help of powerful high-performance video processors. Such TVs correctly form up to three intermediate frames between consecutive frames of a standard 50 Hz video content. As a result, the 200 Hz provides excellent detail even for the complex maneuver of a football player or fast boxer attack.

In addition, TVs with a refresh rate of 200 Hz are great for gamers. Unfortunately, all such models belong to the upper price segment. Of course, the refresh rate is one of the important criteria for choosing a TV. Read the full article

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Frame rate or fps vs screen refresh rate

Frame rate or fps vs screen refresh rate Of course, modern TVs belong to the segment of very complex electronics and their description requires the use of a large number of technical terms and concepts. For example, the discourse on the color rendering requires understanding the differences between HDR10, Dolby Vision, Hybrid Log-Gamma (HLG), Advanced HDR, etc standards, which support different reference color gamut. Of course, even their simplified classification will simplify the user's perception of the discussion arguments. Frame rate (fps) and screen refresh rate also directly affect the quality of playback. In addition, they have approximately the same physical meaning, characterizing the number of frames per second. As a result, some users sometimes confuse them. But the screen refresh rate characterizes the device’s ability to reproduce the maximum number of frames and is measured in Hz (the number of frames per second), and frame rate characterizes the density of video content and is measured in fps (the number of frames in one second of video content). Thus, the screen refresh rate is a technical device characteristic, and fps refers to video shooting. But at the same time, both of them equally affect some aspects of image perception, for example, its smoothness and clarity.

Screen refresh rate

This value characterizes the maximum number of frames reproduced by the screen per second. In other words, a screen with a frequency of 60 Hz provides the image playback of 60 times per second. Today, most models support 60 Hz. But modern matrices in expensive models can provide 120, 144, and even 240 Hz. This value directly affects the smooth reproduction of high-dynamic scenes and the screen flicker. Accordingly, its increase improves smoothness and reduces flicker. Today, companies solve this problem in hardware or using special algorithms of frame interpolation. The first method is more simple, but requires additional costs. They are well suited for games, because the frequency significantly affects the playback quality in high-dynamic games. Many even call them gaming TVs. The second method uses frame interpolation, forming additional frames in video content. The rapid development of this direction stimulated even the emergence of a separate value - the indices of dynamic scenes. Almost all segment leaders use their own frame interpolation technologies. Today this list includes: - Motion Clarity Index (MCI) – LG; - Clear motion rate (CMR), Picture Quality Index (PQI) – Samsung; - Picture Mastering Index (PMI) - LG; - Perfect Motion Rate (PMR) - Philips; - Motionflow XR - Sony; - Active Motion & Resolution(AMR) - Toshiba; - Backlight scanning BLS - Panasonic; - Clear Motion Index (CMI) - Thomson; - Subfield Motion - Samsung plazma. Unfortunately, the methods of indices calculation are not unified and companies use different algorithms. Moreover, the marketing component also negatively affects their objectivity. Therefore, for more than a decade, some experts periodically argue about the effectiveness of indexation. Of course, these indices fundamentally different from the actual screen refresh rate.

Frame Rate

Frame Rate or Frames Per Second (FPS) or Frame Frequency characterizes the number of frames in one second of video content. This concept was first used by photographer Eadweard Muybridge, who experimented with chronophotographic shooting of moving objects with several cameras. In other words, FPS characterizes the number of frames in one second of a video content, and the screen refresh rate indicates the possibility of its playback on the screen. Thus, a 50 Hz screen displays with losses the 60 fps video content . Of course, the optimal choice requires taking into account this aspect. For example, an expensive display with a frequency of 144 Hz and above will be redundant to play 30 FPS video content. As known, frame rate is 25 fps for Europe and 30 (29.97) fps for USA due to objective reasons for the cinema development. But in recent years, the development of digital technologies has stimulated some changes. Today video content for various standards supports: - 1080i - interlaced standard with a frame rate of 25 or 30 (29.97) fps; - 1080p - standard with progressive scanning, allowing the use of 24, 25, 30, 50 or 60 fps; - 720p - standard with progressive (line-by-line) scanning, allowing the use of 50 or 60 fps; - SD - standard digital television 50 or 60 fps; - Analog signal - 25 fps. As known, shooting a moving object blurs its contour in the motion direction. But distortion directly depends on the distance of the object displacement in one frame. Therefore, increasing the frequency reduces the distance and, accordingly, the motion blur. 1 second / 25 fps = 0.04, but 1 second / 60 fps = 0.016.

FPS perception

Actually, the FPS affects the realism of perception, which depends on the playback smoothness, and flicker, which provokes fatigue. Experiments confidently demonstrate the disappearance of the difference in visualization at a frequency of 20-25 Hz and above, i.e., the person does not perceive the difference between 30 and 60 fps. In fact, it's a sign of a healthy nervous system. For example, some painful conditions with high-amplitude electrical brain rhythms, for example, due to head injuries, poisoning, oxygen starvation, etc. are often accompanied by the flickering of visual images and their painful perception. In contrast, a healthy brain limits visualization to a reasonable level. But on the other hand, our eyes use the physiological analogue of framerate to improve the detail of the object contours. Microtremor of the eye muscles provides constant eye trembling for fixing a static image that enters the brain. The frequency of their admission to the optic brain reaches 90 fps. Further, the brain processes the individual images, transforming them into a moving image. This complex, but effective system sometimes fails, for example, due to muscle injury, which are necessary for microtremor. This situation often arises, for example, in boxers after knockout. In this case, its physiological fps decreases several times and the brain begins to actively create its own pictures, generating hallucinations. Thus, increasing the video content fps reduces the load on the brain, providing the necessary information from the outside. According to many experts, fatigue from the perception of video content is inversely proportional to its fps. In addition, fps affects image detail. For example, 60 fps HD provides better detail compared to 30 fps in 2K resolution (Simon Cooke, Microsoft, 2014 research).

Conclusion

Increasing the frame rate (frames per second) and screen refresh rate (Hz) reduces screen flicker and, as a result, fatigue, and improve smoothness, image detail and, as a result, image quality. But, of course, fps depends on the video content. Therefore, the TV must support it, including the ability to connect to the input of the TV. Today, the market offers models with HFR (high frame rate) technology, which supports 60 and even 120fps. This video perfectly illustrates the FPS impact on the video content perception. Read the full article