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Frame rate (expressed in or FPS) is the
frequency Frequency is the number of occurrences of a repeating event per unit of time A unit of time is any particular time Time is the indefinite continued sequence, progress of existence and event (philosophy), events that occur in an apparen ...

frequency
(rate) at which consecutive
image An image (from la, imago) is an artifact that depicts visual perception Visual perception is the ability to interpret the surrounding environment (biophysical), environment through photopic vision (daytime vision), color vision, sco ...

image
s ( frames) are captured or displayed. The term applies equally to
film A film, also called a movie, motion picture or moving picture, is a work of visual art The visual arts are art forms such as painting Painting is the practice of applying paint Paint is any pigmented liquid, liquefiable, ...

film
and
video camera A video camera is a camera A camera is an optical Optics is the branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural ...

video camera
s,
computer graphics Computer graphics deals with generating images with the aid of computers. Today, computer graphics is a core technology in digital photography, film, video games, cell phone and computer displays, and many specialized applications. A great dea ...

computer graphics
, and
motion capture Motion capture (sometimes referred as mo-cap or mocap, for short) is the process of recording the motion (physics), movement of objects or people. It is used in Military science, military, entertainment, sports, medical applications, and for val ...
systems. Frame rate may also be called the , and be expressed in
hertz The hertz (symbol: Hz) is the unit Unit may refer to: Arts and entertainment * UNIT Unit may refer to: Arts and entertainment * UNIT, a fictional military organization in the science fiction television series ''Doctor Who'' * Unit of action ...

hertz
. Frame rate in electronic camera specifications may refer to the maximal possible rate, where, in practice, other settings (such as exposure time) may reduce the frequency to a lower number.


Human vision

The temporal sensitivity and resolution of
human vision Visual perception is the ability to interpret the surrounding environment (biophysical), environment through photopic vision (daytime vision), color vision, scotopic vision (night vision), and mesopic vision (twilight vision), using light in ...
varies depending on the type and characteristics of visual stimulus, and it differs between individuals. The human
visual system The visual system comprises the sensory organ A sense is a biological system A biological system is a complex network which connects several biologically relevant entities. Biological organization spans several scales and are determined b ...
can process 10 to 12 images per second and perceive them individually, while higher rates are perceived as motion. Modulated light (such as a
computer display A computer monitor is an output device that displays information in pictorial or text form. A monitor usually comprises a electronic visual display, visual display, electronic circuit, some circuitry, a casing, and a power supply. The display dev ...
) is perceived as stable by the majority of participants in studies when the rate is higher than 50 Hz. This perception of modulated light as steady is known as the
flicker fusion threshold The flicker fusion threshold, or flicker fusion rate, is a concept in the psychophysics of Visual perception, vision. It is defined as the frequency at which an intermittent light stimulus appears to be completely steady to the average human observ ...
. However, when the modulated light is non-uniform and contains an image, the flicker fusion threshold can be much higher, in the hundreds of hertz. With regard to image recognition, people have been found to recognize a specific image in an unbroken series of different images, each of which lasts as little as 13 milliseconds.
Persistence of vision Persistence of vision traditionally refers to the optical illusion that occurs when visual perception of an object does not cease for some time after the rays of light proceeding from it have ceased to enter the eye. The illusion has also been des ...
sometimes accounts for very short single-millisecond visual stimulus having a perceived duration of between 100 ms and 400 ms. Multiple stimuli that are very short are sometimes perceived as a single stimulus, such as a 10 ms green flash of light immediately followed by a 10 ms red flash of light perceived as a single yellow flash of light.


Film and video


Silent films

Early
silent film A silent film is a film A film, also called a movie, motion picture or moving picture, is a work of visual art The visual arts are art forms such as painting Painting is the practice of applying paint, pigment, color or oth ...

silent film
s had stated frame rates anywhere from 16 to 24 frames per second (fps), but since the cameras were hand-cranked, the rate often changed during the scene to fit the mood. Projectionists could also change the frame rate in the theater by adjusting a
rheostat A potentiometer is a three- terminal resistor with a sliding or rotating contact that forms an adjustable voltage divider. If only two terminals are used, one end and the wiper, it acts as a variable resistor or rheostat. The measuring instrume ...
controlling the voltage powering the film-carrying mechanism in the
projector image:IFA 2012 IMG 5767.JPG, 200px, Acer inc., Acer projector, 2012 A projector or image projector is an optical device that projects an image (or moving images) onto a surface, commonly a projection screen. Most projectors create an image by shin ...
. Film companies often intended that theaters show their silent films at higher frame rates than they were filmed at. These frame rates were enough for the sense of motion, but it was perceived as jerky motion. To minimize the perceived flicker, projectors employed dual- and triple-blade
shutters
shutters
, so each frame was displayed two or three times, increasing the flicker rate to 48 or 72 hertz and reducing eye strain.
Thomas Edison Thomas Alva Edison (February 11, 1847October 18, 1931) was an American inventor and businessman. He developed many devices in fields such as electric power generation Electricity generation is the process of generating electric power from s ...

Thomas Edison
said that 46 frames per second was the minimum needed for the eye to perceive motion: "Anything less will strain the eye." In the mid to late 1920s, the frame rate for silent films increased to between 20 and 26 FPS.


Sound films

When
sound film A sound film is a motion picture with synchronization, synchronized sound, or sound technologically coupled to image, as opposed to a silent film. The first known public exhibition of projected sound films took place in Paris in 1900, but decad ...
was introduced in 1926, variations in film speed were no longer tolerated, as the human ear is more sensitive than the eye to changes in frequency. Many theaters had shown silent films at 22 to 26 FPS, which is why the industry chose 24 FPS for sound films as a compromise. From 1927 to 1930, as various studios updated equipment, the rate of 24 FPS became standard for 35 mm sound film. At 24 FPS, the film travels through the projector at a rate of per second. This allowed simple two-blade to give a projected series of images at 48 per second, satisfying Edison's recommendation. Many modern 35 mm film projectors use three-blade shutters to give 72 images per second—each frame is flashed on screen three times.


Animation

In drawn
animation Animation is a method in which figures Figure may refer to: General *A shape, drawing, depiction, or geometric configuration *Figure (wood), wood appearance *Figure (music), distinguished from musical motif *Noise figure, in telecommunication ...
, moving characters are often shot "on twos", that is to say, one drawing is shown for every two frames of film (which usually runs at 24 frame per second), meaning there are only 12 drawings per second. Even though the image update rate is low, the fluidity is satisfactory for most subjects. However, when a character is required to perform a quick movement, it is usually necessary to revert to animating "on ones", as "twos" are too slow to convey the motion adequately. A blend of the two techniques keeps the eye fooled without unnecessary production cost. Animation for most "
Saturday morning cartoon "Saturday-morning cartoon" is a colloquial term for the original animated series An animated series is a set of animated Animation is a method in which Image, figures are manipulated to appear as moving images. In traditional animation, images ...
s" was produced as cheaply as possible and was most often shot on "threes" or even "fours", i.e. three or four frames per drawing. This translates to only 8 or 6 drawings per second respectively.
Anime is hand-drawn and computer animation " technique Computer animation is the process used for digitally generating animated images. The more general term computer-generated imagery Computer-generated imagery (CGI) is the application of ...

Anime
is also usually drawn on threes.


Modern video standards

Due to the
mains frequency The utility frequency, (power) line frequency (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United St ...
of electric grids, analog television broadcast was developed with frame rates of 50 Hz (most of the world) or 60 Hz (Canada, US, Japan, South Korea). The frequency of the electricity grid was extremely stable and therefore it was logical to use for synchronization. The introduction of color television technology made it necessary to lower that 60 FPS frequency by 0.1% to avoid "
dot crawl 300px, Enlarged detail from a video source exhibiting dot crawl. Note the distinctive checkerboard pattern on the vertical edges between yellow and blue areas. Dot crawl is a visual defect of color analog video standards when signals are transmitte ...

dot crawl
", a display artifact appearing on legacy black-and-white displays, showing up on highly-color-saturated surfaces. It was found that by lowering the frame rate by 0.1%, the undesirable effect was minimized. , video transmission standards in North America, Japan, and South Korea are still based on 60  / 1.001 ≈ 59.94 images per second. Two sizes of images are typically used: 1920×1080 ("1080i/p") and 1280×720 ("720p"). Confusingly, ''interlaced'' formats are customarily stated at 1/2 their image rate, 29.97/25 FPS, and ''double'' their image height, but these statements are purely custom; in each format, 60 images per second are produced. A resolution of 1080i produces 59.94 or 50 1920×540 images, each squashed to half-height in the photographic process and stretched back to fill the screen on playback in a television set. The 720p format produces 59.94/50 or 29.97/25 1280×720p images, not squeezed, so that no expansion or squeezing of the image is necessary. This confusion was industry-wide in the early days of digital video software, with much software being written incorrectly, the coders believing that only 29.97 images were expected each second, which was incorrect. While it was true that each picture element was polled and sent only 29.97 times per second, the pixel location immediately below that one was polled 1/60 of a second later, part of a completely separate image for the next 1/60-second frame. Film, at its native 24 FPS rate could not be displayed without the necessary pulldown process, often leading to "judder": To convert 24 frames per second into 60 frames per second, every odd frame is repeated, playing twice, while every even frame is tripled. This creates uneven motion, appearing stroboscopic. Other conversions have similar uneven frame doubling. Newer video standards support 120, 240, or 300 frames per second, so frames can be evenly sampled for standard frame rates such as 24, 48 and 60 FPS film or 25, 30, 50 or 60 FPS video. Of course these higher frame rates may also be displayed at their native rates. Frame rate in electronic camera specifications may refer to the maximal possible rate, where, in practice, other settings (such as exposure time) may reduce the frequency to a lower number.


Frame rate up-conversion

Frame rate up-conversion is the process of increasing the
temporal resolutionTemporal resolution (TR) refers to the discrete resolution of a measurement ' Measurement is the number, numerical quantification (science), quantification of the variable and attribute (research), attributes of an object or event, which can be used ...
of a video sequence by synthesizing one or more intermediate frames between two consecutive frames. A low frame rate causes
aliasing In signal processing Signal processing is an electrical engineering subfield that focuses on analysing, modifying, and synthesizing signals such as audio signal processing, sound, image processing, images, and scientific measurements. Sig ...

aliasing
, yields abrupt motion artifacts, and degrades the video quality. Consequently, the temporal resolution is an important factor affecting video quality. Algorithms for FRC are widely used in applications, including visual quality enhancement, video compression and slow-motion video generation.


Methods

Most FRC methods can be categorized into
optical flow Optical flow or optic flow is the pattern of apparent motion Image:Leaving Yongsan Station.jpg, 300px, Motion involves a change in position In physics, motion is the phenomenon in which an object changes its position (mathematics), position over ...
or kernel-based and pixel hallucination-based methods.


Flow-based FRC

Flow-based methods linearly combines predicted optical flows between two input frames to approximate flows from the target intermediate frame to the input frames. They also propose flow reversal (projection) for more accurate image warping. Moreover, there are algorithms that gives different weights of overlapped flow vectors depending on the of the scene via a flow projection layer.


Pixel Hallucination-based FRC

Pixel Hallucination-based methods use deformable
convolution In mathematics Mathematics (from Ancient Greek, Greek: ) includes the study of such topics as quantity (number theory), mathematical structure, structure (algebra), space (geometry), and calculus, change (mathematical analysis, analysis). ...
to the center frame generator by replacing optical flows with offset vectors. There are algorithms that also interpolates middle frames with the help of deformable convolution in the feature domain. However, since these methods directly hallucinate pixels unlike the flow-based FRC methods, the predicted frames tend to be
blurry "Blurry" is a song by the American rock music, rock band Puddle of Mudd. It was released in October 2001 as the second single from the album ''Come Clean (Puddle of Mudd album), Come Clean''. Composition The song is written in the key of E-flat ...
when fast-moving objects are present.


Instruments

;AviSynth MSU Frame Rate Conversion Filter: The AviSynth MSU Frame Rate Conversion Filter is an
open-source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use the source code, design documents, or content of the product. The open-source model is a decentralized softwar ...
tool intended for video frame rate up-conversion. It increases the frame rate integer times. It allows, for example, to convert a video with 15 fps into a video with 30 fps. ;Adobe Premiere Pro: Adobe Premiere Pro is a commercial video editing software program that allows you to slow down your video using optical flow and time remapping effects to conventionally shot footage to create better looking and smoother slow motion. ;Vegas Pro: Vegas Pro also is a commercial video editing software program. There is
method
to make slow motion video too. To perform it you need to choose the motion magnitude in your video and percentages of playback speed. ;Topaz Video Enhance AI: Topaz Video Enhance AI has the Chronos AI model uses deep learning to increase video frame rate without artifacts. This algorithm generates new frames that are often indistinguishable from frames captured in-camera. ;Advanced Frame Rate Converter (AFRC): Main advantage of AFRC algorithm is using of several quality enhancement techniques such as adaptive artifact masking, black stripe processing and occlusion tracking: :*adaptive artifact masking technique allows to make artifacts less noticeable for eyes thus increasing the integral quality of processed video; :*black stripe processing allows to avoid artifacts which are commonly appeared in interpolated frames in case of black stripe presented near frame edges; :*occlusion tracking performs high quality restoration of interpolated frames near edges in case of presence of motion with direction to/from the frame edge.


See also

* Delta timing *
Federal Standard 1037C Federal Standard 1037C, titled Telecommunications: Glossary of Telecommunication Terms, is a United States The United States of America (USA), commonly known as the United States (U.S. or US), or America, is a country Contiguous United St ...
* Film-out *
Flicker fusion threshold The flicker fusion threshold, or flicker fusion rate, is a concept in the psychophysics of Visual perception, vision. It is defined as the frequency at which an intermittent light stimulus appears to be completely steady to the average human observ ...
* Glossary of video terms *
High frame rate In motion picture technology—either film A film, also called a movie, motion picture or moving picture, is a work of visual art The visual arts are art forms such as painting Painting is the practice of applying paint P ...
*
List of film formats This list of film formats catalogues formats developed for shooting or viewing motion pictures A film, also called a movie, motion picture or moving picture, is a work of visual art The visual arts are art forms such as painting ...
*
Micro stuttering__notoc__ Micro stuttering is a term used in computing to describe a quality defect A defect is a physical, functional, or aesthetic attribute of a product or service that exhibits that the product or service failed to meet one of the desired speci ...
*
MIL-STD-188 200 px, Cover of CHQ’s commercial reprint of the MIL-STD-188 Military Standards series MIL-STD-188 is a series of U.S. military standards relating to telecommunications. Purpose Faced with "past technical deficiencies in telecommunications syst ...
*
Movie projector A movie projector is an optics, opto-mechanics, mechanical device for displaying Film, motion picture film by projecting it onto a movie screen, screen. Most of the optical and mechanical elements, except for the illumination and sound devices ...
* Moving image formats *
Time-lapse photography seeds germinating, a 10-day time-lapse in roughly 1 minute File:GeraniumFlowerUnfurl2.gif, 300px, Blossoming Pelargonium, geraniums; 2 hours are compressed into a few seconds Time-lapse photography is a technique in which the frequency at which ...
*
Video compression In signal processing, data compression, source coding, or bit-rate reduction is the process of encoding information using fewer bits than the original representation. Any particular compression is either Lossy compression, lossy or Lossless comp ...


References


External links


"Temporal Rate Conversion"
a very detailed guide about the visual interference of TV, video & PC (
Wayback Machine The Wayback Machine is a digital archive An archive is an accumulation of Historical document, historical records – in any media – or the physical facility in which they are located. Archives contain primary source documents that have ...

Wayback Machine
copy)
Compare frames per second: which looks better?
a web tool to visually compare differences in frame rate and motion blur. {{DEFAULTSORT:Frame Rate Film and video technology Temporal rates