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Frame rate, most commonly expressed in frame/s, frames per second or FPS, is typically the frequency (rate) at which consecutive images (frames) are captured or displayed. This definition applies to film and video cameras, computer animation, and motion capture systems. In these contexts, frame rate may be used interchangeably with frame frequency and refresh rate, which are expressed in hertz (Hz). Additionally, in the context of computer graphics performance, FPS is the rate at which a system, particularly a GPU, is able to generate frames, and refresh rate is the frequency at which a display shows completed frames.[1] In electronic camera specifications frame rate refers to the maximum possible rate frames could be captured, but in practice, other settings (such as exposure time) may reduce the actual frequency to a lower number than the frame rate.[2]

Human vision

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Further information: Motion perception

The temporal sensitivity and resolution of human vision varies depending on the type and characteristics of visual stimulus, and it differs between individuals. The human visual system can process 10 to 12 images per second and perceive them individually, while higher rates are perceived as motion.[3] Modulated light (such as a computer display) is perceived as stable by the majority of participants in studies when the rate is higher than 50 FPS. This perception of modulated light as steady is known as the flicker fusion threshold. 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.[4] 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.[5] Persistence of vision 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.[6]

Film and video

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Silent film

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Early silent films had stated frame rates anywhere from 16 to 24 frames per second (FPS),[7] 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 controlling the voltage powering the film-carrying mechanism in the projector.[8] Film companies often intended for theaters to show their silent films at a higher frame rate than that at which they were filmed.[9] 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, so each frame was displayed two or three times, increasing the flicker rate to 48 or 72 FPS and reducing eye strain. Thomas Edison said that 46 frames per second was the minimum needed for the eye to perceive motion: "Anything less will strain the eye."[10][11] In the mid to late 1920s, the frame rate for silent film increased to 20–26 FPS.[10]

Sound film

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When sound film 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 film as a compromise.[12] From 1927 to 1930, as various studios updated equipment, the rate of 24 FPS became standard for 35 mm sound film.[3] At 24 FPS, the film travels through the projector at a rate of 456 millimetres (18.0 in) per second. This allowed simple two-blade shutters 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.[10]

Animation

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This animated cartoon of a galloping horse is displayed at 30 drawings per second, and the fast motion is on the edge of being objectionably jerky.

In drawn animation, moving characters are often animated on twos, meaning one drawing is displayed for every two frames of film. Since film typically runs at 24 frames per second, this results in a display of only 30 drawings per second.[13] 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 and controls production cost.[14]

Animation for most "Saturday morning cartoons" firstly introduced in the mid-1960s 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 also usually drawn on threes or twos.[15][16]

Modern video standards

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See also: List of broadcast video formats

Due to the mains frequency of electric grids, analog television broadcast was developed with frame rates of 50 FPS (most of the world) or 60 FPS (Canada, US, Mexico, Philippines, 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", 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.

As of 2025, 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 interlaced or 1080p progressive) and 1280 × 720 (720p). Confusingly, interlaced formats are customarily stated at half 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 × 720 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 developers believing that only 29.97 images were expected each second. 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.

At its native 24 FPS rate, film could not be displayed on 60 FPS video 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.[17][18]

Electronic camera specifications

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In electronic camera specifications, frame rate refers to the maximum possible rate frames that can be captured (e.g. if the exposure time were set to near-zero), but in practice, other settings (such as exposure time) may reduce the actual frequency to a lower number than the specification frame rate.[19]

Computer games

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In computer video games, frame rate plays an important part in the experience as, unlike film, games are rendered in real-time. 60 frames per second has for a long time been considered the minimum frame rate for smoothly animated game play.[20] Video games designed for PAL markets, before the sixth generation of video game consoles, had lower frame rates by design due to the 50 Hz output. This noticeably made fast-paced games, such as racing or fighting games, run slower;[21] less frequently developers accounted for the frame rate difference and altered the game code to achieve (nearly) identical pacing across both regions, with varying degrees of success. Computer monitors marketed to competitive PC gamers can hit 360, 500 FPS, or more.[22] High frame rates make action scenes look less blurry, such as sprinting through the wilderness in an open world game, spinning rapidly to face an opponent in a first-person shooter, or keeping track of details during an intense fight in a multiplayer online battle arena. Input latency is also reduced.[23] Some people may have difficulty perceiving the differences between high frame rates, though.[24]

Frame time is related to frame rate, but it measures the time between frames. A game could maintain an average of 60 frames per second but appear choppy because of a poor frame time. Game reviews sometimes average the worst 1% of frame rates, reported as the 99th percentile, to measure how choppy the game appears. A small difference between the average frame rate and 99th percentile would generally indicate a smooth experience. To mitigate the choppiness of poorly optimized games, players can set frame rate caps closer to their 99% percentile.[25]

When a game's frame rate is different than the display's refresh rate, screen tearing can occur. Vsync mitigates this, but it caps the frame rate to the display's refresh rate, increases input lag, and introduces judder. Variable refresh rate displays automatically set their refresh rate equal to the game's frame rate, as long as it is within the display's supported range.[26]

Frame rate up-conversion

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Low frame rate video
Video with 4 times increased frame rate

Frame rate up-conversion (FRC) is the process of increasing the temporal resolution of a video sequence by synthesizing one or more intermediate frames between two consecutive frames. A low frame rate causes 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

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Most FRC methods can be categorized into optical flow or kernel-based[27][28] and pixel hallucination-based methods.[29][30]

Flow-based FRC

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Flow-based methods linearly combine 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 give different weights of overlapped flow vectors depending on the object depth of the scene via a flow projection layer.

Pixel hallucination-based FRC

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Pixel hallucination-based methods use deformable convolution to the center frame generator by replacing optical flows with offset vectors. There are algorithms that also interpolate 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 when fast-moving objects are present.

See also

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References

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Revisions and contributorsEdit on WikipediaRead on Wikipedia

Frame rate

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Frame rate is the frequency at which consecutive still images, known as , are captured or displayed in moving-image media such as , video, and digital , typically measured in per second (fps). This metric determines the smoothness and perceived quality of motion, with higher rates reducing blur and enhancing realism by more closely approximating continuous movement. In motion picture production, 24 fps emerged as the global standard in the late 1920s, driven by the need to synchronize projected film with optical soundtracks while minimizing costs and ensuring the persistence of vision illusion. This rate, originally selected as a compromise between technical feasibility and economic efficiency during the transition from silent films (often 16–18 fps) to "talkies," remains the benchmark for cinematic storytelling due to its characteristic motion aesthetic. For broadcast television, regional standards vary: 25 fps for PAL systems in much of and , derived from 50 Hz power grids to avoid flicker, and 29.97 fps (non-drop or drop-frame variants) for in , adjusted from 30 fps to accommodate color encoding. These rates, formalized by organizations like the of Motion Picture and Television Engineers (SMPTE) and the (ITU), ensure compatibility across legacy analog and modern digital workflows. Higher frame rates, such as 48, 50, 60, or even 120 fps, are increasingly adopted in , , and like gaming to capture fast action with greater clarity and reduce judder. SMPTE standards, including extensions in ST 12-3 for timecode, support these elevated rates up to 120 fps for applications requiring enhanced , such as and ultra-high-definition streaming. Frame rate selection influences visual fidelity, storage, bandwidth, and processing demands. Frame rate mismatches can cause artifacts such as or desynchronization in and playback. Additionally, altering the frame rate metadata without re-encoding (while keeping the codec copy settings) preserves the original frame count but changes the playback speed and duration, with a higher specified frame rate resulting in faster playback and shorter duration (or vice versa).

Fundamentals

Definition and Units

Frame rate is defined as the number of frames, or individual still images, displayed or captured per second in moving media such as film, video, or animation. This metric specifically quantifies the frequency at which consecutive frames are presented to create the illusion of motion, distinguishing it from shutter speed, which refers to the duration of exposure for each individual frame during capture, and refresh rate, which measures how frequently a display device updates its screen image, often independently of the source content's frame rate. The primary unit for frame rate is frames per second (fps), a standard adopted across modern film, television, and digital video production to ensure consistency in playback and synchronization. In early cinema, frame rates were occasionally notated in frames per minute (fpm) due to hand-cranked mechanisms that operated on a per-minute basis; for instance, the common 24 fps rate equates to 1440 fpm through simple multiplication by 60 seconds per minute. Notation for frame rates includes both integer values, such as 24 fps for cinematic standards or 30 fps for broadcast video, and fractional values like 23.976 fps, which is used for compatibility with television systems by slightly slowing 24 fps content to align with the 29.97 fps video rate derived from historical broadcast color encoding adjustments. Integer rates provide exact timing for simplicity, while fractional rates ensure seamless integration in legacy workflows without introducing audio pitch shifts or timing drifts. The frame rate can be calculated using the basic equation: fps=total number of framesduration in seconds\text{fps} = \frac{\text{total number of frames}}{\text{duration in seconds}} This formula allows for precise determination of the rate from recorded media duration and frame count, forming the foundation for standards in production and post-processing.

Measurement Techniques

For analog film, frame rate measurement traditionally involves counting the perforations along the film strip (e.g., 16 per frame in 35mm film) over a known length and correlating it with the mechanical speed of the camera or projector, often calibrated using tachometers or stroboscopic devices to verify consistent cranking or motor rates. In hand-cranked systems, practical checks included filming a reference clock or rotating object to assess playback smoothness against expected fps equivalents like 16-18 fps (approximately 960-1080 fpm). In and playback environments, frame rate measurement relies on specialized tools and instruments designed to analyze signal timing, metadata, and frame sequences accurately. Hardware instruments such as waveform monitors are commonly used to visualize and levels alongside timing information in broadcast and live production settings, enabling verification of and rate consistency in SDI or signals. Oscilloscopes, particularly those with video-specific triggering capabilities, facilitate precise timing analysis of frame intervals by capturing electrical signal waveforms from video sources, helping detect deviations in frame delivery rates during . Software analyzers like MediaInfo provide a unified interface for extracting frame rate from file containers, displaying details such as average and real-time frame rates without full decoding. Similarly, FFprobe, part of the FFmpeg suite, offers command-line-based probing of streams to report frame rate metrics in both human-readable and parseable formats. Practical techniques for measuring frame rate include manual or automated frame counting over defined time intervals, where the total number of frames is divided by the duration to compute frames per second (fps). This method is effective for verifying constant frame rates (CFR) in offline and can be implemented using software tools that enumerate frames from decoded streams. High-speed camera is employed to identify discrepancies in recorded footage, such as irregular frame intervals caused by shutter variations or motion artifacts, by capturing the output at rates exceeding the source video's fps for temporal comparison. Software-based metadata extraction from file formats further simplifies measurement; for instance, in MP4 containers, tools parse box structures like 'tkhd' or 'mdhd' to retrieve and timescale data, yielding the nominal frame rate embedded during encoding. metadata in certain camera-generated videos also stores frame rate tags, accessible via standard libraries for quick verification. Measuring frame rate presents challenges, particularly with variable frame rates (VFR) compared to CFR, as VFR videos exhibit fluctuating inter-frame that complicate accurate averaging and can lead to playback inconsistencies without proper handling. In compressed streams, such as H.264-encoded MP4s, direct frame rate assessment often requires partial or full decoding due to allocation affecting timestamp reliability, increasing computational demands and potential errors in metadata-only probes. VFR footage from consumer devices exacerbates these issues, as frame dropping or duplication during recording introduces uncertainty in speed and timing calculations, necessitating advanced forensic techniques for resolution. A specific example of measuring fps in a digital video file involves using FFprobe via the command line for a file named input.mp4. First, run ffprobe -v quiet -print_format json -show_streams input.mp4 to output data, including the video stream's r_frame_rate (real-time rate, e.g., "30/1" for 30 fps) and avg_frame_rate fields under the relevant stream object. For CFR verification, compute the effective rate by extracting frame count with ffprobe -v quiet -count_frames -select_streams v:0 -show_entries stream=nb_read_frames -of csv=p=0 input.mp4 (yielding the total frames) and duration via ffprobe -v quiet -show_entries format=duration -of csv=p=0 input.mp4 (in seconds), then divide frames by duration. This process confirms the frame rate without re-encoding, though for VFR, avg_frame_rate provides an approximation while full stream analysis may reveal variations.

Human Perception

Temporal Resolution Limits

The human visual system processes motion through mechanisms involving , where the retains an image for approximately 1/15 to 1/10 of a second (0.067 to 0.1 seconds) after stimulus offset, depending on brightness, and retinal refresh rates determined by photoreceptor response times. This persistence allows discrete to blend into perceived continuous motion when presented rapidly enough, with the critical flicker fusion (CFF) threshold marking the frequency at which appear steady. For stationary lights, the average CFF threshold is around 50-60 Hz, though it can reach 90 Hz under high and contrast conditions. In motion scenarios, the effective threshold is lower due to reduced sensitivity to temporal changes in moving stimuli. Temporal resolution, the eye's ability to distinguish successive visual events, varies widely among individuals and contexts, with studies indicating an average limit of 10-12 distinct per second for basic motion detection in standard conditions. Higher resolutions, up to 60 images per second or more, are achievable for some individuals, particularly experts like athletes or pilots, and with high-contrast or rapidly changing stimuli, where can extend beyond 100 Hz. Early experiments, such as those by Jan Evangelista Purkinje in 1823, demonstrated these limits through observations of afterimages and the persistence of visual impressions from brief flashes, laying foundational insights into how the eye integrates temporal signals. Several factors influence , including age, which lowers the CFF threshold in older adults due to slowed neural processing; lighting conditions, where higher elevates the threshold by shortening integration times; and the distinction between foveal and , with the fovea supporting higher rates (up to 60 Hz) compared to the periphery (around 20-30 Hz) owing to denser photoreceptors. A basic model approximates the CFF threshold as the reciprocal of the photoreceptors' integration time, reflecting the duration over which visual signals are temporally summed before detection of flicker fails: Threshold frequency≈1integration time of photoreceptors\text{Threshold frequency} \approx \frac{1}{\text{integration time of photoreceptors}} This equation, derived from retinal physiology, typically yields thresholds aligning with observed values of 50-60 Hz for integration times around 16-20 ms under photopic conditions.

Flicker and Motion Blur Effects

Flicker in video and film arises from the intermittent illumination during projection or display, leading to perceived brightness fluctuations when frame rates are low, such as below 24 frames per second (fps). At these rates, the human visual system detects the on-off cycles as strobing or judder, creating an unnatural, jerky motion appearance that disrupts smooth perception. This effect is exacerbated in early cinema projections, where single-blade shutters produced only 16-24 light pulses per second, making flicker highly noticeable. The 180-degree shutter rule addresses these issues by setting the shutter open time to half the frame interval, promoting natural motion portrayal through balanced exposure that introduces sufficient blur to mask strobing while avoiding excessive sharpness. For a 24 fps production, this equates to a of approximately 1/48 second, blending frames perceptually into continuous movement. Motion blur occurs because each frame captures motion over a finite exposure time, smearing fast-moving objects and contributing to realistic perception when appropriately tuned. The duration of this blur is determined by the exposure time per frame, given by the formula: Blur duration=shutter angle fractionframe rate\text{Blur duration} = \frac{\text{shutter angle fraction}}{\text{frame rate}} where shutter angle fraction is the shutter angle in degrees divided by 360. For instance, at 24 fps with a 180-degree shutter (fraction = 0.5), the blur duration is 0.5 / 24 ≈ 1/48 second, which aligns with natural eye response for everyday motions. A classic example is the , an artifact where rotating spokes appear stationary or reversing direction if their rotational frequency aliases with the frame rate, as demonstrated in perceptual models of sampled motion. Early mitigation techniques included double-bladed (or twin-blade) shutters in projectors, which doubled the interruption to 48 cycles per second at 24 fps, rendering flicker imperceptible above the critical fusion threshold of the . In video-to-film transfers, pulldown patterns like 3:2 pulldown distribute frames to simulate even motion, reducing judder from mismatched rates such as 24 fps to 30 Hz displays. Modern LED displays face similar challenges from (PWM) dimming, which can induce low-frequency flicker; higher refresh rates (e.g., 120 Hz or above) and elevated PWM frequencies mitigate this by exceeding perceptual thresholds. Research on high frame rates (HFR) indicates preferences for rates like 48 fps, which diminish motion blur and judder compared to 24 fps, as evidenced in viewer studies where HFR footage scored higher in motion quality for dynamic scenes, though some report unnatural "hyper-realism" without adjusted shutter angles. These findings, drawn from controlled tests with expert and general audiences, highlight 48 fps as a threshold for reducing artifacts in action-heavy content, such as in HFR implementations for films like . Online demonstrations provide practical illustrations of the visual effects of low frame rates on motion, such as stuttering and judder. The Frames Per Second Comparison Demo features animated examples, including moving spheres, at preset frame rates (15, 25, 48, 60 FPS) to demonstrate stuttering and jerky motion. The TestUFO Frame Rates Demo displays moving objects and text side-by-side at various rates to highlight differences in smoothness and jumpy motion.

Comparative Perception in Animals

Temporal resolution varies across species, with some animals exhibiting higher frame rate perception than humans due to differences in visual system adaptations. For instance, cats perceive motion at approximately 100 frames per second (fps), compared to the human range of 30-60 fps under typical conditions. This enhanced temporal resolution allows cats to detect rapid movements, such as those of prey, more effectively. Veterinary experts attribute this to cats' higher critical flicker fusion threshold, influenced by their retinal structure and faster neural processing. Similar variations exist in other animals; for example, dogs perceive around 70-80 fps, while birds like pigeons can reach up to 140 fps. These differences highlight evolutionary adaptations to specific ecological niches.

Historical Evolution

Silent Film Era

The origins of frame rate in cinema trace back to the late 19th century, with early experiments in motion picture technology emphasizing individual viewing devices over projection. Thomas Edison's Kinetograph camera, developed in the early 1890s, recorded images at approximately 40 frames per second (fps) on 35mm , while the accompanying peepshow viewer played back films at similar speeds, typically ranging from 40 to 46 fps to ensure smooth motion without excessive flicker. These rates were chosen to balance perceptual smoothness with the mechanical limitations of the continuous-loop film transport system, though actual speeds varied due to manual operation. A pivotal advancement came in 1896 with , which enabled public screenings and operated at variable speeds, typically 16 to 24 fps, facilitating the transition from peephole devices to large-audience projection. This device used perforated 35mm film pulled intermittently by sprockets, with projector speeds dictated by the operator's hand-cranking to maintain consistent pull-down and reduce film wear. Meanwhile, the Lumière brothers in established a more economical standard with their Cinématographe in 1895, filming and projecting at 16 fps, which halved the film consumption compared to Edison's higher rates and made widespread production feasible. Throughout the silent era, frame rates remained variable, often between 16 and 18 fps for hand-cranked cameras and projectors, influenced by technical constraints such as the need for uniform perforation spacing on film stock to enable reliable sprocket engagement and transport. Projector mechanisms, reliant on manual cranking, introduced inconsistencies, while economic pressures—stemming from the high cost of raw celluloid film—encouraged lower rates to minimize material usage without compromising the illusion of motion. These factors resulted in non-standardized speeds across productions, with rates sometimes exceeding 20 fps for smoother effects in theatrical settings. Standardization efforts intensified in the mid-1920s as the Society of Motion Picture Engineers (SMPE, later SMPTE) sought uniformity for theatrical projection. In 1927, following surveys of existing practices, the organization adopted 24 fps as the standard for 35mm film, reflecting an average of observed speeds and preparing the industry for synchronized , though many silent films continued to vary until full implementation. This rate balanced perceptual needs with mechanical reliability, marking the close of the silent era's experimental phase.

Sound and Color Film Transitions

The introduction of synchronized sound to motion pictures in the late marked a pivotal shift in frame rate standards, as variable speeds common in the silent era—typically ranging from 16 to 22 frames per second—proved incompatible with the precise timing required for audio . Sound systems demanded a constant film speed to align image and audio tracks without distortion or drift, leading to the adoption of a fixed rate that balanced technical needs with production costs. The system, developed by and implemented by starting in 1926, established 24 frames per second (fps) as the new benchmark for films. This rate, equivalent to 90 feet of per minute, was selected to ensure sufficient resolution for optical and disc-based recording while minimizing usage compared to higher speeds. The landmark release of in 1927, the first feature-length with extensive synchronized , utilized Vitaphone at 24 fps, accelerating the industry's transition from silent production. Concurrently, Fox's Movietone optical process, introduced in 1927, also aligned with 24 fps to compete with Vitaphone, though early implementations occasionally varied slightly before standardization. By the early 1930s, the Society of Motion Picture Engineers (SMPE), in coordination with the Academy of Motion Picture Arts and Sciences, formalized 24 fps as the universal standard for sound cinema through technical bulletins and recommendations, solidifying its role in theatrical exhibition. (Note: The 1932 efforts primarily refined related specifications like aperture dimensions, but frame rate consensus built on prior sound-era agreements.) The arrival of color processes in and formats in the 1950s preserved this 24 fps foundation, ensuring compatibility across evolving technologies. Technicolor's three-strip system, debuting in the 1932 short , operated seamlessly at 24 fps, as the dye-transfer printing process did not alter the underlying frame rate mechanics. Similarly, the 1953 introduction of by 20th Century Fox maintained 24 fps while employing anamorphic lenses to achieve a 2.55:1 , allowing theaters to project sound-era films without speed adjustments. Central to these transitions was the need for audio-frame , where 24 fps provided an even count of per second, facilitating precise alignment with waveforms recorded on the film's optical track. This rate ensured that audio cycles—requiring consistent linear film for up to several kilohertz—matched image progression without slippage, a necessity absent in silent film's flexible speeds. Later adaptations, such as transferring 24 fps film to non-matching video formats, introduced pulldown patterns like the 2:3 sequence, which repeats (two fields from one frame, three from the next) to convert to 30 fps playback while preserving temporal integrity and pitch.

Broadcast Television Standards

Broadcast television standards for frame rates originated in the analog era, shaped by technical constraints and regional power grid frequencies. In the United States, the standard was approved by the in March 1941, establishing a frame rate of 30 frames per second for black-and-white transmissions, comprising two interlaced fields per frame at 60 fields per second. This rate aligned with the 60 Hz (AC) power supply prevalent in , minimizing visible flicker from electrical interference in early cathode-ray tube receivers. Experimental work on traces back to , but the 1941 approval marked its formal adoption for , effective from July 1, 1941. With the addition of color broadcasting in 1953, the frame rate was precisely adjusted to 29.97 frames per second (and 59.94 fields per second) to allocate spectrum for the color subcarrier without overlapping the , a change necessitated by the limitations of the existing infrastructure. In contrast, European standards developed later to address color transmission challenges. The Phase Alternating Line (PAL) system, introduced in on August 25, 1967, at the International Radio Exhibition in , standardized at 25 frames per second with 50 interlaced fields per second. This rate synchronized with the 50 Hz grids common across much of , reducing hum bars and flicker effects similar to NTSC's design. The Sequential Color with Memory () standard, first broadcast in in 1967, also adopted 25 frames per second and 50 fields per second, using 625 scan lines like PAL but with a different color encoding method to enhance transmission stability over long distances. These 50 Hz-derived rates provided a smoother integration with local electrical systems, though they resulted in slightly slower motion portrayal compared to NTSC's higher cadence. The shift to in the late and early preserved these legacy frame rates for while introducing greater flexibility. The Advanced Television Systems Committee (ATSC) standard, implemented in the United States starting in 1995 and fully transitioned by 2009, retained 29.97 frames per second (59.94 fields per second) as the primary rate for standard-definition content, alongside support for fractional rates like 23.976 frames per second to accommodate 24 frames per second film transfers without temporal speedup or judder. Similarly, the standards, widely adopted in since 1995, maintained 25 frames per second (50 fields per second) to align with PAL and origins. These digital frameworks eliminated many analog artifacts but kept the regional divides rooted in power grid frequencies—60 Hz influencing North American rates and 50 Hz shaping European ones—to ensure seamless integration with existing equipment and content libraries. High-definition television (HDTV) upgrades further expanded options within these standards. ATSC for HDTV, rolled out progressively from 1998, supports 1080p progressive scan at frame rates of 24, 30, and 60 frames per second, enabling cinematic film emulation at 24 fps, broadcast-style delivery at 30 fps, and smoother motion for sports or action at 60 fps, all while accommodating the traditional 29.97 fps for compatibility. DVB-T and DVB-S implementations similarly allow 1080p at 25 and 50 frames per second, with optional 24 fps for international film content. These enhancements marked a departure from strict interlaced field rates, prioritizing progressive formats for improved vertical resolution, though global variations persist due to entrenched infrastructure.

Media Production Applications

Live-Action Film and Video

In live-action and , the standard frame rate of 24 frames per second (fps) has long been established as the norm for achieving a cinematic aesthetic, characterized by a subtle motion blur that mimics the look of traditional projection. This rate provides a balance between visual continuity and the artistic "dreamy" quality desired in narrative filmmaking, where higher rates might eliminate the intended blur. For television and video content, 30 fps is commonly used in to deliver a more realistic and fluid motion suitable for broadcast standards, while 60 fps enhances smoothness for dynamic scenes like or action sequences without altering the overall perceptual realism. Production decisions around frame rates often revolve around trading off motion smoothness against the preservation of a "filmic" blur, where lower rates like 24 fps introduce intentional motion artifacts that contribute to emotional immersion, contrasting with the hyper-real clarity of higher rates that can make scenes feel overly sharp or video-like. (HFR) experiments, such as the 48 fps used in Peter Jackson's The Hobbit: An Unexpected Journey (), aimed to reduce blur and increase detail for 3D viewing but sparked debate over whether the heightened realism detracted from the cinematic illusion. For slow-motion effects, footage is typically captured at 120 fps or higher to allow for conformed playback at 24 fps, extending the duration of action sequences while maintaining temporal detail and avoiding judder. In production workflows, on-set monitoring often occurs at the native capture frame rate to ensure accurate assessment of motion and exposure, with directors and cinematographers using tools like external recorders or camera viewfinders calibrated to these rates. During , conforming involves aligning high-frame-rate clips to a master timeline, such as 24 fps in software like , where the project settings dictate playback speed and interpolation to integrate slow-motion elements seamlessly without altering the overall narrative pace. Specific implementations, like IMAX's adoption of 48 fps for select releases after 2016—including sequences in (2022)—leverage dual-rate projection to enhance immersion in large-format screenings while offering fallback to 24 fps for broader compatibility.

Animation Processes

In traditional animation, playback is standardized at 24 frames per second (fps), but the production process varies based on style and budget. Full animation, exemplified by Disney classics like Snow White and the Seven Dwarfs (1937), typically involves creating 24 unique drawings per second, known as animating "on ones," to achieve fluid, lifelike motion. In contrast, limited animation reduces the drawing count for efficiency; for instance, South Park employs an "on twos" technique, producing 12 unique drawings per second that are held for two frames each during 24 fps playback, resulting in an effective rate of 12 fps. This approach, common in television series, prioritizes expressive poses and dialogue over continuous motion while maintaining cinematic playback speed. In (CGI) pipelines, frame rates are configurable to suit project needs, with software like defaulting to 24 fps for film-oriented workflows. Animators set keyframes at this rate for final output, but real-time previews in the often render at higher rates, such as 60 fps, to simulate smoother motion and aid iterative adjustments without full computation. Animation Studios has adhered to a 24 fps standard for feature films since (1995), ensuring compatibility with theatrical projection, though internal simulations for elements like cloth or fluids may use higher sub-frame rates—up to several times the base rate—to capture complex dynamics accurately before downsampling to 24 fps. Stylistic choices in frequently manipulate effective frame rates to evoke specific moods or emphasize action. Lower rates, such as 8-10 fps, produce jerky, motion that heightens tension or comedic timing, as seen in select sequences for dramatic impact. Conversely, smooth 3D animations, particularly in CGI, target 30 fps or above to convey realism and fluidity, aligning with viewer expectations for lifelike movement in contemporary productions. These decisions balance artistic intent with technical constraints, drawing on established practices to enhance narrative expression.

Digital Camera Specifications

Digital cameras' frame rates are primarily constrained by sensor architecture, with and global shutter designs imposing distinct limitations on maximum achievable frames per second (fps). sensors, prevalent in most consumer and mid-range professional models, expose and read out pixels line by line from top to bottom, leading to potential (known as the jello effect) in fast-moving scenes and capping fps due to sequential readout times that can exceed the exposure interval at high speeds. Global shutter sensors, by contrast, expose and read the entire frame simultaneously, eliminating readout delays and distortion, thereby supporting significantly higher fps without compromising image integrity; for example, the Sony α9 III utilizes a full-frame global shutter to deliver up to 120 fps bursts with full and autoexposure tracking. Resolution trade-offs further dictate frame rate specifications, as higher pixel counts increase data volume and processing demands, often forcing reductions in fps to maintain manageable bandwidth and heat levels. In 2020s cameras, 4K (ultra-high definition) recording at 60 fps has become standard for smooth motion in professional workflows, while 8K resolutions typically limit to 30 fps due to the quadrupling of pixels straining sensor readout and encoding capabilities, as evidenced in the Nikon Z9, which achieves 8K/60p only through optimized internal processing but defaults to lower rates for extended recording. Professional cinema cameras like the ARRI Alexa series exemplify tailored specifications for high-frame-rate needs, with the Alexa 35 supporting up to 120 fps in Super 35 format at full 4.6K resolution, often windowed to 2K for even higher rates in slow-motion applications. Action-oriented devices such as GoPro's HERO13 Black prioritize slow-motion versatility, offering 240 fps at 1080p (full HD) for capturing dynamic sequences like sports or stunts. Consumer smartphones, including the iPhone 16 Pro (as of 2024), reflect advancing capabilities with 4K video up to 120 fps, balancing portability and battery life against computational overhead. Variable frame rate (VFR) support enhances flexibility in digital cameras by permitting non-constant fps within a single recording, which is encoded via standards like H.264 (AVC) and H.265 (HEVC) to accommodate variable bit rates and timestamps. This capability is particularly useful for seamless transitions between normal and slow-motion playback, as implemented in professional camcorders like the AG-CX350, which allows VFR from 1 fps to 60 fps in full HD mode. By 2025, sensor advancements have elevated high-frame-rate options for (VR) and immersive applications, with stacked designs enabling rates like 360 fps at 900p or 400 fps at (HD-equivalent) in cameras such as the HERO13 Black, facilitating smoother 360-degree capture and reduced motion artifacts in VR content.

Digital and Interactive Media

Computer Graphics Rendering

In rendering, particularly for non-interactive applications such as (VFX) and simulations, frame rate dictates the of the output sequence, influencing both production workflows and final . Rendering pipelines typically involve sequential on CPU or GPU hardware, where each frame requires processing , , , and . The time to render a single frame depends on scene complexity, hardware capabilities, and algorithm efficiency, often measured in seconds or minutes per frame for high-fidelity offline rendering. For film VFX, a target frame rate of 24 frames per second (fps) is standard to align with cinematic motion standards, as seen in tools like Houdini where default animation settings are configured at 24 fps to facilitate seamless integration into 24 fps projects. Optimization techniques are crucial in offline rendering to adhere to production deadlines, especially when rendering hundreds or thousands of . Adaptive sampling methods dynamically adjust the number of samples per based on local variance, allocating computational resources more efficiently to noisy regions while undersampling uniform areas, thereby reducing overall render time without compromising quality. This approach is particularly valuable in Monte Carlo-based , common in VFX pipelines, where it helps meet tight schedules by balancing with temporal constraints across . A key aspect of time estimation involves calculating total render duration, which can be approximated as the product of the frame count and per-frame computation time; for geometry-intensive scenes, per-frame time scales with polygon count divided by GPU throughput (e.g., triangles processed per second). Formally, Total time=frames×(polygonsGPU throughput)\text{Total time} = \text{frames} \times \left( \frac{\text{polygons}}{\text{GPU throughput}} \right) This model highlights how hardware upgrades or scene simplification can accelerate workflows, though actual times vary with additional factors like complexity. Beyond VFX, frame rate standards in extend to outputs. Web animations typically target 60 fps for smooth performance on varied devices, while (UI) applications in software aim for 60 fps to ensure fluid responsiveness and reduce perceived latency. In tools like , the real-time viewport preview operates at up to 60 fps using simplified rendering (e.g., ) for interactive editing, contrasting with the final offline output at 24 fps via Cycles for photorealistic sequences, allowing artists to iterate efficiently without waiting for full renders.

Video Games and Real-Time Simulation

Technical standards for frame rates in video games and virtual reality (VR) emphasize smoothness, low latency, and user comfort, differing markedly from traditional film standards. While cinematic content adheres to 24 fps for a stylized motion blur effect, gaming targets 60 fps as the baseline for console and PC platforms to ensure fluid visuals and responsive controls, with higher rates like 120 fps or more providing enhanced immersion on capable hardware. In VR specifically, standards recommend 90-120 fps to minimize motion sickness by closely matching the fluidity of natural head movements, as lower rates can exacerbate sensory mismatches leading to nausea. For instance, comparing 24 fps to 120 fps reveals substantial differences: at 120 fps, frame delivery time is approximately 8.3 ms versus 41.7 ms at 24 fps, resulting in reduced input lag and smoother motion perception, which is critical for competitive gaming and VR experiences. In video games and real-time simulations, frame rate targets are established to ensure smooth interactivity and responsiveness, with 60 frames per second (fps) serving as the standard for console gaming, including on the PlayStation 5 (PS5). This benchmark balances visual fidelity and performance, allowing developers to prioritize stable gameplay in performance modes without excessive hardware demands. On personal computers (PCs), higher targets of 120 fps or more are common for users with high-refresh-rate monitors (120–144 Hz or higher), enabling fluid motion in competitive titles and reducing input lag for enhanced player control. Vertical synchronization (V-Sync) is frequently employed to align the game's frame rate with the display's refresh rate, preventing screen tearing by buffering frames, though it may introduce minor latency if the target exceeds the monitor's capabilities. Higher frame rates in PC gaming provide significant benefits by improving motion smoothness, reducing perceived latency, and enhancing overall immersion, particularly in fast-paced environments. CPU and GPU reviews typically compare and rank the performance of reviewed devices against other currently available popular hardware by benchmarking frame rates achieved in demanding scenarios, such as rendering complex scenes in AAA titles, to assess relative capabilities for sustained high-fps output. Assuming a PC monitor capable of up to 144 Hz refresh rate, the user experience difference between 144 fps and a lower rate like 60 fps is substantial, with 144 fps delivering noticeably smoother visuals, lower input lag (approximately 7 ms frame delivery time versus 16 ms at 60 fps), and improved responsiveness in dynamic, fast-paced scenarios, making gameplay feel more reactive and less choppy. In typical AAA games, such as first-person shooters or open-world adventures, a faster fps makes a perceptible difference by enhancing player reaction times, reducing motion blur, and increasing enjoyment through greater fluidity and immersion, without the stutter or lag often experienced at lower rates; studies confirm that higher frame rates directly improve player performance and quality of experience in these contexts. Maintaining consistent frame rates presents significant challenges, particularly frame time variance, which measures inconsistencies in the duration required to render each frame and often results in perceptible stutter even when average fps remains stable. For instance, spikes in frame time can disrupt smooth motion, making feel choppy despite an overall 60 fps average. Advanced rendering techniques like ray tracing exacerbate these issues by increasing computational load; at launch in December 2020, Cyberpunk 2077's ray-traced modes on consoles such as the PS5 and Series X targeted 30 fps in quality modes to accommodate the intensive lighting and reflection calculations, leading to noticeable performance trade-offs compared to non-ray-traced performance modes at 60 fps. In virtual reality (VR) and augmented reality (AR) simulations, frame rate requirements are more stringent to mitigate motion sickness, with a minimum of 90–120 fps recommended to minimize sensory conflicts between visual cues and vestibular feedback. Studies indicate that 120 fps represents a critical threshold, significantly reducing simulator sickness symptoms like nausea compared to 60 or 90 fps, as higher rates better replicate natural head movement perception. To achieve these targets on varied hardware, adaptive quality scaling dynamically adjusts rendering resolution or graphical details in real-time, scaling down during demanding scenes to maintain frame rates and scaling up when resources allow, thereby optimizing immersion without compromising user comfort. A pivotal advancement in addressing frame rate limitations is NVIDIA's Deep Learning Super Sampling (DLSS), introduced in 2018, which leverages AI-driven upscaling to boost fps while preserving image quality. By rendering at lower internal resolutions and using tensor core-accelerated neural networks to reconstruct higher-resolution frames, DLSS enables ray-traced games to reach 60–120 fps on mid-range hardware, reducing the performance penalty of real-time effects without perceptible quality loss.

Technical Enhancements

Frame Rate Conversion Overview

Frame rate conversion becomes necessary when content captured or produced at one frame rate must be adapted for distribution or playback on systems operating at a different rate, such as transferring 24 frames per second (fps) footage to 29.97 fps broadcast television. This mismatch arises from historical standards where aimed for cinematic motion at 24 fps, while required higher rates to accommodate interlaced scanning and color subcarrier signals. In modern contexts, real-time up-conversion is common in smart televisions to match incoming signals, like 24 fps content, to the display's native , such as 60 Hz, ensuring compatibility without playback interruptions. Basic methods for frame rate conversion include frame duplication for up-conversion and decimation for down-conversion. In up-conversion, such as from 24 fps to 29.97 fps for , techniques like 3:2 pulldown duplicate frames in a repeating pattern—three frames from the source become two fields, and the next two become three—to fill the target rate without altering playback speed. For down-conversion, decimation involves selectively dropping frames to reduce the rate, preserving by removing redundant or interpolated ones while minimizing motion discontinuity. In digital video file transcoding, changing the frame rate of an existing video while preserving the original duration and playback speed requires inserting additional frames when up-converting. It is not possible to increase the frame rate significantly (for example, from 8 fps to 60 fps) without re-encoding if the original duration and speed must be maintained, as this necessitates generating new frames, typically through duplication of existing ones. Modifying only the frame rate metadata without re-encoding (e.g., ffmpeg -i input.mp4 -c:v copy -r 60) retains the original number of frames and causes the video to play faster with a shortened duration (7.5 times faster for an 8 fps source to 60 fps target). To preserve duration and speed, re-encoding is required, and frame duplication can be performed using tools such as FFmpeg's fps filter. To avoid any quality loss from re-encoding, a lossless codec should be used. An example command using lossless H.264 encoding is:

bash

ffmpeg -i input.mp4 -vf fps=60 -c:v libx264 -qp 0 -preset veryslow output.mp4

ffmpeg -i input.mp4 -vf fps=60 -c:v libx264 -qp 0 -preset veryslow output.mp4

This duplicates frames approximately 7.5 times per original frame on average (since 60/8 = 7.5) to achieve 60 fps while encoding losslessly. Poor frame rate conversion can introduce artifacts like judder, a stuttering effect from uneven frame repetition or mismatched timing, particularly noticeable in panning shots. Conversely, matching the native frame rate during playback eliminates such issues, delivering smoother motion and preserving the intended aesthetic, as seen when avoiding pulldown in progressive displays. In practical applications, Blu-ray players often handle 24p output directly for film content, outputting at 24 fps when connected to compatible displays to bypass conversion artifacts. Streaming services like enforce standards such as 23.976 fps for cinematic deliveries, ensuring consistent frame rates across devices and reducing conversion needs during encoding and playback.

Interpolation and Motion Compensation Methods

Frame interpolation techniques form the core of many frame rate up-conversion algorithms, aiming to synthesize intermediate frames between existing ones to increase temporal resolution. Simple linear blending, the most basic method, generates new frames by averaging the pixels of adjacent input frames, such as creating a midpoint frame as It=It−1+It+12I_t = \frac{I_{t-1} + I_{t+1}}{2}, where ItI_t is the interpolated frame at time tt. This approach is computationally efficient but often results in motion blurring and artifacts in scenes with significant movement, as it assumes no pixel displacement between frames. In contrast, estimation provides a more sophisticated by computing dense motion vectors that describe trajectories across frames, enabling accurate warping and synthesis of intermediate content. methods, such as those in Real-Time Intermediate Flow Estimation (RIFE), estimate bidirectional flows between input frames and use them to generate non-linearly interpolated frames, supporting arbitrary timesteps without relying on pre-trained models. Under a assumption, the displacement vector for an intermediate frame can be approximated as d⃗=p⃗next−p⃗currentΔt\vec{d} = \frac{\vec{p}_{next} - \vec{p}_{current}}{\Delta t}
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