Motion interpolation

Motion interpolation, motion-compensated frame interpolation (MCFI), or frame generation, is a form of video processing in which intermediate film, video or animation frames are synthesized between existing ones by means of interpolation, in an attempt to make animation more fluid, to compensate for display motion blur, and for fake slow motion effects.

In computer animation, interpolation (computer graphics) can also be a natural automated process similar to inbetweening, where each frame depicts objects moving fluidly between key frames.

Motion interpolation is a common, optional feature of various modern video devices such as HDTVs and AV receivers, aimed at increasing perceived framerate or alleviating display motion blur, a common problem on LCD flat-panel displays.

A display's output refresh rate, input drive signal framerate, and original content framerate, are not always equivalent. In other words, a display capable of or operating at a high framerate does not necessarily mean that it can or must perform motion interpolation. For example, a TV running at 120 Hz and displaying 24 FPS content will simply display each content frame for five of the 120 display frames per second. This has no effect on the picture compared to 60 Hz other than eliminating the need for 3:2 pulldown and thus film judder as a matter of course (since 120 is evenly divisible by 24). Eliminating judder results in motion that is less "jumpy" and which matches that of a theater projector. Motion interpolation can be used to eliminate judder, but it is only necessary when targeting a framerate not evenly divisible.

The advertised framerate of a specific display may refer to either the maximum number of content frames which may be displayed per second, or the number of times the display is refreshed in some way, irrespective of content. In the latter case, the actual presence or strength of any motion interpolation option may vary. In addition, the ability of a display to show content at a specific framerate does not mean that display is capable of accepting content running at that rate; TVs above 60 Hz do not accept a higher frequency signal from most or any sources, but rather use the extra refresh capability to eliminate judder, reduce ghosting, display stereoscopy, or create interpolated frames.

As an example, a TV may be advertised as "240 Hz", which would mean one of two things:

Motion interpolation features are included with several video player applications.

Some video editing software and plugins offer motion interpolation effects to enhance digitally-slowed video. FFmpeg is a free software non-interactive tool with such functionality. Adobe After Effects has this in a feature called "Pixel Motion". AI software company Topaz Labs produces Video AI, a video upscaling application with motion interpolation. The effects plugin "Twixtor" is available for most major video editing suites, and offers similar functionality.