Devices 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.
Difference from display framerate 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.
Relationship to advertised display framerate 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: • The TV can natively display 240 frames per second, and perform advanced motion interpolation which inserts between 2 and 8 new frames between existing ones (for content running at 60 FPS to 24 FPS, respectively). For
active 3D, this framerate would be halved. • The TV is natively only capable of displaying 120 frames per second, and basic motion interpolation which inserts between 1 and 4 new frames between existing ones. Typically the only difference from a "120 Hz" TV in this case is the addition of a
strobing backlight, which
flickers on and off at 240 Hz, once after every 120 Hz frame. The intent of a strobing backlight is to increase the apparent
response rate and thus reduce blur, which results in clearer motion. However, this technique has little to do with actual framerate. For active 3D, this framerate is halved, and no motion interpolation or pulldown functionality is typically provided. 600 Hz is an oft-advertised figure for
plasma TVs, and while technically correct, it only refers to an inter-frame response time of 1.6 milliseconds. This significantly reduces blur and thus improves motion quality, but is unrelated to interpolation and content framerate. There are no consumer films shot at 600 frames per second, nor any realtime
video processors capable of generating 576 interpolated frames per second. ==Software applications==