There are now a variety of media that have “moving pictures," with this effect created by a sequence of images that show progressive action. Among these are live action films, animations, and hybrid combinations. Frame rate, which is also called frame frequency, is the rate at which either the consecutive frames are produced by the image-capturing device or the rate at which the consecutive frames are displayed or projected. In either case, the measurement is usually given in frames per second, abbreviated fps. In video games, the term frame rate refers to image refresh speed.
Recording, projecting, and display devices may have a range of frame rates at which they can operate or may be set to a single, pre-determined frame rate. The ability to choose frame rates may not be important if one is casually using a digital camera to take video while on vacation. An independent filmmaker shooting a documentary, on the other hand, needs precise control of frame frequency.
Standards for frame rates are different in different places and for different purposes. There are four main standards. NTSC, for National Television System Committee, is a standard for video in the US, Central, America, Japan and several other countries, of 29.97 fps, while the standard for film is 24 fps. In much of Europe, Africa, southern Asia and Australia, the standard, called PAL for Phase Alternating Line, is 25 fps. SECAM, which comes for the French phrase Séquentiel couleur à mémoire, is used in France, countries of the former USSR, and a number of countries in Africa also uses 25 fps. The fourth of the main standards is DVB, for Digital Video Broadcasting.
Material can be converted from one frame rate to another. One way in which this can happen is during the editing process in which the raw video from a camcorder, for example, is reviewed and altered in a program like QuickTime 7 Pro or Final Cut Pro. The time for doing this is when the file is exported. Among the settings that can be adjusted, including frame size, codec, and the delivery method to optimize for, the desired frame rate of the export can be chosen, and it can be different than the frame rate of the current file.
On the computer, the frame rate affects several characteristics of the product. For one thing, it affects the viewing flow: a higher frame rate has smoother movement transitions. It also affects the file size: the more frames, the larger the file. If a file with a high frame rate is played back on a computer that is not powerful enough to handle it, or someone tries to play it online without having the necessary bandwidth, the result may include stuttering, a slowing of the intended frame rate, or the dropping out of some of the frames.
