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From Wikipedia, the free encyclopedia.

Frame rate, or frame frequency, is the measurement of how quickly an imaging device produces unique consecutive images called frames. The term applies equally well to computer graphics, video cameras, film cameras, and motion capture systems. Frame rate is most often expressed in frames per second (often abbreviated "fps") or, equivalently, Hertz (Hz).

Frame rates in Video Display

Frame rates are considered important in CCTV Video. The frame rate can make the difference between a game that is playable and one that is not. The first 3D first-person adventure game for a personal computer, 3D Monster Maze, had a frame rate of approximately 6 fps, and was still a success, being playable and addictive. In modern action-oriented games where players must visually track animated objects and react quickly, frame rates of approximately 25 (PAL)–30 (NTSC) fps are considered the minimum acceptable.

A culture of competition has arisen among game enthusiasts with regards to frame rates, with players striving to obtain the highest fps count possible. Indeed, many benchmarks released by the marketing departments of hardware manufacturers and published in hardware reviews focus on the fps measurement. Among the fastest cards using the most recent, 3D-heavy games, frame rates of 90–100 fps are not unheard of. This does not apply to all games - some games apply a limit on the frame rate. For example, the Grand Theft Auto series, as of Grand Theft Auto III, applies a standard 30 fps and this limit can only be removed at the cost of graphical stability. It is also doubtful whether striving for such high frame rates is worthwhile. An average 17" monitor can reach 75 Hz, meaning that any performance reached by the game over 75 fps is redundant. For that reason it is not uncommon to limit the frame rate to the refresh rate of the monitor. This is called vertical synchronization. ( It has been tested, however, countless times by leading "first person shooter" players that NOT synchronizing every frame results in better performance in game, at cost of some "tearing" of the images.)

Even with expensive monitors that can reach even higher frequencies, the effect is somewhat lost as the human eye has difficulty in perceiving differences in frame rates above around 50–60 fps. Indeed, this is why televisions operate at 50 Hz and 60 Hz with PAL and NTSC standards respectively.

This choppyness is not a perceived flicker, but a perceived gap between the object in motion and its afterimage left in the eye from the last frame. A computer samples one point in time, then nothing is sampled until the next frame is rendered, so a visible gap can been seen between the moving object and its afterimage in the eye.

The reason computer rendered video has a noticeable afterimage separation problem and camera captured video does not is that a camera shutter interrupts the light two or three times for every film frame, thus exposing the film to 2 or 3 samples at different points in time. The light can also enter for the entire time the shutter is open, thus exposing the film to a continuous sample over this time. These multiple samples are naturally interpolated together on the same frame. This leads to a small amount of motion blur between one frame and the next which allows them to smoothly transition.

An example of afterimage separation can be seen when taking a quick 180 degree turn in a game in only 1 second. A still object in the game would render 60 times evenly on that 180 degree arc (at 60 Hz frame rate), and visibly this would separate the object and its afterimage by 3 degrees. A small object and its afterimage 3 degrees apart are quite noticeably separated on screen.

The solution to this problem would be to interpolate the extra frames together in the back-buffer (field multi-sampling), or simulate the motion blur seen by the human eye in the rendering engine. Currently most video cards can only output a maximum frame rate equal to the refresh rate of the monitor. All extra frames are dropped.

High frame rates are also for creating performance "reserves" as certain elements of a game may be more GPU intensive than others. While a game may achieve a fairly consistent 60 70 fps, it may drop below that at times, and a higher frame rate can ensure that this is not noticeable.

Frame Per Second

From Wikipedia, the free encyclopedia.

Frame rates in Video Display