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Videos are made out of frames. In simple terms, each frame is a picture

Framerate is a property of video that indicates how many frames the video displays per second. It is denoted in FPS (frames per second). Common video framerates are 23.976 (NTSC/Film), 25 (PAL) and 29.97 (NTSC).

Types of Frames:

There are several different types of video frames when video compression is used.

  • I picture (key frames) - frames that do not reference other frames, and so they contain all the information needed to render the current frame. Usually occur at scene changes. Compression rate of about 7:1
  • P picture (predictive) - references earlier I and P frames, storing differences data. Compression rate of about 20:1
  • B picture (bi-predictive) - references past and future frames. Compression rate of about 50:1