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 23.976/24 (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