The frame rate of a video source is determined by how fast the source repaints the screen with a new frame. For example, with the (M) NTSC system, the screen is repainted about once every 30th of a second for a frame rate of about 30 frames per second. For (B,D,G,H,I) PAL, the frame rate is 25 frames per second. For computer displays, the frame rate is now usually 72-75 frames per second.