576i refers to interlaced video encoded with 288 line fields, forming a final Frame 576 Pixels tall. Although 576i is sometimes used to refer to PAL, they're not the same thing. It can be used to refer to a PAL signal that's been digitized, such as captured analog TV, assuming the Capture conforms to the 576 line standard established by ITU-R BT.601.
In addition to captured PAL, other common formats using 576i video are Standard Definition DVB, EDTV, DVD, DV, and SVCD. 576i is most suitable for TV content shot or edited on videotape or other analog tape sources like home videos. However, since PAL uses a single framerate for progressive and interlaced video, it's also possible to capture or encode progressive video in an interlaced format.
Regardless of the format it's encoded in, or exact resolution of a 576i video file, they generally have the standard PAL framerate of 25fps.
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Digital Video Fundamentals - Resolution and Aspect Ratio
