Scanning Method
Video frames are composed of individual lines, scanned from the top of the screen to
the bottom. Lines may be scanned progressively (one line at a time), or interlaced
(every other line during one scan, and then the alternate lines on a subsequent scan).
SD video uses interlaced scanning, while high definition formats may use either
interlaced or progressive scanning. For more information, see Volume IV, Appendix A,
“Video Formats.”