576i component video

This chapter details the scanning, timing, sync structure, and picture structure of 576i25 video. The scanning and timing information applies to all variants of 576i25 video, both analog and digital. The sync information relates to component analog, composite analog, and composite digital systems. 576i video represents stationary or moving two-dimensional images sampled temporally at a constant rate of 25 frames per second. A frame comprises a total of 625 horizontal raster lines of equal duration uniformly scanned top to bottom and left to right, with 2:1 interlace to form a first field and a second field. Scanning lines in the second field are displaced vertically by half of the vertical sampling pitch, and delayed temporally by half of the frame time, from scanning lines in the first field. To define vertical sync, the frame is divided into intervals of halfline duration. Each halfline either contains no sync information, or commences with the assertion of a sync pulse having one of the three durations, each having a tolerance of ± 100 μs. Sync in 576i systems contains several differences from 480i sync.