Active picture

The area of a TV frame that carries picture information. Outside the active area there are line and field, or frame, blanking which roughly, but not exactly, correspond to the areas defined for the original 525- and 625-line analog systems. In digital versions of these, the blanked/active areas are defined by ITU-R BT.601, SMPTE RP125 and EBU-E.

For 1125-line HDTV (1080 active lines), which may have 60, 30, 25 or 24 Hz frame rates (and more), the active lines are always the same length: 1920 pixel samples at 74.25 MHz, a time of 25.86 microseconds, defined in SMPTE 274M and ITU-R.BT 709-4. Only their line blanking differs so the active portion may be mapped pixel-for-pixel between these formats.

DTV standards tend to be quoted by only their active picture content, eg 1920 x 1080, 1280 x 720, 720 x 576, as opposed to analog where the whole active and blanked areas are included, such as 525 and 625 lines. For both 625 and 525-line formats active line length is 720 luminance samples at 13.5 MHz = 53.3 microseconds. In digital video there are no half lines as there are in analog. The table below shows blanking for SD and some popular HD standards.

Analog Format625/50525/601125/60I1125/50I1125/24P
Active lines 576487108010801080
Field 1 lines2419222245/frame
Field 2 lines25192323-
Line Blanking12μs10.5μs3.8μs9.7μs11.5μs

Active Picture