Active picture

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The part of a video signal that carries picture information. Outside the active picture area is the blanking interval, a period of time that old CRT based receivers needed to allow them to reset the magnetic fields which deflected the beam in a CRT. The blanking interval can be further divided into line and field, or frame. Active picture and blanking intervals were defined for the old 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. ITU-R 709 etc

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.