High-definition television

High-definition television (HDTV) is a digital television broadcasting system with higher resolution than traditional television systems (standard-definition TV, or SDTV). HDTV is digitally broadcast because digital television (DTV) requires less bandwidth if sufficient video compression is used.

HDTV broadcast systems are defined threefold, by:

• The number of lines in the vertical display resolution.

• The scanning system: progressive scanning (p) or interlaced scanning (i). Progressive scanning simply draws a complete image frame (all the lines) per image refresh, whereas interlaced scanning draws a partial image field (every second line) during a first pass, then fills-in the remaining lines during a second pass, per image refresh. Interlaced scanning requires significantly lower signal/data bandwidth, but an interlaced signal loses half of the vertical resolution and suffers “combing” artifacts when showing a moving subject on a progressive display (although the worst effects can be mitigated by suitable image post-processing known as ‘deinterlacing’). As some compensation, however, interlaced mode provides finer time-sampling, giving two (half-resolution) image samples in the same time interval as one (full-resolution) image sample in progressive mode.

• The number of frames per second or fields per second.

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