Netyaroze said:
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1080p came from the 1152i 50hz analog HD standard. 1080 lines is the useable picture content of the interlaced analog signal, after cutting away the overscan area. Analog tv uses overscan to give the electron gun time to return to the top of the screen. The headroom was also used to hide extra information, like closed captioning and TeleText. And yes the 1920 simply comes from the 16:9 convention.
The 1152i standard was a cost effective interconnection standard for 50hz CRT HD tvs, which allowed them to run at 31.25 khz horizontal frequency.
In the beginning of HDTV broadcast you would still get extra information in the picture in the form of alternating black and white rectangles at the top of the sccreen. On 4:3 broadcasts you would also see a blue line on the left of the screen, remnant from priming the electron gun for CRT tvs. Nowadays the extra information is hidden away again outside the picture content. But because of that 1080p sets still use overscan (not all anymore) to get rid of the edge information. You should disable overscan for video games and blu-ray by chooosing native or dot by dot format for 1080p. (Most tv's are smart enough to do that automatically for RGB sources, only relevant if you force the console to output a tv signal, and for blu-ray)
