High definition TV (HDTV) is a classification for television sets offering higher resolution.The term HD extends to all digital audiovisual technologies, such as HDV, the best Android TV box and the HDCam. The minimum resolution for HD is 720p (1280×720).
The specifics of HD require a definition of the upper video image (by a factor of two at least) than the SD (Standard Definition). SD has a definition (in PAL mode) of 720 pixels by 576 pixels base height.
Video equipment can be qualified HD whenever they are capable of operating a video signal whose vertical resolution (number of lines) is greater than 720 pixels.
HD requires more advanced technical capabilities, due to the flow and much greater volume of data to be processed, and their more complex coding (HDV, AVCHD).
For example, a DVD movie with a resolution of 576 lines (MPEG 2 PAL) operates an average volume of 4 to 8 GB, while in High Definition, the same movie, more than doubles definition, will operate files up to 9-50 GB MPEG- 4.