High Definition is to mostly mean meaningfully video of superior quality to that of the diffused analogical television standards in the world in the second half the XX century and anchors very diffused today, television standard that reenter in the SDTV or Standard.

Video that our tv and the classical dvds are transmitted have a signal of 720 lines and 576 lines interlaced (or 720x576i). The High definition makes a leap in before enormous, in fact for many people has been considered as a revolution to the peer of the entrance of the color, when there was the White and the Black.

There are varied formats, among which:

The format 720p, commonly called HD READY (the televisions that support it bring the logo HD ready, that is "ready for the High Definition"), introduces a general resolution of 921.600 pixels (1280×720) with progressive scanning, or for every cycle of transmission of a frame (50 or 60 Hzes according to the Countries) the whole picture of the image is transmitted.

The format 1080i, introduce a general resolution of 2.073.600 pixels (1920×1080) with scanning interlacciata, or for every cycle a fully grown semiquadro is alternatively transmitted by the alone equal or odd lines of the image.

The format 1080p, commonly called FULL HD, it is the most recent of three and equivale to the version with 1080i progressive scanning, for which every updating involves all the 1080 lines and the 2.073.600 of pixel of I screen it.

The definition of the programs HDTV is around 4 times superior to that of the fully grown DVD and despite the good efficiency of compression offered by the MPEG-4, the in demand space for their filing it is remarkable however. For this the supports are needed Blu-ray Disc to offer an ability that can reach 50 GBs and over.