(1). The 1080i format has 1080 active lines per picture and 1920 samples per active line and offers 2. 07 million pixels in an image, the term i is interlaced (interlaced). Interlaced mode reduces the demand for bandwidth. The lines are traced alternately 60 times per second, is also called 1080i60, 1080i50 can be depending on the standard used. The number of back (60 or 50) is the frequency in Hertz (Hz) that is transmitted. In this type of scanning each frame is displayed in two phases. During the first, we draw all the lines odd numbers 1 / 50 of seconds and the second lines are drawn in other even-numbered 1 / 50 seconds.
A complete picture is drawn 25 times per second. (1) The 720p format provides 720 active lines per picture and 1280 samples per line, offers 921. 000 pixels per image. The p comes from the progressive (progressive). In a progressive scanning system transmitting the whole picture of pixels in each scanning sequence would be 1 / 50 seconds, or the whole picture is refreshed every time. This type of format is easier to compress and leads to lower bit rates, as well as presenting less interference in the 1080i image. (1). As seen above, the digital signal must pass through a compression process, this implies an encoding before sending, and a view to decoding in the receiver. For this, the HDTV uses standards-based techniques, the most used is the MPEG world, this comparison between two images so that they can be transmitted through the network and uses the first image as reference image (called I-frame), sending only the parts of the following images (called B and P-frame) that differ from the original image.