How Does an HDTV Work?by Billy Kirk
Now and Then
High-definition televisions work because of the way the signal is broadcast, received and displayed. Originally, television stations operated by outputting an inferior analog signal to television customers. What is inferior now was simply the norm before, the only method known. Analog sufficed, but the problem lay in the fact that analog is limited by how much picture and sound data could be sent out in the signal. The move to a digital signal opens this world up significantly. Similarly, the televisions themselves have vastly improved, and now the displays in current, high-definition televisions can handle everything the digital signal can throw its way.
To understand how HDTVs work, we need to understand both how the displays work and how the signal is sent along. The first critical item to understand is bandwidth. The digital signal, compared to the old analog signals, allows for more bandwidth to be sent along the wire to the HDTV. HDTVs, of course, are made to be compatible with this digital signal. The digital signal that is used to shuffle along this information can hold a lot due to superior compression techniques, and the HDTV can receive this information, understand it and display it. Bandwidth limitations being less restricted are what allows HDTVs to work in a fashion so different from SDTVs.
Resolution and Aspect Ratio
HDTVs are not only unique in how they receive the information (and how it is sent), but also how they display it. A standard television has only 480 horizontal lines, which is simply what the image on the set is comprised of. This, in more technical terms, is 480i (interlaced). HDTVs can display high-definition images because of their higher resolution displays, which output more lines per screen. Depending on the HDTV set, this is either 720p (progressive), 1080i (interlaced), or 1080p (progressive), in order from least to most expensive and lowest to highest picture quality. (Progressive scan provides all the horizontal lines at one time, while interlaced scan presents them in two fields, half of the lines displayed in each). Another important consideration with the image is aspect ratio. Originally, standard televisions featured a nearly square shaped 4:3 aspect ratio. HDTV sets provide a widescreen experience, or an aspect ratio of 16:9-perfect for DVDs and such.
HDTVs also excel on the audio department, providing Dolby Digital Standard audio qualification. This promotes a more true and realistic listening experience, because with Dolby Digital 5.1 Surround Sound support, there are actually six channels of audio coming at the viewer.