There are so many acronyms used in defining television technology that is difficult to keep it all straight, and even worse, sometimes the acronyms are almost the same. That's the case with DTV and HDTV. At first glance they would seem to be very similar, and yes they are definitely related, but there are also significant differences as well. DTV stands for Digital TV, and HDTV stands for High Definition TV. To understand DTV, you have to go back before cable and satellite TV to the time when all broadcasts were picked up by antenna. Those television signals were broadcast in analog format, which is severely limited in how much audio and video information it can transmit. Back then all TV sets received analog signals and the main choice you had to make was how large the TV screen was going to be. When first cable and then satellite came on the scene, they changed things dramatically. Instead of just sending analog signals they were able to broadcast in digital instead. That immediately improved both the picture and sound for televisions that were ready to receive digital signals. The improved video was far sharper and smoother than anything before, and the sound quality took a similar leap forward too. So DTV is simply a higher standard for TV broadcasting than was available in previous analog TV systems. HDTV however, is the next evolutionary step in digital broadcasting. It takes DTV to a new level and makes both the television sound and video so much better. For instance, many DTV programs are sent in 525i format, which means that 525 lines of information are displayed on the screen and interlaced, or shown in alternate order. In other words, all the odd lines are shown in 1/10 of a second and then all the even lines are shown in the next 1/20 of a second. Because it all happens so fast you never clearly see the alternating pattern, but it is there. Broadcasts made in HDTV however can reach up to 1080p, which is a standard where 1080 lines of information are shown on the screen and they are all shown together in a progressive scan instead of interlaced. What that means for you is a picture with much higher clarity and definition and action sequences that are much smoother to watch. There are also other features of the HDTV format, including widescreen and Dolby 5.1 surround sound that take television viewing to a whole new level too, so DTV was the start of all of this improved entertainment, but HDTV is where we will really see the benefits unfold for all of us. |
