High definition television (HDTV) is a high-quality, digital video standard that is widely used in film, broadcast television, and streaming. While the high resolution of HDTV makes for a more enjoyable viewing experience, it also means HDTV videos have a large file size and require data compression (called discrete cosine transform, or DCT) to be transmitted quickly. HDTV can also refer to the hardware (made compatible by an HDTV tuner) for viewing HDTV videos, such as plasma, rear screen, OLED, or other types of HDTV systems.
High definition vs. standard definition
Compared to standard definition television (SDTV), HDTV utilizes more pixels and a wider aspect ratio to create a visibly crisper, more realistic image. Specifically, SDTV has an aspect ratio of 4:3 and has a vertical resolution of 480p or lower; HDTV uses an aspect ratio of 16:9 and has a vertical resolution of 720p or higher. (It’s important to note that 720p is usually regarded as HD Ready and 1080p is regarded as Full HD.) The greater number of pixels does not mean an HDTV display is bigger; rather, the higher resolution indicates that a larger quantity of smaller-sized pixels are being used to create the same fixed image.
The screens used in HDTV equipment are also visibly more rectangular than standard definition screens, and they’re also thinner or more compact. One drawback of HDTV is the performance requirements HDTV generally requires more bandwidth than SDTV and can drain battery power on wireless devices more quickly.
HDTV scanning systems
Although HDTV is sometimes processed using interlaced scanning, where the pixels displayed alternate between even and odd rows, the end result is much more favorable when the image is displayed and changed as a whole using progressive scanning. As such, older HD videos are sometimes labeled with “p” or “i” following its number of pixels to discern how it’s scanned (i.e., 720p, for progressive, or 720i, for interlaced).
Most modern recording equipment does not record interlaced video, though, so it has become less common for video parameters to designate the screen system. The “p” notation in most instances today is simply an abbreviation for pixel, as seen in the above comparison of HDTV and SDTV vertical resolutions.
Advancements in both video recording and display technology have led to the rise of 4K (2160p) and 8K (4320p) video resolutions, also known as Ultra HDTV. More does not always mean more, however; some critics of Ultra HDTV have questioned whether the human eye is capable of distinguishing the difference between HDTV and Ultra HDTV. Many optics experts agree that the subjective value of 4K and 8K resolutions depend on a number of factors, including the size of the display and the distance between the viewer and the display.