If we want to get a little more techical, the term HDTV has two meanings.
HDTV Broadcasting
HDTV is part of the Digital TV (DTV) Broadcast Standard, administered by the ATSC (Advanced Standards Television Committee). In 2009, TV broadcasting in the U.S. switched from analog to digital (DTV), which includes HDTV. Not all DTV transmissions are HDTV. A DTV channel can be used for multiple standard resolution (SDTV – 480i/p) subchannels or one or two HDTV channels (720p or 1080i) in combination with one or two SDTV subchannels.
720p
ABC and FOX broadcast, and ESPN, Fox Sports Networks, Disney Channel, Freeform, and National Geographic cable channels provide HDTV content using 720p resolution. (720 lines or pixel rows sent progressively). 720p provides a smooth image due to progressive scan implementation, with 30 percent more detail than 480p. 720p is considered high-definition but takes up less bandwidth than 1080i.
1080i
PBS, NBC, CBS, CW, and Telemundo broadcast, and most cable and satellite programmers such as TNT, Showtime, and HBO use 1080i resolution. 1080i signals are sent in alternate (interlaced) fields. This means half the video frame information is sent at a time.
Where 1080p Fits In
1080p wasn’t initially included with HDTV broadcast standards. HDTVs can’t accept a 1080p broadcast signal, it is accessible mostly on Blu-ray discs and select streaming, cable, and satellite programming. 1080p isn’t used for TV broadcasts because it takes up more bandwidth as each frame is sent progressively, rather than divided into two fields with half the image information as in 1080i.
1080i and 1080p have the same total pixel resolution (1,920 x 1,080 or about 2 million pixels total). 1080p provides smoother motion with than 1080i.1080i saves bandwidth space for TV broadcasters, which can be used for supplementary channels.
Displaying Content on HDTVs
An HDTV is required to receive and display HDTV broadcasts and other HD content. High Definition resolution sources may include:
Antenna combined with a digital tuner in the HDTV. HD cable or HD satellite service. HD cable DVR, HD satellite DVR, or TIVO-HD or similar device. Blu-ray Disc player. Upscaling DVD player or recorder with HDMI output. This is not true HD but provides a better image on an HDTV than a standard DVD player without upscaling. High-definition HDV or AVCHD format camcorders, and compact hard drive and memory card camcorders that have HDMI output connections.
Standard resolution sources that can be displayed on an HDTV include:
Any remaining low-power analog TV broadcasts.VHS VCRs.Standard resolution analog and digital camcorders.DVD players, DVD recorders, DVD recorder/hard drive combinations, and DVD recorder/VCR combinations that don’t feature HDMI outputs or upscaling.
How Analog TV Is Different From HDTV
The U.S. analog TV standard was NTSC which was administered by the National Television Standards Committee. Adopted in 1941, it became widely used after World War II until its discontinuation on June 12, 2009. NTSC employed a system consisting of a frame with 525 scan lines. Each frame is transmitted in two fields of 262 lines. Of those lines, only about 486 are used for visible video display. This means analog TV transmissions had an approximate resolution of 480i when translated into pixels.
Analog TV signals were transmitted in a similar manner as analog radio (Video in AM, Audio in FM).Analog TV transmissions are subject to interference, such as ghosting and snow, depending on the distance and geographical location of the TV receiving the signal (HDTV signals are either on or off past at a specific distance).Analog TV channel bandwidth restricts the resolution and quality of the image to standard definition.
Although the transition from analog to DTV and HDTV broadcasting has been in place since 2009, many consumers may still be watching remaining low-power analog TV stations, analog cable, and VHS VCRs, on an HDTV.
What About 4K and 8K?
The next change in broadcast TV standards (ATSC 3.0 or NextGen TV) includes 4K resolution; farther down the road, we’ll see 8K. As TV stations upgrade equipment and TV makers add updated tuners into TVs and set-top boxes, consumers will be able to receive and watch 4K TV transmissions. Unlike the analog to DTV/HDTV broadcast transition, the transition to 4K is currently voluntary. 8K TV broadcasts and streaming will be available on a wide basis at some point but not until beyond 2025 (although Japan has started via satellite). In the meantime, what you see on an 8K TV is upscaled from lower-resolution sources.
