Here are the 18 ATSC digital TV formats:
Format . Vertical . Horizontal . Aspect . Scan Mode . Frame
...........Scan ..... Pixels .... Ratio ..... ....... Rate
...........Lines......................................(fps)
HDTV:
1080p.....1080.......1920........16:9....Progressive..24
1080p.....1080.......1920........16:9....Progressive..30
1080i.....1080.......1920........16:9....Interlaced ..30
720pC.. ...720.......1280........16:9....Progressive..24
720pC.. ...720.......1280........16:9....Progressive..30
720pC.. ...720.......1280........16:9....Progressive..60
EDTV:
480p .. ...480.......704.... ....16:9....Progressive..24
480p .. ...480.......704.... ....16:9....Progressive..30
480p .. ...480.......704.... ....16:9....Progressive..60
480p .. ...480.......704.... ....4:3 ....Progressive..24
480p .. ...480.......704.... ....4:3 ....Progressive..30
480p .. ...480.......704.... ....4:3 ....Progressive..60
480p .. ...480.......640.... ....4:3 ....Progressive..24
480p .. ...480.......640.... ....4:3 ....Progressive..30
480p .. ...480.......640.... ....4:3 ....Progressive..60
SDTV:
480i .. ...480.......704.... ....16:9....Interlaced ..30
480i .. ...480.......704.... ....4:3 ....Interlaced ..30
480i .. ...480.......640.... ....4:3 ....Interlaced ..60
HD Monitors
Now a display in order to be considered HD it would have to be able to display the pixels noted in one of the 6 HDTV formats. This boils down to 2 resolutions: 1280x720 and 1920x1080. Therefore for a display to be considered HD it would have to have at least enough pixels in each direction to make a 1280x720 picture. Displays can have more pixels than that minimum and still be considered HD, for example there are plasmas that have 1366x768 (Zenith P50W38) that are HD displays. They receive a signal from a set top box and scale it from 1280x720 to fit the 1366x768 screen.
HD Ready TVs
In order for the term TV to be used the unit needs to have some form of a TV tuner built in. HD ready TVs will have one or more NTSC (analog) tuners built in to qualify as a TV and will have inputs for an external HD source, such as a ATSC STB, HD cable box, HD satellite receiver, etc. These inputs maybe component video, DVI or HDMI and may allow for any or all of the HDTV formats. The display section will be capable of at least one of the 6 HDTV display formats.
HD Built-In
When the manufacturer includes an ATSC (DTV) tuner then it is tagged with the term HD built-in. Normally there will be NTSC tuner(s) built in also and the display section will be capable of at least one of the 6 HDTV display formats.
HD Capable or Compatable.
Here the manufacturers are trying to attach a display that is not really HD to the HD term in order to make the display more marketable. Many EDTV plasmas will allow a HD signal to be sent to the display where the display will convert it to the native EDTV resolution. While they are not a HD display, they can advertize the HD compatability. I have a couple of customers that bought EDTVs thinking they were getting HDTVs due to the HD compatable term.
Bottom Line
In order to view a HD picture, the screen must be able to display enough pixels to be considered HD. It does not matter what resolution you can input into the display, it matters what the resolution the display will output.
Last Note
There are a number of manufacturers that have decided to market the new 42" plasmas that have a resolution of 1024x768 as HD displays. According to the ATSC they are not HDTVs. I'm not sure why they are allowed to use the term HDTV, but they do. Be sure to use a critical eye when deciding between one of these near HD displays and a true HD 50" display.