Question Bob, and sounds like you're the man to know...
Whats the difference between 720p, 720i, 1080p, and 1080i??
I don't get it... (course I'm still using CRT's...
OL JR
PS. which is better (ok pros/cons) of LCD's vs. plasmas...
TIA!
A problem you run into on some of the digital HD stations is the broadcast image is smaller than your set's screen.
You wind up with bars not just at the top and bottom but on the side too. That's because that is the size of the HD signal's image.
So suddenly your 32" TV now only has a 24" picture.
Fortunately most digital stations have a non-HD signal with it.
You can get like chanel 25-1 will have the call letters of WEYI HD and 25-2 will have a full size picture just not in HD with call letters of just WEYI.
It's really confusing for my wife.
There is a button on the remote that says "zoom" but when you push it a message comes on the screen that says "The aspect ratio for this channel cannot be changed".
Now one great way for us more technically gifted people to "pay it forward" is to help some of your neighbors figure out digital TV. Like the elderly couple down the block that just don't have a clue.
It's really getting complicated to watch TV now!
There's pros and cons with both formats, but unless you live in a fringe area, the pros of DTV far exceed the conns.
The only real pro about analog tv is that you can always see or hear something if it's there. The picture may be snowy and barely visible, but at least you might be able to get some useful info.
A DTV picture is either there or not. Inside a DTV there's a microprocessor that decodes the digital data stream and generates the picture. In order to determine what's really there, a typical DTV needs about 2 seconds worth of data before it generates a picture, so if the signal is weak or fading in and out, you get the "blue" (or black or whatever color you background happens to be) screen of death: nothing. If there's heavy rain or snow, the data stream can be interupted an you can either get a broken up picture, a freeze frame or the "blue" screen of death.
The old analog 4:3 TV signal maps into a VGA screen (640x480) very well and corresponds to the standard 4:3 DTV 480 p fromat. The real benefit to the viewer is that the old NTSC analog format really has a resolution of only ~320 horizontal dots vs the 640 of the standard DTV format, so that your basic DTV signal has twice the resolution as analog and visually appears much sharper. HDTV is a higher resolution in a widescreen 16:9 format broadcast in either 720p or 1080i formats. (Already described previously in earlier posts.)
The biggest advantage of (H)DTV for the broadcaster is that more information can be transmitted in the same bandwidth. You can transmit 4 DTV channels in the same bandwidth as 1 analog channel. For example, in the Boston area, public TV WGBX channel 44.0 analog has 4 DTV channels 44.1 (WGBX in DTV), 44.2 (World), 44.3 (Create)and 44.4 (Kids). ION has done the same by replacing the analog channel with 4 DTV channels. Many other stations broadcast HDTV on their XX.1 channel in either 720p or 1080i and use the xx.2 channel for 480p DTV broadcast.
How your picture looks depends on how you have your DTV setup. For most folks the "normal" picture format option is the best unless you always want a full screen image and can put up with seeing a lot of short, fat people.
Different camera types decode into the "normal" screen mode to sometimes provide less than a full screen image. Most folks purchase 720p HDTVs so that's what I'll concentrat on. (You won't notice a difference between 720P and 1080P unless a screen is > 40" anyway and as there are no broadcast in 1080P anyway, there's no reason to spend the extra buck for 1080p on smaller TVs.)
When viewing 4:3 480p DTV on a 16:9 720p HDTV there will be sidebars on the left and right sides of the screen in the "normal" mode of viewing. If you zoom in to fill the screen, you can either get short, fat people, or clip or the top and bottom of the picture reducing the vertical resolution by 25 % to 360 horizontal scans.
It costs a lot of money to convert a station from NTSC analog to HDTV formats, so they are still using older cameras for some in studio programming, remotes, and have fast libraries in the analog format. These inages have to be converted to the new DTV and HDTV formats for broadcast and it's not always done in the best manner, so you can get less than full screen images when viewing a poorly converted analog 4:3 and widescreen 16:9 formats in the "normal" mode. The 4:3 640 x 480 converted images are centered in the 1280 x 720 screen, and the 16:9 widescreen format could be as small as 854 x 360. As time goes on, the stations will get better in their format conversions and I think most of this will disappear.
Hope this helps.
Bob
