 Black Belt
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HDTV's and HD explained. Worry no more.
I have seen a ton of threads on here recently from people asking about HDTV's, HD and what it all means. Well I decided to make this thread to help people who are still confused, or are thinking about entering the HD world. I compiled from various sources.
HDTV High definition Television is the first major change to TV since color was introduced in the 1950's. HDTV signals are digital instead of analog like 'standard' TV's, digital HDTV images are much clearer, and HDTV sound is far superior to standard television.
4:3 TV screen
The difference between HDTV and regular TV
Standard TV
* A standard TV breaks up each image into 480 lines. It very quickly draws these lines on the screen in two passes of 240 lines each. It first draws all the even-numbered lines, then draws the odd-numbered lines. This odd/even drawing is called an interlaced image. Because the TV draws these lines so quickly, they appear as one image. This interlacing of the 480 lines that makes up each image on a standard TV is known as 480i. 480i means the picture is made up of 480 lines that are interlaced.
* Standard television is broadcast over the air with an analog signal. Because of this analog broadcast signal, the image is susceptible to interference. If you have ever seen TV "snow" or TV "ghosts" you know how poorly an analog TV signal can look.
* Standard TV signals have an analog sound signal. Sometimes the sound is transmitted in stereo.
* Standard TV's have an aspect ratio of 4:3. This means a standard television screen is nearly perfectly square.
High Definition Television (HDTV)
* A true HDTV image is transmitted in 1080i format. This means that each image is broken up into 1080 lines, and the HDTV draws them interlaced between odd and even lines, 540 lines at a time. Because the image is made up of far more image lines than standard TV, the image is far more clear and colorful. Most HDTV's also support 720p which is an image made up of 720 lines drawn progressively or, all at once. Some newer HDTV's also support 1080p, 1080 lines, drawn progressively (at the same time). As a comparison, a DVD is recorded in a format 480p, but if you watch it on a standard TV, it will display as 480i. If you think that a DVD is clear and colorful, it is nothing compared to a good 720p or 1080i HDTV image!
* High Definition Television signals are transmitted digitally. Because the nature of digital is either "on" or "off", there is no snow and no static with HDTV. You either have a 100% digitally perfect image, or you have no image at all. Sometimes, if the signal is fluctuating between good and bad, you may encounter digital "blocks" or "tiling" in the image. This is as close to digital static that you will find.
* HDTV sound can transmit in stereo or digital 5.1 surround
* High Definition TV's have an aspect ratio of 16:9, making them rectangular. Because of the wider image format, HDTV's display movies as they were intended to be displayed in the theater.
All HDTV is digital, but not all digital is HDTV!
HDTV is, by definition digital, but this does not mean that all digital is High Definition! Most cable companies and all satellite TV services offer digital transmission and digital TV channels, but this does not necessarily mean these channels are HDTV! Most digital channels are simply a standard 480i television signal transmitted through the cable, or via the satellite digitally. This amounts to a very clear image, and no snow or static, but the image is still a standard, 480i, 4:3 television image. Most cable and satellite TV companies charge more to enable HDTV service. In most cases you also need an HDTV cable or satellite box made to work with your particular cable or satellite provider in order to receive their HDTV channels.
1080p, waste of money?
Is 1080p essential? Not really. If you already own an HDTV, don’t feel that you’ve thrown your money out the window. The difference between 1080p and 720p on smaller displays is almost indistinguishable. You start to notice the different in 1080p when you get above 42 inches.
Currently, 1080p TV's will not accept signals in the future from cable/sat companies. THis is due to a few factors. One being the new technology currently in development to broadcast 1080p signals at an affordable rate. It could mean a new version of HDMI or various other things. YOu might only need to hook your cable into a switch, which will convert it and use the proper signal for TV but currently, no TV's have any of this technology. You can on the other hand receive conventional 1080p signals from things such as the PS3, Xbox 360 or stand alone HD-DVD/ BLu Ray players.
Twit.tv afford a good podcast on this last year.
So to be clear. 99 percent of HDTV's on the market today, DO NOT accept future 1080p TV/sat signals. That means if you want to watch TV shows, or anything aside from Blu Ray movies or video games in 1080p in the future, you might need a new TV
Is 720p better then 1080i? YES
What is better, 720p or 1080i? This has been a topic of discussion for a long time. If only taking into account the technical aspects, the answer is simple. 720p is better than 1080i. The reason?
Although 1080i has 1080 lines of vertical resolution (against 720 lines of 720p) and 1920 pixels (against the 1280 pixels of 720p) per line, the fact that 1080i is interlaced, causes an overall lower resolution (in practice) than 720p.
This may seem like an outlandish comment, but keep with me. How can a 1920x1080 signal have a lower resolution than 1280x720 one? Again, the interlaced signal is the reason and that is why I stated “in practice” in the previous paragraph.
Although there’s a 720p30 format, TV stations broadcast 720p HDTV in its highest variant (720p60), delivering images with a 1280x720 resolution at a rate of 60 frames per second. That is why we said previously that the typical abbreviations used by most are too simplistic and fail to paint the entire picture.
Here’s the deal. Like I mentioned above, the horizontals pixels (1280 in 720p and 1920 in 1080i) are really pixels per active line and when the interlacing process breaks the 1920x1080 image into two fields, the amount of horizontal lines per field is reduced to 540. As a result the vertical resolution of the field is also reduced to half the initial resolution of the image (frame). In the case of a 1080i signal, the resolution drops from 2 megapixels of a 1920x1080 frame to 1 megapixel in a 540i field. As a matter of a fact, it is because of this that many detractors of 1080i have proposed to call the format “540i”.
But the key to all the discussions is to never forget that we are not looking at a static image, but instead at moving images that create the illusion of motion. For that reason it’s not the resolution of each image that really matters, but the pixels per second we watch - also known as “temporal resolution”.
When you do the math, you see that 1080i60 (and also 1080p30) only delivers 12% more pixels per second than 720p60. This is why most people can’t tell the difference between 1080i and 720p broadcasting - because their eyes and brain are practically seeing the same number of pixels per second.
Only when static images or small changes in the scene are displayed is that the improvement of 1080i over 720p in HDTV broadcasting is noticeable. As soon you focus on fast moving visuals, 720p looks as good as, or better, than 1080i. This is why it is the preferred format for broadcasting sports.
Normal TV looks like shit on my HDTV
Well of course it does. People often complain about watching SDTV on their HDTV's due to the picture quality becoming worse. The reason this happens is because the standard 480i picture is being stretched across a screen with more then double the pixels.
Take a picture on your computer for example. If you double click on the picture it will pop up and look exactly how you took it. It will be clear (obviously assuming you have a good camera) and everything will be easy to see. Now, if you zoom in on the picture and more then double it's size, it no longer looks as good. You see pixels and it looks distorted. This is the same effect that is taking place on your TV.
How do you fix it? Simple. You will never be able to turn a normal TV signal into an HD one. However you can upscale it. Many stand alone DVD players, and new stand alone Blu Ray players offer upscaling. What this does is allow you to run your cable into player, then out to your HDTV. Inside the player a process takes control, and upscales the standard 480i image to 1080i, 720p or 1080p. It also does many other things, such as smooth out the pixels, multi samples and makes the colours much more vibrant (like digitally restoring an old photo). However, all you need to know is it makes your SDTV signals look 10 times better on your HDTV. Tho it won't look as good as a true native HD signal, it's still very nice.
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Not the original Titan.
Last edited by Titan416 : 01-14-2008 at 05:18 PM.
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