Consumer Video Education Blog

When you go into any store that sells TV and video equipment, you have probably seen all these numbers and letters but are confused by all the choices?.  What exactly do these letters and numbers mean and what exactly is the difference? 

Let’s look at the letters first;  SD, ED and HD.  SD stands for Standard Definition.  This is what you have been viewing on your TV for the past 50 years.  Until the advent of High Definition, you could only get your TV in one format and thus never had heard or seen the term SD.  SD has the resolution of 480 lines and is broadcast in interlaced format meaning that only 240 lines (or every other line) are shown at one time and they are alternated at 60HZ or 60 times per second … much faster than the human eye can perceive.   ED is a new version of television that sits between SD and HD and was created as a transition step by the manufacturers to make getting into newer “higher” definition TV less of a financial hit as the HD sets were going for $2000 and up.  ED sets are generally 480 lines put support both interlaced and progressive scans and wide-screen formats.  In the early years of HD, ED televisions were more common, but now that the price of real HD TVs have come down to under $500, it is almost impossible to find a EDTV being sold.  HD is now probably the most well know format for TV.  It is everywhere we look, in every newspaper ad and sales flyer and it is almost impossible to find a SDTV.  High Definition (HD) is now the new standard for viewing broadcast video.  They come in three different screen resolution formats and in a couple of dozen different sizes and in prices from about $200 to $6000.

Now lets look at the HD resolution numbers; 720 and 1080.  These numbers refer to the number of lines (or vertical resolution) that the TV or monitor can show.  Obviously, the higher the number the better the picture quality.  That’s a given.  BUT that little letter following the number plays almost as big a part in the actual picture quality.  

The letters “i” and “p” stand for Interlaced and Progressive and what this means is how the picture is presented for viewing.  Interlaced means that only half of the lines are shown at any given time and alternate between the two sets.  This happens so fast that you never see this bouncing back and forth.  Conventional TV (non HD of SD … Standard Definition) has always done this.  When TV was invented and available for the consumer, this was the only way that the resolution or picture quality was achievable because of the limited technology.  Now, with the capabilities of the current state of the art electronics, the new way of transmitting pictures is what is called Progressive scan.  What progressive scanning does is it shows all the picture information at once.  So a 720p TV or monitor would, theoretically have the same picture quality as a 1440i TV (even though there is no such thing). 

Can you see the difference?  Not really.  Most picture content would look good with either type of set.  Where the difference lies is in motion and with still images.  Because with a progressive scan TV you are actually seeing twice as much video content in the same time frame, the perceived picture quality is better.  When HD first hit the market, you could only get 720p resolution because of technology restrictions.  Progressive scan displays required much more information, twice as fast and limited the number of lines that could be broadcast.  With new technology, the current standard is 1080p.  This is mainly due to such innovations as mp4 (MPEG4) video encoding, DVT transmissions and other super hi-tech tricks that allow huge amount of video (and audio) data to occupy the same space to give us images that 20 years ago weren’t even science fiction.

Because of the new push to 1080p, manufacturers and retailers are pushing the 720p HDTVs, many now selling way below $500 for a 32 inch TV!  Will you be loosing picture quality?  Theoretically, but unless you are buying something over 50 inches in size, you will probably never notice any difference.  The good news is that as time goes on, these ‘old’ 720p sets will further drop in price because they are “old technology”.  Oh, and if you are going to purchase one in the near future, make sure that it has an “ATSC” (Advanced Television Systems Committee) tuner.  That is the designation for a digital tuner (DTV).  Older sets have only NTSC (National Television Systems Committee) tuners and will require a converter in order to receive over-the-air broadcasts.  Some stations have already ceased broadcasting in analog (NTSC) but all will follow suit on June 12, 2009.  Some HDTVs will have both tuners installed, just make sure that the ATSC option is in there or you will still have to get a converter (which would be counter productive).