Guide to HDTV Formats – Part 1 720p, 1080i, and 1080p HDTV

The majority of TVs sold today are 1080p HDTVs, yet 1080p is one of three main HDTV formats in use: 720p, 1080i and 1080p. And as from this year, we also have a new HD technology for home entertainment called 4K.

Despite the increasing presence of HDTV sets, there is still a lot of consumer confusion about the different HDTV formats. As a result, the TV industry is often takings consumers for a ride by directing them to buy the more expensive higher resolution HDTVs even at screen sizes when is impossible to perceive the added picture detail afforded by these formats.

In the first part of this article, we discuss the differences between 720p, 1080i, and 1080p. In the process, we explain the strengths and weaknesses of each by seeing how these differences impact image quality, and how the actual supported resolution is affected by bandwidth limitations in the TV broadcast system.

In the second part, we discuss the latest emerging 4K HD, explaining what this HD technology is all about, and why in our opinion, in-home 4K is a foolish concept that is extremely expensive and that lacks the ‘WOW’ factor many expect!

1080p HDTV… the hot spec in HDTV formats!

In 2007, the Electronics Consumer Association estimated that there were 60.6 million HDTV sets in US households, representing an HD penetration of 36%. At that time, it was estimated that a third of these HD households had multiple TV sets, with the second or third HDTV being a 1080p TV.

A lot has changed since then and the number of 1080p HDTVs surpassed 720p TVs; 1080p sets have become the ‘de facto’ standard at anything above and including 32-inch. It is the drastic fall in price of HDTV sets during the last years that led to a sharp increase in the presence of HDTVs, and in particular of Internet-connected, 1080p LED HDTVs; the latter most appealing factor being their ultra-slim profile.

This trend has been brought about despite the higher price of 1080p HDTVs and the almost non-availability of broadcast programming in 1080p!

In fact, at the time of this write-up, the only commercially available 1080p content comes in the form of high-definition discs from Blu-ray and the few satellite TV services like DirecTV that offers HDTV in 1080p/24-30 format for pay-per-view movies that are downloaded in advance via satellite or on demand via broadband internet. The irony is that the increase in the presence of HDTV sets in the home has not brought about a better consumer understanding of high definition television. Surveys have constantly shown that the average HDTV owner does not even know if s/he is watching HD programming or not! Unfortunately, TV makers and retailers are often riding over this lack of consumer understanding to push the more expensive 1080p HDTVs even at screen sizes where difference in picture detail between a 720p and 1080p set is unperceivable.

This push by the TV industry is such that it has brought about the almost complete elimination of 720 HDTVs from TV lineups except for the few lonely 42-inch and 50-inch entry-level plasma TVs. In the case of LCD TVs, the situation is even worse if you are after a cheap HDTV as 720p TVs generally top out at 32-inch.

There is a very simple reason for this. 1080p sets carry a higher price and yes… a higher profit margin. Production costs are only marginally higher than those of 720p HDTVs even though the average retail price difference between 720p and 1080p sets seems to imply the contrary; the few entry-level 50-inch 720p HDTVs available for 2012 are selling at an average price that is 33% less than an equivalent entry-level 1080p HDTV.

To justify this move, TV makers and retailers profess that 1080p HDTV sets deliver better resolution and improved performance than 720p HDTVs. In addition, 1080p sets are often bundled with a more appealing feature set—irrespective of whether these features are of any use in everyday viewing—to help sell 1080p HDTV sets at an even higher price!

It is true that 1080p HDTVs deliver improved picture resolution, but…

Does the additional picture detail afforded by 1080p sets always imply a better picture than a 720p HDTV especially when it comes to available HDTV broadcast content?

And how does 1080i—the predominant format used by the TV broadcast industry—relate to 1080p when it comes to picture performance?

HDTV Formats Explained: It is all an issue of ‘Image Resolution’

There are currently a number of different HDTV formats as adopted by the Advanced Television Systems Committee (ATSC), based on 720p, 1080i, and 1080p, using refresh rates that vary between 24Hz and 60Hz. The basic difference between these HDTV formats is mainly one of image resolution. Image resolution in fixed-pixel displays is often a hot topic; for many TV buyers, the obvious choice is a 1080p HDTV, often referred to as full-HD, ultra-HD or higher HD by some TV manufacturers.

720p is on the lower-end of the scale with an image resolution of 1280 pixels by 720 lines. The other two formats both support 1920 pixels horizontally by 1080 lines. In other words, both 1080p and 1080i HDTV formats support the same theoretical image resolution. However, there is a significant difference in the way 1080i (interlaced) and 1080p (progressive) formats build the image, a difference that may render the 720p format more suitable to display certain image content than the higher resolution 1080i format.

So… do not simply jump to the conclusion as to which HD format is best; each HD format has its strengths and weaknesses.

1080i HDTV

Up to a few years ago, this was considered as the reference standard in HDTV. Nearly all first-generation HDTVs were rear-projection sets that supported this standard. This format boasts a picture resolution of 1920 pixels by 1080 horizontal lines that are painted on the screen in two interlaced halves (hence the ‘1080i’ label). It first paints all 540 even-numbered lines on the screen (referred to as even-field), and then proceed with the painting of all 540 odd-numbered lines (or odd-field). These two fields together form a single image frame of 1080 lines.

This process is repeated 60 times per second, each time painting only half of the lines per frame. This means that the entire image is painted on the screen in two separate passes, 30 times every second.

Because of the way the interlaced process paints the screen, picture information contained in adjacent odd and even lines in an interlaced image is 1/60th of a second out-of-synch with the next or previous line. The image difference between the two halves of the picture would show up in what are referred to as ‘interlaced artifacts’. This is not an issue with slow-moving or static content, but these artifacts become more pronounced with fast moving objects. In other words, this impacts the type of image content best viewed on an interlaced display.

720p and 1080p HDTV

In contrast, progressive-scan formats—480p enhanced-DTV, 720p HDTV, and 1080p HDTV—display each individual line sequentially in a single pass to build up the complete frame. This means that in progressive scan video, image information between adjacent lines is displayed in a timelier manner. This makes progressive scan capable of delivering a smoother, cleaner image, especially with sports and other fast-changing motion-intensive content.

Effective Resolution: Which is the best HDTV format – 720p, 1080i, or 1080p?

720p vs. 1080i

TV stations would normally broadcast in either 720p or 1080i but not both; the predominant format is 1080i. This in itself is not an issue; all present HDTV sets can display pictures in any HDTV format by up-converting or down-converting to the set native resolution, i.e. the one in which the set is designed to display the image.

From a pixel-count perspective, 1080i supports better spatial resolution than a 720p HDTV. In fact, 1080i supports a pixel count of over 2 million pixels as against the 0.92 million pixels supported by 720p HDTV. But in reality, the situation is somewhat different when it comes to an interlaced format.

As expressed earlier on, the differences between the two halves of an interlaced image lead to interlaced artifacts. To reduce the visibility of these artifacts, filtering is applied to the vertical resolution of an interlaced signal. This reduces the real image vertical resolution to some 60% of the number of scan lines supported by the 1080i interlaced format. Furthermore, 1080i material is limited to around 1440 pixels horizontally to reduce transmission bandwidth requirements; this reduces the overall effective resolution of the 1080i format to around 0.93 million pixels.

It is thus clear that the actual difference in effective resolution between 720p and 1080i is almost negligible. And this apart from the fact that a 720p display is capable of a better flicker-free picture when dealing with fast action TV content.

Yet there is another issue against interlaced video, that of digital compression of images. Digital image compression is more efficient with progressive video at the source than interlaced video. High definition digital TV broadcast uses the same 6MHz maximum allocated broadcast bandwidth in the US as with standard definition analog TV. This means it is necessary to apply compression to make high definition images fit into the space allocated for a broadcasting TV channel.

What about the 1080p HDTV Format?

The situation with 1080p HDTV is totally different. The horizontal resolution of 1080p HDTV content is equal to the number of scan lines since there is no need to reduce this as in the case of interlaced material. This means 1080p supports the full 2.07 million pixels (1920 x 1080 pixels) as against the effective 0.93 million pixels in 1080i video and 0.92 million in 720p HDTV. And this apart from the added advantage that 1080p enjoys over 1080i in that all 1080 lines are displayed in a single pass.

In other words, the 1080p HDTV format enjoys the best of both worlds; it has the spatial resolution of 1080i HDTV material and the smooth stable image of a progressive scan format. It is a case where if you want the very best in high definition television, 1080p HDTV is the way to go, but

As things stand today, except for the few 1080p pay-per-view TV services, there is no 1080p HDTV broadcast and there is little chance broadcasters will jump to 1080p any time soon due to bandwidth limitations. Even Xbox 360 and PlayStation 3 high-definition games are usually in 720p though the user can upscale these to 1080i or 1080p in the console user settings. The only way to enjoy true 1080p HDTV commercially available content apart from hooking a PC to your HDTV set is a Blu-ray disc.

A technical note:

Apart from CRT, interlaced formats are not an option with fixed-pixel microdisplay technologies–DLP, plasma and LCD; these are essentially progressive-scan technologies that have to convert interlaced video (480i or 1080i) to progressive-scan to display the content. This explains why TV manufacturers moved from 720p to 1080p, skipping 1080i.

Yet there is another important issue specific to fixed-pixel displays. These have to convert incoming video irrespective of format or resolution to the screen native resolution. The process involves up/downscaling of the video resolution to match that of the display; in the case of interlaced video, it also involves deinterlacing. These processes introduce errors that are often overlooked by TV buyers despite impacting picture quality.

Unfortunately, how well an HDTV scales an image or deinterlace video content is not something that can be put in the set specifications list.

1080p HDTV Sets are readily available but… what about 720p HDTVs?

As already indicated in this article, 1080p HDTV sets have become the predominant TV technology in use today as more TV makers are focusing their TV line-ups on 1080p sets. In particular, this is true with LCD and LED HDTVs where TV makers have shifted almost completely away from 720p HDTVs for anything larger than 32-inch. In other words, if you want to enjoy the price advantage of a 720p TV at the larger 42-inch to 50-inch screen size, your only present option is a plasma TV.

The present price advantage of a 50-inch 720p plasma HDTV can be anything from $200 to $300 over an equivalent entry-level $1,000 1080p HDTV. This is the price difference between the 50-inch LG PA4500 720p HDTV and the equivalent 1080p entry-level 50-inch 50PA6500; it is also the difference between the 50-inch 720p XT50 featured here and the 1080p UT50 series of Panasonic plasma HDTVs.

It is true that apart from the higher resolution, 1080p HDTVs generally come with slightly improved connectivity and a few other enhanced features such as the full Viera Connect on the UT50 series. But these features does not add anything to the TV picture and are there mainly to help justify the higher price of 1080p HDTVs.

The bottom line: When is a 1080p HDTV worth the extra expensive if a 720p equivalent is available?

There is no straight answer; it depends on what are your requirements, yet there are a few facts you should know before making any decision:

Image Detail: 1080p sets are capable of producing spectacular sharp images. However, because of the limitations with 1080i broadcast content detailed above, it is extremely unlikely you will see any difference in image detail with 1080i broadcast content between a 720p and a 1080p HDTV set, even on large 50-inch plus HDTVs.

Viewing Distance: You will not perceive any difference in image detail between 720p and 1080p on a 50-inch TV from 10 feet away. You have to go bigger for the extra image resolution to start making any difference; you also have to sit at 1.5 to 2 times the screen width and feed your 1080p HDTV set with a pristine quality 1080p encoded material to enjoy full detail supported by 1080p HDTV. More on ‘TV viewing distance’ can be found in our guide here.

Availability of 1080p Content:  Keep in mind that apart from HD discs and the few satellite TV content, true 1080p HDTV encoded material is still almost non-existent; and it is unlikely that the majority of present HDTV broadcast content will be available in 1080p when considering the bandwidth requirements.


The whole equation in favor of 1080p HDTV sets is changing fast. The present marginal difference in price between 720p and 1080p HDTV sets and the lack of 720p HDTVs has already made 1080p HDTVs often the only viable option to consider.

Yet the 1080p option makes more sense if you plan to go really big. Consider a 1080p HDTV for anything bigger than 50-inch especially if you plan to use your TV to watch more Blu-ray movies than broadcast content, or if you prefer to sit closer to the TV screen than twice the screen width to enjoy a wider angle of view.

Similarly, go for a 1080p HDTV if you plan to use your TV as a big computer monitor. Though icons and text may appear too small on a 1080p TV, and you may have to re-scale the desktop to fit, a 1080p display set gives you some added flexibility when it comes to computer connectivity – especially if your video card supports full 1080p resolution over an HDMI connection.

If none of these issues represent a priority, and you are on a tight budget, you may very well opt for 720p HDTV if available at the screen size you are looking for; rest assured that high definition content will still look great!

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