Deciphering the high-definition TV alphabet soup

2 December 2008

With Multichoice making a great deal of noise about its recent launch of an HDTV channel and rumours abounding that by 2010 the country's national broadcaster will be capable of providing its viewers with HDTV coverage of the soccer world cup, more consumers are considering the purchase of a television that's capable of making use of the new, higher quality entertainment standard.

Darryl Squara, LG and Samsung product manager at Tarsus Technologies believes that there is still some confusion in this market because of a complete change in terminology when high-definition televisions became available.

"Nobody has done a good job of educating the market about the changes," he says.

Instead of opting for the mainstay of quoting a horizontal and vertical pixel resolution as an indication of picture quality, Squara explains that manufacturers chose to quote the number of vertical pixels as a measure of 'definition'.

"Complicating matters even further," he adds, "they also decided to tack an 'i' or a 'p' onto the end of this new naming methodology, indicating whether the display delivers an interlaced or progressive (non-interlaced) scan picture, respectively.

"Combine these two new terms and it's not surprising that the market is confused," he adds.

While terms like 720p, 1080i and 1080p are confusing to the average television buyer, Squara says the new terminology can be easily explained.

Starting with resolution, he explains that the 720 part in a 720p set's specifications indicates that the vertical pixel count of the display is 720.

"So a television set with a resolution of 1280 pixels wide and 720 pixels high, has an HD resolution of 720 pixels," he says.

"The same rule applies to a display with a resolution that is 1920 pixels wide and 1080 pixels high. As the vertical resolution suggests, this display would have a HD resolution of 1080," he says.

For interlaced and progressive scan sets, there's a simple rule too. "When interlacing sets refresh the picture displayed on-screen, they do so by refreshing all of the odd lines of pixels (lines 1, 3, 5, 7, 9 etc. all the way to 719) on one pass, and then all of the even lines of pixels (lines 2, 4, 6, 8, 10 etc. all the way to 720) on the following pass.

"It therefore takes two passes to refresh an entire picture," he says. "Progressive scan sets on the other hand refresh every single line of pixels with every pass and thus deliver a much faster picture - one that's more suited to sport and other fast-moving action," he says.

"Once one grasps this naming convention, it becomes relatively second nature to decipher that a 1080i television set is capable of displaying 1080 lines of pixels, but will only refresh every alternate line of pixels since it's interlaced," Squara says.

"It's important to note that this new naming convention isn't always used," he says. "Some television manufacturers prefer to use the terms 'HD-Ready' or 'Full-HD'." Thankfully these two terms are easy to decipher.

Squara says that quite simply, Full-HD always denotes that a set is capable of a vertical pixel resolution of 1080. While HD-Ready could mean the same, it generally denotes that a set supports a minimum vertical pixel resolution of 720. "

So while an HD-Ready television might be capable of displaying in excess of 720 vertical lines of pixels, one can only count on it being capable of this feat and nothing more. Since manufacturers never undersell their products, nine times out of 10, HD-Ready means 720p resolution," he says.

Although the current Multichoice HD signal is broadcast in 720p, Squara says that his honest recommendation is for customers to look at purchasing a Full-HD television rather than one that's just HD-Ready.

"The only sure thing in the technology market is change and progress," he says, "and since televisions tend to be devices purchased for the long term, customers will be best served by a set that's capable of weathering revisions in technology and more importantly improvements in broadcast quality.

"I wouldn't go much above a 1080p display, however - a Full-HD set should be more than capable of servicing a household for the coming decade and in some cases, longer," he says.

"I would far rather recommend customers spend the extra money on a larger set from a reputable brand name," he says.

"This is a new market and one can never be too careful," he concludes.