It's one of today's buzz-words: 1080p. But what exactly does 1080p mean? Here, we explain the background to the technology - from the ground up.

Back in the day: CRT TVs such as this one barely showed up the problems associated with de-interlacing.

To understand how today's top format works, you'll first need to know the basics. Traditional TV services the world over all have the same inherent problem: interlacing. Broadcasters in Europe transmit 25 images per second - not as complete, "progressive" images, but rather as 50 "interlaced" images. The TV camera splits the image into horizontal lines. Initially, it samples the uneven-numbered lines - the first, third, fifth, and so on. These then form the first interlaced image; the second consists of the even-numbered lines - 2, 4, 6, and so on.

Conventional tube-based TVs plot the images on their screens in exactly same way. When this technology was developed, CRT screens were small, not very bright, and not particularly sharp; the disadvantages of interlacing - flicker on horizontal or diagonal lines - were therefore barely problematic. The bigger and brighter the screens become, however, the more obvious the effect. Unlike CRTs, for technical reasons, LCD and plasma TVs always work progressively. Ideally, therefore, TV images would also be recorded and transmitted progressively - and in full HDTV resolution (1,920 x 1,080 pixels). In short: in 1080p format.

Movies on Blu-ray discs are already stored in this way - here, the signal has the original movie frame-rate of 24 pictures per second. Flat-panel TVs display each image - depending on the exact model - two, three, or four times.

Many HD camcorders and digital cameras with video functions also record progressively, with 24, 25, or 30 frames per second, depending on the manufacturer. But the cameras don't always record in 1080p - often, they'll only do 720p (1,280 x 720 pixels). Many high-definition channels are broadcast in 720p - but with 50 full ("progressive") images per second.

And how things have changed: A great example of the modern flat-panel TV, Sony's LCD Sony KDL-40 W 5500 cleanly de-interlaces all types of input signal, delivering a high-quality, natural-looking picture. For more information about Sony 1080p TVs see our Sony 1080p overview.

The ideal is obviously 1080p with 50 or 60 frames per second, since this would mean full, flicker-free sharpness and the best motion depiction; at present, sadly, many studios and broadcasters lack the necessary technology. But connect a modern computer to a flat-panel TV via HDMI, and Full HD at 50- or 60-hertz frame rates becomes a possibility, since the PC's graphics card can deliver this format. In our reviews, we discuss each TV's ability to accept and display 1080p signals - read more in the LCD TV reviews and plasma TV reviews sections.