You will already be familiar with standard definition television and you will have heard about high definition, but what about near High Definition?

This is a term that is used by Television manufacturers for a system that enhances the quality of Standard Definition pictures on televisions to near High Definition.

Is there any need for a Near High Definition Television?

Whilst there is an increasing amount of HD content available via Sky and Freesat it isnt possible to watch all available programs in High Definition. The only other sources of HD are Blu-ray and downloads from the internet. Furthermore if you arent prepared to pay a monthly subscription or pay for Blu-ray discs then the choice is limited to Freesat or a small selection of On Demand programmes and movies from Virgin Media or Tiscali. With such a limited choice of High Definition content the television manufacturers believe there is a case for near High Definition televisions that upscale the picture to allow you to make the most of your HD television.

Standard Definition Broadcasts

A TV picture consists of 1000s of little cells known as pixels. Broadcasts in the UK use the PAL system which in standard definition has 576 horizontal lines of 768 pixels across the screen or 768 x 576 pixels.

When a television picture is broadcast the moving picture is broken down in to frames. These frames are actually split in to two half fields A and B, where the A field consists of the odd lines and the B frame consists of the even lines. This type of picture is known as an interlaced image. When the two fields of each frame are combined or interlaced they create a complete frame as each field is alternately scanned or painted onto the television screen. Where the odd and even fields are displayed alternately each showing 25 times a second or 50 times a second when displayed alternately together, hence the term a 50hz picture.

The total number of pixels that a television screen has is known as the resolution. A high resolution or High Definition (HD) picture has more pixels than a Standard Definition picture. HD TVs will generally have a sharper picture, or will be capable of displaying a sharper picture, than a Standard Definition TV.

All UK high definition broadcasts are either at 720 p (1280pixels x 720pixels) or 1080i (1920pixels x 1080pixels). You will need a television of a specification of at least HD Ready which will be able to display a 720P broadcast. There arent any broadcasts of 1080 P ( 1920pixels x 1080pixels ) material in the UK at this moment in time. To take advantage of the full reolution of a 1080P tv set you will have to view either Blu-Ray discs or downloads from the internet.

The quality of the picture of a Full HD 1080P TV compared to an ordinary SD TV is around five times greater than a standard definition and hence the reason for the terrific image quality.

On TVs that have Near HD they use an upscaler to transform an SD picture into 1080P.

An Upscaler is also referred to as an Upconverter which converts the resolution of a source signal. Upscaler can convert low resolution images to a resolution that fills the screen. When a Full HD 1080P TV, with a resolution of 1920x1080 pixels, receives a signal from a DVD or a Freeview broadcast of 768x576 pixels it has to upscale the image to fill the screen. It does this because the two resolutions are different and if it didnt upscale the image then some parts of the screen wouldnt be filled by the picture and it would be smaller the screen.

The upscaling process is done by the TV using a digital video processing chip which interlaces the input signal and then the advanced algorithms and filters interpolate the picture by creating the missing lines and pixels that are required to fill the screen. This process matches the input resolution with the TVs native resolution.

The ability of a TV to upscale an image is dependant on how good the source input and the quality of upscaler chip. The quality of upscaling chips varies from TV to TV as does the quality of other internal components and the actual screen which affect the quality of the picture displayed.

An upscaler is required by all LCD and Plasma TVs so that they are compatible with the various source resolutions that they may be presented with so that they fill the native resolution of the screen. It may seem that the Near HD TVs arent doing anything different to any other LCD or Plasma TV but it is how they do it that is different. The Near HD TVs use a more powerful upscaling processor chip which means that they are much better at upscaling than ordinary TVs.

No matter how sophisticated the algorithms are that guesstimate how the additional pixels should look an upscaled SD image isnt as good as an actual true 1080P HD picture.

Toshiba has a near HD upscaling technology called Resolution + which they incorporate in their ZV range of televisions that they say will vastly improve the quality of a Standard Definition picture. They use the powerful upscaling cell processor that is used in the Sony PS3 which upscales any image to 1080p resolution.

The cell processor compares neighbouring frames and aggregates the pixel detail to raise the definition of the picture. The effect of this is that the picture has sharper image edges with subdued 3-D noise. Furthermore the colour palette is more lifelike because the blue and greens are improved to minimise the loss of clearness that can be caused by an upscaler. Also due to the contrast being enhanced the dark areas are even darker but the light areas sustain their luminance. The SD images are crisp and rich and have sharp edge detail with improved texture however the flat areas are not changed.

DVD Players with Near HD

Near HD differs to progressive scan which combines two interlaced field images into full frames which are together displayed at the same time giving smoother motion. Also this enhances the vertical resolution and prevents artifacts such as line flicker which is flickering between the lines. Whilst progressive scan uses the 2 fields of a frame to produce a full frame it doesnt create extra lines and pixels in the way that upscalers do.

An upscaling DVD player uses the same methods as an upscaling television. There are a number of upscaling DVD players from different manufacturers but non of these work in the same way as the Toshiba XDE model which deinterlaces the picture before upscaling it from 576i lines to 1080P Near High Definition quality. The picture on the Toshiba upscaling DVD player is improved with images that are extra detailed with brilliant colours and enhanced contrast by employing the methods used on the Toshiba Near HD TVs.

So should you buy a Near HD TV or DVD Player?

Obviously a 768 x 576 image isnt as good as a 1,920x1,080 image and no amount of digital processing will make them the same but a good upscaler is able to produce something that is closer. If you arent prepared to purchase films on Blu-ray, or pay a monthly subscription for high definition channels, and you arent happy with the limited HD content that is available on Freesat then a near HD product is the right choice. It isnt as good as a genuine HD 1080p source but it does deliver noticeable improvements in the picture quality on virtually all content including 480i, 576i, 720p (DVD, Standard Definition TV broadcasts and Video Games) all of which it will upscale to 1080p.

The Near HD TVs offer the ultimate flexibility with the ability to enhance almost any source. As more HD options become available either chargeable or free the TV is capable of receiving and displaying 1080P sources so you wont need to upgrade your TV. Toshiba is the only company that offers Near HD TVs and a DVD Player but others will follow soon.