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Scaling DVD to Get the Most from Your HDTV Set (19/4/2006)

By Roy Ping, NeoDigits

The home theatre environment has certainly come a long way over the past 60 years. Back then, the typical home theatre experience involved the entire family huddled around a black and white analogue set in the living room, watching the same TV programme as every other person in the country. It certainly is an archaic concept to most of us nowadays when, thanks to recent technological advancements, we can enthusiastically devour cinema theatre-quality experiences in the comfort of our own private spaces.

Enter the HD experience

The advent of high definition (HD) technology has resulted in HD TVs becoming a feature of our domestic spaces. Fifteen per cent of homes in the United States have an HDTV, with numbers growing steadily. As the insatiable appetite for the HD experience grows, the consumer market is expanding from niche to mainstream. But misconceptions surrounding the technology and capabilities of the product still abound.

The misconceptions

As a manufacturer of HD DVD players, we understand about consumers' desires to reap all the benefits their HDTV's promise. Some of the most frequently asked questions are 'What resolution should I choose from my DVD player that is best suited to my LCD TV?', 'Will 1080i work well on my TV?', and 'How can I get the best high definition resolution from my TV?'

We have also noticed some misconceptions that have come into play. One common mistake is to wrongly interpret HDTV specifications that read something like 'This TV supports 720p and 1080i high definition video input' as meaning that the HDTV will support 720p and 1080i resolutions. The truth is, very few HDTV screens have a 'native' resolution that can match 1080i.

The thing to note is that each LCD, plasma and DLP TV has its own native resolution. To answer the above questions therefore, we must first find out what the 'native resolution' of the TV is. Older-generation plasma TV screens, for example, only have a resolution of 852 x 480, while the new generation plasma TV screens have a higher resolution of 1024 x 1024.

Video signal scaling

The diagram below shows how the video source, such as a DVD player, talks to the HDTV to play images.

Video output scaled to match TV display resolution

Step 1
The video source will output a resolution signal that is different to the HDTV's native resolution.

Step 2
This video signal passes through a video processor called a scaler. This scaler has a processing chipset that upscales or downscales the received video signal to match the native resolution of the HDTV's screen.

Step 3
The scaler sends this processed signal to the screen to display the image in the TV's native resolution.

The external scaler is able to work with both analogue and digital input signals. The problem is, a digital signal from a DVD player will have been somewhat processed by the DVD player's graphic processor. If the signal has to be processed again, i.e. upscaled or downscaled by an external scaler, the quality will not be as good as if it were processed and scaled just once in the DVD player's graphic processor. For this reason, some people will open their DVD player, put additional lines on the DVD player's graphic processor in order to get the original 'unprocessed' video signal, and connect it to the external scaler. This is not recommended however, as it is very complicated and expensive to do, and will void the warranty of the DVD player.

Choosing the right video source

The key to getting the best images possible on your HDTV is to choose a video source that can directly output a digital signal at the same resolution as your HDTV's screen, thus bypassing the scaler. This will result in a sharper, crisper image. DVD players that are able to do this will be equipped with HDMI (High-Definition Multimedia Interface). HDMI is the new standard for 'pure digital' connection, and was designed as a common interface for devices from set-top boxes to digital TVs.

DVD players with HDMI will allow you to choose from a number of resolutions for matching purposes. An example of such a DVD player is NeoDigits' HELIOS HVD2085, which offers 11 output options.

The NeoDigits HELIOS HVD2085 HD upscaling DVD player

Conclusion

The key to getting the most out of your HDTV is finding out what your display panel's native resolution is, then matching your video source's HDMI output to this specific resolution. Owners of DVD players that offer a large choice of resolution-matching options will have a higher chance of getting the right match for their HDTVs, and are able to reap the benefits from a larger pool of HDTVs, no matter what the brand, model or resolution.

Not all DVD players on the market however, offer a wide range of resolutions. So if the native resolution of your particular screen is not available from the options on the DVD player, the best thing to do is opt for the next nearest resolution, whether it is slightly higher of lower, and then test by trial and error to see which of the two images appears sharper.

Roy Ping is Chief Technical Officer for NeoDigits, a technology company focused on bringing the latest high-tech DVD solutions to the home theatre market.

www.neodigits.com