High Definition Television Explained

High Definition TV or HDTV is the largest change to broadcasting and television ever since the introduction of colour. Flat panel lcd televisions and plasma televisions with a minimum screen resolution of 1280 x 720 pixels are known as HD Ready and are able of displaying current HD broadcasts.

What does ‘HD ready’ mean ?

If a flat panel tv carries the HD Ready label it will function with a HD signal and will be able to display a HD picture. televisions that are specified to meet the requirements of the HD Ready logo must have a minimum picture resolution of (1280 pixels x 720 pixels) i.e. 720 vertical lines in 16:9 widescreen, where the signal received is either 720p/50 or 1080i/25 picture formats and to be capable of accepting HD – the ’50′ or ’25′ is the amount of frames per second. They must also able to receive HD inputs by either DVI or HDMI and on Component Inputs.

For a 1366 x 768 pixels HD ready TV, if it receives a 1080i signal then scalers inside the flat panel tv will down convert the picture to fit the 768 lines flat panel tv. This is done using complex algorithm sequences in the scaler which systematically crops the image down to the resolution of the screen. If the signal is at 720p then the signal will be slightly upscaled to fill the 768 vertical lines with complicated algorithms.

If a HD Ready television receives a full HD signal of resolution 1920 x 1080 pixels the picture signal has to be interpolated or altered down to show the image. One to one mapping of the pixels is not achievable.

What is ‘HD ready 1080P’ ?

If a plasma tv or lcd tv has a ‘HD ready 1080p’ badge it has enough pixels to display the full 1080p signal with pixel for pixel mapping without interpolation. A 1080p flat screen lcd television or plasma tv is 1920 x 1080 pixels where the 1080 is the vertical resolution and the ‘p’ is for progressive scan. A HD Ready 1080p widescreen lcd television or plasma tv is the maximum screen resolution in the UK for high definition and thus the term ‘full’. Any plasma television or lcd tv with this resolution can show 1080i and 1080p signals without up or down scaling, and by way of one to one pixel mapping. Connectivity must be by either HDMI or DVI inputs. HD Ready 1080p full hd televisions must be able to display a 1080p/24 or 1080p/50 signal where the 24 and the 50 represent the number of frames per second.

When a 1080p HD tv receives s 720p input it will upscale (or oversample) the signal to the resolution of the 1080p HDTV widescreen with complex internal software algorithms.

What is a Full HD TV ?

Early HD tv’s didn’t have the ‘HD Ready 1080p’ logo and might not be compatible with this specification and may not show selected signal inputs.

Interlaced or Progressive

Interlaced picture have two fields that are alternated to create a frame where every other line is displayed on each frame. So the odd lines are on one field and the even lines are on the other field. When the two fields containing the odd and even lines are shown consecutively for each frame at twice the frame rate this is known as Interlacing.

Interlaced pictures on video have more fluid movement due to each field being shot at a different time. Interlacing initially benefited CRT (cathode ray tube) tv’s by improving the picture quality and using the same amount of broadcast bandwidth.

In the UK PAL televisions operates at 25 frames a second with 50 fields a second. A broadcasted signal that is Interlaced requires half the signal bandwidth of a Progressive signal. A progressive signal has a scan rate of 50 full frames per second in contrast with an interlaced signal which has half the frame speed.

Interlaced pictures on recordings made for television or with a video camera aren’t able to be displayed on normal definition LCD televisions and Plasma tvs. This is because the picture isn’t created with an electron scan like tube televisions so LCD televisions and Plasma TVs don’t benefit from the interlaced picture signal. Flat screen widescreen televisions have internal processing to make a progressive scanned picture from a interlaced image – i.e. Deinterlacing.

Progressive Scanning

Each frame has all of the lines from the image on a progressive scanned picture instead of either the even or odd lines as with an interlaced image. Progressive scanning is a means of transmitting, storing and displaying the image.

Progressive scan has the benefit of superior vertical resolution than interlaced images with the same frame rate and no interlace artifacts or blurring, and therefore less eye strain. Also better results are possible for scaling to higher resolutions than the equivalent interlaced sources. For the best scaling results full frames work the best but interlaced video sources must be deinterlaced prior to being scaled and this can cause very noticeable combing artifacts.

What is the difference between the 720p/50 and 1080i/25 formats?

A 1080i/25 (1,920×1080 pixel resolution) interlaced signal has to some extent better horizontal resolution on still pictures than a progressive scanned 720p/50 (1,280×720 pixel resolution) image. However on interlaced moving pictures there are inter line twitters which lower the subjective vertical resolution. The twitter is caused by the frames being slightly different. Both 720p/50 and 1080i/25 are used by broadcasters depending on their preference and bandwidth availability.

Smoother motion is created with 720p progressive scanned pictures, particularly on slow-motion, compared to 1080i interlaced pictures. Better still pictures are produced with interlaced 1080i signals. By means of good quality built in processing a 1080i signal will appear superior on a 1080 television compared to a 720p source. The one you should choose, will depend on the type of images being predominantly displayed, either static or moving, and your preferences.

The conversion of a progressive source such as 1080p/50 into an interlaced configuration such as 1080i/25 is easier than the conversion of an interlaced signal to a progressive format.

What is 1080p/24 ?

This is 1080p at 24 frames per second. This gives the greatest picture quality with the 1080p picture decoded directly from the Blu Ray disc at 24 frames per second, and then sent to the flat panel HD Television. The 24 frames per second is the same rate as the original cinema film. The Television will then create additional frames to increase to either 48 or 72 frames per second creating middle frames that make the picture more fluid.

Sources of HDTV

All HD TV broadcasts are now at either 720p/50 or 1080i/25 and are can be viewed to their full benefit on HD Ready widescreen televisions. At present the only broadcasters of high def. TV are by satellite on Freesat and Sky digital hd, and on the web on BT vision, and on cable by Virgin media. The only sources of Full HD 1080p are either by download on the internet and on Blu ray. The Xbox 360 can give a 720p/50 image for video gamesand the Playstation 3 can offer a 1080p image for games.

Conclusion

HD enhances the viewing experience and makes TV more engaging. If you don’t aim to use a Blu ray player, Playstation 3, or to download films from the internet then a HD ready tv will almost certainly suffice. However if you want to future proof yourself against the likelihood of future full HD 1080p broadcasts then the full HD 1080p models are the ones to buy. Clearly, if you already possess, or are going to buy a Blu ray player, Playstation 3 or to you are going to down load full HD films then the full HD 1080p television is the logical choice.

Before you buy any electrical products online, make sure you check Armadeus Cornelius’ excellent website for more information on HD Ready TV, and also Discount Flat Screen TVs

High-Definition Multimedia Interface – HDMI Cables

HDMI cables are just one component to the new HDMI standard in audio and video connection. To fully experience a high-definition home theater, one must invest in HDMI gear. Every new high definition television (HDTV) has at least two HDMI inputs, and other paraphernalia (including DVRs, DVD players, Blue-ray players, game consoles, and computers) feature HDMI outputs to deliver high-quality audio and video. While these new technologies can sometimes seem confusing and exorbitantly priced, having a single HDMI cable handle both images and sound has the potential to make home theater design and set up much easier.

High-Definition Multimedia Interface, HDMI, transmits the HD video and high resolution audio through a single cable. One HDMI cable take the place of three analog component video cables and six audio cables. Therefore the HDMI cables remove a lot of your cable clutter problems

With an HDMI cable you will receive high quality audio and video. Your pictures are sharper and your audio is crisper and clearer. HDMI cables work best with fixed pixel displays such as LCD, plasma or DLP screens and projectors. A HDMI cable allows to hear and view your show with out any changes from it original format.

In addition, HDMI cables offer higher quality than any other cable available at this time. With high-definition video of up to 1080p resolution at 60 frames per second, it surpasses any competition. It can also carry eight channels of 24-bit audio at 192kHz.

HDMI cables support two-way communication between the video and display, enabling the remote control devices connected by HDMI cables. Another advantage of HDMI cables are that they are fully backward compatible with DVI using a DVI-to-HDMI cable adaptor. The current standard of HDMI requires products being made with new versions of the HDMI be entirely backward compatible with earlier HDMI products.

Originally HDMI cables were created for high definition home theaters, today they have become an industry standard. HDMI cables can work effectively when stretching to distances of 10 meters or greater. This makes them ideal for any distance projects, while eliminating unnecessary cable clutter. HDMI cables also provided better quality of audio and video.