The introduction of HDTV or high definition tv signifies the most significant development in the specification of broadcasting and television ever since colour. For a flat panel widescreen television to receive and benefit from a high definition signal it must have a screen resolution of 1280 x 720 pixels and be labelled HD Ready.
What makes a Television 'HD Ready' ?
Any television that is HD Ready is capable of receiving and displaying a HD picture. To meet this specification the television must have a picture resolution of at least 1280 pixels x 720 pixels. They must be able to receive a signal that is 1080i/25 or 720p/50, where the 1080 or 720 is the number of vertical lines, the 'i' is for an interlaced picture and the 'p' is for a progressive scan picture, and the 25 and the 50 are the number of frames displayed each second. In addition the televisions must have either DVI or HDMI and Component signal input connectors.
Any TV that has a screen resolution of 1366 X pixels 768 pixels and is HD Ready will use internal scalers to convert a 1080i signal down to the 768 lines; if it receives a 720p signal the internal circuits will upscale the image to 768 lines. The procedure of converting down or up is made with highly developed software to fill the screen.
Most HD ready televisions do not have sufficient pixels to offer true pixel-for-pixel mapping without interpolation of the higher HD resolution (1920 x 1080 pixels).
What is 'HD ready 1080P' ?
Any TV that carries the 'HD ready 1080p' is naturally capable of displaying a 'full' 1080P signal with enough pixels to offer true pixel-for-pixel mapping without interpolation. A HD ready 1080p flat screen television has a picture resolution of (1920 pixels x1080 pixels) i.e. 1080P, where '1080' is the vertical resolution of the picture and the 'P' is for Progressive scan. HD ready 1080P is the maximum resolution available in the UK on HD tvs hence the 'full' term. These sets will display 1080p and 1080i video without distortion i.e. with 1:1 pixel mapping. They also have HDMI or DVI HD input at 1080p HD and display signals that are at either 24 or 50 frames per second.
If a 720p signal is received by a 1080p tv it is oversampled (or upscaled) to fill up the resoltion of the 1080p HD TV by way of sophisticated software.
Full HD
Older full HD flat panel tv's may possibly not fulfill all 'HD Ready 1080P' requirements.
Interlaced Picture or Progressive Picture ?
An Interlaced Image involves arranging the scan lines of one frame into two fields where one field contains the odd lines and another field contains all of the even lines - so each field has half the resolution. The two fields of the frame are alternately displayed in sequence at a rate that is twice as fast as the actual frame rate, this is known as Interlacing.
When a image is interlaced, moving pictures on video seem to have smoother motion since each field of the frame are shot at different times. The system of picture interlacing was in the first place used to enhance the quality of the picture on tube tvs using the equivalent amount of bandwidth for the broadcast signal.
The UK broadcast standard is known as PAL which operates with 25 full frames per second or 50 fields per second. Interlacing the signal means that half the picture information is in each field so half the bandwidth is required for broadcasting in comparison to a Progressive signal at 50 full frames per second.
CRT (Cathode Ray Tube) tv or the old CRT tvs are able to show interlaced images made for television or on a video camera because they have an electron scan. Flat panel lcd TVs and plasma tv's aren't able to display such signals without the use of progressive scanning or deinterlacing.
Progressive scan delivers benefits.
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 way 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 hence less eye strain. Also better results are possible for scaling to higher resolutions than the comparable interlaced sources. For the best scaling results full frames work the best but interlaced video sources have got to be deinterlaced before being scaled and this can cause extremely noticeable combing artifacts.
The differences between 720p/50 and 1080i/25 formats
A 1080i/25 (1,920x1080 pixel resolution) interlaced signal has slightly better horizontal resolution on still pictures than a progressive scanned 720p/50 (1,280x720 pixel resolution) image. But on interlaced moving pictures there are inter line twitters which lower the subjective vertical resolution. The twitter is caused by the frames being a little different. Both 720p/50 and 1080i/25 are used by broadcasters depending on their inclination and bandwidth availability.
Progressive scanning 720p gives more fluid motion, especially on slow-motion, than an interlaced 1080i signal. But interlaced 1080i signals give better static resolution. If the internal processing is competent enough a 1080i signal on a 1080 display will still seem superior than the 720p material. The best one depends on whether you are to display more static images or more moving pictures and what is more important to you.
When a HD Ready tv receives a 1080p/50 signal it can alter the picture into a 1080i/25 image much easier than a full HDTV can convert a 1080i signal into 1080p.
What is 1080p/24 ?
This is 1080p at 24 frames per second. This gives the greatest picture quality with the 1080p picture decoded straight from the BlueRay disc at 24 frames per second, and then sent to the flat panel HD TV. The 24 frames per second is the same rate as the original cinema film. The Television will then create additional frames to multiply to either 48 or 72 frames per second creating middle frames that make the picture more fluid.
HDTV Sources
All high def. TV broadcasts are at present at either 720p/50 or 1080i/25 and are can be viewed to their full benefit on HD Ready widescreen tv's. Currently the only broadcasters of HD television are by satellite on Freesat and Sky digital hd, and over the web on BT vision, and on cable by Virgin media. The only sources of Full HD 1080p are either by download over the internet and on Blueray. The Xbox 360 be capable of give a 720p/50 image for games and the Playststion 3 can give a 1080p image for games.
In conclusion
The added sharpness and vividness of a HD television picture enhances the viewing experience. Unless you have, or expect to buy a Blueray player, Playstation 3 or you are going to down load 1080p HD films off the internet a HD Ready television will be good enough. The only problem with this is that if any broadcaster decides to commence transmitting in HD in the near future your purchase wont be able to take full advantage of the additional screen resolution. Thus if you need to cover every possibility then purchase a full 1080p HD television.
What makes a Television 'HD Ready' ?
Any television that is HD Ready is capable of receiving and displaying a HD picture. To meet this specification the television must have a picture resolution of at least 1280 pixels x 720 pixels. They must be able to receive a signal that is 1080i/25 or 720p/50, where the 1080 or 720 is the number of vertical lines, the 'i' is for an interlaced picture and the 'p' is for a progressive scan picture, and the 25 and the 50 are the number of frames displayed each second. In addition the televisions must have either DVI or HDMI and Component signal input connectors.
Any TV that has a screen resolution of 1366 X pixels 768 pixels and is HD Ready will use internal scalers to convert a 1080i signal down to the 768 lines; if it receives a 720p signal the internal circuits will upscale the image to 768 lines. The procedure of converting down or up is made with highly developed software to fill the screen.
Most HD ready televisions do not have sufficient pixels to offer true pixel-for-pixel mapping without interpolation of the higher HD resolution (1920 x 1080 pixels).
What is 'HD ready 1080P' ?
Any TV that carries the 'HD ready 1080p' is naturally capable of displaying a 'full' 1080P signal with enough pixels to offer true pixel-for-pixel mapping without interpolation. A HD ready 1080p flat screen television has a picture resolution of (1920 pixels x1080 pixels) i.e. 1080P, where '1080' is the vertical resolution of the picture and the 'P' is for Progressive scan. HD ready 1080P is the maximum resolution available in the UK on HD tvs hence the 'full' term. These sets will display 1080p and 1080i video without distortion i.e. with 1:1 pixel mapping. They also have HDMI or DVI HD input at 1080p HD and display signals that are at either 24 or 50 frames per second.
If a 720p signal is received by a 1080p tv it is oversampled (or upscaled) to fill up the resoltion of the 1080p HD TV by way of sophisticated software.
Full HD
Older full HD flat panel tv's may possibly not fulfill all 'HD Ready 1080P' requirements.
Interlaced Picture or Progressive Picture ?
An Interlaced Image involves arranging the scan lines of one frame into two fields where one field contains the odd lines and another field contains all of the even lines - so each field has half the resolution. The two fields of the frame are alternately displayed in sequence at a rate that is twice as fast as the actual frame rate, this is known as Interlacing.
When a image is interlaced, moving pictures on video seem to have smoother motion since each field of the frame are shot at different times. The system of picture interlacing was in the first place used to enhance the quality of the picture on tube tvs using the equivalent amount of bandwidth for the broadcast signal.
The UK broadcast standard is known as PAL which operates with 25 full frames per second or 50 fields per second. Interlacing the signal means that half the picture information is in each field so half the bandwidth is required for broadcasting in comparison to a Progressive signal at 50 full frames per second.
CRT (Cathode Ray Tube) tv or the old CRT tvs are able to show interlaced images made for television or on a video camera because they have an electron scan. Flat panel lcd TVs and plasma tv's aren't able to display such signals without the use of progressive scanning or deinterlacing.
Progressive scan delivers benefits.
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 way 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 hence less eye strain. Also better results are possible for scaling to higher resolutions than the comparable interlaced sources. For the best scaling results full frames work the best but interlaced video sources have got to be deinterlaced before being scaled and this can cause extremely noticeable combing artifacts.
The differences between 720p/50 and 1080i/25 formats
A 1080i/25 (1,920x1080 pixel resolution) interlaced signal has slightly better horizontal resolution on still pictures than a progressive scanned 720p/50 (1,280x720 pixel resolution) image. But on interlaced moving pictures there are inter line twitters which lower the subjective vertical resolution. The twitter is caused by the frames being a little different. Both 720p/50 and 1080i/25 are used by broadcasters depending on their inclination and bandwidth availability.
Progressive scanning 720p gives more fluid motion, especially on slow-motion, than an interlaced 1080i signal. But interlaced 1080i signals give better static resolution. If the internal processing is competent enough a 1080i signal on a 1080 display will still seem superior than the 720p material. The best one depends on whether you are to display more static images or more moving pictures and what is more important to you.
When a HD Ready tv receives a 1080p/50 signal it can alter the picture into a 1080i/25 image much easier than a full HDTV can convert a 1080i signal into 1080p.
What is 1080p/24 ?
This is 1080p at 24 frames per second. This gives the greatest picture quality with the 1080p picture decoded straight from the BlueRay disc at 24 frames per second, and then sent to the flat panel HD TV. The 24 frames per second is the same rate as the original cinema film. The Television will then create additional frames to multiply to either 48 or 72 frames per second creating middle frames that make the picture more fluid.
HDTV Sources
All high def. TV broadcasts are at present at either 720p/50 or 1080i/25 and are can be viewed to their full benefit on HD Ready widescreen tv's. Currently the only broadcasters of HD television are by satellite on Freesat and Sky digital hd, and over the web on BT vision, and on cable by Virgin media. The only sources of Full HD 1080p are either by download over the internet and on Blueray. The Xbox 360 be capable of give a 720p/50 image for games and the Playststion 3 can give a 1080p image for games.
In conclusion
The added sharpness and vividness of a HD television picture enhances the viewing experience. Unless you have, or expect to buy a Blueray player, Playstation 3 or you are going to down load 1080p HD films off the internet a HD Ready television will be good enough. The only problem with this is that if any broadcaster decides to commence transmitting in HD in the near future your purchase wont be able to take full advantage of the additional screen resolution. Thus if you need to cover every possibility then purchase a full 1080p HD television.
About the Author:
Armadeus Cornelius has almost 20 years experience in the electrical industry. To find out more go to his web site for more information about HD Ready TV. Otherwise you can go to his on-line electrical store for LCD HD TV & Plamsa HD TV Discounts.
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