July 3, 2010
In its early stages of development, television employed a combination of optical, mechanical and electronic technologies to capture, transmit and display a visual image. By the late 1920s, however, those employing only optical and electronic technologies were being explored. All modern television systems rely on the latter, although the knowledge gained from the work on electromechanical systems was crucial in the development of fully electronic television.
The first images transmitted electrically were sent by early mechanical fax machines, including the pantelegraph, developed in the late 1800s. The concept of electrically powered transmission of television images in motion was first sketched in 1878 as the telephonoscope, shortly after the invention of the telephone. At the time, it was imagined by early science fiction authors, that someday that light could be transmitted over wires, as sounds were.
The idea of using scanning to transmit images was put to actual practical use in 1881 in the pantelegraph, through the use of a pendulum-based scanning mechanism. From this period forward, scanning in one form or another has been used in nearly every image transmission technology to date, including television. This is the concept of “rasterization”, the process of converting a visual image into a stream of electrical pulses.
In 1884 Paul Gottlieb Nipkow, a 23-year old university student in Germany, patented the first electromechanical television system which employed a scanning disk, a spinning disk with a series of holes spiraling toward the center, for rasterization. The holes were spaced at equal angular intervals such that in a single rotation the disk would allow light to pass through each hole and onto a light-sensitive selenium sensor which produced the electrical pulses. As an image was focused on the rotating disk, each hole captured a horizontal “slice” of the whole image.
Nipkow’s design would not be practical until advances in amplifier tube technology became available. The device was only useful for transmitting still “halftone” images—represented by equally spaced dots of varying size—over telegraph or telephone lines.  Later designs would use a rotating mirror-drum scanner to capture the image and a cathode ray tube (CRT) as a display device, but moving images were still not possible, due to the poor sensitivity of the selenium sensors. In 1907 Russian scientist Boris Rosing became the first inventor to use a CRT in the receiver of an experimental television system. He used mirror-drum scanning to transmit simple geometric shapes to the CRT.
Scottish inventor John Logie Baird demonstrated the transmission of moving silhouette images in London in 1925, and of moving, monochromatic images in 1926. Baird’s scanning disk produced an image of 30 lines resolution, just enough to discern a human face, from a double spiral of lenses. This demonstration by Baird is generally agreed to be the worlds first true demonstration of television, albeit a mechanical form of television no longer in use. Remarkably, in 1927 Baird also invented the world’s first video recording system, “Phonovision”—by modulating the output signal of his TV camera down to the audio range he was able to capture the signal on a 10-inch wax audio disc using conventional audio recording technology. A handful of Baird’s ‘Phonovision’ recordings survive and these were finally decoded and rendered into viewable images in the 1990s using modern digital signal-processing technology.
In 1926, Hungarian engineer Kálmán Tihanyi designed a television system utilizing fully electronic scanning and display elements, and employing the principle of “charge storage” within the scanning (or “camera”) tube.
Also in 1927, Herbert E. Ives of Bell Labs transmitted moving images from a 50-aperture disk producing 16 frames per minute over a cable from Washington, DC to New York City, and via radio from Whippany, New Jersey. Ives used viewing screens as large as 24 by 30 inches (60 by 75 centimeters). His subjects included Secretary of Commerce Herbert Hoover.
In 1927, Philo Farnsworth made the world’s first working television system with electronic scanning of both the pickup and display devices, which he first demonstrated to the press on 1 September 1928.
The first practical use of television was in Germany. Regular television broadcasts began in Germany in 1929 and in 1936 the Olympic Games in Berlin were broadcast to television stations in Berlin and Leipzig where the public could view the games live.
So that`s how it all began….
May 17, 2010
For those of you who like history and technical information, here is an extract from the Wikipedia`s definition.
The British high definition TV service started trials in August 1936 and a regular service in November 1936 using both the (mechanical) Baird 240 line and (electronic) Marconi-EMI 405 line (377i) systems. The Baird system was discontinued in February 1937. In 1938 France followed with their own 441 line system, variants of which were also used by a number of other countries. The US NTSC system joined in 1941. In 1949 France introduced an even higher resolution standard at 819 lines (768i), a system that would be high definition even by today’s standards, but it was monochrome only. All of these systems used interlacing and a 4:3 aspect ratio except the 240 line system which was progressive (actually described at the time by the technically correct term of ‘sequential’) and the 405 line system which started as 5:4 and later changed to 4:3. The 405 line system adopted the (at that time) revolutionary idea of interlaced scanning to overcome the flicker problem of the 240 line with its 25 Hz frame rate. The 240 line system could have doubled its frame rate but this would have meant that the transmitted signal would have doubled in bandwidth, an unacceptable option.
Color broadcasts started at similarly higher resolutions, first with the US NTSC color system in 1953, which was compatible with the earlier B&W systems and therefore had the same 525 lines (480i) of resolution. European standards did not follow until the 1960s, when the PAL and SECAM colour systems were added to the monochrome 625 line (576i) broadcasts.
Since the formal adoption of Digital Video Broadcasting‘s (DVB) widescreen HDTV transmission modes in the early 2000s the 525-line NTSC (and PAL-M) systems as well as the European 625-line PAL and SECAM systems are now regarded as standard definition television systems. In Australia, the 625-line digital progressive system (with 576 active lines) is officially recognized as high definition.
In 1949, France started its transmissions with an 819 lines system (768i). It was monochrome only, it was used only on VHF for the first French TV channel, and it was discontinued in 1985.
In 1958, the Soviet Union developed Тransformator (Russian: Трансформатор, Transformer), the first high-resolution (definition) television system capable of producing an image composed of 1,125 lines of resolution aimed at providing teleconferencing for military command. It was a research project and the system was never deployed in the military or broadcasting.
In 1969, the Japanese state broadcaster NHK first developed consumer high-definition television with a 5:3 aspect ratio, a slightly wider screen format than the usual 4:3 standard. The system, known as Hi-Vision or MUSE after its Multiple sub-Nyquist sampling encoding for encoding the signal, required about twice the bandwidth of the existing NTSC system but provided about four times the resolution (1080i/1125 lines). Satellite test broadcasts started in 1989, with regular testing starting in 1991 and regular broadcasting of BS-9ch commenced on 25 November 1994, which featured commercial and NHK programming.
In 1981, the MUSE system was demonstrated for the first time in the United States. It had the same 5:3 aspect ratio as the Japanese system. Upon visiting a demonstration of MUSE in Washington, US President Ronald Reagan was most impressed and officially declared it “a matter of national interest” to introduce HDTV to the USA.
Several systems were proposed as the new standard for the USA, including the Japanese MUSE system, but all were rejected by the FCC because of their higher bandwidth requirements. At the same time that the high definition systems were being studied, the number of television channels was growing rapidly and bandwidth was already a problem. A new standard had to be radically efficient, needing less bandwidth for HDTV than the existing NTSC .
Rise of digital compression
Since 1972, International Telecommunication Union‘s radio telecommunications sector (ITU-R) ITU-R has been working on creating a global recommendation for Analogue HDTV. These recommendations however did not fit in the broadcasting bands which could reach home users. The standardization of MPEG-1 in 1993 also led to the acceptance of recommendations ITU-R BT.709. In anticipation of these standards the DVB organisation was formed, an alliance of broadcasters, consumer electronics manufacturers and regulatory bodies. The DVB develops and agrees on specifications which are formally standardised by ETSI.
DVB created first the standard for DVB-S digital satellite TV, DVB-C digital cable TV and DVB-T digital terrestrial TV. These broadcasting systems can be used for both SDTV and HDTV. In the USA the Grand Alliance proposed ATSC as the new standard for SDTV and HDTV. Both ATSC and DVB were based on the MPEG-2 standard. The DVB-S2 standard is based on the newer and more efficient H.264/MPEG-4 AVC compression standards. Common for all DVB standards is the use of highly efficient modulation techniques for further reducing bandwidth, and foremost for reducing receiver-hardware and antenna requirements.
In 1983, the International Telecommunication Union‘s radio telecommunications sector (ITU-R) set up a working party (IWP11/6) with the aim of setting a single international HDTV standard. One of the thornier issues concerned a suitable frame/field refresh rate, with the world already strongly demarcated into two camps, 25/50Hz and 30/60Hz, related by reasons of picture stability to the frequency of their main electrical supplies.
The IWP11/6 working party considered many views and through the 1980s served to encourage development in a number of video digital processing areas, not least conversion between the two main frame/field rates using motion vectors, which led to further developments in other areas. While a comprehensive HDTV standard was not in the end established, agreement on the aspect ratio was achieved.
Initially the existing 5:3 aspect ratio had been the main candidate, but due to the influence of widescreen cinema, the aspect ratio 16:9 (1.78) eventually emerged as being a reasonable compromise between 5:3 (1.67) and the common 1.85 widescreen cinema format. (Bob Morris explained that the 16:9 ratio was chosen as being the geometric mean of 4:3, Academy ratio, and 2.35:1, the widest cinema format in common use, in order to minimize wasted screen space when displaying content with a variety of aspect ratios.)
An aspect ratio of 16:9 was duly agreed at the first meeting of the IWP11/6 working party at the BBC‘s Research and Development establishment in Kingswood Warren. The resulting ITU-R Recommendation ITU-R BT.709-2 (“Rec. 709“) includes the 16:9 aspect ratio, a specified colorimetry, and the scan modes 1080i (1,080 actively interlaced lines of resolution) and 1080p (1,080 progressively scanned lines). The current Freeview HD trials use MBAFF, which contains both progressive and interlaced content in the same encoding.
It also includes the alternative 1440×1152 HDMAC scan format. (According to some reports, a mooted 750 line (720p) format (720 progressively scanned lines) was viewed by some at the ITU as an enhanced television format rather than a true HDTV format, and so was not included, although 1920×1080i and 1280×720p systems for a range of frame and field rates were defined by several US SMPTE standards.)
Demise of analog HD systems
However, even that limited standardization of HDTV did not lead to its adoption, principally for technical and economic reasons. Early HDTV commercial experiments such as NHK’s MUSE required over four times the bandwidth of a standard-definition broadcast, and despite efforts made to shrink the required bandwidth down to about two times that of SDTV, it was still only distributable by satellite with one channel shared on a daily basis between seven broadcasters. In addition, recording and reproducing an HDTV signal was a significant technical challenge in the early years of HDTV. Japan remained the only country with successful public broadcast analog HDTV. Digital HDTV broadcasting started in 2000 in Japan, and the analog service ended in the early hours of 1 October 2007.
In Europe, analogue 1,250-line HD-MAC test broadcasts were performed in the early 1990s, but did not lead to any established public broadcast service.
Inaugural HDTV broadcast in the United States
HDTV technology was introduced in the United States in the 1990s by the Digital HDTV Grand Alliance, a group of television companies and MIT. Field testing of HDTV at 199 sites in the United States was completed August 14, 1994. The first public HDTV broadcast in the United States occurred on July 23, 1996 when the Raleigh, North Carolina television station WRAL-HD began broadcasting from the existing tower of WRAL-TV south-east of Raleigh, winning a race to be first with the HD Model Station in Washington, D.C., which began broadcasting July 31, 1996. The American Advanced Television Systems Committee (ATSC) HDTV system had its public launch on October 29, 1998, during the live coverage of astronaut John Glenn‘s return mission to space on board the Space Shuttle Discovery. The signal was transmitted coast-to-coast, and was seen by the public in science centers, and other public theaters specially equipped to receive and display the broadcast.
European HDTV broadcasts
Although HDTV broadcasts had been demonstrated in Europe since the early 1990s, the first regular broadcasts started on January 1, 2004 when Euro1080 launched the HD1 channel with the traditional Vienna New Year’s Concert. Test transmissions had been active since the IBC exhibition in September 2003, but the New Year’s Day broadcast marked the official start of the HD1 channel, and the start of HDTV in Europe.
Euro1080, a division of the Belgian TV services company Alfacam, broadcast HDTV channels to break the pan-European stalemate of “no HD broadcasts mean no HD TVs bought means no HD broadcasts…” and kick-start HDTV interest in Europe. The HD1 channel was initially free-to-air and mainly comprised sporting, dramatic, musical and other cultural events broadcast with a multi-lingual soundtrack on a rolling schedule of 4 or 5 hours per day.
These first European HDTV broadcasts used the 1080i format with MPEG-2 compression on a DVB-S signal from SES Astra‘s 1H satellite at Europe’s main DTH Astra 19.2°E position. Euro1080 transmissions later changed to MPEG-4/AVC compression on a DVB-S2 signal in line with subsequent broadcast channels in Europe.
In the following six years, the number of HD channels broadcasting to Europe has grown considerably, particularly from the pay-TV broadcasters. At the end of 2009, there were 114 HD channels broadcasting from Astra satellites.
|European HD Channels via Astra by Country (end 2009)|
The number of households able to view HD channels has also increased. According to SES Astra, at the year-end 2009 there were 6 million households receiving HD channels via Astra satellites, and it is expected that by 2013 there will be 24.7 million households in Europe watching HD channels via satellite.
|European HD-via-Astra Homes by Country/Region (end 2009)|
May 9, 2010
With Freeview+ you’ll get all the benefits of tape-free digital recording on top of access to Freeview’s great range of TV and radio channels.
All you need to do is buy a digital TV recorder with the Freeview+ logo, plug it in and away you go. The real plus is there’s no subscription to worry about, just sit back and enjoy free TV whenever you want.
With the great functions available from Freeview+, TV viewing has never been better. You are free to control your TV entertainment experience. Pause, record and rewind live TV to fit around your work and play. You’ll never miss a thing especially as you can now record an entire series at the touch of a button.
April 15, 2010
The 11th Doctor Who initially had the nation divided, will he be as good as David Tennent or will he completely bomb! BBC Wales must take full credit for their choice of Matt Smith who has slipped seamlessly into the role.
This type of production must be taken seriously and really demands a serious size Flat Screen TV.
The special effects become even more spectacular when viewed on a large flat screen TV. An important thing to bear in mind is that as you will have spent a very large amount of money on a television you do need to have it installed by a professional and that is where you need to call an expert such as Mark Williams of TV Aerial and Satellite Services
So let the programme have all of the sound effects and not your TV FALLING OFF THE WALL because it wasn`t properly installed.
March 28, 2010
There are always people who use clever and persuasive tactics try to make a fast buck on the back of something new, like digital switchover.
If you think you’ve been ripped off, or paid a deposit to a trader you’re now worried about, or suspect there’s a rogue trader working door-to-door in your area, call the Consumer Direct helpline (08454 04 05 06). Calls cost 4p per minute from a BT landline; from mobile and non BT lines call costs may vary.
Consumer Direct can also give you advice on your cancellation rights and getting any unsatisfactory work put right. To find out how, visit the Consumer Direct website. If you prefer face-to-face help and advice go to your local advice agency or Citizens Advice Bureau.
Some local councils have set up ‘doorstoppers’ schemes to tackle doorstep crime. Residents get stickers and mirrors for their doors, advice on fitting door chains and how to deal with cold callers.
Check on the Consumer Direct website, your local Citizens Advice Bureau, or library to see if there’s a scheme in your area.
Tips for avoiding scams
- Remember that no one from Digital UK or Switchover Helpscheme will call unexpectedly without an appointment.
- Demand identification from uninvited callers – and call the company to check they are who they say they are.
- Don’t agree to any work on the spot. Take time to think about what work (if any) you want done.
- Only buy goods and services you need for switchover from reputable retailers and traders that carry the digital tick logo
- If an offer seems too good to be true – in a leaflet, advert, by phone, e-mail or personal approach – it probably is. Be wary and read the details of the deal carefully.
March 24, 2010
For all you footie fans the forth coming world cup is about to take over your life.
So picture this, you are on the sofa, a few beers chilling nicely, and you are going to watch the match on a small screen… NOooooooo… Now that doesn’t seem right, does it?
So now is definitely the time to seriously think about buying a flat screen TV.
There are certainly some amazing deals up for grabs from all of the major retailers, and even some retailers that even I didn’t realise sold TV`s, such as Marks and Spencer.
Once you have purchased your dream TV you now need to consider where is the best place to have the screen installed so that you get maximum viewing potential. Having spent I am sure a princely sum of money on your screen that last thing you want is for it to fall off the wall.
Now that is why you need a professional to sort it out for you. It` s a bit similar to asking a brain surgeon to clean out the drains………… It just doesn’t work that way !
The solution is very simple, just click on this link and an engineer will be with you in no time at all.
So all you then have to arrange is the beer, the mates, may be a pizza and enjoy the games.
March 8, 2010
Deciding to buy a plasma screen most probably caused a huge debate about, how much to spend, and what model to choose, and most probably arguments about who has the remote !
March 2, 2010
From 2008 -2012 a rolling program is in place to change all televisions in the UK over to a digital signal. TV campaigns have been on our screens advising us of why and when it`s going to happen.
So are you ready ?
I expect you are wondering why we need to change, so here come`s the technical stuff explanation.
Digital is now the best technology for broadcasting TV. To make sure everyone in the UK can receive it, the signal needs to be available for free everywhere, ideally through a normal aerial. At present, around 74% of households are in areas where this is possible. Digital signals for the rest of the country can only be switched on when the existing analogue ones are switched off. After switchover almost everyone (at least 98.5%) will be able to receive digital TV through an aerial
Here are a few helpful hints and tips to get you prepared
To make sure you keep your TV service, you will need to convert your TV to digital before the switchover happens in your region. Don`t Panic – Digital switchover doesn’t apply to radio.
If you can already watch more than five channels, it is probably digital already. If not, you will need to adapt it by connecting it to a digital set-top box, or replace it. This applies to all the TV sets in your home, and to any recorder (video or DVD) that you use to record from the TV.
So if you have dreamed of having a top of the range Plasma TV, now is a good time to make the change.
When will switchover happen in my area?
Digital UK, an independent organisation, is co-ordinating the switchover. You will get plenty of advance warning, and there will be lots of information and help available. The switchover will happen between now and 2012, one region at a time.
Going digital is not difficult and need not be expensive. For more information, please visit Digital UK.
Can I get help with the switchover ?
The Government has announced a Help Scheme for some people who may have difficulty in going digital. This scheme is being funded by the BBC licence fee. If you are eligible you will receive equipment, help with installation and follow-up support, either free or for a subsidised fee. The Help Scheme is available to people who are aged 75 or over, or registered blind or partially sighted, or entitled to certain social security benefits. For more information, please visit Switchover Help Scheme