WATCH LIVE TV - HOW?
"
Watch live TV" redirects here. For other uses, see TV (disambiguation).
Television is a system for transmitting and receiving moving pictures and sound at a distance that uses a diffusion mechanism. Transmission can be made using radio waves, television networks, cable or satellite TV IPTV. The receiver of the signals is
Watch live TV.
The word "television" is a hybrid of the Greek τῆλε (tele, "far") and the Latin visiōnem (accusative of visio "vision"). The term television relates to all aspects of transmission and television programming. Sometimes abbreviated as
Watch live TV. This term was first used in 1900 by Constantin Perski in the International Electrical Congress of Paris (CIEP).
The World Television Day is celebrated on November 21
Watch live TV commemorating the date held in 1996 the first World Television Forum at the United Nations.
A Philips LCD TV.
TV Braun HF 1, a German model of the 1950's
Watch live TV.
The provision of content services in the form of Video on Demand and / or Internet Streaming are not classified as TV services. The emergence of television that can connect to the Internet in recent years of the first decade of the century, opens the possibility of so-called smart TV where they mix and combine contents of the conventional transmission (broadcast) with another arriving via the Internet.
Contents [hide]
1 History
1.1 Early developments
1.2 Electronic Television
1.2.1 Image Capture
1.2.2 The video signal
1.3 The development of TV
1.3.1 The color TV
1.3.1.1 Current TVC Systems
1.3.2 High Definition
1.3.2.1 The aspect ratio
1.3.2.2 The PALplus
1.3.3 Digitization
2 Types of
Watch live TV
2.1 analog broadcast
2.2 Dissemination digital
2.2.1 Terrestrial Television
Cable
Watch live TV 2.3
2.4 Satellite TV
2.5 IP Television (IPTV)
2.6 The 3D
Watch live TV
3 Types of
Watch live TV
3.1 Features
4 See also
4.1 Emissions television
5 References
6 Bibliography
7 External links
[Edit]
Main article: History of television.
The concept of television (distance vision) can be traced back to Galileo and his telescope. However, not until 1884, with the invention of Paul Nipkow disk Nipkow made significant progress to create a medium. The change would bring the television as we know it today, it was invented by Vladimir Zworkyn iconoscope and Philo Taylor Farnsworth. This would lead to an all-electronic television, which had a much better frame rate, higher definition picture and illumination.
[Edit] Early developments
On the origins of
Watch live TV of television were exposed several mechanical solutions, such as the Nipkow disc in 1910, but these mechanical systems were discarded in favor of fully electronic collection systems today.
In 1925, Scottish inventor John Logie Baird made the first real experience using two disks, one in the emitter and the receiver, who were attached to the same axis so that its rotation was synchronous and separated by 2 mm.
The first public television broadcasts of the BBC made in England in 1927, and CBS and NBC in the U.S. in 1930. In both studies used mechanical systems and programs are not issued on a regular schedule.
The first station programming and regular schedule was established in 1930 in Berlin by the local branch of the National Socialist German Workers but those responsible for Nazi propaganda were not aware of the possibilities of the medium and continued to use the radio.
The emissions program started in England in 1936, and United States on April 30, 1939, coinciding with the inauguration of the Universal Exhibition in New York. Scheduled broadcasts were interrupted during World War II and resumed when it ended.
[Edit] Television electronic
1937 began regular
Watch live TV transmissions of electronic television in France and the United Kingdom. This led to rapid development of the television industry and a rapid increase in viewers, but the small screen
Watch live TV were very expensive. These releases were made possible by the development of the following elements at each end of the chain: the cathode ray tube and the iconoscope.
[Edit] Image Capture
The iconoscope is based on the principle of photoelectric emission: the image is projected onto a mosaic of photoelectric cells that emit electrons that cause the image signal. It was used in the U.S. between 1936 and 1946.
The vidicon tube is a 2.2 cm diameter and 13.3 cm long based on the photoconductivity of some substances. The optical image is projected onto a conductive plate which, in turn, is scanned by the other side by a very thin electron beam.
The Plumbicon is based on the same principle as the vidicon, however, the photoconductive plate comprises three layers: the first, in contact with the collector plate, and the third is formed by a semiconductor, the second lead oxide . Thus, originates a diode which is reverse biased, as a result, the current through each elementary cell in the absence of light, is extremely low and the sensitivity of Plumbicon under these characteristics, very high on
Watch Live TV.
Main article: Video signal.
The signal transduced from the image contains the information on this, but necessary, for restructuring, which has a perfect synchronism between the deflection scanning and deflection in the representation.
The exploration of an image is done by decomposition, first frames to those who call boxes and then in lines, reading each frame. To determine the number of frames needed to be able to reconstruct a moving image and the number of lines for optimal playback quality and the optimal perception of
Watch Live TV color (color TV) were performed numerous empirical studies and scientific, the human eye and the way they perceive. It was found that the number of frames must be at least 24 to second (then used for other reasons 25 and 30) and that the number of lines must be greater than 300.
The video signal itself is composed of image information corresponding to each line (in the 625-line PAL and NTSC 525 in each box) grouped into two groups, the odd and the even lines of each frame, each of these groups are called field lines (the PAL system used 25 frames per second while NTSC 30). This information must be added to the sync, both frame and line, that is, both vertically and horizontally. The box being divided into two fields per frame have a vertical sync and it signals the beginning and the field type, ie when it starts, when the odd field and even field begins. At the beginning of each line it is added to the line synchronizing pulse or horizontal (with modern color
Watch live TV also adds information about the timing of the color).
The image coding is performed between 0 V to 0.7 V and the black to white. For the sync pulses are incorporated -0.3 V, which gives a total amplitude of the video waveform of 1 V. The vertical sync are constituted by a series of pulses from -0.3 V to
Watch live TV provide information about the type of field and even times each.
The sound, audio call is treated separately throughout the production chain and is then emitted by the video in a carrier next to the charge of transporting the image.
The development of TV
Central Control at a
Watch live TV broadcaster.
Cameras on a
Watch live TV set.
It is the late twentieth century where the television becomes technological flag of countries and each will develop their systems of national and private
Watch live TV . In 1953 he creates Eurovision associating several European countries connect their
Watch live TV systems using microwave links. A few years later, in 1960, establishing Mundovisión beginning to make links with geostationary satellites covering the whole world.
The television production was developed with the technical advances that allowed the recording of video and audio signals. This allowed the recording of programs that could be stored and later released. In the late 50s of the twentieth century developed the first video recorders and cameras with interchangeable lenses in a revolving turret in front of the picture tube. These advances, along with the development of machines necessary for mixing and electronic generation of other sources, allowed development of very high production.
In the 70s Zoom lenses were introduced and began to develop smaller recorders which allowed the recording of the news in the field. cameras were born for Electronic News. Soon after he began to develop equipment based on digitizing the video signal and digital signal generation, born of these developments the digital effects and graphic palettes. While the control of machines meant mounting post rooms, by combining several elements he could perform complex programs.
The development of television did not stop the transmission of image and sound. He soon saw the advantage of using the channel to provide other services. This philosophy was implemented in the late 80's of the twentieth century teletext broadcasts news and information in text format using the free space information video signal. Also implemented was enhanced sound systems, television born in stereo or dual sound and providing exceptional quality, the system managed to prevail in the market was the NICAM.
The color
Watch live TV
See also: List Introduction of color television in different countries
NTSC
PAL, or switching to PAL
SECAM
No Information
Distribution of TV systems in the world.
In 1928, experiments were performed in the transmission of color images. In 1940, Guillermo González Camarena patented in Mexico and the U.S., Trichromatic System Field Sequential.
In 1948, Goldmark, based on the idea of Baird and Camarena, developed a similar system called field sequential system. The success was such that the Columbia Broadcasting System purchase for their TV broadcasts.
The next step was the simultaneous transmission of color images of each trinoscopio called. The trinoscopio occupied three times more radio spectrum and monochromatic emissions, above, was inconsistent with them while very expensive.
The high number of black and white televisions required the color system was developed to be compatible with monochrome emissions. This support should take place in both directions, emission color to black and white receptions and receptions emissions in monochrome color.
In search of compatibility born the concept of luminance and chrominance. The luminance information portal brightness, light, image, corresponding to white and black, while the chrominance carries color information. These concepts were presented by Valensi in 1937.
In 1950 the Radio Corporation of America (RCA) develops a picture tube carrying three electron guns, the three beams were capable of impacting small phosphor dots of colored, called phosphors, using a mask, the Shadow Mask or Trimask. This allowed the tubes without trinoscópicos so bulky and cumbersome. The electron beam on impact with the luminophores emitting light corresponding primary color by additive mixture generates the original color.
While the receiver were implemented in the three guns for the three primary colors in a single element, in the issuer (the camera) were kept separate tubes, one for each primary color. To separate the light is passed that makes up the image by a dichroic prism that filters each primary color to its corresponding sensor.
[Edit] Current systems of TVC
EBU color bars seen in a MFO and a vectorscope.
The first color television system developed respecting the dual compatibility with monochrome television was developed in 1951 by a group of engineers led by Hirsh in the laboratories of the Corporation in the U.S. Hazeltime This system was adopted by the U.S. Federal Communication Commission (FCC) and was the NTSC stands for National Television System Commission. The system caught on and spread throughout North America and Japan.
The basic signals used are the luminance (Y), which gives brightness and is shown in monochrome receivers, and the color components, the two color difference signals, the RY and BY (red minus luminance and blue minus luminance). This double selection allows for a differentiated treatment to the color and brightness. The human eye is more sensitive to variations in brightness and definition of the color, this makes the bandwidths of both signals are different, which facilitates transmission and both signals should be implemented in the same band whose width is adjusted.
The amplitude modulated NTSC two carriers of the same frequency shifted 90 ° are then aggregated, QAM or quadrature. In each of the carriers is modulated one of the differences in color, the resulting signal amplitude indicates the color saturation and tint or hue phase thereof. This chrominance signal is called. Modulation axes are located so that takes care of the fact that the eye is most sensitive to color flesh, this is the shaft I is oriented towards the orange and Q to the magenta. As the suppressed carrier modulation is needed to send a burst of the same for generators to the receiver can synchronize with it. This saves or burst is usually on the front porch of the line synchronizing pulse. The chrominance signal is added to the luminance signal by composing the total image.
Changes in the phase of the video signal when it is transmitted errors dye, ie color (color changes of the image).
The NTSC was the basis of which left other researchers, mainly in Europe. In Germany, developed by a team led by Walter Bruch subsanaba a system phase errors, this system is PAL, Phase Altenating Line.
For this, the subcarrier phase alternates in each line. Subcarrier which modulates the RY component, which is called V PAL has a 90 ° phase line and from 270 in the next. This makes the phase errors that occur in the transmission (and affecting the same and in the same direction on both lines) are compensated for the representation of the image to see a line next to each other, if the integration of image for color correction is undertaken by the human eye have called PAL S (PAL Simple) and if done by an electronic circuit D PAL (PAL Delay, delayed). The PAL was proposed as pan-European color system in the Oslo Conference, 1966. But no agreement was reached as a result of Western European countries, with the exception of France, adopted PAL while France Eastern Europe and SECAM.
In France, developed by researcher Henri de France a different system, SECAM, "Couleur À SÉquentiel Mémoire" which bases its action in the transmission sequence of each color component FM modulated such that a line sends a component and the next the other component. Then the receiver combines them to deduce the color of the image.
All systems have advantages and disadvantages. While the NTSC and PAL difficult editing the video signal by the color sequence in four eight fields, respectively, the SECAM system made it impossible to work mixing video signals.
[Edit] High Definition
Main article: HDTV.
The system of standard definition television, known by the initials "SD", has, in PAL, a definition of 720x576 pixels (720 horizontal dots per line and 576 vertical dots corresponding to the active lines of PAL) this makes a PAL image having a total of 414,720 pixels. NSTC are maintained in dots per line but the number of active lines is only 525 which gives a total of 388,800 pixels of the pixels being slightly wider and slightly higher in PAL at NSTC.
28 have been developed different systems for HDTV. There are differences in terms of pictures, number of lines and pixels and a scan. They can be grouped into four main groups of which two have already become obsolete (those concerning the rules of the SMPTE 295M, 240M and 260M) remaining two differ mainly in the number of active lines, one of 1080 active lines (SMTP 274M) and one of 720 active lines (SMTP 269M).
In the first group, with 1,080 active lines, there are differences in frame rate and of samples per line (although the number of samples per active line time remains in 1,920) also changes the form of sweeping, there is progressive scan or interlaced. Likewise occurs in the second group, where the active lines are 720 samples per 1280 having active line time. In this case the shape is always progressive scanning.
In the system of HD of 1,080 lines and 1,920 samples per line we have 2,073,600 pixels in the image and the HD system of 720 lines and 1,280 samples per lines have 921,600 pixels on the screen. Relative to conventional systems have the resolution of 1,080 lines system is 5 times greater than that of PAL-five and a half times that of NTSC. With the 720 lines of HD is 50% higher than in PAL and 66% higher than in NTSC.1
The high resolution also calls for a redefinition of changing the color space gamut triangle.
[Edit] The aspect ratio
Old black and white TV.
In the 1990's began to develop systems for HDTV. All these systems, in principle analog increased the number of image lines and the aspect ratio changed from the format used hitherto, aspect ratio 4/3, to a landscape format of 16/9. This new format, more pleasing to the eye was established as standard even on standard definition broadcasts.
The aspect ratio is expressed by the width of the screen relative to the height. The standard format hitherto had an aspect ratio of 4/3. The adoptee is 16/9. The compatibility between the two aspect ratios may be performed in different ways.
An image of 4/3 that will be viewed on a screen 16/9 can be presented in three different ways:
With vertical black bars on each side (pillarbox). Maintaining the ratio of 4/3 but losing part of the active display area.
Enlarging the image until it fills the screen horizontally. Loses part of the image at the top and bottom thereof.
Deforming the image to fit the format of the screen. It uses the entire screen and is the whole image, but with altered geometry (the circles are ellipses with the major diameter oriented from right to left).
An image of 16/9 which is to be seen on a screen of 4/3, similarly, has three ways to be seen:
With horizontal bars above and below the picture (letterbox). You see the whole picture but lose screen size (there are several letterbox formats depending on the visible part of the image you see (the bigger it becomes more cuts), we use the 13/9 and 14/9 .)
Enlarging the image to fill the screen vertically, losing the sides of the image.
Deforming the image to fit the aspect ratio of the screen. You see the whole image across the screen, but with altered geometry (the circles are ellipses with the major diameter oriented from top to bottom) .1
[Edit] The PALplus
Main article: PALplus.
In Western Europe, where the television system of most countries is the PAL was developed with support from the European Union, a format somewhere between high definition and standard definition. This format was called PALplus and although it was supported by the administration failed to materialize.
The PALplus was an extension of PAL to transmit images of 16/9 without having to spend vertical resolution. In a normal TV receiving a landscape image with black bars above and below it (letterbox) of 432 active lines. The PALplus sent additional information to fill the black bars reaching 576 lines of vertical resolution. By auxiliary signals that were on the lines of the vertical sync interval commanded PALplus receiver indicating whether the collection had been made in progressive scan or interlaced. The system was extended with the so-called "Colorplus" it improved color decoding.
[Edit] The digitization
Digital Terrestrial Television in the world.
In the late 80's of the twentieth century began to develop scanning systems. The digitization of television has two distinct parts. On one side is the digitization of production and the other of the transmission.
With regard to production systems were developed several scanning. The first of them were based on digitizing the composite video signal unsuccessful. The approach of the components of the digitized video signal, ie the luminance and color differences, which was found most suitable. Was initially developed signal systems in parallel, with thick wires of a wire needed for each bit, that cable soon replaced by the transmission time multiplexed words corresponding to each of the signal components also This system allowed us to include audio, embebiéndolo to that information, and various other utilities.
To maintain the quality needed for the production of TV standard developed CCIR-601 Studio Quality. While it allowed the development of other less demanding standards for the field of light production (EFP) and electronic news gathering (ENG).
The difference between the two fields, the production quality of study and ENG as the magnitude lies in the bit stream generated in the digitization of the signals.
Reducing the bit rate of the digital video signal resulted in a series of algorithms, all based on the discrete cosine transform domain both spatially and in time, that reduced the flow enabling the construction of more affordable equipment . This allowed them access to small production companies and TV broadcasting leading to the rise of local television.
As for transmission, scanning the same was made possible by compression techniques able to reduce the flow to less than 5 Mbit / s, we must remember that the original flow of a signal quality of study is 270 Mbit / s. This compression is called MPEG-2 that produces flows between 4 and 6 Mbit / s without appreciable loss of subjective quality.
Digital TV transmissions have three main areas depending on the shape of the same even though they are similar in technology. Transmission is by satellite, terrestrial cable and satellite radio, this is known as DTT.
The advance of information technology, both hardware and software, led to production systems based on computer processing of the television signal. Storage systems such as VCRs, became replaced by video and computer servers to store files passed their information on hard disks and data tapes. Video files include metadata is information concerning its contents. Access to information is from their own computers where they are video editing programs so that the resident information in the file is accessible in real time by the user. Actually the files are structured in three levels, online, for that very frequent usage information that resides on server hard disks, the near-line, frequently used information that resides on data tapes and they are in large automated libraries and the deep archive where the information is out of line and accurate incorporation into the system manually. All this is controlled by a database containing the seats where the information residing in the system.
Incorporating information system via the so-called function of intake. The sources can be generated and formats are converted by computer or video converter to computer files. The deposits made in the field by teams of ENG or EFP recorded in formats compatible with the storage using media other than magnetic tape, existing technologies are blue ray DVD (Sony), ram memory recording (Panasonic) and hard disk recording (Ikegami).
The existence of the video server enables the automation of releases and informational programs by making lists of issue.
[Edit] Types of TV
Sony analog TV.
Broadcast analog
See also: frequencies of TV channels
Television until recently, early twenty-first century, was completely analog and way of reaching viewers was through the air with radio waves in the VHF and UHF. Soon came the cable network channels that distributed the cities. This distribution was also performed with analog signal, the cable networks may have assigned a band, mostly to perform the tuning of the channels that come through the air along with the cable coming. Its development depends on the laws of each country, while in some developed rapidly, as in England and America, in others like Spain have had almost no importance until the late twentieth century law allowed installation.
The satellite, which allows the arrival of the signal to remote areas of difficult access, development, from technology launches, allowed the commercial provision for the distribution of television signals. The satellite performs two key functions, to allow links signals from one point to another in the world, using microwave links, and the distribution of the signal distribution.
Each of these types of emission has its advantages and disadvantages, while cable guaranteed to arrive in optimal signal without interference of any kind, requires an expensive facility and a center to perform the embedding of the signals, known header. You can only understand a cable run in urban agglomeration where people make profitable investments in the infrastructure. Another advantage of the cable is to provide a return path for creating interactive services independent of other systems (usually for other broadcast uses the phone line for the return). The satellite, high cost in building and launching can reach places inaccessible and remote. It also has the advantage of services available to viewers, which enable the commercial exploitation and cost efficiency. Satellite communication is one of the most important military logistics and many operating systems used in civil have a strategic background to justify the economic investment. Radio transmission is the most popular and more widespread. The investment of the distribution network signal is not very expensive and allows, through the network of transposers necessary to reach remote, rural in nature. The signal is much less immune to noise and in many cases the reception suffers. But it is the normal way of distributing TV signals.
[Edit] Digital Broadcasting
EBU Color Bars in YUV format.
Main article: digital TV.
These forms of delivery have remained with the birth of digital television with the advantage that the type of signal is very robust to interference and the emission standard is designed for good reception. We must also say that accompanies the television signal a series of extra services that give value to the programming and that the legislation has included an entire field for the implementation of pay-TV in its various forms.
The spread of digital television is based on the DVB Digital Video Broadcasting and is the system used in Europe. This system has a common part for satellite broadcasting, cable and terrestrial. This common portion corresponds to spatial signal flow and the unusual is that it adapts to each mode of transmission.
In the U.S.
States.
