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Possibilities of digital television. Equipment for IPTV or OTT

From the editor

Our life today is unthinkable without devices that use advanced technologies. But, using them every day, do we understand their essence? “We don’t need to know that,” some will say. “It would be interesting to know about this at least in general terms,” others will say, “but it’s too complicated.” We decided to try to introduce our most inquisitive readers to the course of modern technological achievements by turning to specialists in this field. Of course, many will skip these pages, but those who take the time and effort to read them will be able to understand the basic principles of the technology that opens up so many new possibilities for us.

The article we bring to your attention is just brief introduction into a huge topic that can be called “Development Directions modern television" In the future, we plan to introduce you to such concepts as high-definition television, mobile television, 3D television, etc.

We are in the thick of a new technological revolution— mass distribution of digital television broadcasting. Digital television- these are fundamentally new opportunities, this is interactivity, this is a medium for delivering multimedia traffic, etc. Therefore, the transition from traditional analogue television to digital is not just complex technical problem, but a serious factor operating in the economic and social plans on a global scale.

Programs for every taste

The opportunity that opens up to transmit a large number of channels allows you to significantly expand the range of programs offered to the user.

If previously the viewer had to search for the program he was interested in, and then coordinate his affairs with the time of its broadcast, then digital television successfully solves both of these problems. Each genre has a place on a specific channel.

For example, lovers of serious music, for whom concerts were previously shown at most once a week and on holidays, now have several 24-hour channels at their disposal. And for sports fans digital technology provides almost a channel for every sport. If this continues, then soon all the athletes will take their places in front of the TVs and there will be no one to perform. For those who like cinema, provided huge amount films, lovers of nature and travel, without leaving home, will visit any corner of the planet, and viewers interested in what is happening in the world will be able to regularly get acquainted with latest news, learn about the weather and stock market reports.

More lines, less clutter

Digital technologies bring a studio-quality signal to the mass audience with virtually no distortion. It becomes possible to transmit video images of high definition television - HDTV - High Definition Television) with a number of scan lines from 720 to 1080 and higher (16:9 format) versus 480-625 lines regular television(4:3 format). Much more efficiently used frequency range: instead of one analogue television channel, you can create several digital ones, i.e. The number of accepted programs is increasing sharply.

What are the main advantages of digital methods of transmitting, processing and storing information?

First of all, this is an increase in noise immunity, achieved in digital circuits. As is known, the possibility of error-free transmission of information is primarily determined by the signal/interference ratio in the communication channel. To obtain sufficiently good subjective image quality when receiving an analog television signal, this ratio at the TV input should be about 50 dB, i.e. the signal amplitude must be at least 300 times greater than the rms value of the interference voltage. If this is not the case, then interference pulses inevitably appear on the screen in the form of flickering white and black dots (noise, “snow”), moire and colored “torches” at transitions. Digital television is capable of filtering impulse noise from the useful signal, even if it is greatly weakened and noisy. Thanks to the separate transmission of brightness and color signals in digital television, cross-brightness-chrominance distortions are eliminated and high resolution is achieved. The quality of image reproduction is practically independent of the signal propagation medium and is determined only by the perfection of the equipment.

The use of digital methods eliminates many disadvantages analog systems, including signal distortion during its formation, processing and transmission, which accumulates with an increase in the number of conversions, re-receptions and re-recordings. Digital methods Data compression and modulation provide the possibility of multi-program television broadcasting, in which signals from several broadcast programs can be transmitted over one channel. Given the shortage broadcast channels in big cities and limited ability satellite repeaters, this property of a digital signal turns out to be very relevant.

Only "zeros" and "ones"

In analog electronics, many types of signal processing are known: amplification, limiting, modulation, demodulation, etc. To carry them out they are used physical processes in elements and assemblies of electronic circuits.

Digital signal processing involves performing mathematical operations on the numbers that make it up. Such digital processing makes it possible to solve problems that were not available in analog technology, for example:

Coding of television signals to reduce the required transmission bandwidth communication channels (signal compression or compression);

Conversion of television formats;

Digital signal filtering;

Coding of television signals to reduce the influence of interference.

What do the concepts “digital” and “digital” mean, which are now widely used in radio electronics?

In analog (non-digital) devices and systems, information is transmitted, processed and stored in the form of continuously changing physical quantities— analog signals. Their values ​​at each moment correspond to the values ​​of physical quantities, for example, voltage, current, etc.

In digital devices, any information is in the form of a sequence of numbers. To transmit information, binary numbers are used, each digit (bit) of which can take one of two values: logical zero (low signal level) or logical one ( high level). If b binary digits are used, then each number (word) can take one of 2b values. For example, 8-bit (eight-bit, one-byte) non-negative binary numbers take values ​​from 00000000 ( decimal number 0) to 11111111 (decimal 255). Digital signal processing devices, or DSPs (Digital Signal Processing) use various shapes representation of any numbers (including negative and fractional).

Perform sampling

Let's try to convert analog signal to digital, taking one period of an ordinary sinusoid as the original analog signal. To do this we need to perform the following operations:

Discretization in time, i.e. replacing a continuous analog signal with a sequence of its values ​​at discrete moments (Fig. 1a). They are sequences of short pulses, the amplitudes of which at selected moments correspond to instantaneous values continuous signal. Such pulses are called sample values ​​(samples) or samples. The time interval of the TD between samples is called the sampling interval;


Rice. 1a

Quantization by level, which consists in finding for each signal sample the lowest allowed level closest to it from the set of fixed levels used, called quantization levels (Fig. 1b). These levels divide the entire range of sample values ​​into a finite number of intervals called quantization steps. There is no need to accurately transmit reading values, since the human eye has a finite resolution in terms of brightness. This allows you to split the entire range of sample values ​​into a finite number of levels. If you choose it large enough so that the difference between the two closest levels is ultimately not noticeable to the viewer, it becomes possible, instead of transmitting all sample values, to transmit only a certain number of their discrete values;


Rice. 1b

Coding (digitization), as a result of which the number (code) of the found quantization level is presented in the form binary number in parallel or serial form..

Sampling of an analog signal can thus be carried out both in terms of time and in terms of signal magnitude. “Removing” the code values ​​from the vertical scale in Fig. 1b, we get sequential presentation quantized levels of the received digital signal in binary code. Our original smooth sine wave turned into the following sequence of numbers: 011, 100, 101, 110, 101, 100, 011, 010, 001, 001, 010, 011.

All of the above operations are usually performed in one device - analog-to-digital converter, ADC (English ADC - Analogue-to-Digital Converter). The reverse conversion of the digital signal to analog is carried out by a digital-to-analog converter, DAC (DAC - Digital-to-Analogue Converter).

Flow of information

What is unique about the digital signal? First of all, in its simplicity: as already mentioned, only two values ​​are used: logical 0 and 1. Such a digital signal can be easily protected by coding, weakened or damaged places in it can be updated, and copied without loss of quality.

Digital signal free from the inherent disadvantages of an analog signal, however, it has many times more information compared to an analog signal, and this significantly increases the requirements for the signal path and its bandwidth. Thus, a classic analog television signal is content with a stream transmission rate of up to 20 megabits per second (Mbps), and for a stream digital information an order of magnitude higher speed is required. HDTV bit rate high resolution and 16:9 format can reach 1 Gbps.

Thus, transferring the entire path from the studio to the viewer to a digital system can be carried out in two ways: firstly, by radically increasing the power and expanding the transmission channel bandwidth, and secondly, by changing the volume of transmitted information. The second method turned out to be more realistic and profitable. In this regard, methods for reducing volume were developed - the so-called digital information compression methods.

Compression: lossy and lossless

Depending on how the data is converted, there are two compression methods. The first does not allow the loss of a single bit of information and is used when compressing, for example, text information. The second allows for the loss of some information and is successfully used when converting sound and image, i.e. information that each individual perceives differently and this does not affect subjective perception.

Compression of moving images uses a combination of eliminating irrelevant information and reducing so-called redundant information. Redundancy is due to the fact that in a sequence of adjacent frames depicting the same scene most frame remains, as a rule, unchanged. For example, in a scene of a cyclist riding against a natural background, the individual frames differ by only a few percent of the total image area. Identical parts of adjacent frames can be quickly identified and recorded in digital memory and update much less frequently than other frames, for example, after every eighth frame, and in between add only partial changes to them.

Elimination of irrelevant information (English irrelevancy) is based on the characteristics of human vision, which does not distinguish details beyond a certain boundary of perception. The easiest way to remove events is of minimal duration, which are least perceived by vision.

At the initiative of ISO (International Organization for Standardization) and IEC (International Electrotechnical Commission), the MPEG (Motion Picture Expert Group) was founded in 1988 with the task of creating data compression systems. The group has created a number of compression standards, the most interesting of which for digital television are MPEG-2 and MPEG-4.

The MPEG-2 standard, intended primarily for television broadcasting, was adopted back in 1994, and in 1995 it became international. In accordance with it, the video signal is compressed 20-40 times, which makes it possible to transmit a digital television signal over existing television channels high quality or 4-10 regular television programs.

Adopted in 1994, the MPEG-4 standard provides even greater compression ratios than MPEG-2. This standard was created primarily for the transmission of audiovisual information over narrowband communication channels, and is now widely used as a means of recording films and video programs on laser discs. In addition, only this standard is capable of providing interactivity, i.e. the ability for the user to influence the process of transmitting information to him by asking and selecting options according to back channel communications.

To be continued

Text: Alexander Peskin, associate professor at Moscow State Technical University. N.E. Bauman

Good afternoon, dear readers of the blog site. I’ll start with a little background. Some time ago my daughter was born and accordingly she began to grow up. By the summer, our whole family moved out of town, where, as it turned out, it was simply necessary to have a TV to watch cartoons and, accordingly, for parents to relax their brains by watching a movie or the news. Before our arrival, an old antenna was installed on the roof of the house, which made it possible to view at most three channels, and then in very poor quality with constant ripples and disappearance of the picture.

Looking at the neighbors' roofs installed antennas, and after talking with the owners personally, I realized that you can’t do without certain equipment here. Having read on the pages of our vast Runet, I identified for myself two main options for viewing free digital terrestrial television:

  • Tricolor TV Very common equipment in suburban areas. But the cost with installation seemed too high for me (on my own without special tools tune satellite dish You won’t succeed, you definitely need specialists here). Yes, and annual subscription fee somehow it was annoying, because, in my opinion, outside the city, a TV is not a thing for which you need to shell out so much money (unless, of course, you live there all year round). Tricolor naturally has its advantages, allowing you to view much more more channels than using regular .
  • Digital terrestrial TV using . If having a huge number of television channels in your dacha is not important for you, then I suggest you consider the option of purchasing and installing inexpensive equipment that allows you to receive about twenty channels in excellent quality.

A huge role when choosing the second option is played by the choice of a high-quality antenna and receiver, as well as distance from television towers.

Let's first figure out step by step what digital television is, what format the antenna and set-top box should support, and also consider a simple installation option.

What is digital terrestrial television dvb t2

Recently there has been a nationwide transition to digital standard broadcasting. In fact, dvb t2 is a transmission and reception technology compressed image and sound in best quality, with subtitles output and use digital channels(where DVB is European standard). The Government of the Russian Federation decided to distribute digital signal broadcasting everywhere by 2015, thereby providing every home with high-quality and stable reception. On at the moment Most towers have already been converted to broadcast exactly this format, but analog transmission the signal is still working.

However, at the moment, not all television towers allow transmitting the number of TV channels that are included in the main packages for free digital terrestrial television. When installing an antenna and a set-top box at home, you must understand that you will not receive more than twenty channels, and if the distance from the transmitting tower is quite high and there are tangible obstacles, then in the end you can only watch ten main channels on your TV. In fact, this issue is resolved by purchasing more powerful antenna And good receiver with an amplifier, but we’ll talk about what’s needed for digital terrestrial TV a little later.

Multiplex - combining into a single digital package television channels.

The first digital terrestrial television multiplex:

Second digital TV multiplex (list may change):

Before we move on to the next part of this article, I advise you to use the official website of the Russian television and radio broadcasting network http://rtrs.ru/dtv/ to determine the distance of a particular tower from your home and, accordingly, determine the possibility of viewing one or two multiplexes. The figure below shows a map displaying information posted on the site, the link to which I provided above.

If you look closely, there are several tabs at the top of the map. When you select the “RTRS-1 TV Channel Package” tab, you will determine which towers broadcast exactly the first multiplex, and by selecting the other “RTRS-2 TV Channel Package” tab, accordingly, the presence of the second multiplex. When switching from tab to tab, the color of the towers will change and accordingly inform us about this or that opportunity. More details on how to choose suitable direction and you can read the tower in a separate article on my blog.

For example, my suburban area is located near the village of Pervomaiskoye. The first thing I did was point the antenna exactly there, but as it turned out later, the second multiplex on this tower had not yet been launched and I had to turn the antenna towards St. Petersburg.

I think we have figured out a little what dvb t2 digital terrestrial television is, now let's talk about what you need to purchase to get a clear picture and good reception.

What is needed for digital television

So, in order to organize high-quality signal reception, you need to understand that the equipment must be no less high-quality. There are cases when people located close to the relay tower managed to catch both multiplexes simply on a bare wire coaxial cable. We will consider a more serious approach to choosing everything you need to watch free digital TV.

Antenna selection

I will not dive quite deeply into the descriptive part of the advantages and disadvantages of all types of television antennas, since I wrote about this in some detail in a separate article, but I will try to talk about the main nuances.

Terrestrial digital terrestrial television is broadcast on decimeter waves, on the same as analog television. Accordingly, any antenna to which you previously received a signal may be suitable for you. The only thing is that it is not a fact that it will be able to provide high-quality digital reception at a great distance from the TV tower.

But from my own experience I can say that it is better to purchase a high-quality receiver in advance so as not to have headaches later.

If you settled on the second option, then I suggest you make a choice aside active antenna. In most cases, this type is suitable. You can read about other varieties in the article I linked to earlier.

I also advise you to pay attention to the presence of the inscription “DVB T2” on the packaging, informing that this device is intended specifically for the purposes that you are going to implement.

Selecting a receiver or the ability to connect directly to a TV

Recently, a huge variety of televisions with all sorts of functions have appeared on sale. In one of the articles on my blog I already talked about this, but this opportunity opens only if you have direct connection to the Internet.

Often, such TVs have the ability to directly receive a digital signal and include a so-called decoder that allows you to convert the received signal into a high-quality image without connecting third-party equipment. After connecting the cable from the antenna, it is enough to start automatic search channels.

However, what to do if you have old TV, and this most often happens at the dacha, where people take outdated equipment from the city? In this case, special equipment called a receiver or in common parlance comes to the rescue set-top box. This device allows you to convert the received signal and transmit a high-quality picture, and will not be difficult for anyone.

Additional components

We have more or less figured out the basic equipment, but we shouldn’t forget about the little things that we can’t do without.

Cable – It is worth paying considerable attention to the choice of cable, since the quality of reception and protection from possible interference. When installed near power lines, the image may be distorted. So it’s worth paying attention to the cable screen so that it is not made of cheap foil, as well as the cost, which is in this case directly proportional to quality.

Plugs, connectors, splitters – In order to complete the connection, you also need to purchase the required number of plugs from the store, one for the TV, one for the antenna, and, if necessary, for connecting a splitter.

The splitter is designed to divide the signal between several devices, which makes it possible to watch free digital terrestrial television on several TVs at once.

As with the antenna, pay attention to the quality of the product and its cost. These components can also help with cable breakage and its further extension, and read about how to do this in a separate section.

So we figured out what is needed for digital TV and at the same time came to the end. If something remains unclear for you, then do not hesitate to leave questions in the comment field where I, or the readers of my blog, will help you understand your problems.

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Types of digital TV

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For TV viewers:

  • Possibility to connect in one day to a high quality signal no wires, no dish and without the permission of the building manager;
  • Digital television moves together with you for a new apartment and a dacha;
  • TV programs in broadcast format(high definition television), while the possibilities of new plasma TVs will be fully used;
  • View TV programs in mobile transport: tram, bus, city train, private car ( Mobile TV);
  • Opportunity take part in the program directly during the broadcast. A way to order goods, services or study remotely without leaving home ( Interactive TV).

    For broadcaster:

    • Placement of new TV channels due to a tenfold increase in the possibility of frequency resources.
    • Increase in television viewing time - daytime prime time will be added to the traditional morning/evening prime time due to the reception of a television signal in private and public transport and on mobile phones, computers, PDA;
    • Expanding the signal coverage area to the entire relay area (at least 3 times);
    • Reducing broadcasting costs due to the fact that the costs of operating one television transmitter are divided among several broadcasters;
    • High image quality due to the use of HDTV technology (high definition television);
    • Possibility of implementing fundamentally new projects of interactive programs.

    Digital Television - a method of transmitting and receiving a compressed digital video signal, is modern alternative traditional analog television and provides significantly morehigh image quality with equal costs.

    According to the concept of development of television and radio broadcasting in Russian Federation in the coming years, it is expected massive transition from analogue television broadcasting to digital.
    “If we talk about the social aspects of this issue, then this is, first of all, overcoming the so-called digital inequality,” the minister defined the main goal of introducing the Digital Television project on the territory of the Russian Federation information technology and connections Leonid Reiman

    Modern digital technologies open up qualitatively new opportunities for society to receive and transmit information.

    Advantages of digital terrestrial TV:

    • Mobility. Terrestrial digital television, unlike other types of digital TV, delivers the signal to the consumer without unnecessary wires. No need to purchase expensive equipment, stretch cables, call specialists. All you need is a TV, almost any UHF antenna, digital receiver and availability of electricity! This autonomous system, You can take it with you to car trip, in the summer, go to the country and watch TV with the same quality as in the city. In the future, digital broadcast programs will “move” to mobile phones.
    • High picture quality And soundtrack, high quality of broadcast channels. When transmitting a signal, the main problem of “analog” is the impact of various interferences on the signal, but digital TV is practically not subject to interference.
      Required signal level for high-quality viewing of TV channels in digital format much lower than analog. In other words, where analog TV will be very weak with noise and interference, the digital signal will pass through in the quality in which it is generated in television studios.
    • Increasing the number of transmitted channels through the use of the advanced MPEG-4 format. This standard improves the image compression algorithm. Therefore, over time, the number of transmitted channels will not be inferior to cable TV.
    • Reliable signal reception is possible even on the first floors of a building, where the antenna can only catch the reflected signal, without direct visibility of the transmitting tower.
    • Simple and fast connection . Anyone can connect to digital television in one day without the involvement of specialists, without wires, without a dish and without the permission of the building manager.
    • Additional services. Digital set-top box– this is not only high-quality TV anywhere in the region, but also a mass nice additions: soon subscribers of terrestrial digital television will have access to the Internet, TV Guide and much more.


    Options digital broadcasting

    Digital broadcast standards
    There are several families of digital broadcasting standards. First of all, this is the DVB family ( Digital Video Broadcasting), a common open European standard for digital multimedia transmission, adopted by the European Broadcasting Union ETSI (European Transmission Standards Institute) and ensuring high quality broadcasting.
    DVB has four main modifications:

    Other families of digital TV are implemented in Japan (ISDB - Integrated Services Digital Broadcasting), in North America And South Korea(ATSC - Advanced Television Systems Committee).

    In the Sverdlovsk region broadcasting is carried out in standard DVB-T. The second stage is planned to launch DVB-H.

    Digital signal transmission is carried out in MPEG-4 format.
    This standard improves the image compression algorithm and reduces the required data transfer rate for broadcasting TV or radio programs, which allows you to increase the number of programs in the broadcast channel bandwidth.
    The MPEG-4 compression format was chosen for the economic feasibility of using the frequency resource. Only the set-top box-receiver offered by our company has the ability to receive digital television signals in MPEG-4 format.

Residents of large Russian cities are already quite familiar with digital television - many Internet providers offer television broadcasts via cable, and where it is problematic to extend cable, many install satellite systems. But most often by digital television they mean terrestrial television, and it is still rare in our country. But very soon it will become commonplace.

Experiments and tests of digital terrestrial television DVB-T standard We have been doing this since 2000, and in 2012 we started using the more advanced DVB-T2 standard. According to the Minister of Communications and mass communications Nikiforov, in 2018, digital television will finally replace traditional analogue television, which will simply be turned off as unnecessary. And everyone who does not disdain watching the “box” will have to master digital.

To receive DVB-T2 you need either modern TV, supporting this standard, or a set-top box that can be connected to almost any TV. The first option, of course, is more convenient - the set-top box will add an extra remote control to you, and you can only switch channels using it.

Digital television has many advantages. First of all, this is a reliable reception where analog does not provide decent picture quality. Moreover, digital gives a clear image where analog already shows only interference and a little sound.

The second is the ability to transmit high-parity content. Nowadays, looking at a standard TV picture with 512 lines is already unbearably painful (although humans, of course, are tenacious creatures and get used to everything). DVB-T2 allows you to transmit HDTV (up to 1080 lines), UHDTV (up to 4320 lines), 3D pictures, and all this with high-quality sound.

Third - related services, such as teletext, TV guide (program guide), digital radio, interactive services(the ability to choose a movie, vote on a TV show, etc.), and much more, which, in principle, is well known to cable TV users. But all this is not via cable, but via air, and you can even receive it with an indoor two-horn antenna.

Fourth is the ability to encode content. This means that the telecom operator can charge per view directly from the subscriber. If you want to watch some special channels that are not shown for free, add some money to your account and watch it for yourself. This big advantage, because otherwise you’ll have to watch exclusively the first ten federal channels and a few locals.

Regarding free channels, then all television broadcast operators in Russia are required by law to broadcast free of charge the channels of the first multiplex (package) - these are Channel One, Russia-1, Match TV, NTV, Channel Five, Russia-K, Russia-24, Karusel, OTR and TV Center. There is a second multiplex, it is no longer available everywhere, but it is also free. It includes REN TV, Spas, STS, Domashny, TV-3, Friday!, Zvezda, Mir, TNT and Muz-TV. Anything beyond these multiplexes can be broadcast by the operator for money.

To start watching digital TV right now, you need to buy either a TV or a set-top box with DVB-T2 support, and from 2018 you will have to do this, according to Nikiforov.

First of all, digital television solves the problem of freeing up a scarce limited resource and more effective use available.

So in the case of broadcast, cable and satellite television in the same band it is possible to broadcast a group of channels, and not just one, as happens in analogue.

The use of terrestrial digital television, in addition to freeing up frequencies that can be used for mobile communications and other needs, radically increases efficiency by reducing the amount of equipment, especially television transmitters, which consume a significant amount of energy, and backbone network Signal transmission, like transmitters, requires less operating costs in this case. The use of synchronous broadcasting (SFN) generally allows broadcasting on a single frequency within large areas. Which automatically frees up frequencies at the boundaries of broadcasting zones.

Over the past 10 years, a pay TV market has formed in Russia, while no one has given much thought to the quality and development of free television broadcasting. It’s logical, after all, if in development pay television(cable, satellite, interactive and IP television) large commercial structures are interested, then develop free content Only the state can, but it already has enough worries. Therefore, the population used, and the majority still uses, analog television, which is not of the highest quality. It is worth noting separately that over the last decade, Russian residents have bought themselves good flat-panel TVs, on which the analog signal does not look the best.

But justice still exists, and in December 2009, the Government of the Russian Federation approved the federal target program “Development of television and radio broadcasting in the Russian Federation for 2009–2015.” This is where the development of terrestrial digital television in Russia begins.

Terrestrial television is one of the methods of transmitting a television signal through electrical vibrations high frequency, which freely propagate in the surrounding space over considerable distances in the form of radio waves. These signals are transmitted from television centers by special antennas, each television channel At the same time, it is distributed on a special dedicated frequency. By the way ethereal method Television transmissions also exist via satellite and cable.

Digital television is a technology for transmitting a television signal through digital encryption, that is, if in the case of analog television the signal is not compressed in any way and is transmitted in its natural form. This signal can be easily caught by an antenna and broadcast to the screen using a regular TV tuner. Roughly speaking, the digital signal is converted into binary code and exactly the code from which it is transmitted is transmitted. digital tuner collects picture and sound.

There are a lot of examples of transitions to digital; it’s enough to remember that once upon a time there were film cameras and film cassettes. They were replaced by CDs and digital cameras. In them, information began to be stored in binary code. Essentially the same process occurs with television, only unlike the examples given, the television infrastructure costs big money, and businesses are ready to invest money only in cable and satellite TV, since they can be easily monetized.

But in general, digital television has many advantages compared to analog TV.



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