In our article, you will find out the advantages of digital television over analog, what are their differences and differences.
Digital television has already firmly entered our life and will soon finally replace the "usual" (analog) one - to understand this fact, just look into any online store of satellite television 3dsattv.ru and get acquainted with the offered assortment by clicking on the link. However, if you stop an “average” passer-by on the street, he will hardly be able to clearly and clearly answer the question of how analog television differs from digital and what are the main advantages of the latter. Let's try to answer this question briefly, but clearly - and with examples.
The basics
Television is a technology for transmitting the illusion of a moving image for the human eye / brain, based on a simple physiological fact: with a sequential change of static images starting from about 16 pieces per second, a person ceases to distinguish individual images (frames) and instead feels the appearance of movement. For transmission, each frame is decomposed into lines, which are then transmitted sequentially, one after the other. Since the minimum lower limit of perception of this illusion also differs from person to person, in television (as in cinema) the lower limit of the frame rate is raised to at least a few tens of seconds (25 or even 50, if we are talking about half frames - images consisting only of even or only odd lines). The need to transform * analog * images into half-frames was caused by a technical necessity, since at the time of the creation of television, electronics were very imperfect.
Practical examples
Below are still images from the same scene, for signals transmitted through the cable network of the same operator: the difference between digital and analog television with the same resolution (total number of lines and number of elements per line) is obvious.
Visually, the difference between digital television is expressed in the absence of "shadows" (the result of re-reflection of the transmitted signal from cable inhomogeneities) and noise / interference "blurring" the image, as well as a significantly greater apparent image clarity.
Principles of digital TV
Its essence lies in analog-to-digital conversion, which is carried out when shooting an image on a photosensitive CCD matrix - or when digitizing a video stream of an analog image from a source with special high-speed analog-to-digital converters. The received data is encoded in a certain way, and then redundant / verification information is added to the digital stream, which makes it possible to control its integrity, as well as to completely restore it in case of damage not exceeding a critical value. In the next two stills, it is clear * how does analog television * differ from digital in terms of reaction to strong (image-destructive) interference.
It is clearly seen that here the most significant difference between digital and analogue television is in the block structure: a damaged digital video stream leads to the disintegration of the image "into squares", while in analogue a series of damaged lines "falls out" and synchronization breaks down. From a purely user point of view, a significant difference between digital and "conventional" television lies in the fact that as new algorithms for compression and processing of video information are invented, the image quality increases, and often its reception can be carried out on the same equipment if you upgrade (update) decoding the video stream of the program (the so-called "firmware", "microcode" or "firmvari"). Below for comparison is a freeze frame of the so-called. high-definition television (HD TV) from the same network / provider, similar in plot - this is the most vivid demonstration * of the advantages of digital television over analog * (what other new functionalities of consumer television equipment offers users of technical progress can be found out on their own.
It is also important to note that the gradual abandonment of analog television systems is taking place not only in the world, but also in Russia: according to the official data already published, state support for the analog television signal relay systems will be completely stopped in 2018.
Summary
For those wishing to compare point by point * analog and digital television, the difference * can be summarized as follows:
- broadcasting a digital signal is less energy-intensive - the provider does not need a high-power transmitter;
- the digital signal occupies a smaller frequency range - accordingly, with the same congestion of the radio air, a much larger number of television channels can be broadcast to consumers without creating interference;
- unlike analog, digital signal is much less susceptible to any type of interference and can be restored without loss of quality during retransmission - it is much easier for providers to work with it;
- as technology develops, users have the opportunity to receive more and more high-quality content in higher resolution - “simple” digital TV, HDTV, ultra-high definition (UHD) television, and so on;
- both redundant (noise-immune) encoding / decoding and encryption algorithms are easily applicable to a digital signal - therefore, a digital TV provider gets the opportunity to flexibly provide video content on a paid basis;
- from a purely user point of view, digital TV logically leads to the creation of "TV-on-demand" - the user watches only what he wants and can save content without losing its quality, use an external video archive, and so on;
- multilingual support appears (a choice between various accompanying video audio streams in different languages), as well as multilingual subtitles, opportunities for the transmission of additional information about video content are expanded (including broadcasting an extended program guide along with a video stream);
Single-lever or two-valve mixer - which is better to choose?
The faucet is an indispensable fixture in the kitchen and bathroom. From all the variety of models on sale, buyers will have to choose the option that will be most convenient to use. Most often it is necessary to make a choice between single-lever models and two-valve models. Knowing the features of each option, you can make the right decision. Turning to the Forvater store, you don't need a lot to buy plumbing [...]
ATVs as a mode of transport - the history of emergence and distribution
ATVs as a form of transport appeared relatively recently - much later than motorcycles or cars. What caused the popularity of ATVs? ATVs as a form of transport appeared relatively recently - much later than motorcycles or cars. They were invented by the cunning Japanese - in the 70s, the US90 three-wheeled vehicle intended for farmers was thrown onto the American market. Farmers have embraced [...]
Digital television is rapidly gaining popularity in our country, but many people still do not know how it is fundamentally different from the good old analog TV.
Description of analog and digital television
It is easy to guess that analog and digital television are based on analog and digital signals, respectively. The analog signal goes continuously, which means that in the event of any outside influence, it becomes vulnerable, which leads to a worse picture and sound quality. The undoubted advantage of an analog signal is the ability to receive it using a simple terrestrial antenna. You can also use the services of a cable TV provider. We can say that the analog signal is already outdated today, since it is significantly inferior to the digital signal in a number of important parameters - quality, safety, etc.
Modern TVs are designed primarily to work with a digital signal, although they also have an analog connector. It's just that the analog signal is not able to reveal the full potential of modern plasma and LCD TVs; only a digital signal can give the best picture quality. It, in contrast to analog, comes in compact "portions" that are separated by pauses, and therefore it is very difficult to influence such a signal. Even when transmitting a digital signal over a very long distance, the picture and sound quality remains at the highest level. Among other things, a digital signal allows you to transmit much more channels than an analog one, so subscribers who connect to digital television receive more than a hundred TV channels of a wide variety of topics.Comparison of analog and digital television
Alas, analog television today has virtually no clear advantages over digital broadcasting, except perhaps the ability to "catch" a signal using a conventional antenna. However, digital television can also be mobile using a digital signal receiver. Considering that regardless of the distance, the digital signal remains tamperproof and protected from interference and guarantees a high level of quality, the advantages of digital television become quite obvious.
TheDifference.ru determined that the difference between analog and digital television is as follows:
Digital television provides a higher level of signal quality and protection. The analog signal was and remains vulnerable to external influences and cannot provide such a high-quality image.
Digital television is more mobile - today you can receive a digital signal while on the road or far from home.
Analogue television is not capable of providing as many channels as digital television. Due to the peculiarities of the digital signal, when connecting to digital TV, the subscriber can get access to several hundred different TV channels.When dealing with television and radio broadcasting, as well as modern types of communication, very often you have to come across terms such as "Analog signal" and "Digital signal"... For specialists in these words there is no mystery, but for people who are ignorant, the difference between "figure" and "analogue" may be completely unknown. And yet there is a very significant difference.
When we talk about a signal, we usually mean electromagnetic oscillations, which induce an EMF and cause fluctuations in the current in the receiver antenna. Based on these vibrations, the receiving device - TV, radio, walkie-talkie or cell phone - makes up an "idea" of what image to display on the screen (in the presence of a video signal) and what sounds to accompany this video signal.
In any case, the signal of a radio station or a mobile communication tower can appear in both digital and analog form. After all, for example, sound itself is an analog signal. At the radio station, the sound received by the microphone is converted into the already mentioned electromagnetic oscillations. The higher the sound frequency, the higher the output oscillation frequency, and the louder the speaker speaks, the greater the amplitude.
The resulting electromagnetic vibrations, or waves, propagate through space using a transmitting antenna. So that the air is not clogged with low-frequency interference, and so that different radio stations have the opportunity to work in parallel, without interfering with each other, the vibrations resulting from the effect of sound are summed up, that is, "superimposed" on other vibrations that have a constant frequency. The last frequency is usually called "carrier", and it is to its perception that we tune our radio receiver in order to "catch" the analog signal of the radio station.
In the receiver, the opposite process takes place: the carrier frequency is separated, and the electromagnetic oscillations received by the antenna are converted into sound oscillations, and the familiar voice of the speaker is heard from the speaker.
Anything can happen in the process of transmitting an audio signal from the radio to the receiver. Third-party interference may occur, the frequency and amplitude may change, which, of course, will affect the sounds emitted by the radio receiver. Finally, both the transmitter and the receiver themselves introduce some error during signal conversion. Therefore, the sound reproduced by an analog radio receiver always has some distortion. The voice can be quite playable despite the changes, but the background will be hiss or even some wheezing caused by interference. The less confident the reception, the louder and more distinct these extraneous noise effects will be.
In addition, the terrestrial analog signal has a very weak degree of protection against unauthorized access. For public radio stations, this, of course, does not matter. But during the use of the first mobile phones, there was one unpleasant moment associated with the fact that almost any outside radio receiver could easily be tuned to the desired wavelength to eavesdrop on your telephone conversation.
Analog broadcasting has such disadvantages. Because of them, for example, television promises to become fully digital in a relatively short time.
Digital communications and broadcasting are considered to be more immune to interference and external influences. The point is that when using "digital" the analog signal from the microphone at the transmitting station is encrypted into a digital code. No, of course, the flow of numbers and numbers does not spread into the surrounding space. The sound of a certain frequency and volume is simply assigned a code from radio pulses. The duration and frequency of the pulses are predefined - it is the same for both the transmitter and the receiver. The presence of an impulse corresponds to one, the absence - to zero. Therefore, this connection is called "digital".
A device that converts an analog signal into a digital code is called analog-to-digital converter (ADC)... And the device installed in the receiver and converting the code into an analog signal corresponding to the voice of your friend in the speaker of a GSM cell phone is called a "digital-to-analog converter" (DAC).
During digital signal transmission, errors and distortions are virtually eliminated. If the impulse becomes a little stronger, longer, or vice versa, then it will still be recognized by the system as a unit. And zero will remain zero, even if some random weak signal appears in its place. For ADC and DAC, there are no other values like 0.2 or 0.9 - just zero and one. Therefore, interference to digital communications and broadcasting has little effect.
Moreover, the "digit" is also more protected from unauthorized access. Indeed, in order for the DAC of the device to be able to decrypt the signal, it is necessary that it "knows" the decryption code. The ADC together with the signal can transmit the digital address of the device selected as the receiver. Thus, even if the radio signal is intercepted, it cannot be recognized due to the absence of at least a part of the code. This is especially true.
So here differences between digital and analog signals:
1) The analog signal can be distorted by interference, and the digital signal can be either clogged with interference at all, or arrive without distortion. The digital signal is either exactly there, or completely absent (or zero, or one).
2) The analog signal is available for perception by all devices operating on the same principle as the transmitter. The digital signal is reliably protected by a code, it is difficult to intercept it if it is not intended for you.
Recently, more and more information about the transition from analogue to digital broadcasting began to appear on the information network, in this regard, many questions appear on this topic, all kinds of rumors and assumptions are generated. In this article, I want to clarify what is the difference between "analog" and "digital" broadcasting in an accessible and understandable language for a common user (at least as far as possible).
First, let's figure out what an "analog" signal is.
Analog signal
As always, I will explain it with a simple example. For example, let's take the transmission of voice information from one person to another.
During a conversation, our vocal cords emit a certain vibration of different tonality (frequency), and volume (sound signal level). This vibration, having traveled some distance, enters the human ear, acting there, on the so-called auditory membrane. This membrane begins to vibrate with the same frequency and vibration strength as our vocal cords emitted, with the only difference that the vibration strength due to overcoming the distance weakens somewhat.
So, the transmission of voice speech from one person to another can be safely called
analog signal transmission, and here's why.Here the fact is that our vocal cords emit the same sound vibration that the human ear itself perceives (what we say, we hear), that is, the transmitted and received sound signal has a similar pulse shape, and the same frequency spectrum sound vibrations, or in other words, "analogous" sound vibration.
Here, I think it's clear.
Now, let's look at a more complex example. And for this example, let's take a simplified diagram of a telephone set, that is, the telephone that people used long before the advent of cellular communications.
During a conversation, voice sound vibrations are transmitted to the sensitive membrane of the handset (microphone). Then, in the microphone, the audio signal is converted into electrical impulses, and then goes through the wires to the second telephone receiver, in which, with the help of an electromagnetic converter (speaker or earpiece), the electrical signal is converted back into an audio signal.
In the example above, again, "analog" signal conversion is used. That is, the sound vibration has the same frequency as the frequency of the electrical impulse in the communication line, as well as the sound and electrical impulses have a similar shape (that is, similar).
In the transmission of a television signal, the analog radio television signal itself has a rather complex pulse shape, as well as a sufficiently high frequency of this pulse, because it transmits both audio information and video over long distances.
With the "analog signal", I think they sorted it out.
Over time, the number of TV channels has increased, the number of subscribers has also increased at telephone exchanges, and the Internet has appeared. As a result, the bandwidth of analog transmission of information has ceased to meet modern requirements. This applies to both terrestrial, wire and broadcasting lines of signal transmission and reception, and of course satellite communication lines.
Now, let's understand what a "digital" signal is.
As an example, "digital signal", let us take the principle of information transmission using the well-known "Morse code". For those who are not familiar with this type of transmission of textual information, below I will briefly explain the basic principle.
Earlier, when signal transmission over the air (using a radio signal) was still developing, the technical capabilities of the transmitting equipment did not allow the transmission of a speech signal over long distances. Therefore, instead of speech information, we used text information. Since the text consists of letters, these letters were transmitted using short and long pulses of an electric tone signal.
Such transfer of textual information was called - transfer of information using "Morse code".
The tonal signal, by its electrical properties, had a higher bandwidth than the speech signal, and as a result, the range of the transmitting equipment increased.
Units of information in such signal transmission were conventionally called "dot" and "dash". A short beep was a dot, and a long beep was a dash. Here, each letter of the alphabet consisted of a specific set of dots and dashes. For example, the letter A was denoted by the combination " .- "(dot-dash), and the letter B "- ... "(dash-dot-dot-dot), and so on.
That is, the transmitted text was encoded using dots and dashes in the form of short and long segments of a tone signal. If the words "ABC MORSE" are expressed using dots and dashes, then it will look like this:
The digital signal is based on a very similar principle of coding information, only the units of information themselves are already different there.
Any digital signal consists of a so-called "binary code". Here, for units of information, logical 0 (zero), and logical 1 (unit).
If, as an example, we take an ordinary pocket flashlight, then if you turn it on, it would seem to mean a logical unit, and if we turn it off, then the logical zero.
In digital electronic microcircuits, a certain level of electrical voltage in volts is taken as logical units 1 and 0. So, for example, a logical unit will mean 4.5 volts, and 0.5 volts for a logical zero. Naturally, for each type of digital microcircuits, the values of the voltages of logical zero and one are different.
Any letter of the alphabet, as in the example with the Morse code described above, in digital form, will consist of a certain amount zeros and ones, located in a certain sequence, which, in turn, are included in the packets of logical pulses. For example, the letter A will be one burst of pulses, and the letter B with another package, but in a letter B the sequence of zeros and ones will be already different than in the letter A(that is, a different combination of the arrangement of zeros and ones).
In a digital code, you can encode almost any type of transmitted electrical signal (including analog), and it does not matter if it is a picture, video signal, audio signal, or text information, and these types of signals can be transmitted practically simultaneously (in a single digital stream).
A digital signal, by its electrical properties (as in the example with a tone signal), has a higher information transmission capacity than an analog signal. Also, a digital signal can be transmitted over a greater distance than an analog one, and without reducing the quality of the transmitted signal.
1. In digital format, much more information can be transmitted than is possible in analog signal transmission.
So, for example, if one TV channel was previously transmitted in an analog satellite signal, then in a digital stream 5, 10 or more. The same applies to terrestrial transmission of sound, images, text information, etc.
This is especially true recently, given the tremendous growth in transmitted information (an increase in the number of television and radio channels, an increase in the number of telephone subscribers, an increase in the number of Internet users and the speed of Internet lines).
2. As I already mentioned, when transmitting a digital signal, the quality of the signal itself remains practically unchanged. That is, what we transmit is what we receive, without deteriorating the quality of the parameters of the information transmitted in the signal.
When transmitting a digital television signal, the viewer will no longer see such a defect as "snowing image", as it was in an analog signal with poor reception. In the digital transmission of TV channels, the picture quality can only be good, or there will be no picture at all if the reception is poor (that is, either yes or no).
As for the digital transmission of telephone conversations, here, with good quality, both a whisper and a shout can be transmitted, both low tones and high tones, and here it is no longer important at what distance the telephone subscribers are.
These are of course not all the benefits. digital signal before analog, but I think that's enough to understand what is behind the "number" future and this future applies to both terrestrial and satellite transmission of information.
Further, I would like to talk a little about terrestrial terrestrial television and radio broadcasting (broadcasting a radio signal over the air), but directly, about the digital transmission of a television radio signal, and what you need to have to receive such terrestrial digital broadcasting.
Digital terrestrial television.
Despite the fact that many viewers have long since switched to cable or satellite television, broadcasting still does not lose its relevance, even in analog format.
Now (at the time of this writing), in the Russian Federation, analog broadcasting is mainly used, and digital terrestrial television broadcasting itself is successfully operating so far only in a few zones. But be that as it may, digital television is the future, which means that the moment will come when it will come to your home.
Main advantage etheric television broadcasting, whether it is analog or digital, this is of course mobility... Television broadcasts of terrestrial television, you can not only watch at your home, or in the country, but also while on a bus, in a tram, or in a private car, receiving a radio signal on a telescopic antenna. In cable TV, you are already tied to the cable itself, and when receiving a satellite signal to your satellite dish.
What you need to have to receive digital broadcastingUnfortunately, television receivers (televisions) designed to receive analog television will no longer be able to receive a digital terrestrial signal. But in any case, this does not mean that you have to go to the store and buy a new TV capable of receiving digital TV.
In order for you to be able to receive digital broadcasting on a TV that supports only an analogue broadcasting signal, you just need to purchase a so-called digital television broadcasting receiver (or, in other words, a digital terrestrial receiver).
Digital terrestrial receiver (receiver), connected to the TV through the antenna jack or through a low-frequency audio-video cable. In this case, the terrestrial antenna is no longer connected to the antenna jack of the TV, but to the jack of the digital receiver itself. The general diagram of such a connection is shown in Fig. one.
The general principle of such a technique will be as follows:
The digital terrestrial radio signal will be received by the terrestrial antenna, from the antenna this signal will come to the digital receiver, and from the receiver the analog signal will go to your TV. Here, the TV will already be used as a monitor, and switching between TV channels will take place from the remote control of the digital terrestrial receiver (receiver).
Here I think, it should be mentioned, and about the reception of sound radio stations.
To receive a digital signal from broadcasting stations, old-style radio receivers (supporting the reception of analogue broadcasting) will also no longer work, and you will need a special radio receiver that supports the reception of a digital radio signal.
Benefits of digital terrestrial TV:
* As mentioned earlier, the main and most important advantage of digital terrestrial TV is of course mobility. You can watch your favorite programs not only at home, but also while on the road. Also, possibly in the future, digital terrestrial TV can be viewed on a mobile phone.
* Digital terrestrial TV is the ability to receive images and sound in very good quality.
* According to its electrical properties, or rather electromagnetic properties, a digital signal can be transmitted over a greater distance than an analog one, and without reducing the quality of the transmitted signal.
Here, it should also be taken into account that the digital radio signal is more resistant to the electromagnetic interference that surrounds us (interference can come both from nearby electrical and radio devices, and power lines passing nearby).
* In digital format, significantly more TV channels can be transmitted, while the picture and sound quality will be much better than with analog signal transmission.
* The undoubted advantage of digital broadcasting is, of course, ease of setup, while, for example, installing and configuring satellite television requires certain knowledge and skills.I think, of course, this is not the whole list of advantages of digital broadcasting over analogue, but, as they say, wait and see.
With these words, John began his Gospel, describing times beyond our era. We begin this article with no less snobbishness, and in all seriousness we declare that in the broadcasting business "there was a signal in the beginning."
In television, as in all electronics, the signal is the basis. Speaking of it, we mean electromagnetic oscillations that propagate in the air using a transmitting antenna and cause fluctuations in the current in the receiving antenna. The ether wave can be presented both in continuous and in impulse form, which significantly affects the final result - the quality of TV reception.
What is analog TV? This is television, familiar to everyone, which even the parents of our parents have seen. It is broadcast in an unencrypted way, its basis is an analog signal, and it is received by a usual analog TV, familiar to us from childhood. Currently, in many countries, the process of digitizing an analog signal, and therefore terrestrial television, is being carried out. In some European countries this process has already been completed and analogue terrestrial TV is switched off. There are reasons for this, which this article suggests to understand.
Differences between digital and analog signals
For most people, the distinction between analog and digital signal can be completely subtle. And yet, their difference is significant and is not just the quality of the TV broadcast.
An analog signal is the received data, which we see, hear and perceive as the world that surrounds us. This method of generating, processing, transmitting and recording signals is traditional and still very common. The data is converted into electromagnetic waves, reflecting the frequency and intensity of the phenomena according to the principle of complete correspondence.
A digital signal is a set of coordinates describing an electromagnetic wave, which is not inaccessible for direct perception, without decoding, since is a sequence of electromagnetic pulses. Speaking of the discreteness and continuity of signals, they mean, respectively, “acceptance of values from a finite set” and “acceptance of values from an infinite set”.
An example of discreteness can be school grades, which take values from the set 1,2,3,4,5. In fact, digital video is often created by digitizing an analog signal.
Moving away from theory, in fact, the following key differences between analog and digital signals can be distinguished:
- analog television is vulnerable to interference, introducing noise into it, while the digital pulse is either completely blocked by interference and is absent, or comes in its original form.
- any device can receive and read an analog signal, the operation of which is based on the same principle as the broadcast of the transmitter. The digital wave is intended for a certain "addressee", and therefore, it is resistant to interception, since securely encoded.
Image quality
The quality of the TV picture provided by analog TV is largely determined by the TV standard. The frame, which carries with it analog broadcasting, includes 625 lines with an aspect ratio of 4 × 3. Thus, an old picture tube displays an image from television lines, while a digital image is made up of pixels.
With poor reception and interference, the TV will "snow" and hiss, not giving the viewer the image and sound. In an attempt to make improvements to this situation, at one time, it was implemented.
Other possibilities
Despite the rapid development of electronic technology and the advantages of digital over analog, there are still areas where analog technology is indispensable, such as professional audio processing. But, although the original recording may not be worse than the "number", after editing and copying it will inevitably be noisy.
Here is a set of basic operations that can be performed on an analog stream:
- strengthening and weakening;
- modulation, aimed at reducing its susceptibility to interference, and demodulation;
- filtering and frequency processing;
- multiplication, summation and logarithm;
- processing and changing the parameters of its physical quantities.
Features of analog and digital television
The narrow-minded opinion about the collapse of terrestrial TV and the transition to broadcasting technologies of the future is somewhat unfair, already because viewers are replacing the concepts: terrestrial and analogue TV. After all, under the terrestrial it is customary to mean any television broadcast on a terrestrial radio channel.
Both "analog" and "digital" are varieties of terrestrial TV. Despite the fact that analogue television differs from digital television, their general principle of broadcasting is identical - a television tower broadcasts channels and guarantees a high-quality signal only in a limited radius. In this case, the digital coverage radius is shorter than the range of the unencoded stream, which means that the repeaters must be installed closer to each other.
But the opinion that "digital" will bypass "analog" in the end is true. Television viewers in many countries have already become “eyewitnesses” of the conversion of an analog signal into a digital signal and enjoy watching TV programs in HD quality with might and main.
Features of terrestrial television
The existing terrestrial television system uses analog signals for the transmission of a television product. They travel through high-level waves to reach terrestrial antennas. In order to increase the broadcast coverage area, repeaters are installed. Their function is to concentrate and amplify the signal, transmitting it to remote receivers. Signals are transmitted with a fixed frequency, so each channel corresponds to its own frequency and is assigned in the order of numbering on the TV.
Advantages and Disadvantages of Digital TV Broadcasting
The information transmitted using a digital code is practically free of errors and distortions. The device that digitizes the original signal is called an analog-to-digital converter (ADC).
To encode pulses, a system of ones and zeros is used. To read and convert the binary-decimal code, a device called a digital-to-analog converter (DAC) is built into the receiver. Neither ADC nor DAC have half values, such as 1.4 or 0.8.
This method of encrypting and transmitting data gave us a new TV format, which has many advantages:
- changing the strength or length of the impulse does not affect its recognition by the decoder;
- uniform broadcast coverage;
- in contrast to analogue broadcasting, reflections from the obstacles of the converted broadcast add up and improve reception;
- broadcast frequencies are used more efficiently;
- reception on analog TV is possible.
The difference digital television from analog
The difference between analogue and digital broadcasting is easiest to see by presenting the summary characteristics of both technologies in a table.
Digital tv Analog TV The digital image resolution is 1280 × 720 for a total of 921600 pixels. In the case of the 1080i scan format, the image resolution is 1920 × 1080, which gives an impressive result: more than 2 million 70 thousand pixels. The maximum resolution of an analog "picture" is approximately 720 × 480, which gives a total of over 340,000 pixels. Sound Audio, like video, is transmitted without distortion. Many programs are accompanied by a surround stereo signal. Sound quality varies. Receiver The cost of a TV adapted for digital reception is several times higher than the price of a conventional TV. An analog TV is reasonably priced. TV channels Watching digital channels gives the viewer a wide choice: a large number and thematic focus of TV channels. Number of programs up to 100. Other Reception of programs on one TV. Additional services such as "private broadcasting", "virtual cinema", "program storage", etc. The ability to connect more receivers and watch multiple programs at the same time. Outcome The new television brings with it excellent picture and sound quality, the ability to create a multimedia home station for play, work and study. However, the high cost of adapted TVs and the unhurried introduction of TV coding technology on the Russian market have so far left it behind the existing television. Good old TV gives way to digital in picture and sound quality. Nevertheless, the price of the receivers and the ability to distribute the signal to more TVs (the ability to watch several programs at the same time) is a significant plus. Antenna sensitivity for TV
There is no one-size-fits-all recipe for the ideal antenna, but there are imperatives that must be met in order for it to receive analog and digital signals. With increasing distance from the broadcasting object, these requirements increase. In particular, the sensitivity of the receiver - its ability to pick up weak in intensity TV signals. Often they are the reason for the blurry image. This problem is solved with the help, which significantly increases the sensitivity of the antenna and removes the question: how to connect it to digital television? The same TV, and the same antenna, only a digital terrestrial tuner will appear near the TV.
What is antenna pattern
In addition to the sensitivity of the antenna, there is a parameter that determines to what extent it is able to focus energy. It is called directional gain, or directivity, and is the ratio of the radiation density in a given direction to the average radiation density.
The graphical interpretation of this characteristic is the antenna pattern. At its core, this is a three-dimensional figure, but for the convenience of work, it is expressed in two planes located perpendicular to each other. With such a flat diagram at hand and comparing it with a map of the area, you can plan the area for receiving an analog video signal with an antenna. A number of useful practical characteristics of a teleantenna can also be derived from this graph, such as side and return intensities and retention rates.Which signal is better
It should be admitted that, despite the many improvements implemented in the field of analog presentation of information, this method of broadcasting has retained its shortcomings. These include distortion during transmission and noise during playback.
Also, the need to convert an analog signal to digital is caused by the unsuitability of the existing recording method for storing information in semiconductor memory.
Unfortunately, the existing TV has practically no obvious advantages over digital, excluding the ability to receive a signal with a conventional TV antenna and share it between TVs.
Any signal, be it analog or digital, is an electromagnetic wave propagating at a specific frequency. Depending on what signal is propagated, the device receiving this signal determines which image to display on the screen, respectively, with sound.
For example, a TV tower or radio station can transmit both analog and digital signals. Sound is transmitted in analog form, and already through the receiving device is converted into electromagnetic waves. As already mentioned, vibrations propagate at a certain frequency. The higher the frequency of the sound, the higher the vibrations, as a result, we get a louder sounding voice at the output.
In general terms, the analog signal propagates continuously, while the digital signal propagates discretely (discontinuously), i.e. the amplitude of the oscillations takes on certain values per unit of time.
If we continue the example of an audio analog signal, we get a process in which electromagnetic waves propagate using a transmitter (antenna). Because the propagation of the analog signal occurs constantly, then the oscillations are summed up, and a carrier frequency appears at the output, which is the main one, i.e. the receiver is tuned to it.
In the receiver itself, this frequency is separated from other vibrations, which are converted into sound.
The disadvantages of transmitting information using an analog signal are obvious:
- There is a lot of interference;
- More unnecessary information is transmitted;
- Signal transmission security
If in radio broadcasting the transmission of information using an analog signal is less noticeable, then in television, the issue of switching to digital transmission is extremely important.
The main advantages of a digital signal over an analog one are:
- Higher level of protection. The security of digital signal transmission is based on the fact that the "digit" is transmitted in encrypted form;
- Ease of signal reception. The digital signal can be received from any distance from the residence;
- Digital broadcasting is capable of providing a huge number of channels. It is this opportunity that provides digital television fans with a large number of TV channels for watching films and programs;
- The transmission quality is several orders of magnitude higher than in analogue broadcasting. The digital signal provides filtering of the received data, and it is also possible to restore the original information.
Accordingly, special devices are used to convert an analog signal to a digital one, and vice versa.
- A device that converts an analog signal to a digital signal is called an analog-to-digital converter (ADC);
- A device that converts a digital signal to an analog signal is called a digital-to-analog converter (DAC).
Accordingly, the ADC is installed in the transmitter, and the DAC is installed in the receiver and converts the discrete signal into an analogue one corresponding to the voice.
Why is the digital signal more secure?
The digital signal transmission is encrypted and the digital-to-analog device must have a decryption code. The ADC can also transmit the digital address of the receiver. Even if the signal is intercepted, it will be impossible to completely decipher it due to the absence of a part of the code. This property of digital transmission is widely used in mobile communications.
Thus, the main difference between analog and digital signal is the different structure of the transmitted signal. Analog signals are a continuous stream of oscillations with varying amplitude and frequency.
Digital signal - discrete (intermittent) oscillations, the values of which depend on the transmission medium.
Sometimes consumers have a question about how the signal is transmitted in television.
In television, before transmitting a signal in digital form, the analog signal must be digitized. After that, it is necessary to choose in which medium the transmission will take place: copper cable, ether, fiber-optic cable.
For example, many users are convinced that cable television is only digital data transmission. This is not true. Cable television is both analog and digital signal transmission.
The difference between digital and analogue television is most easily illustrated by the difference between digital and analogue sound or photography. If in analog a television picture and a sound track are encoded using an analog electrical signal, then in digital, respectively, digital coding is used.
At the end of the 90s, only analog color television existed in our country. The French coding system SECAM was used on the air. Older readers will probably remember that on videotapes one could find films encoded using alternative systems - PAL or NTSC, for comfortable viewing of which a VCR with their support was needed.
To watch digital TV on a computer, a small USB module and UHF antennas are enough
The main disadvantages of the analogue are weak protection against interference, as well as a rather wide bandwidth of the radio frequency spectrum required for the transmission of one channel.
Therefore, on air we were limited to a maximum of two dozen color channels, and on cable networks, on average, 70 (with rare exceptions).
If your TV is not equipped with a digital channel receiver, you can buy a separate decoder that supports the DVB-T2 standard. With an analog signal, it is quite difficult to make a service convenient for the user and the operator (with the ability to quickly connect / disconnect channel packages, etc.). In addition, the analog needs high-power transmitters with a large coverage area. Receivers need a high signal level to get a good picture, which means that the frequency spectrum in the radio air is used very irrationally: in neighboring territories it is impossible to transmit on one channel, competent frequency planning is required.
The digital signal is free of these disadvantages. The main advantage of the digital is that the coded channel can be compressed using modern algorithms (the same MPEG). How exactly to encode the signal and how to compress it is determined by the standard. Today in Europe and Russia the main family of standards is DVB - the "brainchild" of the international consortium DVB Project.
The family includes standards for satellite, terrestrial, cable and mobile television, differing in compression ratio, noise immunity and other parameters (important, depending on the transmission medium used). However, in the press recently, the terrestrial standard (in the case of Russia - DVB-T2) is most often called “digital”. Let's start with him.
From analogue to digital on air: the Russian version
Given the advantages of digital, the global community began the transition to modern broadcasting standards in the early 2000s. In all countries, this process went (and continues to go) simultaneously with the "optimization" of radio air, which is actively used not only by television broadcasters, but also by mobile operators, the military and other consumers.
By compressing into 1 analog television channel, for example, in the DVB-T2 standard, it allows you to fit up to 10 digital channels with approximately the same picture quality. In addition, a portion of the spectrum frees up the aforementioned reductions in transmitter power. Within one country, these processes are regulated by the state, and on a continental scale - by various interstate agreements.
According to one such agreement, Russian border territories should eventually stop broadcasting in analog format. So the transition from analog to digital television determines not only the desire for new technologies, but also the responsibility to the closest neighbors.
Inexpensive USB adapters for receiving digital channels can be found not only for the PC ... 
... but also for smartphones and tablets. At the same time, they will be connected via micro-USB The transition from analog to digital television on the air in our country began in 2009. At that time, the DVB-T standard, which had already been introduced in a number of European countries, was taken as a basis.
It must be understood that television is a chain of interaction of a whole list of intermediaries between a content producer and its consumer, each of which has a fleet of analog equipment to be replaced. The state project involves the renewal of only part of this chain - distribution and transmission equipment.
In some cases, the state helps with the purchase of new filming equipment for television studios.
But viewers have to think about replacing "receivers" on their own. All these difficulties do not allow at one moment to switch to a new standard, wherever such transformations are undertaken.
And in our country, the transition went even more difficult. At first, a very high pace was taken, but after a few years “the horses were changed at the crossing”, saving time at the next evolutionary step: it was decided to introduce a more advanced second generation of the “terrestrial” standard - DVB-T2, which ensures the placement of a larger number of digital channels on the frequency analog channel bandwidth (compared to DVB-T).
It should be noted that in this case, the transition does not imply any increase in the resolution of the broadcast picture. The project includes only a change in the way it is presented, and we should expect HD quality on air only in the distant future (the standard supports HD, but at the state level it was decided not to touch this topic yet).
Today, DVB-T2 transmitters are already operating practically throughout the country. Somewhere so far, only 1 multiplex is enabled (a packet that takes the place of one analog channel); in other areas, the second was included. This means that, having the appropriate receiving equipment, you can watch 20 channels of good quality from the air for free.
Although from the very beginning of the transition, it was said that by 2015 our country should completely switch to digital and turn off analog, while the issue of shutdown was postponed, so analog television continues to function.
Photo: manufacturing companies
Purchase of scrap metal
The main and priority line of activity of the Metallrutorg company is the purchase of scrap metal. It is profitable for any supplier to work not with small resellers, but with a permanent partner who offers favorable prices and loyal conditions. Many enterprises ask themselves how to make additional profit and hand over unnecessary scrap metal? In this case, the main thing is to find a reliable company that is officially registered and [...]
