We dreamed so much about replacing numbers about and analog technologies in the 80s and 90s, which they did not notice, as in many directions they reached the final stage of this process. This stage is called analog switchoff - that is, literally, “switching off anal about ha. It comes when the digital version of a particular technology, product, process, pulls over the dominant number of users - and the decision is made to turn off the analog version.
The solution can be either market-driven (as with audio records that have ceased to be produced due to lack of demand) or top-down (as with television, which is gradually being replaced by digital). But anyway last years showed that immediately after this, unexpected strengths anal about ha, which I would not like to lose. That is, it’s kind of embarrassing to return, and it’s completely wrong to turn away!
We have already seen how this happens with music and sound in general, books, newspapers and magazines (remember ""). Now we have to experience the same thing with the radio. Not immediately, however, and not soon, but - the process of disconnection has begun. Norway was the first to decide on it, which by the end of the year intends to forcibly switch all state radio channels to digital broadcasting, while turning off FM at the same time. Following it, Switzerland, Great Britain, Denmark and some others follow the same course. And it is worth watching this process at least in order not to step on the discovered rake later.
The analog radio has been an almost eternal thing: even models released half a century ago can still be used today. Digital receivers will not live that long for sure! Changing standards will probably force them to be updated as often as we update today. mobile phones.
Norway is starting a scheduled shutdown of state-owned FM stations as of this week. Within a year they will stop broadcasting in FM format and will be transferred to DAB. What is FM - everyone knows. This term simultaneously understands both the range (VHF: 88 - 108 MHz in the West, or down to 65 MHz in the social block) and the modulation method (frequency). Throughout the second half of the 20th century, FM served as a synonym for quality sound: frequency modulation in combination with an ultrashort wavelength, they make it possible to transmit a stereo signal and place dozens of stations in the range. FM has disadvantages, for example, a small range (compared to MW and HF; FM is heard only a little further than the line of sight), but this did not prevent it from becoming the de facto standard for music broadcasting in cities.
And now the change is coming. DAB (from digital audio broadcasting - digital audio broadcasting) is a relatively new thing: public experiments with it began only in the second half of the 90s. Meaning: broadcasting a digital signal, not an analog signal, at a speed of 128 kbps, in the range just above FM, using noise-correcting coding and the MP2 compressor popular in the past. The receiver, accordingly, is needed digital, that is, it will have to be bought new, but this promises serious benefits. In general, the benefit of switching radio to digital standard, circular: absolutely everything wins!
Firstly, DAB is beneficial to broadcasting regulators: they can sell more licenses and fit more stations in the band ( digital signal less susceptible to distortion from adjacent frequencies).
Secondly, DAB is beneficial for radio station holders, because it allows you to load the transmitter many times more efficiently, and also to conduct encrypted broadcasts that are available only for a fee.
Third, DAB benefits listeners. Unlike analogue broadcasting, the quality of which decreases continuously as you move away from the station, the quality of digital broadcasting is consistently high - up to a certain critical distance, after which the power of the received signal drops below the permissible level and reception stops, or there are too many errors.
That's the theory. And tell someone this fifteen years ago, when the fashion for replacing anal was raging about ha figure, no one would doubt the veracity of these words. Today, however, already about half of the radio listeners in the countries mentioned above use DAB on a daily basis. And the reviews ... so-so! Why? Several reasons are cited.
Looking ahead: DAB is already obsolete and should be replaced by more modern standard. But worse than that, implemented in different countries different variants digital radio. In Russia, for example, approved as a priority international standard DRM. First, it turned out that the noise immunity of digital radio transmission is greatly exaggerated. No one even remembers that such a signal cannot be received even at a small distance from cities: the reception radius digital stations always less than for FM. But even in cities and on major roads, due to difficult terrain and distances, there are areas where the DAB signal weakens below acceptable levels. And then the figure manifests itself with worst side: the sound either disappears altogether, or turns into a meaningless gurgling - while an FM station would be heard, albeit with interference, but legibly! It is also worth adding here that the digital receiver is much more complicated and expensive, and is also naughty when moving with high speed: already moving faster than 120 km / h, it reduces the reception quality.
Secondly, it suddenly surfaced that DAB is an outdated standard. It is customary to encode sound using MP2, which (at the used transmission speeds) does not give a sound quality close to CD or even FM! When experiments with DAB were just starting to be set up, it didn’t matter, but today, when it comes to complete shutdown FM, the situation appeared in a different light. There is a solution: the DAB + standard uses a modern codec from the MPEG-4 family, only old DAB receivers are incompatible with it! And this has brought suspicions of foul play among DAB supporters: what if the replacement of FM with DAB is intended only so that corporations will profit from the sale of new receivers, and then profit every year from upgrades?
Finally, thirdly, many people doubt the declared readiness of DAB stations for emergencies. After all, state radio stations are used, among other things, for transmitting signals to alert the population about emergencies. But if FM could be accepted by everyone, then DAB in the same Norway - God forbid that every second resident (the rest simply do not digital receivers). And digital communications have the famous property of “falling” first in natural disasters and catastrophes. Will it happen again with DAB?
As a result, the question of the reasonableness of turning off FM no longer seems idle. Will digital radio ever replace analog radio? Or will it remain only an optional addition to the ancient, but by no means obsolete technology? What do you think?
Hey Geektimes.
Digital broadcasting is gradually being introduced into various countries. In Europe and Australia it is the DAB/DAB+ standard, in the US HD Radio, in China CDR (China Digital Radio). Of the benefits for the user - more pure sound through the digital stream, additional services(e.g. song title and artist name on the receiver screen), and, in the case of DAB, more stations compared to FM. Digital radio capable receivers are already relatively inexpensive, starting at about $40.
Russia has not yet officially joined any of the standards, but if it does, it will most likely be DAB. Its test operation has already been carried out in Moscow, and the receivers of the European market for the Russian Federation are geographically more accessible than the American ones. New European cars (of which, again, there are more than American ones) are often already equipped with a DAB receiver. In the meantime, for test purposes, anyone can run DAB at home, with an SDR transceiver.
(Image Source/Getty)
Details under the cut (careful, a lot of long and boring configs).
How it works
Unfortunately, different standards are incompatible with each other.European DAB is an MP2 or AAC stream transmitted using ODFM in channels with frequencies from 174 to 239 MHz. More than 30 channels are possible, the width of each is about 1.5 MHz, several stations can be transmitted simultaneously in the channel. According to Wikipedia, using DAB at 192kbps is 3 times more efficient in terms of number of stations than regular FM.
The spectrum of one DAB channel on the SDR screen looks like this:
For comparison, FM stations look like this at the same scale:
in the American HD Radio went the other way digital channels added "on the side" to the existing FM stations. This made it possible not to allocate new frequencies and leave compatibility with old receivers. The downside is that in large cities the FM broadcast is already busy. On the other hand, even maximum number 50 stations for FM is quite good, listeners most likely do not need more.
The HD Radio spectrum looks like this (screenshot from youtube):
Chinese CDR decided to copy the American approach, alas, my zero knowledge of Chinese is not enough to find more detailed information on it.
As for the receivers, their price on amazon is from $ 30 for the most simple models, up to >100$ for more advanced ones with touchscreen, Wifi or color screen.
But "the Chukchi is not a reader", so we will launch a test radio in the DAB / DAB + format ourselves. Unfortunately, HD Radio will not be launched, the format is closed, and there are no encoders available for it.
Launching DAB/DAB+
The process is actually not complicated, but very painstaking in terms of creating the necessary configs. For the test, we need Linux and a transferable SDR like HackRF or USRP.1. Compiling the project
Linux is needed to compile the encoder. I used Ubuntu finished image for VirtualBox was downloaded from http://www.osboxes.org/ubuntu/ .Compiling ODR-AudioEnc
First you need to compile DAB/DAB+ audio encoder, you can find it at github.com/Opendigitalradio/ODR-AudioEnc .
Git clone https://github.com/Opendigitalradio/ODR-DabMux.git cd ODR-DabMux/ ./bootstrap.sh ./configure make sudo make install
Compiling ODR-DabMod
This is a modulator that actually sends data to the transmitter. The assembly principle is the same, the command for downloading:
Git clone https://github.com/Opendigitalradio/ODR-DabMod.git
If any libraries are missing during the build, they must be installed using apt-get.
Now all the parts of the project are assembled, and with all this we will try to take off.
2. Configuration
Unfortunately, USRP did not work in virtual machine, and put full Linux I was too lazy to drive. Therefore, I did not consider the streaming mode - the multiplex was assembled from pre-prepared mp3 files, and the resulting IQ file was launched under Windows. Yes, for the home streaming and it’s not necessary, there was no task to make a “pirate station”.Data preparation
There will be 2 channels in our multiplex, for which I downloaded 2 mp3 files from youtube and named them (who would have guessed) sound01.mp3 and sound02.mp3 respectively.
Convert files to WAV with a bitrate of 48000:
ffmpeg -i sound01.mp3 -ar 48000 sound01.wav
ffmpeg -i sound02.mp3 -ar 48000 sound02.wav
Convert them to DAB format:
odr-audioenc --dab -b 128 -i sound01.wav -o prog1.mp2
odr-audioenc --dab -b 128 -i sound02.wav -o prog2.mp2
The output should be 2 files prog1.mp2 and prog2.mp2.
Creation of a multiplex
First you need to create a file that describes the configuration of our "radio station". Let me remind you that in one DAB channel there can be many stations, each with its own parameters.
Create a file "config.mux" with the following text:
General ( dabmode 1 nbframes 2000 ; Set to true to enable logging to syslog syslog false ; Enable timestamp definition necessary for SFN ; This also enables time encoding using the MNSC. tist false ) remotecontrol ( telnetport 0 ) ensemble ( id 0x4fff ecc 0xec ; Extended Country Code local-time-offset auto international-table 1 label "mmbtools" shortlabel "mmbtools" ) services ( srv-p1 ( label "Station1" ) srv-p2 ( label "Station2" ) ) subchannels ( sub-p1 ( type audio inputfile "prog1.mp2" bitrate 128 id 10 protection 4 ) sub-p2 ( type audio inputfile "prog2.mp2" bitrate 128 id 11 protection 4 ) ) components ( comp-p1 ( service srv-p1 subchannel sub-p1 ) comp- p2 ( service srv-p2 subchannel sub-p2 ) ) outputs ( output1 "file://output.eti?type=raw" )
The config describes the channels that will be in the multiplex and their data sources. The nbframes parameter specifies how many frames to create, 2000 frames corresponds to approximately one minute of playback.
Once the file is saved, create the multiplex:
odr-dabmux config.mux
The output should be a file output.eti, in my case its size was 12MB.
Broadcast
There are two possibilities here. On "real" Linux, odr-dabmod can directly transfer data to the transceiver, but it did not work under VM. Therefore, as an output parameter, I specified a raw file that will contain data compatible with Gnu Radio.
Create a config.ini file:
transport = file source = output.eti loop=0 digital_gain=0.9 rate=2048000 output = file format = complexf_normalised ;format = s8 filename = output.iq
Here key moment- output format and its type. For USRP, I use the complexf_normalized format, for HackRF, in theory, 8-bit s8 will do.
Save the config, start the conversion:
odr-dabmod config1.ini
All! The output should be config.iq, in my case about 700MB in size per minute of recording (IQ float format). We copy it to the "main" computer, and Linux can be closed.
3. Testing
As I said earlier, I don’t have a DAB receiver, the Chukchi is not a reader, I don’t listen to the radio at all :) For testing, I used the RTL-SDR “whistle” and a free programWe dreamed so much about replacing numbers about and analog technologies in the 80s and 90s, which they did not notice, as in many directions they reached the final stage of this process. This stage is called analog switchoff - that is, literally, “switching off anal about ha. It comes when the digital version of a particular technology, product, process, pulls over the dominant number of users - and the decision is made to turn off the analog version.
The solution can be either market-driven (as with audio records that have ceased to be produced due to lack of demand) or top-down (as with television, which is gradually being replaced by digital). But in any case, recent years have shown that immediately after this, unexpected strengths of anal are discovered. about ha, which I would not like to lose. That is, it’s kind of embarrassing to return, and it’s completely wrong to turn away!
We have already seen how this happens with music and sound in general, books, newspapers and magazines (remember ""). Now we have to experience the same thing with the radio. Not immediately, however, and not soon, but - the process of disconnection has begun. Norway was the first to decide on it, which by the end of the year intends to forcibly switch all state radio channels to digital broadcasting, while turning off FM at the same time. Following it, Switzerland, Great Britain, Denmark and some others follow the same course. And it is worth watching this process at least in order not to step on the discovered rake later.
The analog radio has been an almost eternal thing: even models released half a century ago can still be used today. Digital receivers will not live that long for sure! Changing standards will probably force them to be updated as often as we update mobile phones today.
Norway is starting a scheduled shutdown of state-owned FM stations as of this week. Within a year they will stop broadcasting in FM format and will be transferred to DAB. What is FM - everyone knows. This term simultaneously understands both the range (VHF: 88 - 108 MHz in the West, or down to 65 MHz in the social block) and the modulation method (frequency). Throughout the second half of the 20th century, FM served as a synonym for high-quality sound: frequency modulation, combined with an ultrashort wavelength, made it possible to transmit a stereo signal and place dozens of stations in the range. FM has disadvantages, for example, a small range (compared to MW and HF; FM is heard only a little further than the line of sight), but this did not prevent it from becoming the de facto standard for music broadcasting in cities.
And now the change is coming. DAB (from digital audio broadcasting - digital audio broadcasting) is a relatively new thing: public experiments with it began only in the second half of the 90s. Meaning: broadcasting a digital signal, not an analog signal, at a speed of 128 kbps, in the range just above FM, using noise-correcting coding and the MP2 compressor popular in the past. The receiver, accordingly, is needed digital, that is, it will have to be bought new, but this promises serious benefits. In general, the benefits of transferring radio to a digital standard are circular: absolutely everything wins!
Firstly, DAB is beneficial to broadcasting regulators: they will be able to sell more licenses and fit more stations in the band (the digital signal is less susceptible to distortion from neighboring frequencies).
Secondly, DAB is beneficial for radio station holders, because it allows you to load the transmitter many times more efficiently, and also to conduct encrypted broadcasts that are available only for a fee.
Third, DAB benefits listeners. Unlike analog broadcasting, the quality of which decreases continuously as you move away from the station, the quality of digital broadcasting is consistently high - up to a certain critical distance, after which the received signal power drops below the permissible level and reception stops, or there are too many errors.
That's the theory. And tell someone this fifteen years ago, when the fashion for replacing anal was raging about ha figure, no one would doubt the veracity of these words. Today, however, already about half of the radio listeners in the countries mentioned above use DAB on a daily basis. And the reviews ... so-so! Why? Several reasons are cited.
Looking ahead: DAB is already obsolete and should be replaced by a more modern standard. But worse than that, different versions of digital radio are being introduced in different countries. In Russia, for example, the international DRM standard has been approved as a priority. First, it turned out that the noise immunity of digital radio transmission is greatly exaggerated. No one even remembers that such a signal cannot be received even at a small distance from cities: the reception radius of digital stations is always less than for FM. But even in cities and on major roads, due to difficult terrain and distances, there are areas where the DAB signal weakens below acceptable levels. And then the figure shows itself from the worst side: the sound either disappears altogether, or turns into a meaningless gurgling - while the FM station would be heard, albeit with interference, but legibly! It is also worth adding here that the digital receiver is much more complicated and expensive, and also acts up when driving at high speed: already moving faster than 120 km / h, it reduces the reception quality.
Secondly, it suddenly surfaced that DAB is an outdated standard. It is customary to encode sound using MP2, which (at the used transmission speeds) does not give a sound quality close to CD or even FM! When the DAB experiments were just starting, it didn't matter, but today, when it comes to turning off FM completely, the situation appears in a different light. There is a solution: the DAB + standard uses a modern codec from the MPEG-4 family, only old DAB receivers are incompatible with it! And this has brought suspicions of foul play among DAB supporters: what if the replacement of FM with DAB is intended only for corporations to cash in on the sale of new receivers, and then cash in every year on upgrades?
Finally, thirdly, many people doubt the declared readiness of DAB stations for emergencies. After all, state radio stations are used, among other things, for transmitting signals to alert the population about emergencies. But if FM could be accepted by everyone, then DAB in the same Norway - God forbid that every second inhabitant (the rest simply do not have digital receivers). And digital communications have the famous property of “falling” first in natural disasters and catastrophes. Will it happen again with DAB?
As a result, the question of the reasonableness of turning off FM no longer seems idle. Will digital radio ever replace analog radio? Or will it remain only an optional addition to the ancient, but by no means obsolete technology? What do you think?
Digital Audio Broadcasting (DAB) is a technology that allows digital radio programs to be broadcast. DAB technology is used in 21 countries, mainly in Europe. In Russia, radio using this technology is only planned for use in 2019-2020.
Digital audio broadcasting is guaranteed to be different from analog FM radio. It also allows more efficient use of the available frequencies. Digitization reduces the cost of broadcasting because fewer transmitters are used.
DAB and DAB+ standards
The first DAB transmitters used the MP2 (MPEG Audio Layer II) codec, after some time it was decided to switch to the HE-AAC v2 codec. Thus the DAB+ format was born. DAB radio is not compatible with the newer audio compression standard, and DAB+ radios are compatible with both codecs. Also added to DAB+ is an implementation of Reed-Solomon correction coding, which eliminates errors in transmission. Some DAB radios can be adapted to receive DAB+ by updating their software and marked as updated.
The HE-AAC v2 codec used in DAB provides better sound quality than other solutions used for effective compression broadcasting. Using this codec, perfect reproduction of the original is obtained at 300 Kbps. analogue traditional broadcasting in the FM band is a bit rate of 160-192 kbps. Even at 128Kbps, the sound is close to the original. Broadcasters differentiate bit rates depending on the station's profile. For example, programs intended for listeners with special needs have the bitrate set at 128 kbps for popular programs 112 kbps is set, while 64 kbps can be used for information flow, for example. When reading these values, it should be borne in mind that the declared indicators may not always correspond bandwidth audio. For example, if a station advertises a bit rate on maximum level in DAB+ (192 kbps), this means that the audio bit rate is no more than 175 kbps, and it can be even lower if the station attaches so-called accompanying data.
DAB frequencies
In accordance with the Special Agreement in Wiesbaden in 1995, frequencies in the range of 174-230 MHz were allocated for digital radio in Europe. In a number of countries (including Norway), digital radio also occupies the frequencies 230-240 MHz. European broadcasters may also be granted the right to use parts of the L-band (1452-1492 MHz), but this is rarely practiced.
History of digital radio development
Professional DAB receivers were released already in the mid-90s, while consumer models appeared on the market in the summer of 1998. Home radios in updated version(DAB+) were sold at the end of 2007. In 2016, the first smartphone to support DAB + appeared: LG Stylus.
Digital Audio Broadcasting has not replaced analog FM broadcasts. Although it is available in an area with over half a billion people, the number of purchased DAB/DAB+ radios is estimated to be over 30 million (2014 data). However, significant progress has been made in Europe in building DAB+ infrastructure, so plans have been developed in several countries to phase out analog radio. Norway should phase out the use of analogue FM transmitters in 2018, Switzerland could implement exemptions in 2020-2024, and Sweden in 2022 or 2024. Car manufacturers can help popularize digital terrestrial broadcasting, with some offering DAB/DAB+ radios as standard equipment or options. Unlike the digitization of television, the European Union did not require member states to turn off analog signal, but perhaps in the future an EU decision will be made regarding the digitization of radio receivers - in 2015 it asked for support from the commission of the European organization WorldDMB, promoting the introduction of DAB / DAB +.
Adapter for DAB connection in the car In addition to DAB+, there are other digital technologies in which broadcasters are interested, such as radio broadcasts included in digital television packages ( terrestrial DVB-T, satellite DVB-S and cable DVB-C). Internet radio is also developing dynamically. In some countries, apart from DAB+ partially complying with the DMB standard (which additionally allows video content to be emitted), the DAB+ DVB-H, DVB-SH and DRM+ standards have also been fully developed.
Criticism of the system
Although the HE-AAC v2 codec used in DAB+ provides better audio quality than other solutions used to efficiently compress broadcast material, many broadcasters broadcast their programs at lower than recommended bitrates. For example, the German Radio Horeb transmits at 48 kbps and some musical programms(including the BBC Asian Network) are broadcast in the UK at 64 kbps mp2, which equates to approximately 50 kbps in the mp3 standard. This number means seven times less data transfer rate than broadcast best quality, available on the sender's website, having a quality of 360 kbps. In addition, unlike FM station programs, which may be received with noise and interference when receiving a signal, loss of a digital radio signal will cause a complete interruption in reception. More prevalent than FM, also have motion-related glitches.
