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DAB and DAB+
DAB, Digital Audio Broadcasting, is considered to be the future of radioin Europe, Australia and some other parts in the world. DAB, of better, DAB+,is transmitted in the old VHF Band III, and a single transmission takes abandwidth of 1.5 MHz. A DAB transmission usually contains a number ofservices, packed in an ensemble.
While transmissions are analog by nature, the content of a DAB transmissionis digital. For a decoder like Qt-DAB the world starts withsamples, digitalsamples arriving with a rate of 2048000 I/Q samples per second.The conversion from the analog signal received by the antenna,somewhere around 220 MHz and astream of samples with an IF of 0, is far beyondthe scope of Qt-DAB and similarprograms. For this conversion, Qt-DAB (and other decoders) depends onan SDR converter, such as the SDRplay device, an Adalm Pluto or an RT2832 based dabstick.While there are enormous differences between different devices, they all havein common that they do what is needed: with an antenna receiving signalsand converting them to a stream of IQ samples.
Since the DAB data is digital, basically anything that can be representeddigitally can be made part of the transmission.Next to audio (after all it is radio), slides can be - and are frequently -transmitted, of course text messages are part of the transmission, traffic information andfile transfer are possible, and one of the options is to redirect thecontents of a service to an IP address.
Non-audio data can be made part of an audio service (the so-called PADservices), or it can be madeinto a data service, the latter usually send as a stream of packets.
DAB started in the end of the previous century with MP2 basedframes to carry the audio content, later on DAB+ was introduced with AACas (main) encoding for the audio. AAC has a number of advantages over MP2with repect to quality and density of the encoding, it has as disadvantagethat it complicates the decoding process and its incompatibility: DAB+ datacannot be decoded with a first generation DAB receiver.
While the underlying technology for DAB and DAB+ is the same,the audio encoding of DAB+ is incompatible withthe audio encoding for DAB. Modern implementations of DAB radio's (andDAB decoders like Qt-DAB, dabMini and QiRX) can handle both DAB and DAB+.
Different from e.g. AM and FM, and a big advantage of digitaltransmissions, is that more transmitterscan transmit the DAB signal on the same frequency,in the same neighbourhood, a so-called Single Frequency Network (SFN).The transmitted digital signalis such that when a receiver receives signals from morethan one transmission, it is ableto 'focus' on one of the signals and extract the data transmittedby that transmitter.So, rather than one large, heavy transmitter somewhere central to covera large region or even a country, a whole range of small, lightweighttransmitters can work on the same frequency to cover a large area.Sitting in my lazy chair, I receive DAB signals - using a simple whip -from3 (sometimes 4) transmitters, all within a range of 10 to 15 km, most of themtransmitting the same signal.
It is interesting to see what the effect of receiving multiple transmissionson the same frequency is though. The digital DAB signalis transmitted in 'DAB frames' of 196608 * 1 / 2048000seconds (since sampling is with 2048000 I/Q samples per second, a DAB frametakes 196608 samples).In such a 'DAB frame',the first part, around 2600 samples, taking slightly more than one millisecond,is transmitted with an amplitude that is (almost) zero.The first data block followingthis NULL period, also with a suration of slightly more than1 millisecond contains predefined data.
The 'gap' and the predefined block of data make it easy tosynchronize the receiver with the incoming datastream, and todetermine the correction to be applied on the frequency (if any).Part of the synchronization is done by correlation.The correlation, as shown in the pictures above, shows the differencebetween handling the signal from a single receiver or the signalfrom multiple receivers. In the right picture one sees at least3 peaks, meaning that from (at least) three transmitters data is received.From the correlation picture it can be deduced that the signal being handled,the one with the peak on sample 504, the second largets peak is aroundsample 465, since the samplerate is known, we can deduce that the differencein arrival time of these transmissions is around 20 micro seconds.
The accompanying spectrashow that while the amplitudes of the transmitted signal are(more or less) constant (not taking into account the starting 'gap'),the amplitudes shown in the spectrum when receiving more than onetransmitter are essentially a mess. The way decoding worksmakes that even when the spectrum is as messy as shown, bits can be extractedwith an accuracy, sufficient to have them translated to audio and data.
What is further interesting is that small clock errorsin sampling do not invalidatethe input. The spectrum scope as displayed with Qt-DAB shows - as oneof the indicators - the offset of the number of samples, measuredover 10 frames, i.e. 10 * 196608 minus the actual number of samplesfound.For simple SDR hardware - e.g. the RTLSDR based dabsticks -the offset per DAB frame can be well over 20 samples. Obviously,more expensive devices have more accurate clocks,e.g. for the SDRplay the offset is (almost) zero.The picture above shows the result of(a recording of) an RTLSDR stick, with 204 missing samples per 10 DAB frames(the number on the bottom line of the picture).
The (obvious) reason that even the offset as seen with RTLSDR sticks doesnot prohibit the software to do a good job in decoding is thatthe DAB data is encoded in the frequency domain, rather than directlyfrom the samples (in the time domain). Since the contribution of anindividual sample in the time domain contributes only a little tothe data in the frequency domain, an offsetof a few samples in data blocks of 2048 samples does not disturb the spectrumderived from the datablocks in a way that decoding is impossible.A few simple tests with Qt-DAB show that if the synchronizationis off for even more than 100 samples, decoding is still possible.
Qt-DAB and dabMini
DAB technology is also interesting from a software point of view. After all,all processing of the samples is done in software, and with 2048000complex samples per second, with about 100 FFT transforms per second,with lots of viterbi decoding and Reed-Solomon error repair,and with a variety of different SDR devicesto support, developing software provides lots of challenges.
Qt-DAB and its family are the result, they provide DAB (DAB+) decodingfor a whole range of devices, and the architecture is such that additionsand changes are made easily.
Currently Qt-DAB (and most of my other software) supports thedevices as shown in the picture below. Top right a LimeSDR in a yellowenclosure, clockwise, the Adalm Pluto, two RSP devices (RSP II and Ia),the tiny RT2832 based 'DAB' stick, the HackRF and the small (slightlyolder) AIRSPY.
Of course, Qt-DAB supports file input as well, both '.iq' (.raw) 8 bitfiles as generated by osmocom software, 16 bits '.sdr' file as generatedby Qt-DAB and xml files are supported. (Qt-DAB further supportsin input through an IP port, and, in a limited way support using Soapyand - for Windows - Extio interfaces.)
Qt-DAB is built from the perspective that the useris in full control: not only are there buttons on the GUI to show differentdisplays, to scan, to select a device etc etc, the '.ini' file, i.e.the file where configuration data is stored, contains lots of settingsfor the user.
Lots of selections are possible, and to ease life, lots of selections aremaintained between program invocations. As an example, the device,the channel and the program that were active when shutting down the programare stored and used as start up parameters.Presets are maintained between program invocations,
One of the recent additions is that the gain setting per channel iskept. Comes in handy when using the preset selection:when selecting a service in a different channel than the currentone, the correct settings for the new channel are set automatically.
Another recent addition is color setting. I hestitated a long time beforeadding colors, after all, different people have different ideas aboutfavorite colors. However, in the end colors were added to thebuttons and the displays, in such a way that color setting and modificationcan be done from within the GUI, just by clicking with the right mouse button.
For those who want an idea on what can be received, the GUIcontains a scan functionthat will scan the selected band (usually Band III, but user defined bandsare also possible), and show (and save) data of allensembles and services detected.
Of course, from time to time we do not need all the whistles and bellsthat Qt-DAB provides, we just want a list of services and the ability toselect one. That is why dabMini was developed.
Already years ago,variants of Qt-DAB were developed with small, limited GUI's, dabradio andqml-dab being examples.However, while the software of Qt-DAB was (is) continuously improved, there was hardly any maintenance for the other software, and the organization in different repositories did not help either.
dabMini therefore is built on the same set of sources as Qt-DABand is part of the same source tree as Qt-DAB.Any change in the non_GUI elements of the software of Qt-DAB thereforeautomatically applies to dabMini.
dabMini just provides a minimal GUI,device selection is automatic, next to service selection there are easyways to iterate over the channels and the services.Of course dabMini supports presets, and a recent addition was a mutebutton, to stop any audio from eaching the soundcard for a given amount of time.
A third family member of the Qt-DAB family is dab-2. dab-2 is for mea vehicle to experiment. While most of its implementation is sharedwith the Qt-DAB program, there are some fundamental differencesbetween Qt-DAB and dab-2.dab-2 is also part of the Qt-DAB sourcetree, dab-2 shares its GUI with thatof Qt-DAB, the widgets for the devices differ though.
Documentation
It took a while, but I found time to write a pretty completeuser's guide. That guidenot only contains a detailed description of the widgets in the GUI,it contains a description of the possible (few) command line parametersand a detailed description of the - possible user's - settingsin the '.ini' file. It further contains a detailed description of howto configure and create an executable, how to add a deviceand - last but not least - a description of the mini version of Qt-DAB, i.e. dabMini and how to build an executable for it.
Note that while there is no separate description for dab-2 - after alldab-2 might change daily - most of the settings for Qt-DAB also apply todab-2.
Support for other devices
Obviously there exist an almost infinite amount of other devices,the way Qt-DAB is built makes it pretty easy to add support for an other device.A well-defined interface exists that any device handler should implement,the user's guide contains a section describing in detail whatfunctions must be implemented and what files need tobe adapted and how to modify the configuration parameters.Anyone is invited to add another device to the list of supported devices.
The xml file format
While Qt-DAB (still) provides the opportunity to dump the incoming datain a PCM formatted file (2 channels, 16 bit integer, 2048000 rate),and - obviously - is able to process that data as well as 8 bit 'raw' files,an addition is made to support 'xml files'
To promote interoperability between QIRX and Qt-DAB (and possibly others),Clemens Schmidt (the author of QIRX) and I defined and implemented thexml file format.
An xml formatted file contains - next to the raw data - a precise descriptionof that data. That way, raw data from a variety of devices can be usedas input to the afore mentioned programs. The advantage is clear,the data recorded is the data as picked up by an input device, unaltered.
The description - written in XML, and contained in the first segmentof the file - contains (a.o) the name of the device used and thenumber of bits per sample. A detailed description of the format can be foundhere
Currently, both QIRX and Qt-DAB provide a reader, able to handlexml files, furthermore, the various device handlers in Qt-DABare equipped with a dump button to generate such a file.
Where to find Qt-DAB software.
Qt-DAB - the sourcetree and executables - is to be found in this repositoryon github.
For Linux (on an x64 PC) a precompiledversion of Qt-DAB is available as an appImage.For Windows there are installers for all threemembers in the sourcetree, Qt-DAB, dabMini and sdrplayDab(see the releases pagein that repository).
However for the RPI's or other targets, one has tostart with the sources, install some libraries and build an executable.
The user's guide contains extensive instructions to create andexecutable, both for Qt-DAB and its little sister dabMini.
Friends of Qt-DAB-3.X
The sources for Qt-DAB-3.X are also used as basis for a number of derivedprograms, two of which will be briefly discussed here: a DABscanner and aDAB library a.k.a dab-cmdline.
For these (and a number of other) programsa repository exists on Github, most of them with an extensiveREADME, containing a description and details for constructing anexecutable.
The DAB scanner
While Qt-DAB now offers the opportunity to scan the band and save a description of the ensembles and services found in a file,DAB scanner is a program to continuously monitor (selected)channels in a given band and report on the received ensemble (if any).The program is developed for DX purposes, it is an ideal tool to monitora band for a longer period.
The scanner can operate in two modes, continuous modeand controlled mode.
In continuous mode the duration of the scan is not specified,scanning continues until explicitly stopped.To allow focusing on selected channels,a skipfile can be selected, in which the channels that are to bepart of the scan are marked as such.The contents of such a skipfile can be modified dynamically.
In this continuous mode, one selects askipfile on program start up, if none exists, one will be created.
The output of the scanner is a text file, readableby a spreadsheet program such asLibreOfficeCalc.
Each time an ensemble is detected, details of theservices in that ensemble are written out (such as in the picture above).Obviously, running the scanner for a couple of hours will generate a lotof output, therefore a second file, a summary file is generated aswell.The summary file contains just a single line for each recognizedensemble.
If the mode controlled is selected, the scanner will runa specified number of times, the number determined bythe value chosen for the spinbox, and generates a text filewith a description of the ensembles and services encountered.
At the end, the scanner will show an overview of the result ofthe last scan over the band (similar to the scan output of the Qt-DAB program).
Dtmb Software Driver Software
The DAB scanner supports most of the devices that are supported by Qt-DAB,i.e. the SDRPlay (using the 2.13 or the 3.06 library), the AIRspy,DABsticks and the Adalm Pluto. The Linux version can beconfigured to support theLimeSDR, the Hackrf and the ip client as well(since I do not have working dll's for thesedevices I do not offer support for the Windows version).
Where to find the DAB scanner program
The sources for the DAB scanner - with an appImage foruse under Linux x64, and an installer foran executable on Windows - can be found in this repository
The DAB library (a.k.a. dab-cmdline)
The DAB library, a.k.a. dab-cmdline,is a library providing the functionality todecode a DAB data stream. It is used to create (a.o) commandline programs to listen to a single service in a given band,without any form of GUI.
The repository contains a number of example programs, using theDAB library, either as a binary library or connecting directlyto its sources.
Invocation of such an example programs, with some parameters specified, issomething like
dab-sdrplay-2 -M 1 -B 'BAND III' -C 12C -P 'Radio 4' -G 80 -A default
In this example, the program was created with the SDRplay as device, it selects Mode 1 and 'BAND III' (which both happen to be the default),Channel '12C' is selected, with a program 'Radio 4', the gain is setto 80 and the output is just 'default'.
The example programs differ in details, example 2 (see thecommand line above) sends the audio output to the (local) soundcard,example 3 sends the audio samples to stdout,example 4 sends the AAC framesfrom the selected DAB+ service to stdout.
One of the example programs is a command line version of a DAB scanner,it will scan the band and save the results of the scan in a (specified) file.
Example program 2 supports the same set of devices as Qt-DAB. Other exampleprograms (after all, they are just examples) most of the basic ones, likethe SDRplay and the RTLSDR sticks.
Where to find the dab-cmdline library
The sources and example programs for the dab-cmdline library can be found in this repository
The repository for dab-cmdline contains an extensive READMEthat describes all (about 10) example programs and discussesthe API of the library.Note however, that the example programs are meant to beexamples, examples 2, 3 and 4 can be configured withthe devices also used for Qt-DAB and dabMini, the remaining examplesare highly experimental. In general: feel free to adapt to your needs.
DRM, Digital Radio Mondiale
Introduction
As well known, DAB is transmitted in theold TV Band III. The bandwidth used is 1.5 MHz, (4 DAB channels takethe width of one TV channel).Less known is that the short and medium waves havetheir own - small band - version of digital radio,Digital Radio Mondiale (DRM for short).
In Europe - with its dense population - DAB (DAB+) seems to be the choice,in more rural areas in the world, e.g India and parts of AfricaDRM transmissions on short wave seem to be the medium.
DRM+, i.e. a version of DRM aiming at replacing FM stations, is currentlyin a rather experimental stage. It seems that in Russia some DRM+ transmissionsare going on. To distinguish, the medium/shortwave version is called DRM30s,while the FM band version is called DRM+.
In Europe, one can receive a few DRM30 - i.e. shortwave - transmissions.Rumenia has still international programs transmitted in DRM,other transmissions that I receive are from Kuwait, India and Nigeria.
What is DRM
DRM, Digital Radio Mondiale, is a standard for digital radioand operated in medium and shortwave broadcast bands.As said, for medium and short wave there is DRM30,for VHF there is DRM+.
DRM30 and DRM+ (and DAB as well) are transmitted in Ofdm, the spectrumof which is easy to recognize: no signal peak as in Am or FM,just a block with (more or less) a constant amplitude over thewhole frequency range of the signal.Using Ofdm blocks of data are transmitted that - using FFT techniques -can be mapped upon blocks of bits. Using some error correction techniques,errors - resulting from channel characteristics - can be corrected.This way, DRM can transmit up to 4 services in a single transmission.
While the basis sample frequency for DAB is 2048000, formost modes in DRM30 it is restricted to 12 Khz.A DRM30 transmission is limited in bandwidth: most transmissionsare 10 KHz, however, transmissions with a width of 20 KHz and 5 Khzare also possible.
In DRM30 there are 4 modes and a number of optionsfor the spectrum to be occupied, the mode and spectrumare to be detected from the characteristics of the datastream.
Processing DRM30 is far more complex than processing DAB (andtherefore technically more interesting), especially thesynchronization requires some effort.
For encoding the data QAM4, QAM16 and QAM64 encodings are used.Far more 'technique' is needed to extract the bits fromDRM than from DAB.
In this report I discuss the approach taken to synchronization in the DRM30 decoderof the swradio-8 and its predecessor.(Since I do not have to publish, it is an (eternal) preliminary version,and in details different from the current implementation,the algorithms are still the same though.)
The swradio-8 receiver with the DRM30 decoder
The swradio-8 program is designed to 'listen' to frequencies on the'shortwave' bands. It takes its input from a hardware SDR deviceand contains a dozen decoders to 'listen' to some common modes.
The sw-radio-8 supports the SDRplay RSP devices: they have a frequencyrange starting at app 100KHz. Furthermore the Hackrf (since it supportsfrequencies starting at 1 Mhz) and RT820 based RT2832 compatible DABsticksare supported.For the latter there is a library supporting frequencies as low as 14 Mhz(the way the signal is dealt with requires a valid I/Q signal) andthe DRM transmissions from Kuwait are around 15 MHz.
The software can also be configured to support the pmSDR device,i.e. using the soundcard, rather than the high-speed wide band SDRdevices.
The implemented DRM30 decoder - limited to a bandwidth of 10 KHz -is able to detect the mode, and correct a limited frequency offset(i.e. up to a few hundred Hz).The picture shows the reception of the transmission from Nigeria,in the early evening in the 19 m broadcast band.
The DRM decoder widget shows at the right hand side 4 colored blocksthat take the value green if everything is OK, otherwise red.Here, all 4 blocks are green meaning that decoding - up to andincluding audio decoding - is successfull.
The middle part of that widget shows at the top that there is only oneservice, that the transmission mode is Mode C, with spectrum 3 (i.e.just a 10 Khz spectrum with two sidebands), that the audio for the selectedmode is AAC, and the name of the transmitting station is 'Voice of Nigeria'.
To the left there are 8 numbers giving some technical informationon the received data.
Some other decoders in the swradio software are:
- AM, USB and LSB,
- psk mode decoder with lots of options,
- rtty mode with lots of options,
- morse code with autodetection of the speed,
- weatherfax,
- amtor for decoding naval (coastguard) messages.
Where to find the swradio-8 software
swradio-8 - sources and executables - can be be found in this repositoryon github.For Linux (on an x64 PC) a precompiledversion is available (an appImage), for Windows an installer isavailable (see the releases pagein that repository), however for the RPI's or other targets, one has tostart with the sources. The README contains extensive instructions for generating an executable.
The drmPlus software for decoding DRM+ and FM.
In some countries DRM+ is chosen to be the medium for digital radio.While DRM30 is developed for short and mediumwave bands,DRM+ is meant to be used in the VHF band.The bandwidth is 100 KHz, and the service data is encoded in either4 QAM or 16 QAM.
Since the few DRM+ transmissions that I know of are in the FM band,the drmPlus, the DRM+ decoder that I developed,is also equipped with an FM decoder.
The picture shows the DRM+ part of the decoder. Since - as said before -there are no DRM+ transmissions in the neighbourhood, the developmentis being done using some files as input. The picture shows that for thegiven file, there are 4 services, and the green spots indicate thatsychronization and decoding is all correct.The widget in the left corner shows the correction that is being carried outon the signal, the blue line indicates the correction to be appliedon the phase, the red line the correction to be applied on the amplitudeof the signal.
The second picture shows the FM part of the decoder. The SDRplay isused as input device (other devices are the RT2832 based 'dab' sticks,the LimeSDR and the HackRF).It also shows the preset list, a list of station names and frequenciesfor fast selection.
As said, there are no DRM+ transmission here, there are hardly DRM30transmissions here, developing software for these modes is mainlydriven by an interest in the technology.
Where to find the drmPlus software.
Sources are - as always - available, they can be found on this repositoryon github. Cooperation to further develop the software would be (very)welcome.
Some other SDR-J software
A general (W)FM decoder
The SDR-J FM software supports - under Linux - next to the SDRPlay,the Adalm Pluto, the AIRspy,DABsticks, HACKrf, limeSDR and a soundcard, the sw-elad-s1is supported when used with a downconverter.Under Windows the support is for the SDRplay, AIRSpy and DAB sticks.
The (W)FM receiver software implements different types of FM decoders,and - as seen on the picture - rds.It works on a rate of 192000 samples/second, data from theinput device is downconverted to this rate if needed.
Operation is simple, the buttons and selectors on the main widgetare equipped with tooltips. Furthermore, frequenciescan be labelled with an appropriate name and stored in apreset list, for easy program selection.
Where to find the (W)FM software
The sourcescan be downloaded from github . In the releases section of that repository one will finda Windows installer.
Spectrumviewer.
The spectrumviewer program just shows the spectrum, up to the selected bandwidth determinedby the selected samplerate. The spectrumviewer software can be configured with the SDRplay,the Adakm Pluto, the AIRspy, the HACKRF and DABsticks.
Operation of the spectrumviewer software is straightforward,tooltips tellthe function of the various buttons and sliders.
The spectrumviewer will open a device that is configured and connected,in case of more devices are configures, it just opens the first onethat it sees.
A frequency can be selected by entering the number in the keypad, terminatingit with either MHz (for interpreting the number as the frequency in MHz)or kHz (for interpreting the number as the frequency in kHz).A scanning function is implemented with which it is possible to look ata wide range of frequencies.
The program shows both a spectrum and a waterfall, here over a range offrequencies in the FM broadcast band.
Since the input is usually wideband, up to 8 or 10 MHz, a decimator ispart of the program, where the decimation rate can be selected.For e.g. an input signal with a width of 8 Mhz,decimation with a factor 100 gives a signal width of80 Khz, making smaller band signals visible.
The set scan selector starts (or stops) scanning though the frequenciesThe 4 selectors to the left of the set scan button determine thefrequency range, the stepsize and the rate at which the frequency changewill occur.
Where to find the spectrumviewer software
The sources are to be found in this repository.The releases section of this repository contains an installer for theWindows version. This installer will install the executable and dependentdll's. It will also install the SDplay library interface, if not installedalready.
An rtlsdr emulator
Many interesting software packages for (sole) use with an RTLSDR compatibledevice exist and are available, dump1090 and acarsdec are typical examples.It would be interesting to have these programs and be able to use themwith other devices, e.g. the SDRplay RSP. The acarsdec software wasextended by me with an option to use the SDRplay, and a derived versionof dump1090 was written with a small GUI and support for the SDRplay(the above mentioned qt-1090 program).
There are, however, other programs as well, e.g. rtl_433, aiswatcher etc. thatare interesting and, somehow, tightly bound to the use of anrtlsdr compatible stick.I realized that it would be easier to write an rtlsdr emulatorusing the SDRPlay device than rewriting all software that I encountered and works only (primarily) with a DABstick.That lead to the development of the rtlsdr emulator for the SDRplay.Implemented as a plugin replacement for the rtlsdr library, either forLinux (librtlsdr.so) or windows ([lib]rtlsdr.dll).
For Windows, the version is extended and a small dialogbox is shown(shown at the top of the picture).The dialog box allows to set both the lna state and the if gain reduction.The emulator was tested with e.g. SDR#.
Dtmb Software Drivers
Note that - while it is working in a number of cases - it is far fromperfect.The sources of the library can be found in the github repository .Operation of the emulator is simple, it is just a replacement of 'librtlsdr.so'under Linux or (lib)rtlsdr.dll under windows (it is assumed that you havethe SDRplay lib installed).
In my environment the emulator works fine with both dump1090 (although qt-1090has a better performance), acarsdec, and others, and on my developmentlaptop the 'standard' librtlsdr.so is replaced by the emulating one.
Documents and non-sdr stuff.
Since my interest is primarily in developing programs,I'm less (better word: not) interested in writing manuals(that no one ever reads anyway), so manuals are pretty much absent.The programs that are equipped with a GUI havetooltips, telling the function of the GUI elements.For the others, read the README and the CMakeLists.txt and/or the xxx.profile. The repository for dab-cmdline contains a fairlyextensive README with descriptions of the different exampleprograms, an example of such a command line and build instructions.
There are some documents though:
A user's guide for Qt-DAB software (both Qt-DAB-3.4 and dabMini) isgiven here. The guide contains a descriptionof the GUI elements, configuration options, how to generate anexecutable, how to add support for a device, and a description ofdabMini (as well as a script to build an executable).
An informal description of the synchronization in the DRM30 decoderis given in this description.The document will be a draft forever, butit contains quite some practical information on issues encounteredin writing the software (the decoder for the sw-radio-8 program)for decoding the DRM30 signal.
For those interested to get an idea of how DAB decoding is implemented,a description of a - slightly limitedand outdated - implementation of the DAB decoder in theprogramming language Adais given.
For those interested in really old stuff that has nothing to do with Software Defined Radio, but happens to be for me one of the funniest projects,this repositorycontains (sources for) an algol 60 to C translator,with a number of example programs. The program was written in plain C around 2002, also as a hobby project at that time.Recently an addition was made: selecting a '-F' as oneof the command line parameters causes the compiler to accept Frenchkeywords, rather than the default British/US style keywords.This manual is a user's guide anddescribes - in about 20 examples - in quite some detail the mappingsof Algol 60 constructs in the resulting plain C code.Actually, the compiler works pretty well on my x64 basedlaptop and my RPI 2 and 3.
Finally ....
In most of the SDR-J software existing dynamic libraries(Linux) and dll's (windows) are used, e.g. libraries for audio output, fft,handling 'wav' files, Reed-Solomon correction, decoding AAC and xHE-AAC,converting samplerates, etc etc, all available under a GPL-V2 or V3.All rights are gratefully acknowledged, andthe SDR-J software is itself also made available under a GPL-V2 licence.
It is - obviously - nice if (some of) this software is useful, there are no guarantees, however.If the software does not fit your purposes,it might just not be the software you are looking for, read the license, that states (a.o):
SDR-J is distributed in the hope that it will be useful,but WITHOUT ANY WARRANTY; without even the implied warranty ofMERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See theGNU General Public License for more details.
The development of this - and other - SDR-J software is a hobby,a 'spare time', project (being retired makes that there is some spare time).As with all hobby projects, support(such as suggestions for improvements, and additions,suggestions for modifications etc) andcontributions (such as code improvements or extensions,providing me with a yet unsupported device, etc) are welcome.
I am grateful to SDRplay ltd for providing me the possibility to usedifferent versions of the SDRplay RSP devices, all wonderful devices.Furthermore, thanks to Benjamin Vernoux for making an AIRSPY device available,to Great Scott Gadgets for making an HACKRF device available,to Robin Getz (Analog Devices) for making an Adalm Pluto device availableand to Jan Willem Michels for making an LimeSDR device available.
Have Fun!!!
Pijnacker, September 2020
Jan van Katwijk
Lazy Chair Computing
J.vanKatwijk-at-gmail-dot-com
Glossary of Printing Terms
Bleed - An image or printed color that runs off the trimmed edge of a page. Bleeds are created by trimming the page after printing.
CYMK - Cyan, magenta, yellow and black. The blending of these inks during printing creates full-color publications and images.
Dummy - An unprinted mock-up of a book, brochure, or 'to-be-printed' piece.
Duotone - A two-color halftone of an image created with two screens, two plates, and two colors. Duotones are made by printing an image with two colors, generally black and a second color. The full range of tones are printed black and the middle range of tones are printed in the second color. The result is a striking image with more richness and depth than a one-color halftone.
Embossing - A shape is pressed into a sheet of paper with a metal or plastic die, creating a raised (embossed) image.
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EPS - Encapsulated postscript file format. (See 'vector')
File Compression - Condensing a file so it takes up less space. (See 'lossless compression' and 'lossy compression').
Foil Stamping - An image created by covering paper with a thin, flexible sheet of metal or other material. The foil, which may be clear or opaque, comes in a range of colors and is carried on a plastic sheet. Stamping separates the foil from the plastic and makes it adhere to the paper. Foil stamping can be combined with embossing or debossing as an added design element.
Hickey - An irregularity in the ink coverage of a printed page. Hickeys are caused by paper or pressroom dust or dirt on the printing blanket which prevents the ink from adhering to the paper surface.
Imposition - The arrangement of pages in a printing form so that, when the sheet they are printed on is folded and trimmed, the pages appear in proper sequence.
JPEG (.jpg) - Joint Photographic Expert Group. A lossy compression method used for storing large bitmap images and displaying images on the web.
Kerning - Adjusting the space between characters.
Leading - Space between lines of type. General rule of thumb is to add two points leading to your type size. For example, 11 point type with 13 point leading.
Lines Per Inch - The number of lines in an inch, as found on the screens that create halftones and four-color process images (for example, 'printed 175-line screen'). The more lines per inch, the more detailed the printed image will be.
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Lossless Compression - A compression method that reduces the size of a file without any loss of data.
Lossy Compression - A compression method that reduces the size of a file with varying or adjustable loss of data. JPEG is an example.
Moiré - A pattern created by printing several repetitive designs on top of each other. In multi-color printing, screens of colored dots print on top of each other. If the angles of the halftone screens of each of the colors are not properly aligned with each other, an undesirable, blurry pattern called 'moiré' appears in the final image.
Resolution - A unit of measure. Image resolution measures the amount of data per inch in an image. Printer resolution measures the amount of detail that a printer or imagesetter can create. Scanner resolution measures the amount of detail that a scanner can capture.
RGB - Red, Green, Blue. These are the colors that create image you see on your monitor.
Pixel - PICture Element. The smallest unit of image data.
Scoring - Pressing a 'channel' into a sheet of paper to allow it to fold more easily.
Self-cover - A booklet having a cover made of the same paper as the inside or text pages.
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Vector - Drawn images, not photographic, composed of a series of points connected with straight or curved lines. These can be filled with color, gradients or patterns. These images are not subject to the resolution or sizing issues of bitmap images. They can be reduced or enlarged without losing image quality.
WYSIWYG - What You See Is What You Get. Software programs such as Adobe InDesign create publications that are WYSIWYG. Software programs such as Microsoft Publisher, Microsoft Word and Wordperfect are not WYSIWYG. Pages change dependent on font usage, print drivers, etc.