Since Qt6 is there for quite a while, it is inevitable to move over to Qt6. While AppImages are built with "old" library versions, AppImage is and will be compiled with Qt5.

To proceed, the current version is parametersized on the Qt version, and will compile with both Qt5 and Qt6 (with qwt 6.20) Parameterization will remain until the AppImages can be made with Qt6.

While the Qt6 based version for Linux works fine, there are some issues with the windows version, probably caused by problems with the required dll's The Windows versions are compiled with Qt5 still.

Qt-DAB is software for Linux, Windows, MacOS and Raspberry Pi for listening to terrestrial Digital Audio Broadcasting (DAB and DAB+). Qt-DAB is continuously under further development, Qt-DAB-6.8 , the stable version of Qt-DAB has - again - some new features, not often seen elsewehere. A good quote indicating what I try to achieve in the continuous development of Qt-DAB software is:

• It is much easier to add features to reliable software, than it is to add reliability to featureful software.

And indeed, it continuously shows that it is fairly easy to add new features.

Of course, as for previous versions, for Qt-DAB-6.8 some predefined versions are available. For Windows three installers are maintained, and for Linux an x64 AppImage is available.

In Qt_DAB-6.8 the "ini" file was reorganized, the old one was a little messy. The "ini" file is named differently, which has has positive effect that running older versions is not affected, as negative effect that it is "empty"

A seemingly minor change from the user's point of view is that now on selecting any channel, the service that was last used on that channel is started.

• Introduction
• Features
• Widgets and scopes
• [A Note on using an RTLSDR device](#a-note-on-using-an-rtlsdr-device]
• Scan control
• Displaying TII data
• Documentation
• Installation on Windows
• Installation on Linux
• Notes on building an executable
• Using user specified bands
• xml-files and support
• Copyright

Qt-DAB is designed to be used with different SDR devices in mind. A simple and clean interface is used and Qt-DAB-6.X has support for a DABsticks, all models of the SDRplay, Airspy, HackRF, LimeSDR, Adalm Pluto etc.

Qt-DAB is being developed under Fedora, and cross compiled - using the excellent Mingw64 toolset - for Windows. For Windows, installers are available, two installers for 32 bit versions and one for a 64 bit version. For Linux, an AppImage, available for x64 Linux, is available, built under an older version of Ubuntu (right now Ubuntu 20, Ubuntu 22 is too new for an AppImage).

Thanks to Richard Huber, Qt-DAB can be compiled on the Mac as well.

Qt-DAB is GUI driven, the full GUI shows 4+ widgets, one of them, the main widget - one with sufficient controls to select channels and service(s) - is always visible. This main widget contains selector for controlling the visibility of (the) other widgets.

• Qt-DAB supports input device:
  • SDR DAB sticks (RTL2838U or similar), with separate libraries for the V3 and V4 versions of the stick,
  • All SDRplay SDR models (RSP I, RSP 1A and 1B, RSP II, RSP Duo, RSP Dx and RSPDxR2), with separate entries for the v2 and v3 library,
  • HACKRF One,
  • Airspy, including Airspy mini,
  • LimeSDR,
  • Adalm Pluto,
  • untested UHD (anyone wants to help testing?)
  • Soapy, a renewed Soapy interface driver is even able to handle other samplerates than the required 2048000 (limited to the range 2000000 .. 4000000),
  • ExtIO (experimental, Windows only),
  • input from a spyServer, with a 8 bit and a 16 bit version,
  • input from an rtl_tcp server.
• Always supported input from files:
  • prerecorded dump (.raw, .iq, '.sdr`, and '.uff' (xml)) files,
• with the possibility of generating such files from the input.
• Qt-DAB records settings and maintains then between program invocations,
• Qt-DAB supports Favorites (i.e. channel, service pairs) for easy switchingbetween services in different ensembles (see below),
• Qt-DAB supports DAB (mp2) and DAB+ (HE-AAC v1, HE-AAC v2 and AAC-LC) decoding,
• Qt-DAB supports MOT SlideShow (SLS) with the possibility of saving the slides, Dynamic Label (DLS) with the possibility of saving the dynamic Label text (the latter by right clicking with the mouse, or saving all dynamic label texts - augmented with channel and time info - in a file),
• Qt-DAB supports automatic reconfiguration of services,
• Qt-DAB supports generating ETI (Ensemble Transport Infterface) files from the selected ensemble.
• Qt-DAB provides different views on the DAB input signal (spectrum, correlation, channel, etc),
• Qt-DAB provides detailed information (including strength and a spectrum view) on the audio in audio services service,
• Qt-DAB recognizes and interprets TII (Transmitter Identification Information) data of - if the received signal is from multiple transmitters - all detectable transmitters, can be made visible simultaeously, and displays the transmitters on a map,
• Qt-DAB supports dumping of the input data of the DAB channel (Warning: produces large raw files!) into .sdr files or .xml file formats and playing them again later (see section on xml format),
• Qt-DAB supports saving audio, either as uncompressed ".wav" files (samplerate 48000, two channels) or saving HeAAC frames from DAB+ services for processing by e.g. VLC,
• Qt-DAB supports showing and saving the ensemble content description and provides advanced scanning possibilities,
• Qt-DAB supports handling ip output from data packets,
• Qt-DAB supports sending TPEG output - when configured - as datagrams to port 8888,
• Qt-DAB supports (automatic) EPG detection and building up a time table,
• Qt-DAB-6.8 supports decoding and displaying journaline when transmitted as subservice,
• Qt-DAB offers scheduling of some operations on services for up to 7 days;
• Qt-DAB allows running an arbitrary amount of services from tne current ensemble as background service. with the output sent to a file,
• Qt-DAB offers options to select other bands, i.e. the L-Band, or channel descriptions from a user provided file and it supports obsolete modes (Mode II and Mode IV),
• The Qt-DAB implementation provides a clean device interface, it is easy to add other devices.

Not implemented:

• Other bands than used for terrestrial broadcasting in Europe (like DAB over cable)

The full GUI for Qt-DAB-6.8 is built up from 4 (four) larger widgets and - depending on the settings - a few smaller ones.

The mainWidget (see picture) is the one widget that is always visible as long as the program is running, it contains settings for controlling the visibility of other widgets. The main widget shows on the left half a list of services (either from the currently selected channel or from the favourites), and it provides all means for selecting a channel and selecting a service. On the right half of the widget is shows the dynamic label, and the slides - if transmitted as part of the service - or a series of default slides.

• touching the ensemble name (NPO (8001) in the picture) makes the content table, i.e. an overview of the content of the ensemble, visible with the possibility of storing the data in a ".csv" format. If the data is visible, touching will hide it;
• touching the small icon left of the name of the selected service (here left of the bold text NPO Radio 5), will show (or hide) the technical widget, a widget showing all technical details as well as strength indicators and a spectrum of the audio of the selected service;
• touching the small icon on top of the latter, the folder/directory in which the slides, the tii log and the log file are written is shown;
• touching the icon showing a speaker controls muting the signal, if no audio is generated, or if the signal is muted, the icon will show this;
• touching the copyright symbol shows (or, if visible, hides) a small widget with some acknowledgements for using external libraries;
• touching with the right hand mouse button the text of the dynamic label (Steely Dan - Reeling In The Years) shows a small menu to put the text on the clipboard;
• the button labeled scan controls the visibility of a the scan handler widget;
• the button labeled http controls the http handler with which a map )with the transmitters) will be shown;
• the button labeled spectrum controls the visibility of the spectrum widget, a widget that contains views on and information of the DAB signal itself;
• the button labeled controls controls the visibility of the so-called configuration and control widget, a widget that contains numerous settings for this software;
• the button labeled favourites controls whether the list of services from the currently selected channel of the list of favourites is shown,
• the button labeled scanlist controls the visibility of the scan list, i.e the list of services seen at the most recent scan.

(Obviously, the colors of the buttons, as well as the font, the font size and the font color of the service list shown can be set by the user, just click with the right hand mouse button on a button).

Qt-DAB supports Favourites, i.e. a list of (channel, service pairs), the list is maintained between program invocations. The services list is shown in one of two modes, selectable by the button (in the picture labeled favourites). In ensemble view mode, the services in the current ensemble are shown, in the favourites view mode, the favourites are shown. In both views, selecting a service is just by clicking on the service name. Of course, when selecting a service in the list of favourites, it might take some time before the software has switched over to the appropriate channel, and has received sufficient information on the new ensemble carried in that channel before being able to select the service in that channel.

Adding a service to the favourites is by clicking on the field in the right hand column, shown in the services list. If - in ensemble mode view - a service is also part of the favourites, the field in the right hand column is marked. Clicking on such a mark removes the service from the list, as does clicking on the field in the favourites view.

The technical widget shows - as the name suggests - some technical details of the selected audio service. If the audio of the service is also transmitted on FM, the FM frequency - derived from additional data in the DAB data - is shown as well.

The buttons at the top of the widget control dumping the audio (".wav" file) resp. the AAC frames into a file. The latter can be processed by e.g. VLC. The three progress bars (quality indicators) for DAB+ give success rates of resp. detecting a DAB+ frame, the RS error repair and the AAC decoding. (For "old" DAB transmissions only a single quality indicator appears).

The - in the picture red - label with text "mot available" turns green if in the selected service mot data (usually slides or text) is detected.

The widget for the spectrum scope is equipped with a tab for selecting one of 6 views on the input signal. In the view shown in the picture above, the spectrum of the incoming DAB signal is shown. One clearly sees that the bandwidth of the signal is app 1.5 MHz (1536 KHz to be precise). To the right of this spectrum, one sees the signal constellation, i.e. the mapping from the complex signals onto their real and imaginary components. If the selector labeled "ncp" is set - as in the picture - the centerpoints of the 4 lobs is shown.

On the right hand side the widget shows some quality indicators of the DAB signal, such as applied frequency correction, remaining frequency error, SNR, some clock offsets and an estimate of the signal quality (for the latter, higher is better).

The ideal form of the spectrum and the signal constellation as shown in the picture above is not often seen with real inputs.

The correlation scope shows the correlation between the incoming signal and predefined data, i.e. the data as they should be. Correlation is used in identifying the precise start of the (relevant) data of the frame in the input sample stream. The picture shows more more peaks, i.e. the signal from more than one transmitter is received.

A DAB signal is received as a sequence of samples, and can be thought to be built up from frames, each frame consisting of 199608 consecutive samples. The first app. 2500 samples of a frame do not carry a signal, the NULL period. The NULL scope shows the samples in the transition from the NULL period to the first samples with data of a DAB frame.

In reality the NULL period is not completely without signal, it contains an encoding of the TII data. The TII scope shows the spectrum of the data in the NULL period. This TII data - when decoded leads to 2 2 digit numbers - is used to identify the transmitter of the signal received, these numbers can be mapped upon a name and location of the transmitter.

The channel scope shows the channel response on the transmitted data, i.e. the deformation of the transmitted signal on the way from transmitter to receiver. The picture shows the cyan colored line, i.e. the channel response on the amplitude, and the red line, i.e. the channel effects on the phase of the samples.

The deviation scope shows the mean deviation of the carriers in the decoded signal, ideally their phase is (a multiple of) 90 degrees. The phases are mapped upon (soft) bits, the larger the deviations, the less reliable these bits are. The Y-axis is in Hz.

The configuration and control widget contains checkboxes, spinboxes and buttons with which the configuration of the decoding process can be influenced.

At starting up Qt-DAB-6.8 for the (very) first time, no device is selected yet, amd the widget is made visible to allow selection of an input device (the combobox at the bottom line right).

For a detailed description of all selectors, see the manual (or read the tooltips).

RTLSDR devices are - because of their price - rather popular. In Qt-DAB different versions for the support library are provided, The windows and Linux versions differ in their implementation, it turns out that under Windows, killing and restarting the "worker" thread on changing a channel might cause a crash, so a different model for implementing the start stop sequences was implemented.

Furthermore, it turns out that for support of the V4 version of the sticks a new version of the library (".dll") is required. Unfortunately, using that library for "older" models (i.e. V3) models of the stick seems the device to make rather "deaf".

So when implementing Qt-DAB for Windows, one chooses between the library support for the V3 or V4 version. Two precompiled versions are available, one with support for the V3 and one with support for the V4 version of the stick.

A separate widget - visible under control of the scan button on the main widget - provides full control on scanning. Qt-DAB provides different scanning modes, with single scannning and continuous scanning.

To allow skipping over given channels when scanning, Qt-DAB supports the notion of a skiptable, in which channels to be skipped can be marked. The show button controls the visibility of the skiptable, skiptables can be loaded and stored in either the ".ini" file (use the "...default" buttons, or can be kept as xml file on a user defined place (the other load/store buttons).

The small table at the bottom of the widget is just for convenience, on scanning it displays the channel name, the ensemble name encountered and the number of services detected in the ensemble.

As mentioned, transmitters (usually) transmit some identifying data, the TII (Transmitter Identification Information) data. Qt-DAB uses a database to map the decoded TII data to name and location of the transmitter.

DAB transmissions are usually transmitted by an SFN (Single Frequency Network), where all transmitters transmit the same content on the same frequency (each with unique TII data). If the DX selector on the configuration and control widget is set, Qt-DAB tries to identify as much as possible transmitters from the SFN and shows them.

The picture shows that in my environment, on channel 12C, the national network, I can identify a couple of different transmitters in the received signal. The left column in the widget shows the transmitter whose data is the data being processed. New is the addition of a "compass" to show the direction from which the signal comes from the selected transmitter.

If the DX mode is set, Qt-DAB-6.8 will save the transmitters that are identified in a text file, in Windows the file in the Qt-DAB-files folder in the home folder, in Linux the file is stored in the Qt-DAB-files folder in the "/tmp" directory. Name of the file is tii-files.txt.

As seen in the table above, distances to the transmitters can be computed. In Qt-DAB the transmitters can be made visible on a map.

Qt-DAB has - on the main widget - a button labeled http, when touched, a small webserver starts that shows the position(s) of the transmitter(s) received on the map. Note that two preconditions have to be met:

• a "home" location has to be known (see the button coordinates);
• the TII database is installed (see the button load table)l

The webbrowser listens to port 8080. By default, the "standard" browser on the system is activated. The configuration and control widget contains a selector for switching this off, so that one might choose one's own browser.

See the manual for entering the home position to Qt-DAB.

An extensive user's guide - in PDF format - for Qt-DAB-6.8 can be found in the "docs" directory in the repository. The manual contains a fairly complete description of the widgets and on configuring for creating an executable (Linux).

For Windows installers can be found in the releases section of this repository

• https://github.com/JvanKatwijk/qt-dab/releases. Such an installer will install the executable as well as required libraries.

ℹ️ The releases section contains 3 Windows installers. One for a 64 bit version, and 2 for a 32 bit version. The 2 versions for 32 bit differ in theit support for RTLSDR type devices. It seems that the support library for the V4 versions of the RTLSDR dongle makes Qt-DAB rather deaf when used with a V3 dongle. The V3 version therefore is equipped with an older version of the support library, and the other version with the library for the V4 version of the dongle. The 64 bit version has support for the V4 stick.

ℹ️ Note that the device libraries for the SDRplay devices and the Adalm Pluto device library are NOT included in the installer, they require - if used - a separate installation. See below for details.

For Linux-x64 systems, an appImage can be found in the releases section of this repository

• https://github.com/JvanKatwijk/qt-dab/releases.

ℹ️ The appImage contains next to the executable Qt-DAB program, the required libraries but not the support libraries for the configured devices. If you want to use a physical device - e.g. a DABstick, an SDRplay, or an AIRspy you need to install the driver libraries for the device as well.

For using an SDRplay device one should download the - proprietary - driver software from the SDRplay site. Note that the "old" 2.13 library does not support the newer SDRPlay device model such as the SDRPlay 1B. the SDRplayDx and the SDRPlay Dx-II. Use the 3.XX library instead. The libraries can be found on the website of SDRplay

• www.sdrplay.com

For using an AIRspy or a Hackrf device, the Ubuntu repository as well as the bullseye repository (for the RPI) provide a working library.

For using an RTLSDR device (a DABstick), the Ubuntu (and bullseye) repositories provide a package. However, using that package one needs the kernel module to be blacklisted, see e.g.

• https://www.reddit.com/r/RTLSDR/wiki/blacklist_dvb_usb_rtl28xxu/

Personally, I prefer to build a version of the library myself, installation is easy, see:

• "https://osmocom.org/projects/rtl-sdr/wiki".

For using the LimeSDR device I went back to the sources and compiled the support library myself, see:

• "https://wiki.myriadrf.org/Lime_Suite".

For installing the support software for the Adalm Pluto I followed the instructions on

• "https://wiki.analog.com/university/tools/pluto/users"

It is strongly advised to use qmake/make for the compilation process, the qt-dab-RC.pro file contains (much) more configuration options than the CMakeLists.txt file that is used with cmake.

Note that the scheme presented below is applied when building the AppImage on Ubuntu 20, and was tested on the "bullseye" system on the RPI. For other distributions (or later Ubuntu versions), names of library packages may be different. Note that in all cases, the development versions (i.e. the versions with the include (".h") files) are required.

For Windows the easiest approach is to install msys/mingw and follow the process as sketched (I use Mingw64 packages on Fedora to cross-compile). Using an MS toolchain on Windows was for me not (yet?) successfull.

• ℹ️ In the repository, the sources for 6.8 are in the subdirectory qt-dab-6.8. The subdirectories contain a *.pro file with configuration information for use with qmake, and a CMakeLists.txt file with configuration information for use with cmake.

• ℹ️ Qt-DAB uses - as the name suggests - the Qt framework, for the time being still the version 5, it uses further the Qwt (version 6.2) library and the gcc compiler suite.

For building the AppImage on Ubuntu 20, I load the required libraries as given below:

• sudo apt-get update
• sudo apt-get install git
• sudo apt-get install cmake
• sudo apt-get install qt5-qmake
• sudo apt-get install build-essential
• sudo apt-get install g++
• sudo apt-get install pkg-config
• sudo apt-get install libfftw3-dev
• sudo apt-get install portaudio19-dev
• sudo apt-get install zlib1g-dev
• sudo apt-get install libusb-1.0-0-dev
• sudo apt-get install mesa-common-dev
• sudo apt-get install libgl1-mesa-dev
• sudo apt-get install libqt5opengl5-dev
• sudo apt-get install libsndfile1-dev
• sudo apt-get install libsamplerate0-dev
• sudo apt-get install libqwt-qt5-dev
• sudo apt-get install qtmultimedia5-dev
• sudo apt-get install qtbase5-dev
• sudo apt-get install libqt5svg5-dev
• sudo apt-get install libcurl4-openssl-dev

Installing cmake is optional, I used it for compiling fdk-aac and the rtlsdr library.

Note that different versions of Ubuntu use a different name for packages, esp. the qwt library

Since - esp. for lower bitrates - libfdk-aac is believed to outperform libfaad in HeAAC decoding, the default in the configuration file is set to fdk-aac. Installing the libfdk-aac library from the repository is

• sudo apt-get install libfdk-aac-dev

• ℹ️ While the libfdk-aac-dev package in both Fedora and Ubuntu 24 seems to work fine, I had some problems with the package from the repository in Ubuntu 20 and 22. For the AppImage, built on Ubuntu 20, a library version was created from the sources to be found as github repository:

• "https://github.com/mstorsjo/fdk-aac"

The sources contain a CMakeLists.txt file, building and installing is straightforward.

Alternatively, one could configure for libfaad, change the configuration to

• CONFIG += faad
• #CONFIG += fdk-aac

and install the libfaad package

• sudo apt-get install libfaad-dev

Qt_DAB-6.8 allows selection between two audio subsystems, i.e. portaudio and Qt_Audio. It turns out that Qt_Audio does not work well on Ubuntu 20 (it does on Fedora and Ubuntu 24 though). Since the AppImage is built on Ubuntu 20, selecting the Qt_Audio subsystem is ignored.

While there are dozens of configuration options, take note of the following ones:

• ℹ️ If compiling on/for an x86_64 PC choose CONFIG += PC, choose CONFIG+=NO_SSE otherwise. When choosing CONFIG += PC the software will then use SSE instructions to speed up some computations.

• ℹ️ Choose between CONFIG += single or CONFIG += double. In the latter case, all computations in the "front end" are done with double precision arithmetic.

• ℹ️ Devices like SDRplay, AIRspy, RTLSDR dongle, LimeSDR, HackRf and Adalm Pluto can be included in the configuration even if no support library is installed. (Note that including Soapy requires Soapy libraries to be installed, so this does not apply for Soapy). Qt-DAB is designed such that on selecting a device in runtime, the required functions from the device library are linked in.

• ℹ️ The Soapy library used in Ubuntu 20 (used for building the AppImage) seems incompatible with Soapy libraries installed on other versions of Ubuntu and other Linux distributions, therefore Soapy is NOT configured for inclusion in the AppImage.

• ℹ️ Choosee CONFIG += tiiLib rather than CONFIG += preCompiled (see step 4), CONFIG+=preCompiled will NOT work since the required sources are NOT open source and not included in the source tree.

• ℹ️ Uncomment the line DEFINES += __THREADED_BACKEND if you intend to have more than one backend running simultaneously. E.g. activating the automatic search for an EPG service starts a separate service if such a service is found. With this setting each backend will run in its own thread.

Run qmake (variants of the name are qt5-qmake, qmake-qt5) which generates a Makefile and then run make. Compiling may take some time. Use make -j XX for speeding up the build process, with XX the amount of parallel threads used. Of course, qmake will complain if not all required libraries can be found.

The repository contains in the subdirectory library a shared library libtii-lib.so for use on an x86_64 PC, that - when installed in e.g. /usr/local/lib - supports loading fresh instances of the database.

Otherwise, unpack the file tiiFile.zip, and copy the resulting file .txdata.tii to the home directory (home folder). (The unpacked file contains a copy of the database for finding the transmitter's name and location.) Identifying transmitters using TII data will work, but no database update can be performed.

If Qt-DAB does not see the database, it will just function without mapping TII data onto names and locations.

ℹ️ Building a version on a fresh install of "bullseye" on the RPI gave a version that wouldn't run: The Qt_PLUGIN_PATH was not set. Setting it as given below solved - for me - the problem:

	Qt_5= /usr/lib/arm-linux-gnueabihf/qt5
	export QT_PLUGIN_PATH=$Qt_5/plugins

While it is known that the DAB transmissions are now all in Band III, there might be situations where it is desirable to use other frequencies. Qt-DAB provides (Unix/Linux builds only) the opportunity to specify one's own band. Specify in a file a list of channels, e.g.

one	227360
two	220352
three	1294000
four	252650

and pass the file on program start-up with the -A command line switch. The channel name is just any identifier, the channel frequency is given in kHz. Your SDR device obviously has to support the frequencies for these channels.

Clemens Schmidt, author of the QiRX program (https://qirx.softsyst.com/) and me defined a format for storing and exchanging "raw" data: .xml-files for easier echange of recordings. Such an xml file contains in the first bytes - up to 5000 - a description in xml - as source - of the data contents. This xml description describes in detail the coding of the elements.

As an example, a description of data obtained by dumping Airspy input:

   <?xml version="1.0" encoding="utf-8"?>
   <SDR>
     <Recorder Name="Qt-DAB" Version="6.X"/>
     <Device Name="AIRspy" Model="I"/>
     <Time Value="Wed Dec 18 12:39:34 2019" Unit="UTC"/>
     <!--The Sample information holds for the whole recording-->
     <Sample>
       <Samplerate Value="2500000" Unit="Hz"/>
       <Channels Bits="12" Container="int16" Ordering="LSB">
         <Channel Value="I"/>
         <Channel Value="Q"/>
       </Channels>
     </Sample>
     <!--Here follow one or more data blocks-->
     <Datablocks>
       <Datablock Number="1" Count="375783424" Unit="Channel">
         <Frequency Value="227360" Unit="KHz"/>
         <Modulation Value="DAB"/>
       </Datablock>
     </Datablocks>
   </SDR>

The device handlers in Qt-DAB support both generating and reading such an .xml file.

While the current implementation for reading such files is limited to a single data block, the reader contains a cont button that, when touched while playing the data, will cause continuous playing of the data in the data block.

The picture shows the reader when reading a file, generated from raw data emitted by an AIRspy device.

Copyright (C)  2016 .. 2024
Jan van Katwijk (J.vanKatwijk@gmail.com)
Lazy Chair Computing

Copyright of libraries used - Qt-DAB, qwt, fftw, portaudio,
libsndfile. libsamplerate, ;ibusb-1, libfaad, libfdk-aac,
- is gratefully acknowledged.

Qt-DAB is distributed under e GPL V2 library,  in the hope that
it will be useful, but WITHOUT ANY WARRANTY; without even the
implied warranty of MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.  See the GNU General Public License for
more details.