Qt-DAB-4 and Qt-DAB-5 is software for Linux, Windows, MacOS and Raspberry Pi for listening to terrestrial Digital Audio Broadcasting (DAB and DAB+).
Table of Contents
- Widgets and scopes
- Installation on Windows
- Installation on Linux x64
- Interfacing to another SDR device
- Using user-specified bands
- xml-files and support
- Differences between Qt-DAB 4 and 5
- Showing a map for TII
- Notes on building an executable
Qt-DAB-XX is a rich implementation of a DAB decoder for use on Linux and Windows based PCs, including some ARM based boards, such as the Raspberry PI 2 and up. It can be used with a variety of SDR devices, including DABsticks, all models of the SDRplay, Airspy etc.
Precompiled versions for Linux-x64 (AppImage) and Windows (an installer) are available.
Thanks to Richard Huber, Qt-DAB can be compiled on the Mac.
- DAB (mp2) and DAB+ (HE-AAC v1, HE-AAC v2 and AAC-LC) decoding
- MOT SlideShow (SLS)
- Dynamic Label (DLS) and the possibility of saving dynamic Labels - augmented with channel and time info - in a file,
- Both DAB bands (and user defined bands) are supported:
- VHF Band III (default),
- L-Band (obsolete now),
- a user defined Band
- Modes I, II and IV (Mode I default, Modes II and IV obsolete, but can be set in the
- Views on the signal: spectrum view incl. constellation diagram, correlation result, TII spectrum and the SNR over time,
- automatic reconfiguration of services,
- Detailed information on reception and selected service (SNR, bitrate, frequency, ensemble name, ensemble ID, subchannel ID, used CUs, protection level, CPU usage, program type, language, alternative FM frequency if available, 4 quality bars),
- If configured, the TII data is mapped upon a transmitter's name, and display of TII (Transmitter Identification Information) data when transmitted,
- Possibility of displaying a map with position(s) of received transmitter(s),
- Presets for easy switching of programs in different ensembles (see section Presets),
- Dumping of the input data of the DAB channel (Warning: produces large raw files!) into
.xmlfile formats and playing them again later (see section on xml format),
- Saving audio as uncompressed wave files, and Saving aac frames from DAB+ services for processing by e.g. VLC,
- Saving the ensemble content description: audio and data streams, including almost all technical data into a text file readable by e.g LibreOfficeCalc
- Advanced scanning function (scan the band, show the results on the screen and save a detailed description of the services found in a file),
- ip output: when configured the ip data - if selected - is sent to a specified ip address (default: 127.0.0.1:8888),
- TPEG output: when configured the data is sent to a specified ip address,
- EPG detection and building up a time table,
- Supports as input device:
- SDR DAB sticks (RTL2838U or similar),
- HACKRF One,
- Airspy, including Airspy mini,
- SDRplay (RSP I, RSP II, RSP Duo and RSP Dx), with separate entries for v2 and v3 library
- Adalm Pluto,
- Soapy (experimental, Linux only),
- ExtIO (experimental, Windows only),
- rtl_tcp servers.
- Always supported input from:
- prerecorded dump (
- prerecorded dump (
- Clean device interface, easy to add other devices.
- Scheduling the start of (channel:service) pairs or operations as frame dump or audio dump, even for days ahead.
- Showing the name of the transmitter received as well as the distance to the receiver and the azimuth.
- background services. Since 4.351 it is possible to run an arbitrary number of DAB+ audioservices (from the current ensemble) as background service with the output sent to a file.
- TPEG: when configured, TPEG messages are being sent to a TCP port; sources for a simple client are part of the source distribution.
- Journaline (an untested Journaline implementation is part of the sources).
- Other bands than used for terrestrial broadcasting in Europe (like DAB over cable)
qt-dab-4 and qt-dab-5, (almost) same functionality, different GUI
Qt-DAB is in two versions, a version 4 and a version 5.
The basic idea behing Qt-5 is to limit the number of controls on the main widget and shift everything, not needed for simple interaction to the configuration widget (which is now called configuration and control) Both versions of Qt-DAB are built from (mostly) the same set of sources, the GUI and the software interfacing the GUI to the rest of the program.
dabMini, i.e. the small version for just listening to a service, is obsolete, the source can be found as subdirectory in the "obsolete" directory.
Of course, the configuration and control widget in Qt-DAB-5 is larger and contains more settings than the configuration and control widget for Qt-DAB-4.
Since the Qt-DAB-5 main widget shows the station labels (if any), the option - available in Qt-DAB-4 - for displaying the station labels on a separate widget is not needed.
The functionality of the versions is (almost) the same, version 5.1 has (most users will not use it though) the possibility of generating "eti" files. If there is serious interest for adding the feature to the Qt-DAB-4 interface, then let me know.
The Qt-DAB-5.2 version has a slightly modified "technical window", it now contains a small spectrum display of the audio output. Both versions have additional the audiorate of the audio service (note that all rates are converted into an audiorate of 48000), and the success percentage of the audio.
In the versions 5.3 and 4.6 the spectrum scope now shows - next to the spectrum of the data in the selected channel, the waterfall of the spectrum and - in the time domain - the border between the NULL period and the first data block.
The right hand side numbers give some information on the (quality) of the signal. In the "ideal" signal, the constellation diagram shows 4 dots, one in each quadrant, in general, the signal will be less ideal. The "std deviation" indicator tells the standard deviation of the dots in the conestallation diagram. Lower is better.
A note on showing a map
Since some time the Qt-DAB versions have a button labeled http, when touched, a small webserver starts that can show the position(s) of the transmitter(s) received on the map.
By default, on starting the server, the "standard" browser on the system will be invoked, listening to port 8080. The configuration (configuration/control) widget contains a selector for switching this off, so that one might choose his/hers own browser.
The feature will not work if
- handling the TII database is not installed on the system, and/or
- you did not provide your "home" coordinates.
The latter is easily done by touching the button "coordinates" on the configuration (configuration/control) widget.
Building an executable for qt-dab: a few notes
While for Linux-x64 and Windows there are precompiled versions, there may be reasons to build an executable. Building an executable is not very complicated, it is described in detail in the manual. Since it is customary to avoid reading a manual, here are the basic steps for the build process.
ℹ️Note that the sources for 4.4.x are now in the subdirectory
qt-dab-s4and for qt-dab-5.x in the subdirectory
- Install required libraries, see section 5.5.3 (page 29) of the manual for 4.4.
- :infoirmation: It turns out that in recent versions of Debian (and related) distributions the lib
qt5-defaultdoes not exist as as separate library.
- It seems to be part of another of the qt5 packages that is installed.
- Be aware that different distributions store qt files on different locations, adapt the INCLUDEPATH setting in the
.profile if needed.
While there are dozens of configuration options, take note of the following ones:
Note on configuring DABsticks (i.e. RTLSDR type devices). The Windows support library does not seem to be able to handle continuous closing and opening the device, something that normally is done on changing a channel. Therefore separate versions of the RTLSDR interface library is made, one special for Windows, and a normal one for Linux.
For including "soapy" in the configuration, soapy software should have been installed, so leave them commented out when not available. iF
For X64 PC's one may choose the option
CONFIG+=PC (for selecting SSE instructions). If unsure, use
For letting the software show the transmitter and the azimuth, choose
CONFIG += tiiLib (see step 4).
qmake (variants of the name are
qmake-qt5) which generates a
Makefile and then run
.txdata.tii (which contains the database data for finding the transmitter's name and location) from
tiiFile.zip into the user's home directory. If Qt-DAB cannot find the file, it will just function without showing the names and without "maps" option.
If running on an x64 PC or bullseye on the RPI you might consider to install
curl to be installed and source code for
libtii-lib.so is not free.
libtii-lib.so contains functionality for uploading a new database version (the "load" button on the configuration widget). If Qt-DAB cannot find the library, it will just function without the additional functionality.
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
Widgets and scopes for Qt-DAB
Qt-DAB always shows a main widget; a number of optional widgets is visible under user control.
Apart from the widgets, already shown, there are
- a configuration widget (V4) or a configuration and control widget (V5)
- a widget with controls for the attached device,
- a widget showing the spectrum of the NULL period between successive DAB frames from which the TII is derived,
- a widget showing the correlations response(s) from different transmitters in the SFN,
- a widget showing the development - over time - of the SNR,
- if configured and data is detected, the time table for the current audio service
Another widget shows when running a scan; the widget shows the contents of the ensembles found in the selected channels. Since 3.5 the possibility exists to save a detailed description of the services in the different channels, in a format easy to process with LibreOffice or comparable programs (a
Depending on a setting in configuration widget, a logo or slide, transmitted as Program Associated Data with the audio transmission, will be shown here or on a separate widget.
An extensive user's guide - in PDF format - for the 4.4 version can be found in the "docs" section of the source tree. The documentation contains a complete description of the widgets, of the values in the
.ini file, on configuring for creating an executable (Linux), and even a complete description on how to add a device to the configuration.
Installation on Windows
For Windows an installer can be found in the releases section, https://github.com/JvanKatwijk/qt-dab/releases. The installer will install the executable as well as required libraries.
The installer will also call the official installer for the dll implementing the 2.3 api for getting access to the SDRplay devices.
Installation on Linux-x64
For Linux-x64 systems, an appImage can be found in the releases section, http://github.com/JvanKatwijk/qt-dab/releases. The appImage contains next to the executable qt-dab program, the required libraries.
Of course it is possible to generate an executable, the manual contains a complete script for Ubuntu type Linux versions.
Interfacing to another SDR device
There exist - obviously - other devices than the ones supported here. Interfacing another device is not very complicated, it might be done using the Soapy interface, or one might write a new interface class.
A complete description of how to interface a device to Qt-DAB is given in the user's manual.
Using user specified bands
While it is known that the DAB transmissions are now all in Band III, there are situations where it might is desirable to use other frequencies. Specify in a file a list of channels, e.g.
jan 227360 twee 220352 drie 1294000 vier 252650
and pass the file on 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.
xml-files and support
Clemens Schmidt, author of the QiRX program (https://qirx.softsyst.com/) and me defined a format for storing and exchanging "raw" data:
.xml-files. Such a 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="3.2-Beta"/> <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 the generation of such an
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 the HackRF device.
Copyright (C) 2016 .. 2022 Jan van Katwijk (J.vanKatwijk@gmail.com) Lazy Chair Computing The Qt-DAB software is made available under the GPL-2.0. The SDR-J software, of which the Qt-DAB software is a part, is distributed 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.