qt-dab is a software dab decoder for use with a dabstick, airspy or sdrplay for RPI and PC
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Qt-DAB Build Status

Qt-DAB is a Software for Windows, Linux and Raspberry Pi for listening to terrestrial Digital Audio Broadcasting (DAB and DAB+). It is the successor of both DAB-rpi and sdr-j-DAB, two former programs by the same author.

Table of Contents


  • DAB (mp2) and DAB+ (HE-AAC v1, HE-AAC v2 and LC-AAC) decoding
  • MOT SlideShow (SLS)
  • Dynamic Label (DLS)
  • Both DAB bands supported:
    • VHF Band III
    • L-Band (only used in Czech Republic and Vatican)
  • Spectrum view (incl. constellation diagram, impulse response, NULL symbol)
  • Scanning function (scan the subsequent channels in the selected band until a channel is encountered where a DAB signal is detected)
  • Detailed information for selected service (SNR, bitrate, frequency, ensemble name, ensemble ID, subchannel ID, used CUs, protection level, CPU usage, program type, language, 4 quality bars)
  • Automatic display of TII (Transmitter Identification Information) data when transmitted
  • Dumping of the complete DAB channel (Warning: produces large raw files!) into * sdr files and playing them again later
  • Saving audio as uncompressed wave files
  • Saving the ensemble content (audio and data streams, including almost all technical data) into a text file
  • Supports various inputs from
    • SDRplay (both RSP I and RSP II),
    • Airspy, including Airspy mini,
    • SDR DAB sticks (RTL2838U or similar), and
    • HACKRF One, and
    • prerecorded dump (*.raw, *.iq and *.sdr)

Not (Not yet or partly) implemented:

  • DMB (Audio and Video)
  • TPEG: when configured, TPEG messages are being sent to a TCP port; sources for a simple client are part of the source distribution.
  • EPG: when configured, the EPG decoding will generate so called EHB files.
  • Journaline (an untested Journaline implementation is part of the sources).
  • ip output: when configured the ip data - if selected - is sent to a specificied ip address (default:
  • Other bands than used for terrestrial broadcasting in Europe (like DAB over cable)


Qt-DAB with sdrplay input

Qt-DAB-2.0 is an implementation of a DAB decoder for use on Linux and Windows based PC's, including some ARM based boards, such as the Raspberry PI, both 2 and 3.

Beside to Qt-DAB, there exists a "light" version, dabradio, an SDRPlay-specific version sdrplayDab and a command-line based version. All three versions with a GUI are implemented in C++, using the Qt framework for the implementation of the GUI. The command-line version is implemented using C++, and does not depend on Qt.

dabradio, sdrplayDab and the Qt-free version, dab-cmdline the "command-line only", version have their own repository on Github.

The Qt-DAB and the dab-cmdline version both support decoding of terrestrial DAB and DAB+ reception from either an AIRSPY, an SDRplay, the HACK RF, or a dabstick (rtl_sdr). The sdrplayDab version is tightly couples to the SDRplay device.

Beside to these C++ based versions, (slightly limited) versions are implemented in Java and Ada, both with their own repository on Github.

The Qt-DAB version also supports input from an rtl-tcp server (see osmocom software) and pre-recorded files (*.sdr, *.iq and *.raw). Obviously there is a provision for dumping the input into an (*.sdr)-file.

Note that if the rtl_tcp server is used as input device, the connection needs to support the inputrate, i.e. 2,048,000 I/Q samples (i.e. 2 * 2,048,000 bytes/second).

Since the Qt-DAB version has to run on a headless RPI 2/3, using the home WiFi, the resulting PCM output can be sent - if so configured - to a TCP port (Sources for a small client are part of the source distribution).

For further information please visit http://www.sdr-j.tk

Some settings are preserved between program invocations, they are stored in a file .qt-dab.ini, to be found in the home directory. See Comment on some settings for more details.

Widgets and scopes

The picture below shows Qt-DAB's main window, with the (few) control buttons, and 5 other widgets

  • a widget with controls for the attached device,
  • a widget showing the technical information of the selected service,
  • a widget showing the spectrum of the received radio signal and the constellation of the decoded signal,
  • a widget showing the spectrum of the NULL period between successive DAB frames,
  • and a widget showing the response(s) from different transmitters in the SFN.

While the main window and the widget for the device control are always shown, each of the others is only shown when pushing a button on the main window. In case a widget is invisible (i.e. not selected), the software to generate a spectrum is bypassed, so not to waste CPU power.

Qt-DAB with SDRplay input


Windows releases can be found at https://github.com/JvanKatwijk/qt-dab/releases. The software is packed in a zipped folder, (windows-bin.zip). The folder - after unpacking - contains the executable (and other executables) as well as the libraries to run the software.

If you want to compile it by yourself, please install Qt through its online installer, see https://www.qt.io/

Ubuntu Linux

If you are not familar with compiling then please continue reading by jumping to chapter appImage which is much easier for Linux beginners.

Ubuntu 16.04 (and on) have good support for Qt5 and qwt (compiled for Qt5). For generating an executable under Ubuntu (16.04 or newer), you can put the following commands into a script. (For Ubuntu 14.04 look into the package manager for Qt4 packages)

  1. Fetch the required components

    sudo apt-get update
    sudo apt-get install qt5-qmake build-essential g++
    sudo apt-get install libsndfile1-dev qt5-default libfftw3-dev portaudio19-dev 
    sudo apt-get install libfaad-dev zlib1g-dev rtl-sdr libusb-1.0-0-dev mesa-common-dev
    sudo apt-get install libgl1-mesa-dev libqt5opengl5-dev libsamplerate0-dev libqwt-qt5-dev
    sudo apt-get install qtbase5-dev
  2. Fetch the required libraries

a) Assuming you want to use a dabstick (also known as rtlsdr) as device, fetch a version of the library for the dabstick

 git clone git://git.osmocom.org/rtl-sdr.git
 cd rtl-sdr/
 mkdir build
 cd build
 sudo make install
 sudo ldconfig
 cd ..
 rm -rf build
 cd ..

b) Assuming you want to use an Airspy as device, fetch a version of the library for the Airspy

sudo apt-get install build-essential cmake libusb-1.0-0-dev pkg-config
wget https://github.com/airspy/host/archive/master.zip
unzip master.zip
cd airspyone_host-master
mkdir build
cd build
sudo make install
sudo ldconfig

Clean CMake temporary files/dirs:

cd host-master/build
rm -rf *

Note that in order for the libraries to be effective, ensure that

a) the path /usr/local/lib is in the load library paths (i.e. it is named in one of the .conf files in the etc/ld.so.conf directory

b) a file exists in the /etc/udev/rules.d directory describing the device, allowing "ordinary" users to access the device.

  1. Get a copy of the Qt-DAB sources
git clone https://github.com/JvanKatwijk/qt-dab.git
cd qt-dab
  1. Edit the qt-dab.pro file for configuring the supported devices and other options. Comment the respective lines out if you don't own an Airspy (mini) or an SDRplay.

4.a. Check the installation path to qwt. If you were downloading it from http://qwt.sourceforge.net/qwtinstall.html please mention the correct path in qt-dab.pro file (for other installation change it accordingly):

INCLUDEPATH += /usr/local/include  /usr/local/qwt-6.1.3

4.b. If you are compiling on/for an RPI2 device, you might want to uncomment the line DEFINE+=THREADED_BACKEND. This will cause a better load balance on the cores of the processor.

4.c. If you are compiling on/for a Linux x64 based PC, you might want to select to uncomment


This will cause the SSE instructions to be used in some parts of the implementation. If you are compiling on/for an RPI2 with Stretch (or comparable system), you might want to uncomment


and if you are compiling on/for an RPI3 with Stretch (or comparable system), you might want to uncomment


If unsure, uncomment only



  1. Build and make
qmake qt-dab.pro

You could also use QtCreator, load the qt-dab.pro file and build the executable.

Remark: The executable file can be found in the sub-directory linux-bin. A make install command is not implemented.

Configuring using the qt-dab.pro file

Options in the configuration are:

a) select or unselect devices

b) select the output: soundcard or TCP connection

c) select or unselect basic MSC data handling

Adding or removing from the configuration is in all cases by commenting or uncommenting a line in the configuration file.

Comment the lines out by prefixing the line with a # in the qt-dab.pro file (section "unix") for the device(s) you want to exclude in the configuration. In the example below, rtl_tcp (i.e. the connection to the rtlsdr server) won't be used.

CONFIG          += dabstick
CONFIG          += sdrplay
#CONFIG          += rtl_tcp
CONFIG          += airspy

In the Windows configuration one may also choose

CONFIG		+= extio

for use with (appropriate) extio handlers

Remark: Input from pre-recorded files (8 bit unsigned *.raw and *.iq as well as 16-bit wav *.sdr files) is configured by default.

Audio samples are - by default - sent to an audio device using the portaudio library. Two alternatives are available:

For selecting the output to be sent to a TCP port, uncomment

#CONFIG         += tcp-streamer         # use for remote listening

The source tree contains a directory sound-client, that contains sources to generate a simple "listener" for remote listening.

For selecting the output to be handled by the Qt system (default device only) uncomment

#CONFIG		+= qt-audio

For basic MSC data handling, i.e. MOT handling etc, uncomment

DEFINES         += MSC_DATA__           # use at your own risk

An experimental configuration parameter is

CONFIG		+= try_epg

If try_epg is configured then EPG (Electronic Program Guide) data will be written to *.xml files. Please select the service carrying EPG data.

If you are compiling/running for an x64 based PC with SSE, then you could set

#CONFIG          += NEON_RPI2
#CONFIG          += NEON_RPI3
CONFIG          += SSE
#CONFIG          += NO_SSE

If you are compiling/running for an RPI2, and want to check whether or not NEON instructions can be used, you could set

CONFIG          += NEON_RPI2
#CONFIG          += NEON_RPI3
#CONFIG          += SSE
#CONFIG          += NO_SSE

If you are compiling/running for an RPI3, and want to check whether or not NEON instructions can be used, you could set

#CONFIG          += NEON_RPI2
CONFIG          += NEON_RPI3
#CONFIG          += SSE
#CONFIG          += NO_SSE

The safest way is - always - to set

#CONFIG          += NEON_RPI2
#CONFIG          += NEON_RPI3
#CONFIG          += SSE
CONFIG          += NO_SSE

Configuring using CMake

The CMakeLists.txt file has all devices and the spectrum switched off per default. You can select a device (or more devices) without altering the CMakeLists.txt file, but by passing on definitions to the command line.

An example:


will generate a makefile with support for

a) the RTLSDR (dabstick) device,

b) for the remote dabstick (using the rtl_tcp connection) and

c) for the spectrum in the configuration.

Other devices that can be selected (beside dabstick and rtl_tcp) are sdrplay, HackRF and airspy. Use -DHACKRF=ON, -DSDRPLAY=ON, or -DAIRSPY=ON after the cmake command if you want to configure them.

The default location for installation depends on your system, mostly /usr/local/bin or something like that. Set your own location by adding

-DCMAKE_INSTALL_PREFIX=your installation prefix

For other options, see the CMakeLists.txt file.

Important: Note that CMakeLists.txt file expects the appropriate Qt version (and - if configured - the qwt library) to be installed.


The current set of sources provides support for both the RSP-I and the RSP-II. Due to an incompatibility between libraries 2.13 and older versions, be certain to have at least 1.13 installed.


The software uses the Qt library and - for the spectrum and the constellation diagram - the qwt library.

The CMakeLists.txt assumes Qt5. If you want to use Qt4, and you want to have the spectrum in the configuration, be aware of the binding of the qwt library (i.e. Qt4 and a qwt that uses Qt5 does not work well).

Raspberry PI

The Qt-DAB software runs pretty well on the author's RPI-2. The average load on the 4 cores is somewhere between 50 and 60 percent.

One remark: getting "sound" is not always easy. Be certain that you have installed the alsa-utils, and that you are - as non-root user - able to see devices with aplay -L

In arch, it was essential to add the username to the group "audio".

The most recent distribution of Raspbian Stretch (i.e. August 2017) supports both Qt5 and a qwt compiled against Qt5.

A (slightly experimental) AppImage is available (see the releases section) developed under and to be used for Raspbian Stretch. Note that the repositories for Raspbian Stretch contain libraries for the rtlsdr Dabsticks and the Airspy, while the API library for the SDRplay can be downloaded from sdrplay.com. So, Qt-DAB can be used without the need for compiling anything.

The AppImage version does not contain the spectrum - I am using it in a headless environment.

Since Raspbian Stretch is a Debian derivate, the description for creating a version under Ubuntu applies.

appImage for x64 Linux systems

https://github.com/JvanKatwijk/qt-dab/releases contains a generated appImage, Qt-DAB-x64.Appimage, which is created on Ubuntu 14.04 (Trusty), and uses Qt4 (so it basically should run on any x-64 based linux system that isn't too old.).

It assumes that you have installed an appropriate usb library, libraries to support either a dabstick (i.e. rtlsdr) or an Airspy are included in the appImage (the appropriate udev rules, i.e. rules to allow a non-root user to use the device through USB, will be installed by the execution of the appImage, that is why it will ask for your password. If you have installed the device of your choice on your system, you can just cancel this request).

If you want to run with an SDRplay, follow the installation instructions for the library from http://www.sdrplay.com . All further dependencies are included.

The appImage is just a self-contained single file which you have to make executable in order to run.

It furthermore contains an (experimental) appImage for use under Stretch on an RPI2/3, Qt-DAB-ARM.AppImage.

All further dependencies are included

For more information see http://appimage.org/

Comment on some settings

Some values of settings are maintained between program invocations. This is done in the (hidden) file .qt-dab.ini in the user's home directory.

Some settings are not influenced by buttons or sliders of the GUI, they will only change by editing the .ini file.

Typical examples are

saveSlides=1 when set to 0 the slides that are attached to audio programs will not be saved. If set to 1 the slides will be saved in a directory /tmp/qt-pictures (Linux) or in %tmp%\qt-pictures (Windows).

picturesPath defines the directory where the slides (MOT slideshow) should be stored. Default is the home directory.

showSlides=1 when set to 0 the slides will not be shown.

has-presetName=1 when set the name of the selected service - that is selected when closing down the program - is kept and at the next invocation of the program, an attempt is made to start that particular service. The name of the service is kept as presetname=xxxx

The background colors of the spectrum can be changed by setting


The Qt-DAB program searches - if available - for TII (transmitter identification information) data in the FIC. If TII data is available, the small label at the bottom of the Technical Details widget will color green, and the main ID if the transmitters is shown. Also the list of geographical positions of the transmitters of the SFN is printed on the terminal. If the identification of the transmitter received can be decoded, it will be shown at the bottom line of the Technical Data Widget.

The periodicity of the search for the data defining the position of the transmitter received can be set by adding a line to the .qt-dab.ini file


where xxx is the number of seconds. Default of the delay is 20 seconds.

A note on intermittent sound

In some cases, in some periods of listening, the sound is (or at least seems) interrupted. There are two different causes for this:

First of all the incoming signal is weak and audio packages do not pass the many controls that are executed. This shows in the widget "technical data", not all the colored bars at the bottom are 100 percent green. An audio package represents 24 milliseconds of audio, loss of a few packages leads to an interruption of the sound.

A second reason has to do with system parameters. Too small a buffersize in the audio driver causes too high a frequency of calls to a callback function. In Linux this shows by an underrun reported by the alsa sound system. The buffer size can be set (in multiples of 256 audio samples) by the value of "latency" in the .ini file. The default value is 1.

On my RPI 2 - with Stretch - latency=2 works best.


Copyright (C)  2013, 2014, 2015, 2016, 2017, 2018
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
GNU General Public License for more details.