Qt-DAB-3.3 is 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.

• Introduction
• Features
• Widgets and scopes
• Presets
• History
• Comment on some settings
• Obsolete properties
• Installation
  • Windows
  • Ubuntu Linux
    • Configuring using the qt-dab.pro file
    • Configuring using CMake
    • Qt
  • Raspberry PI
  • appImage for x64 Linux systems
• Interfacing to another device
• New in Qt-DAB 3.3
• Using other bands than Band III or L Band
• xml-files and support
• Copyright

Qt-DAB-3.3 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.

Some other programs are derived from the sources of Qt-DAB, a "light" version dabradio, an SDRPlay-specific version sdrplayDab, a command-line based version and a stand-alone server version dab-server. The versions with a GUI are implemented in C++, using the Qt framework for the implementation of the GUI. The command-line version dab-cmdline and the dab-server are implemented using C++, and do not depend on Qt.

The dab-server can be installed to run as a "service" on e.g. an RPI, with control - over a bluetooth connection - from an "app" on an Android tablet.

Furthermore, for DX purposes, a dab-scanner is implemented that allows for a continuous scanning of selected channels in a given band. Results are written in a txt file, formatted for use with LibreOffice Calc and comparable programs.

dabradio, sdrplayDab, the dab-scanner and the Qt-free versions dab-cmdline and the dab-server have their own repository on Github.

Qt-DAB-3.3 also supports file input, from pre-recorded files (*.sdr, *.iq and *.raw) and on the aforementionedxml files. Obviously there is a provision for dumping the input into an (*.sdr)-file and - for most configured devices - as xml file.

Finally, Qt-DAB supports input from an rtl_tcp server, if such 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 program 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).

See also the section of configuring Qt-DAB

The picture on top shows Qt-DAB's main window and the other 5 optional widgets:

• a widget with controls for the attached device,
• a widget showing the technical information of the selected service as well as some information on the quality of the decoding,
• 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 from which the TII is derived,
• and a widget showing the response(s) from different transmitters in the SFN,

Another - a sixth - widget shows when running a scan; the widget will show the contents of the ensembles found in the selected channel.

While the main window is always shown, visibility of the others is under user control, the main widget contains a button for each of those.

The buttons and other controls on the main widget are equipped with tool tips briefly explaining the (in most cases obvious) function of the element. (The tooltip on the copyright label shows (a.o) the date the executable was generated.)

The elements in the left part of the widget, below the list of services, are concerned with selecting a channel and service.

To ease operation the channel selector is augmented with a "-" and a "+" button for selecting the previous resp. next channel.

To ease selection of a service, a second pair of "-" and "+" buttons is available, now for selecting the previous resp. the next service on the list.

Different from previous versions is that now some information, previously shown on the "technical data" widget is now shown on the main widget.

Some data on the selected service - if any - is to be found on a separate widget. This widget will show where the data for the service is to be found in the DAB frames, and how it is encoded.

Furthermore, if the service is accompanied by a logo, that logo will be shown here.

The further selectors are concentrated on the bottom part of the right side of the widget. Buttons to make scopes visible, to store input and or output into a file, to select input device and the audio and to scan and store a description of the ensemble are in that section.

During scanning, a separate window will be shown with the results of the scan as shown in the picture.

• 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 (default),
  • L-Band (only used in Czech Republic and Vatican) (see "obsolete properties")
• Modes I, II and IV (Mode I default, oter modes can be set in the ".ini" file)
• Spectrum view (incl. constellation diagram, correlation result, TII spectrum)
• Scanning function (scan the band and show the results on the screen)
• 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)
• Detailed information for other services by right-clicking on their name (bitrate, subchannel ID, used CU's protection level, program type)
• Automatic display of TII (Transmitter Identification Information) data when transmitted
• Presets for easy switching of programs in different ensembles (see Presets)
• Dumping of the complete DAB channel (Warning: produces large raw files!) into * sdr files and playing them again later
• Dumping the input in the aforementioned xml format
• Saving audio as uncompressed wave files
• Saving aac frames from DAB+ services for processing by e.g. VLC
• Saving the ensemble content (description of audio and data streams, including almost all technical data) into a text file readable by e.g LibreOfficeCalc
• ip output: when configured the ip data - if selected - is sent to a specificied ip address (default: 127.0.0.1:8888)
• TPEG output: when configured the data is sent to a specified ip address
• Supports inputs from
  • SDRplay (both RSP I and RSP II), with separate entries for v2 and v3 library
  • Airspy, including Airspy mini,
  • SDR DAB sticks (RTL2838U or similar),
  • HACKRF One,
  • limeSDR,
  • Soapy (experimental, Linux only),
  • prerecorded dump (*.raw, *.iq and *.sdr),
  • xml format files, and
  • rtl_tcp servers
• Clean interface to add other devices, see below.

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

A preset selector is available to store and retrieve "favorit" services. Note that the services are encoded as "channel:serviceName" pair: it sometimes happens that a service appears in more than one ensemble (as example the "Omroep West" service appears in channels 5B and 8A.)

The presets are stored in an xml file, `.qt-dab-presets.xml'.

Qt-DAB-3.3 saves all service names found. Pairs Channel:serviceName will be made (in)visible when touching the appropriate button (the one labeled with "xx").

The data in stored in a file in xml format. The history can be cleared by a click of the right mouse button, clicking on a channel:servicename combination with the left mouse button will cause the QT-DAB software to attempt to set the channel and select the name.

Some settings are preserved between program invocations, they are stored in a file .qt-dab.ini, to be found in the home directory. Settings maintained between program invocations are typically the name of the device used, the channel that was used, the name of the service last used etc.

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

displaycolor=blue
gridcolor=red

If one uses the rtl_tcp handler, the default value for the "port" is 1234, a port can be set in the ".ini" file by setting

rtl_tcp_port=xxx

In selecting a service from the presetlist that resides on another channel implies switching to that channel and waiting until the ensemble in that channel is recognized. The duration of the delay can be specified by setting

switchTime=xxx

where xxx is the amount of milliseconds

The result of the correlation is shown ny the correlation viewer. The correlation takes place on the first datablock of a DAB frame, and if the estimation of the end of the null period is correct, the maximum in the correlation is 504. Since for DAB a single frequency network is used, in general more than one transmitter is received and there are more "peaks" in the correlation. The distance between the peaks is in units of 1/2048000 seconds. While the correlationviewer by default shows the correltion result of the first 1000 samples, this may be reduced by setting

plotLength=xxx

where xxx is the number of samples taken into account.

The current DAB standard eliminated the support for Modes other than Mode 1 and Bands other than VHF Band III. The Qt-DAB implementation still supports these features, however, since they are obsolete, there are no controls on the GUI anymore (the control for the Mode was already removed from earlier versions).

Explicitly setting the Mode and/or the Band is possible by including some command lines in the ".qt-dab.ini" file.

For the Mode, one will add/set a line

dabMode=Mode x, where x is either 1, 2 or 4

For the Band, one will add/set a line

dabBand=band, where band is either VHF Band III or L_Band

For windows an installer is to 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 api for getting access to the SDRplay devices.

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
 cmake ../ -DINSTALL_UDEV_RULES=ON -DDETACH_KERNEL_DRIVER=ON
 make
 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
cmake ../ -DINSTALL_UDEV_RULES=ON
make
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.

3. Get a copy of the Qt-DAB sources

git clone https://github.com/JvanKatwijk/qt-dab.git
cd qt-dab

4. Edit the qt-dab.pro file for configuring the supported devices and other options. Comment the respective lines for devices that you do not have or do not want to support out.

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 RPI2/3 device, you might want to uncomment the line DEFINE+=__THREADED_BACKEND. This will cause a better load balance on the cores of the processor.

5. Build and make

qmake qt-dab.pro
make

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.

Options in the configuration are:

a) select or unselect devices

b) select the output: soundcard or TCP connection

c) select defines related to performance

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-v2
CONFIG		+= sdrplay-v3	
CONFIG		+= lime
CONFIG		+= rtl_tcp
CONFIG		+= airspy
CONFIG		+= hackrf
#CONFIG		+= soapy

DRM+, for which I am writing a decoder in another project, supports, next to the "classic" AAC encoding of audio, the xHE-AAC encoding. Decoding of xHE-AAC encoded audio frames is not supported by the "faad" library, and it is not clear whether or not support will ever turn up.

The fdk-aac (from Fraunhofer institute) turned out to be an excellent alternative, it supports decoding both the AAC and xHE-AAC segments from DRM30 and DRM+. Support for fdk-aac was therefore included in the aforementioned DRM+ decoder.

As an experiment, support for fdk-aac to Qt-DAB is added using the same code that creates the aac output files whenever selected (Thanks to Stefan Poeschel for that).

The ".pro" file now contains - in the section for Unix - two lines with which either fdk-aac or faad can be selected.

CONFIG	+= fdk-aac
#CONFIG	+= faad

As far as I can see, the fdk-aac library can be installed from the repositories of the Linux distribution, of course, you should have the library and the include files ("development package") installed when using it.

The Qt-DAB software does not interpret the TPEG streams, however, the data of these streams can be output. If so configured, the software acts as a simple server.

#CONFIG		+= datastreamer

To handle output of embedded an IP data stream, uncomment

CONFIG		+= send_datagram

#if you want to listen remote, uncomment

CONFIG		+= tcp-streamer		# use for remote listening

otherwise, if you want to use the default qt way of sound out

#CONFIG		+= qt-audio

Comment both out if you just want to use the "normal" way. The source tree contains a directory sound-client, that contains sources to generate a simple "listener" for remote listening.

By default, the name of the service last used is kept between program invocations and it is the one the Qt-DAB software will try to open on the next invocation.

DEFINES		+= PRESET_NAME

The performance of an RPI 2 is such that running the program in a single thread overloads the processor. Uncommenting

DEFINES		+= __THREADED_BACKEND

configures the program to have the backend run in a separate thread.

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, and the new xml-files) is configured by default.

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:

cmake .. -DRTLSDR=ON -DSDRPLAY=ON 

will generate a makefile with support for

a) the RTLSDR (dabstick) device,

b) the SDRPlay device (with 2.13 library).

Other devices that can be selected are sdrplay for library version 3.06, HackRF and airspy. Use -DHACKRF=ON, -DSDRPLAY_V3=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. Note that - when so configured - there are two entries for the SDRplay in the device selector.

• the v2 version uses the 2.13 library,
• the v3 version uses the 3.06 library.

Note that running against the v3 library requires the "daemon" (or service) to run.

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).

Note that Qt4 is considered to be obsolete and its use will - slowly - be phased out.

The Qt-DAB software runs pretty well on the author's RPI-2 and 3 when configured for running the backend in a separate thread. 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 distributions, Raspbian Stretch and Raspbian Buster supports both Qt5 and a qwt compiled against Qt5.

Since Raspbian Stretch is a Debian derivate, the description for creating a version under Ubuntu applies, a script to download all required packages, compile and build a full executable for qt-dab is part of the source tree.

Before running this script, script script-for-devian.txt, copy the script to the parent directory (executing it will load a whole bunch of files.

https://github.com/JvanKatwijk/qt-dab/releases contains a generated appImage, Qt-DAB-x64.Appimage, which is created on Ubuntu 16.04 (Xenial).

Different from previous versions, this version assumes you have installed the support library for the devices you want to use.

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.

If you want to run an RTLSDR based dabstick, please note that the appImage may complain with some Linux distros with a "librtlsdr.so" pre-installed that the kernel module has to be blacklisted. Depending on the distribution, blacklisting is in /etc/modprobe.d/local-blaclist

For compiling and installing a support library for an RTLSDR device, follow the instruction on https://osmocom.org/projects/rtl-sdr/wiki/Rtl-sdr.

For compiling and installing a support library for an AIRspy device, find the sources on https://github.com/airspy/airspyone_host/tree/master/libairspy

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

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

There are - obviously - more devices than 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.

Device handlers are implemented as a class, derived from the class virtualInput. Only a few functions have to be implemented, to set and get the VFO frequency, to inspect the number of samples available and to get a number of samples, to start and stop operating the device and to report on the number of bits per sample. This last function, is used to scale the various spectrum scopes.

A complete description is given in the file "interfacing.txt", in the sourcetree

Two of the (many) areas that still needed addressing in the handling of DAB+ contents were handling

• secondary audio services* and reacting upon a
• change in configuration*.

While not encountered here (the Netherlands), Secondary audio services are seen in BBC transmissions. They are now visible as service and can be selected.

A change in configuration may be that bitrates of channels change, that protection changes, and even that secondary audio services appear or disappear.

Especially interesting is of course what the software should do when - after a change in configuration - the selected secondary audio service is gone.

In Qt-DAB 3.3 a mechanism is included to make secondary audio services visible and selectabe, and to handle a change in configuration. Such a change will manifest itself as a minor disruption (app 20 msec) in the signal of the selected service.

While it is known that the DAB transmissions are in Band III, there are situations where it is desirable to use other frequencies. If you want to experiment with a modulator, connected to an SDR device on different frequencies than the default one (or you want just to have a restricted number of channels from Band III or L Band), Qt-DAB offers a possibility to specify a list of channels to be used. 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.

Clemens Schmidt, author of the QIRX program 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-3.3 support the generation of 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 the Hackrf device.

Copyright (C)  2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020
Jan van Katwijk ([email protected])
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.