DABlin – capital DAB experience

DABlin plays a DAB/DAB+ audio service – from a live transmission or from a stored ensemble recording (ETI-NI, or EDI AF with ETI). Both DAB (MP2) and DAB+ (AAC-LC, HE-AAC, HE-AAC v2) services are supported.

The GTK GUI version in addition supports the data applications Dynamic Label and MOT Slideshow (if used by the selected service).

Screenshots

GTK GUI version

Console version

Requirements

General

Besides Git a C/C++ compiler (with C++11 support) and CMake are required to build DABlin.

On Debian or Ubuntu, the respective packages (with GCC as C/C++ compiler) can be installed using aptitude or apt-get, for example:

sudo apt-get install git gcc g++ cmake

Libraries

The following libraries are required:

• mpg123 (1.14.0 or higher)
• FAAD2
• SDL2

The GTK GUI version in addition requires:

• gtkmm

Usually the glibc implementation of iconv is available. If this is not the case, in addition libiconv is required.

In rare cases, the target architecture does not support atomics. In such a case, DABlin is linked against GCC's libatomic. This lib usually is an (indirect) dependency of GCC itself.

On Debian or Ubuntu, mpg123, FAAD2, SDL2 and gtkmm are packaged and installed with:

sudo apt-get install libmpg123-dev libfaad-dev libsdl2-dev libgtkmm-3.0-dev

On Fedora, mpg123, SDL2, and gtkmm are all packaged and can be installed thus:

sudo dnf install mpg123-devel SDL2-devel gtkmm30-devel

FAAD2 is not packaged in the main Fedora repository, but it is available in RPM Fusion repository. Once you have added RPM Fusion to the repositories, FAAD2 may be installed by:

sudo dnf install faad2-devel

If you do not wish to, or cannot, add the RPM Fusion repositories, you will have to download FAAD2, perhaps from here, and build and install manually.

Alternative DAB+ decoder

Instead of using FAAD2, DAB+ channels can be decoded with FDK-AAC. You can also use OpenDigitalradio's fork, if already installed.

On Debian and Ubuntu, you can install FDK-AAC with:

sudo apt-get install libfdk-aac-dev

On Fedora, RPM Fusion is again needed and, if used, you can:

sudo dnf install fdk-aac-devel

When the alternative AAC decoder is used, the FAAD2 library mentioned above is no longer required.

After installing the library, to use FDK-AAC instead of FAAD2, you have to have -DUSE_FDK-AAC=1 as part of the cmake command.

Audio output

The SDL2 library is used for audio output, but you can instead choose to output the decoded audio in plain PCM for further processing (e.g. for forwarding to a streaming server).

In case you only want PCM output, you can disable SDL output and therefore omit the SDL2 library prerequisite. You then also have to have -DDISABLE_SDL=1 as part of the cmake command.

To enable the PCM output to stdout, the -p parameter has to be used.

It is also possible to disable the output of any decoded audio and instead output the current service as an untouched MP2/AAC stream to stdout. This can be achieved by using the -u parameter.

Surround sound

Services with surround sound are only decoded from their Mono/Stereo core, as unfortunately there is no FOSS AAC decoder which supports the required Spatial Audio Coding (SAC) extension of MPEG Surround at the moment.

Precompiled packages and source-based Linux distributions

Official precompiled packages are available for the following Linux distributions (kindly maintained by Gürkan Myczko):

• Debian
• Ubuntu

On Ubuntu 18.04 you can simply install DABlin from the official package sources (note that the GitHub version may be newer):

sudo apt-get install dablin

Some users kindly provide precompiled packages on their own:

• openSUSE (by Martin Hauke)
• CentOS (by Radio Bern RaBe 95.6); more info

For other distributions you may also want to check the Repology page.

Source-based Linux distributions:

• Gentoo (by Christian Affolter, as part of his delicious-absurdities-overlay)

Compilation

If the gtkmm library is available both the console and GTK GUI executables will be built. If the gtkmm library is not available only the console executable will be built.

To fetch the DABlin source code, execute the following commmands:

git clone https://github.com/Opendigitalradio/dablin.git
cd dablin

Note that by default the master branch is cloned which contains the current stable version. The development takes place in the next branch which can instead be cloned by appending -b next to the end of the above git clone command line.

You can use, for example, the following command sequence in order to compile and install DABlin:

mkdir build
cd build
cmake ..
make
sudo make install

Windows (Cygwin)

DABlin can also be compiled on Windows using Cygwin. The following Cygwin packages are required:

General:

• git
• make
• cmake
• gcc-core
• gcc-g++

DABlin specific (using FDK-AAC for DAB+ services):

• libmpg123-devel
• libfdk-aac-devel
• libSDL2-devel
• libiconv-devel

In addition for the GTK version:

• libgtkmm3.0-devel

Note that the GTK version requires an X server to run e.g. Cygwin/X!

Also note that Cygwin neither needs nor allows to sudo commands, so just execute them without that prefix.

Unfortunately the Cygwin package of FDK-AAC doesn't seem to have been compiled with SBR support, so using FAAD2 for DAB+ services is recommended. However FAAD2 has to be compiled and installed by hand, as there is no Cygwin package. This requires the following additional packages to be installed:

• autoconf
• automake
• libtool

When Cygwin is installed, all the aforementioned packages can be pre-selected for installation by calling Cygwin's setup-<arch>.exe with the following parameter:

-P git,make,cmake,gcc-core,gcc-g++,libmpg123-devel,libfdk-aac-devel,libSDL2-devel,libiconv-devel,libgtkmm3.0-devel,autoconf,automake,libtool

macOS

On macOS, the development environment can be installed by running xcode-select. This installs Git and a C/C++ compiler (clang). All other packages and development libraries can be installed using a package manager such as Homebrew, for example:

xcode-select --install
brew install pkg-config cmake gtkmm gtkmm3 adwaita-icon-theme sdl2 fftw faad2 mpg123

Usage

The console executable is called dablin, the GTK GUI executable dablin_gtk. Use -h to get an overview of all available options.

(Currently no desktop files are installed so it is not easy to start DABlin directly from GNOME Shell. For now, at least, start DABlin from a console.)

DABlin processes DAB ETI-NI or EDI recordings/streams (which may be frame-aligned or not i.e. any data before/after an ETI/EDI frame is discarded). If no filename is specified, stdin is used for input.

You just should specify the service ID (SID) of the desired service using -s - otherwise initially no service is played. The GUI version of course does not necessarily need this.

You can replay an existing recording as follows:

dablin -s 0xd911 mux.eti

In this case a progress indicator and the current position is displayed.

As an alternative a service label can be specified with the -l option. Note that if the label contains spaces, it has to be enclosed by quotes (or the spaces be properly escaped):

dablin -l "SWR1 RP" mux.eti

The parameter -1 (the number one, not the small letter L) simply plays the first service found.

With the console version, instead of the desired service it is also possible to directly request a specific sub-channel by using -r (for DAB) or -R (for DAB+).

Note that the console output always shows the programme type just using RDS PTYs despite the actually used international table ID (which should work in nearly all cases). The GTK version in contrast always shows the correct programme type, based on the transmitted international table ID.

Dynamic FIC messages can be suppressed using -F (currently affects dynamic PTY only).

Date/Time

The console version shows the related parameters as they are received: While the Local Time Offset (LTO) is shown upon any change, the UTC date/time is shown once.

The GTK version in contrast starts to display the local date/time as soon as both mentioned values have been received. The used clock is then resynchronised upon further received UTC date/time.

Announcement support/switching

In terms of announcement support/switching the console version shows the separate details. The GUI combines the received data and in general shows which announcements the current service supports.

During a matching announcement, the corresponding type is highlighted in yellow. An announcement that would lead to a (temporary) switch to a different subchannel leads to cyan highlighting instead e.g. if traffic news of a different channel shall affect also listeners of a different service (which does not have its own announcements).

Hotkeys (GTK GUI version)

To switch the channel instead of the service, press Ctrl in addition.

DAB live reception

If you want to play a live station, you can use dab2eti from dabtools (ODR maintained fork) and transfer the ETI live stream via pipe, e.g.:

dab2eti 216928000 | dablin_gtk

It is possible to let DABlin invoke dab2eti or any other DAB live source that outputs ETI-NI. The respective binary is then called with the necessary parameters, including the frequency and an optional gain value.

You therefore just have to specify the path to the dab2eti binary and the desired channel.

dablin -d ~/bin/dab2eti -c 11D -s 0xd911

Using dab2eti the E4000 tuner is recommended as auto gain is supported with it. If you want/have to use a gain value you can specify it using -g. Instead of auto gain, the default gain can be set using -G (only affects eti-cmdline at the moment).

Instead of dab2eti the tool eti-cmdline by Jan van Katwijk can be used, as it has more sensitive reception (however the CPU load is higher compared to dab2eti) and does not require a E4000 tuner for auto gain. It is part of his eti-stuff.

In addition to specifying the path to the respective binary you also have to change the DAB live source type accordingly by using -D.

dablin -d ~/bin/eti-cmdline-rtlsdr -D eti-cmdline -c 11D -s 0xd911

When enclosed in quotes, you can also pass command line parameters to the binary, e.g. to set some frequency correction (here: +40 ppm):

dablin -d "~/bin/eti-cmdline-rtlsdr -P 40" -D eti-cmdline -c 11D -s 0xd911

In case of the GTK GUI version the desired channel may not be specified. To avoid the huge channel list containing all possible DAB channels, one can also state the desired channels (separated by comma) which shall be displayed within the channel list. Hereby the specified (general) gain value can also be overwritten for a channel by adding the desired value after a colon, e.g. 5C:-54.

dablin_gtk -d ~/bin/dab2eti -c 11D -C 5C,7B,11A,11C,11D -s 0xd911

It may happen that an ETI live stream is interrupted (e.g. transponder lock lost). Later when the stream recovers, DABlin "catches up" on the stream and plays all (available) ETI frames until again in sync. This can lead to several audio buffer overflow messages and respective audible artifacts.

The -I parameter disables the described catch-up behaviour and instead resyncs to the stream after an interruption i.e. continues to play the later received ETI frames in realtime. However this means that the playback is delayed by the amount of all previous interruptions i.e. the news will start some seconds/minutes later compared to live reception because of that.

The GTK GUI version also allows to stop decoding the current channel/service by using the stop button next to the channel combobox. If desired, decoding can then be resumed using the same button again.

The stdin input can also be used for live reception or playback of an EDI AF stream/recording (containing ETI) e.g. with Netcat, Wget or cURL. Hereby the AF layer may also be enclosed with a File IO layer (usually the case for stored EDI transmissions).

Examples:

nc 10.0.0.128 9201 | dablin_gtk -f edi -I

wget -q -O - https://edistream.irt.de/services/3 | dablin_gtk -f edi -I -1

curl -s https://edistream.irt.de/services/3 | dablin_gtk -f edi -I -1

Playing EDI content the -I can be required to prevent ongoing hiccups during playback. In the last two cases, a single service EDI stream for testing purposes is used, so the -1 parameter is used to select the first found service.

Recording a service

With the GTK GUI version the current service can be recorded into a file. To start/stop a recording, the red record button has to be clicked, or the corresponding keyboard shortcut to be pressed. During a recording neither can channel/service be changed, nor can DABlin be closed.

By default all recordings are stored to /tmp. This can be changed by using the -r parameter. The filename of a recording contains the timestamp of the start of the recording and the service name, e.g. 2018-09-02 - 17-53-54 - SWR3.aac.

All recordings are lossless: A DAB service is directly stored in MP2 format. A DAB+ service is packaged into the LATM/LOAS container format. This format is necessary in order to signal the special 960 samples per frame transformation to the AAC decoder for playback.

As both formats are streamable, a recording can already be played while the actual recording is still in progress.

The AAC recordings can be player e.g. by VLC player. FFmpeg will play them as well, but currently does not support the SBR extension together with the 960 samples per frame transformation and will thus only play the AAC core then.

It is possible to enable a recording prebuffer which continuously caches a certain period of time. This allows to record e.g. an already running song or bloopers. When an actual recording is started, the complete prebuffer content is initially written to the recording file. The prebuffer size in seconds is specified using -P e.g. -P 600 for ten minutes.

Secondary component audio services

Some ensembles may contain audio services that consist of additional "sub services" called secondary components, in addition to the primary component. That secondary components can initially be selected by using -x in addition to -s.

In the GTK version in the service list such components are shown prefixed with » (e.g. » BBC R5LiveSportX). Meanwhile the related primary component is suffixed with » (e.g. BBC Radio 5 Live »).

Status output

While playback a number of status messages may appear. Some are quite common (enclosed with round brackets) e.g. due to bad reception, while others are rather unlikely to occur (enclosed with square brackets).

Common

During (re-)synchronisation status messages are shown. Also dropped Superframes or AU are mentioned.

If the Reed Solomon FEC was used to correct bytes of a Superframe, this is mentioned by messages of the format (3+) in cyan color. This shorter format is used as those messages occure several times with borderline reception. The digit refers to the number of corrected bytes within the Superframe while a plus (if present) indicates that at least one byte was incorrectable.

When a FIB is discarded (due to failed CRC check), this is indicated by a (FIB) message in yellow color.

MP2 frames with invalid CRC (MP2's CRC only - not DAB's ScF-CRC) are discarded, which is indicated by a (CRC) message in red color.

Audio Units (AUs) with invalid CRC are mentioned with short format messages like (AU #2) in red color, indicating that the CRC check on AU No. 2 failed and hence the AU was dismissed.

When the decoding of an AU nevertheless fails, this is indicated by an (AAC) message in magenta color. However in that case the AAC decoder may output audio samples anyway.

Uncommon

If the announced X-PAD length of a DAB+ service does not match the available X-PAD length i.e. if it falls below, a red [X-PAD len] message is shown and the X-PAD is discarded. However not all X-PADs may be affected and hence it may happen that the Dynamic Label can be processed but the MOT Slideshow cannot.

To anyhow process affected X-PADs, a loose mode can be enabled by using the -L parameter.

Standards

DABlin implements (at least partly) the following DAB standards:

General

• ETSI EN 300 401 (DAB system)
• ETSI TS 101 756 (Registered tables)
• ETSI TS 103 466 (DAB audio)
• ETSI TS 102 563 (DAB+ audio)
• ETSI ETS 300 799 (ETI)
• ETSI TS 102 693 (EDI) together with ETSI TS 102 821 (DCP)

Data applications

• ETSI EN 301 234 (MOT)
• ETSI TS 101 499 (MOT Slideshow)

TODO

At the moment, DABlin is kind of a rudimentary tool for the playback of DAB/DAB+ services. It is planned to add support for further Program Aided Data (PAD) features.

Slideshow

The GTK GUI version supports the MOT Slideshow. If Slideshow is enabled and the current service signals to transmit a Slideshow, the Slideshow window is displayed. It shows a slide after it has been received completely and without errors.

Currently the following limitations apply:

• slideshows in a separate sub-channel are not supported (just X-PAD);
• the TriggerTime field does not support values other than Now

License

This software is licensed under the GNU General Public License Version 3 (please see the file COPYING for further details).

Please note that the included FEC lib by KA9Q has a separate license!

DABlin - capital DAB experience Copyright (C) 2015-2020 Stefan Pöschel

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program 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.

You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.