SDR-J-DAB 0.99 (revised) Software for SDR: the .SDR-J-DAB 0.99 (revised) Software for SDR: the DAB
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SDR-J-DAB 0.99 (revised)
Software for SDR: the DAB receiver
Jan van KatwijkLazy Chair Computing
October 1, 2015
: 2015, Jan van Katwijk, Lazy Chair Computing
The DAB program is a software program for decoding DAB and DAB+. The program runsunder Windows and Linux, it is developed under Linux and cross compiled - using the Mingw64cross compilation suite - to Windows.
Differences between version 0.99 and previous versions The software now uses theQt5 library, rather than the Qt4 library that was used in the previous versions.
Other modifications to the DAB software, when compared to the previous versions, relateto performance. Several parts of the DAB software were rewritten and the GUI was adapted,such that the DAB program is less resource hungry when running and is compiled for (andwill run on) 32 bits windows.
Since the program now runs on 32 bits windows, it was possible to create an interface toextIO XXX supported devices. As the front page shows, the SDRplay works fine throughthe extIO-SDRplay interface. It was also tested with the extIO-RTL.dll as shown below.
Furthermore, the user interface is reduced in size, also shown in the picture, and finally, thanksto Stefan Poeschel, the problems with the interface with the faad library were solved.
As stated, the software now supports extIO-XXX dlls, next to that, the embeddedsupport for the SDRplay and the RT2832 based sticks in the Windows version is still available.
For the Linux version the configuration file now can be told to include or exclude thesedevices.
Other Platforms The software runs successfully under Windows 7 and Linux. It is devel-oped under Linux (Fedora 21) and is cross compiled for Windows. An attempt is underwayto see whether the software will run on a Raspberry. It will definitely not run on a RaspberryA or B. On an RPI 2 (under Arch Linux) the software was successfully compiled and showssome signs of life, when running however, one of the cores shows a load of 100% and too manyinput samples are lost. The next attempt will be to redistribute the load over more processorcores, but there are no garantees.
The DABreceiver software comes - as usual - in two flavors: for Windows there is a singlezipped folder containing the executable of DAB program as well as some of the required dlls.For Linux, sources are available and one has to create the executables.
2.1 Installation under Windows
Just unpack the zipped file. A folder windows32-bin-dab will be created that contains theexecutables and (almost) all required .dlls. The name of the executable is sdr-j-dabreceiver-0.99.exe.
The extIO SDRplay.dll can - together with the SDRplay API - be installed from www.sdrplay.com,the extIO RTL.dll is found in a variety of places. It is the responsibility of the user to ensurethat the appropriate dlls are loaded.
Note that we need an outputrate of 2048000 IQ samples/second, so it is imperative thatthe device delivers through the extIO XXX.dll a sufficient amount of samples. For the ex-tIO SDRplay, samples are converted from 2000000 Samples/second to the required rate1. Forthe extop RTL.dll, the samples are converted from a rate 2.4M to the required rate. A devicethat delivers a rate lower than 1900000 samples/second will not be accepted.
2.2 Installation under Linux
For developing executables under Linux, the packed sources are available. A brief descriptionof building for Linux is given in section 4 of this manual.
3 Running the DABreceiver
Starting the program is by clicking on its icon or using a command line in a command windowwith the (path)name of the program.
Starting the program will set it in an idle state. Before processing can start, one has toselect a device through clicking on an entry on the appropriate combobox. Supported devicesare:
no device. No input device will be selected, input will consist of nothing;
.raw file input. A file selection menu is displayed for selecting a file with extension.raw. The raw bytes in this file will be the input. Such a file could have been generatedby previous versions of the DABreceiver software. Current dumping creates an .sdrfile.
.sdr file input. A file selection menu is displayed for selecting an input file. Notethat only .sdr files (i.e. with wav files with the correct samplerate (2048000) and 2channels) will be accepted.
1Note that signals from the dll are ignored, it is assumed that the default setting is taken
rtl tcp. Input can be taken from an rtl tcp server. The feature obviously requires a fastconnection to the server. It was tested using a wired connection with the server runningon an RPI2, and the client on my regular laptop.
Windows only: extio. A file selection menu will show up on which an appropriate ex-tIO XXX.dll can be selected.
SDRplay. A Mirics SDRplay as input device is assumed to be connected to an USB port.Output of the SDRplay device - and thus program input - consists of a raw stream of 10bit integer values, mapped onto complex I/Q samples by the software.
DABstick. A DAB-stick as input device is assumed to be connected to an USB port.DAB-stick output - and thus program input - consists of a raw byte stream, mappedonto complex I/Q samples by the software.
If/when a device is selected a small window will appear with settings specific to the device,i.e. gain, offsets etc.
The DAB program uses an .ini file, $(HOME)/.jsdr-dab.ini for obtaining some stateinformation from previous sessions and for some general configuration data. Absence of the.ini file (as will be the case in most cases on a first invocation of the program) will not harmthe program, just some (seemingly) suitable default values will be chosen and - after normalprogram termination - the .ini file will be created.
It is common practice to just start the programs and quit it to obtain an .ini files withdefault values.
After having selected a device (selector labeled 1), the user of the DABreceiver may selecta Mode (selector labeled 4), a band (selector labeled 3), and a channel (selector labeled2). The channels map onto the standardized frequencies for the DAB channels in the selectedband.
Mode is by default set to Mode 1, band to III.Actual running of the program will start after pressing the START button (labeled 5).
When started, the DABreceiver will to try to synchronize with the incoming data: this maytake (quite) some time, depending on the quality of the received signal. In general, as soonas there is time synchronization, one will see dots of the signal will show in the black screen.The more the collection of dots resembles a large X, the better the quality of the signal. Theexecution of the program can be stopped by pressing the QUIT button (labeled 6)
When synchronized, the program will try to identify the name of the ensemble and thenames of the programs encoded within the ensemble. As soon as correct data is found, thenames of the stations covered by the ensemble will be displayed (labeled 8).
Selecting a particular station in the list is by clicking with the mouse on it. Decoding willstart and might lead to sound output.
An output channel is selected using button labeled 9. Saving the intermediate outputcan be done by pressing button labeled 12 for MP2 output or button labeled 13 for AACoutput. In either case a file selection menu will appear with which a file can be selected.Pressing the button again will close the file.
The resulting audio (48000 Hz, stereo) can be saved in a file by pressing button labeled10. The input - transformed to a samplerate of 2048000 - can be saved into an .sdr file bypressing button labeled 11. Again, pressing the button for the second time will cause closingthe file.
Pressing button 7 will cause the software to resynchronize.The slider below the black colored block can be used to enlarge the figure shown on the
black scope.To the right of the black scope, two numbers show. The first one is the estimated length -
in samples - of a frame, this should be 196608. The second one is 2048000, the samplerate.The two numbers shown above the button panel show the small frequency offset resp. the
large frequency offset. When synchronized, the large freqency offset will remain constant,the small frequency offset might change continuously, depending on the reception conditions.Especially when the count of the framelength deviates from the 196608 what is should be, thesystem will see a VFO offset and will compensate that. (Especially for users of the DABstick:
the offset can be quite large due to an offset in the oscillator. One is advised to correct thisusing the ppm selector for the device.)
The numbers on the bottom line left indicate:
the estimated SNR, an SNR of 15 and more is good.
the success rate of FIC decoding, 100 is good,
the success rate of AAC (or for old DAB mp2) decoding, 100 is good.
Information on the received program is in the top lines of the GUI.
The .ini file Many of the settings for the DABreceiver will be read from the .ini file onprogram startup. If no .ini file exists (yet), suitable defaults for the various sliders and selec-tors are chosen. The default location for the .ini file for the DABreceiver is $(HOME)/.jsdr-dab.ini2. The file contains entries
Concurrent is not settable through the GUI, it tells to run the MPEG decoder in a differentthread (value 1) or in the same thread as the rest of the dab decoding (value 0). On a machinewith ma