csdr-eti

This repository contains an implementation of a DAB ETI decoder that can be used as the first stage of a DAB receiver pipeline. It cn demodulate a DAB Mode I Mux from IQ data and output it as the corresponding ETI stream if successful.

The code in this repository is a port of the dab2eti tool from the dabtools project. See below for an acknowledgement of the individual copyright holders and license.

The code has been adopted to work as a generic csdr module that can be used as part of a more complex pipeline. The hardware-specific bindings to the rtl-sdr library have been removed, the module can be fed with IQ data from any available source and is now basically hardware agnostic.

The output stream is the same ETI data as provided by the original project, so it can be used with the same applications. One example is piping the ETI stream into dablin running inside a csdr ExecModule to demodulate the actual audio data.

The main use case for this code is the DAB demodulator pipeline of OpenWebRX.

Copyrights

Based on the dabtools project / dab2eti Copyright by Dave Chapman dave@dchapman.com published under the GPL license.

Based on OpenDAB by David Crawley published under the GPL license.

Based on rtl-dab by David May published under the GPL license.

Viterbi FEC by Phil Karn, KA9Q published under the GPL license.

Please report any errors or shortcomings in these acknowledgements. I do not wish to discredit any of the original authors in any way.

I/O parameters

Input

IQ data as Csdr::complex<float>. This is binary compatible with the C++ native std::complex<float>, FFTW3's fftwf_complex or a basic float[2] containing the respective value for I and Q.
sample rate: fixed at 2048000 S/s.
Use an adequately sized buffer to feed the data. Recommended minimum: 524288 samples.
This demodulator requires very accurate tuning of the desired signal, more accurate than the calibration of most SDRs can be (<1 ppm). For this purpose, the module will write according information to the metadata writer, if provided. This can be used to control a Csdr::Shift() on the input to achieve the necessary precision.

Output

ETI binary stream represented as uint8_t. Can be converted to other 8-bit data types as required.
Data rate is inconsistend, depending on signal quality. Maximum data rate tbd.

Installation

The OpenWebRX project is hosting csdr-eti packages in their repositories. Please click the respective link for Debian or Ubuntu.

Compiling from source

Requirements

Please make sure you install the following dependencies before compiling csdr-eti:

csdr (version 0.18 or later)
fftw3

This project comes with a cmake build. It is recommended to build in a separate directory.

mkdir build
cd build
cmake ..
make
sudo make install

jketterl/csdr-eti