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diff --git a/introduction.tex b/introduction.tex index b80fb93..849849d 100644 --- a/introduction.tex +++ b/introduction.tex @@ -3,6 +3,18 @@ This is the official documentation for the \mmbtools. These tools can be used to experiment with DAB modulation, learn the techniques behind it and setup a DAB or \dabplus transmitter. +This documentation assumes that you are already familiar with base concepts of +the DAB system. To get started with the \mmbtools, understanding how the DAB +transmission chain is structured is a prerequisite. The ``DAB Bible'' by Hoeg +and Lauterbach~\cite{hoeg} and the ``Guide to DAB standards'' from the +ETSI~\cite{etsidabguide} can be used as a starting point. + +In this document, the terms ``DAB'' and ``\dabplus'' are used somewhat +interchangeably, since many parts of the transmission chain are identical +between the two variants. In most cases, ``DAB'' will be used, and ``\dabplus'' +when talking about specific details about the newer version of the standard. + + \section{Purpose} The different programs that are part of the \mmbtools each have their own documentation regarding command-line options and configuration settings, and the @@ -68,13 +80,48 @@ The \mmbtools contain the tools \mbox{ODR-DabMux}, \mbox{ODR-DabMod}, that are useful for the setup of a transmission chain. \subsubsection{ODR-DabMux} -ODR-DabMux implements a multiplexer that is conforming to the DAB -standard~\cite{etsidab}. +ODR-DabMux implements a DAB multiplexer that combines all audio and data inputs +into an ETI output. It can be used off-line (i.e.~not real-time) to generate ETI +data for later processing, or in a real-time streaming scenario (e.g.~in a +transmitter). + +It can read input audio or data from files (``.mp2'' for DAB, ``.dabp'' for +\dabplus), FIFOs (also called ``named pipes'') or a network connection. The +network connection can use UDP or ZeroMQ. The CURVE authentication mechanism +from ZeroMQ can also be used to authenticate the encoder, in order to avoid that +a third-party can disrupt or hijack a programme. + +The ensemble configuration can be specified on the command line using the +options described in the manpage, or using a configuration file. The command +line options are kept to be compatible with CRC-DABMUX, but using the +configuration file is preferred, because it supports more options. + \subsubsection{ODR-DabMod} +ODR-DabMod is a software-defined DAB modulator that receives or reads ETI, and +generates modulated I/Q data usable for transmission. + +This I/Q data which is encoded as complex floats (32bits per complex sample) can +be written to a file or pipe, or sent to a USRP device using the integrated UHD +output. Other SDR platforms can be used if they are able to accept the I/Q data. +The output of the modulator can also be used in GNURadio if format conversion or +graphical analysis (spectrum) is to be done. + \subsubsection{toolame-dab} +TooLAME is a MPEG-1 Layer II audio encoder that is used to encode audio for the +DAB standard. The original project has been unmaintained since 2003, but the +twolame fork that pursues the development removed the DAB framing. + +The toolame-dab fork includes the ZeroMQ output and PAD insertion support, but +the audio coder is the same as the one in tooLAME. + \subsubsection{fdk-aac-dabplus} -\subsubsection{mmbtools-aux} +The fdk-aac-dabplus encoder can be used to encode for \dabplus. The encoder +itself comes from the Android sources, and was written by Fraunhofer. + +The necessary framing and error-correction that \dabplus mandates, the PAD +insertion, the ZeroMQ output and the ALSA input were then added by different +parties. |