diff options
Diffstat (limited to 'introduction.tex')
| -rw-r--r-- | introduction.tex | 137 |
1 files changed, 74 insertions, 63 deletions
diff --git a/introduction.tex b/introduction.tex index b05e64e..ff6357b 100644 --- a/introduction.tex +++ b/introduction.tex @@ -1,13 +1,13 @@ % LICENSE: see LICENCE -\section{Introduction} +\section{Introductions} 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. +experiment with digital audio broadcasting (DAB) modulation, to learn the +techniques behind it, and to set up 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 +This documentation assumes that you are already familiar with the basic concepts +of the DAB system. Understanding how the DAB transmission chain is structured is +a prerequisite for getting started with the \mmbtools. 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 @@ -17,17 +17,22 @@ 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 -opendigitalradio.org wiki\footnoteurl{http://opendigitalradio.org} -contains many explanations and pointers, but there is -no single source of documentation available for the whole tool-set. - -This document aims to solve this, by first outlining general concepts, -presenting different usage scenarios and detailing a complete transmission -setup. -With this document in hand, you should be able to understand all elements -composing a \mmbtools transmission chain, and how to set one up. +The individual programs that make up the \mmbtools each have their own +documentation for command-line options and configuration settings, and the +opendigitalradio.org wiki\footnoteurl{http://opendigitalradio.org} contains many +explanations and pointers, but there is no single source of documentation +available for the whole toolset. + +This document aims to fill this gap, by first outlining general concepts, then +presenting different usage scenarios, and finally, detailing a complete +transmission setup. +With this document in hand, you should be able to understand all of the elements +which go into the \mmbtools transmission chain, and how to set one up. + +Please refer to the bibliography for references on any individual topic that may need +clarification, to the README files in the repositories of the tools that are +going to be presented in this guide, and if you have further questions, get in +touch with us through the mailing-list mentioned on our website. \section{Presentation of the Tools} \subsection{Origins} @@ -38,20 +43,23 @@ started developing a DAB multiplexer. This effort evolved through the years, and was published in September 2009 as \mbox{CRC-DabMux} under the GPL open-source licence. -CRC also developed a DAB modulator, called \mbox{CRC-DABMOD}, which could create -baseband I/Q samples from an ETI file. This I/Q data could then be set to -a hardware device using another tool. For the Ettus USRPs, a ``wave player'' -script was necessary to interface to GNURadio. Only DAB Transmission Mode 2 was -supported. \mbox{CRC-DABMOD} was also released under the GPL in early 2010. +CRC also developed a DAB modulator, called \mbox{CRC-DABMOD}, which was able to create +baseband complex quadrature (I/Q) samples from files or +streams in the ETI format. This I/Q data could then be sent to a hardware device +(for broadcast or laboratory RF measurements) using another tool. For driving +the universal software-defined radio peripherals (USRP) made by the company +Ettus Research, a ``wave player'' script was necessary to interface with GNURadio. +Only DAB Transmission Mode 2 was supported. \mbox{CRC-DABMOD} was also released +under the GPL in early 2010. As encoders, toolame could be used for DAB, and CRC developed a closed-source \mbox{CRC-DABPLUS} \dabplus encoder. -These three CRC-~tools, and some additional services available on the now +These three CRC-tools, and some additional services available on the now unreachable website\footnote{There are some snapshots of the website available - on \url{http://archive.org}.} \url{http://mmbtools.crc.ca} were -part of the \mbox{CRC-mmbTools}. These tools made it possible to set up the -first DAB transmission experiments. + on \url{http://archive.org}.} +\url{http://mmbtools.crc.ca} were part of the \mbox{CRC-mmbTools}. These tools +made it possible to set up the first DAB transmission experiments. In 2012, these tools received experimental support for single-frequency networks, a functionality that has been developed by Matthias P. Brändli during @@ -61,27 +69,27 @@ Because SFNs are mainly used in TM 1, CRC subsequently released a patch to \mbox{CRC-DABMOD} that enabled all four transmission modes. At that point, involvement from CRC started to decline. The SFN patch was -finally never included in the \mbox{CRC-mmbTools}, and as time passed by, the +ultimately never included in the \mbox{CRC-mmbTools}, and as time passed, the de-facto fork on \url{http://mpb.li} was receiving more and more features. Having two different programs with the same name made things complicated, and -the tools were officially forked with the approval of CRC in February 2014, and -given the new name \mbox{ODR-mmbTools}. They are now developed by the +so, with the approval of CRC, the tools were officially forked in February 2014, +and given the new name \mbox{ODR-mmbTools}. They are now developed by the Opendigitalradio association. In April 2014, the official \mbox{CRC-mmbTools} website went offline, and it has -become very difficult, if not impossible to acquire licences for the +become very difficult, if not impossible, to acquire licences for the \mbox{CRC-DABPLUS} encoder. Luckily there is an open-source replacement -available, which was part of Google's Android sources. This encoder has been +available, which was part of Google's Android source. This encoder has been extended with the necessary \dabplus{}-specific requirements (960-transform, error correction, framing, etc.), and now exists under the name -\mbox{fdk-aac}. The encoder \mbox{ODR-AudioEnc} can use this library to encoder +\mbox{fdk-aac}. The encoder \mbox{ODR-AudioEnc} can use this library to encode for \dabplus{}. \subsection{Included Tools} The \mmbtools are composed of several software projects: \mbox{ODR-DabMux}, \mbox{ODR-DabMod}, \mbox{ODR-AudioEnc}, \mbox{ODR-PadEnc}, and other scripts, bits and pieces -that are useful for the setup of a transmission chain. +that are useful when setting up a transmission chain. \begin{figure}[h] \centering @@ -99,50 +107,54 @@ that are useful for the setup of a transmission chain. \subsubsection{ODR-DabMux} 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). +and outputs them in the form of a file in ETI format. This can be used offline +(i.e.~not in real time) to generate ETI data for processing later, or for use 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 +ODR-DabMux can read input audio or data from files (``.mp2'' for DAB, ``.dabp'' for +\dabplus), FIFOs (also called ``named pipes''), or from a network connection. This 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. +from ZeroMQ can also be used to authenticate the encoder, in order to prevent +third parties from disrupting or hijacking programmes. -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. +The configuration of the multiplexer is given in a configuration file, whose +format is defined in the example files in the \verb+doc/+ folder inside the +ODR-DabMux repository. \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. +ODR-DabMod is a software-defined DAB modulator that receives or reads ETI data +in streams or from files, and generates modulated I/Q data which can be used 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. +be written to a file or pipe, sent to a USRP device using the integrated +output for the open-source USRP Hardware Driver (UHD) or to other +software-defined radio (SDR) devices using the +SoapySDR\footnoteurl{https://github.com/pothosware/SoapySDR/wiki} library. + +The output of the modulator can also be sent to a GNURadio flow-graph for +further processing, conversion or analysis using a ZeroMQ interface. \subsubsection{ODR-AudioEnc} The ODR-AudioEnc encoder can be used to encode for DAB and \dabplus. It includes -a toolame-based MPEG encoder, and uses the \mbox{fdk-aac} library as an external +a TooLAME-based MPEG encoder, and uses the \mbox{fdk-aac} library as an external dependency to encode \dabplus{}. -The integrated TooLAME library 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. Because of this, twolame is not suitable for DAB. +The integrated TooLAME library is an MPEG-1 Layer II audio encoder that is used +to encode audio for the DAB standard. +Another encoder called twolame is not compatible with DAB even though it is more +recent than TooLAME, and cannot be used for our application. -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. +The framing and error correction which are needed for \dabplus{}, as well as the +programme-associated data (PAD) insertion, the output to the ZeroMQ interface, +and the input from Advanced Linux Sound Architecture (ALSA) were then added by +different parties. \subsubsection{ODR-PadEnc} -This encoder is able to generate programme associated data that can be injected -into ODR-AudioEnc. It supports DLS, reading from a file, and MOT Slideshow, -where the slides are read from a folder. +This encoder is able to generate programme-associated data (PAD) that can be +injected into ODR-AudioEnc. It supports reading and encoding Dynamic Label +Segment (DLS) from a text file, and reads images from a folder for MOT Slideshow. \subsubsection{etisnoop} Etisnoop is not used in the broadcasting chain directly, but is an analysis tool @@ -155,5 +167,4 @@ Additionally, it can output statistics in YAML format, which is useful in combination with an RTLSDR receiver and the \verb+dab2eti+ tool to monitor transmissions. - % vim: spl=en spell tw=80 et |