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\begin{document}
\begin{titlepage}
\centering
\includegraphics[width=0.3\textwidth]{tu-berlin-logo.pdf}\par\vspace{1cm}
{\scshape\LARGE Technische Universität Berlin\par}
\vspace{1cm}
{\scshape\Large Master Thesis\par}
\vspace{1.5cm}
{\huge\bfseries A Networking Extension for the SoundScape Renderer\par}
\vspace{2cm}
{\Large\itshape David Runge\par}
\href{dave@sleepmap.de}{dave@sleepmap.de}
\vfill
supervised by\par
Henrik von Coler and Stefan Weinzierl
\vfill
{\large \today\par}
\end{titlepage}
\section*{Eidesstattliche Erklärung}
\vspace{1cm}
Hiermit erkläre ich, dass ich die vorliegende Arbeit selbstständig und
eigenhändig sowie ohne unerlaubte fremde Hilfe und ausschließlich unter
Verwendung der aufgeführten Quellen und Hilfsmittel angefertigt habe.\\
Berlin, den \today\par\\
\vspace{2cm}
\noindent\ldots\ldots\ldots\ldots\ldots\ldots\ldots\ldots\ldots\ldots\ldots\\
David Runge
\begin{abstract}
Wave Field Synthesis (WFS) as a technological concept has been around for
many years now and all over the world several institutions run small and
some even large scale setups ranging from single speaker lines to those
facilitating a couple of hundred loudspeakers respectively.\\
The still evolving implementations are driven by several rendering
engines, of which two free and open-source ones, namely sWONDER and
SoundScape Renderer, have (partially) been developed at TU Berlin.\\
The latter due to its current design is not yet able to render for large
scale setups, ie.\ those using several computers to render audio on a
loudspeaker setup, due to the high amount of channels.\\
Its solid codebase however, which additionally offers a framework for many
more renderering types, and the ongoing development, deems further work on
this application a good future investment.\\
This work is about the extension of the SoundScape Renderer's functionality
to turn it into a networking application for large scale WFS setups.
\end{abstract}
\setcounter{tocdepth}{4}
\tableofcontents
\pagebreak
\section{Introduction}
Wave Field Synthesis (WFS) describes a spatial technique for rendering
audio. As such it aims at synthesizing a sound field of desired acoustic
preference in a given listening area, assuming a planar reproduction to be
most suitable for most applications.\\
WFS is typically implemented using a curved or linear loudspeaker array
surrounding the listening area.\\
Several free and open-source renderer applications exist for WFS
environments, with varying stages of feature richness.\\
The proposed work will focus on one of them and its extension towards WFS
on large scale systems.
\section{Spatial audio renderers and their appliance}
\subsection{Wave Field Synthesis}
\subsection{Higher Order Ambisonics and Vector Amplitude Panning}
\subsection{Binaural synthesis}
\section{Free and open-source spatial audio renderers}
To date there exist three (known of) free and open-source spatial audio
renderers, which are all \href{http://jackaudio.org/}{JACK Audio Connection
Kit (JACK)} \citep{website:jackaudio2016} clients:
\begin{itemize}
\item \href{https://sourceforge.net/projects/swonder/}{sWONDER}
\citep{website:swonder2016}, developed by Technische Universität
Berlin, Germany
\item \href{https://github.com/GameOfLife/WFSCollider}{WFSCollider}
\citep{website:wfscollider2016}, developed by
\href{http://gameoflife.nl/en}{Game Of Life Foundation}
\citep{website:gameoflife2016}, The Hague, Netherlands
\item \href{http://spatialaudio.net/ssr/}{SoundScape Renderer (SSR)}
\citep{website:ssr2016}, developed by Quality \& Usability Lab,
Deutsche Telekom Laboratories and TU Berlin and Institut für
Nachrichtentechnik, Universität Rostock
\end{itemize}
Currently only WFSCollider and the SSR are actively maintained and
developed, thus sWONDER, although used in some setups, loses significance.
Generally it can be said, that different concepts apply to the three
renderers, which are about to be explained briefly in the following
sections.
\subsection{WONDER}
sWONDER \citep{baalman2007} consists of a set of C++ applications that
provide binaural and WFS rendering. In 2007 it was specifically
redesigned \citep{baalmanetal2007} to cope with large scale WFS setups in
which several (computer) nodes, providing several speakers each, drive a
system together.\\
In these setups each node receives all available audio streams (which
represent one virtual audio source respectively) redundantly and a master
application signals which node is responsible for rendering what source
on which speaker.\\
It uses Open Sound Control (OSC) for messaging between its parts and for
setting its controls. Apart from that, it can be controlled through a
Graphical User Interface (GUI), that was specifically designed for it.
Unfortunately sWONDER has not been actively maintained for several years,
has a complex setup chain and many bugs, that are not likely to get fixed
any time soon.
\subsection{HOA-Pd}
\subsection{WFSCollider}
WFSCollider was built on top of
\href{https://supercollider.github.io}{SuperCollider} 3.5
\citep{website:supercollider2016} and is also capable of driving large
scale systems. It uses a different approach in
doing so, though: Whereas with sWONDER all audio streams are distributed
to each node, WFSCollider usually uses the audio files to be played on
all machines simultaneously and synchronizes between them.\\
It has a feature-rich GUI in the ``many window'' style, making available
time lines and movement of sources through facilitating what the sclang
(SuperCollider programming language) has to offer.\\
As WFSCollider basically is SuperCollider plus extra features, it is also
an OSC enabled application and can thus also be used for mere
multi-channel playback of audio.\\
Although it has many useful features, it requires MacOSX (Linux version
still untested) to run, is built upon a quite old version of
\href{https://supercollider.github.io}{SuperCollider} and is likely never
to be merged into it, due to many core changes to it.
\subsection{SoundScape Renderer}
SoundScape Renderer (SSR), also a C++ application, running on Linux and
MacOSX, is a multi-purpose spatial audio renderer, as it is not only
capable of Binaural Synthesis and WFS, but also Higher-Order Ambisonics
and Vector Base Amplitude Panning.\\
It can be used with a GUI or headless (without one), depicting the
virtual sources, their volumes and positions, alongside which speakers
are currently used for rendering a selected source.
SSR uses TCP/IP sockets for communication and is therefore not directly
OSC enabled. This functionality can be achieved using the capapilities of
other applications such as \href{http://puredata.info}{PureData}
\citep{website:puredata2016} in combination with it though.\\
Unlike the two renderers above, the SSR is not able to run large-scale
WFS setups, as it lacks the features to communicate between instances of
itself on several computers, while these instances serve a subset of the
available loudspeakers.
\section{Extending Sound Scape Renderer functionality}
The SSR, due to its diverse set of rendering engines, which are made
available through an extensible framework, and its relatively clean
codebase, is a good candidate for future large scale WFS setups. These type
of features are not yet implemented though and will need testing.\\
Therefore I propose the implementation and testing of said feature, making
the SSR capable of rendering on large scale WFS setups with many nodes,
controlled by a master instance.\\
The sought implementation is inspired by the architecture of sWONDER, but
instead of creating many single purpose applications, the master/node
feature will be made available through flags to the ssr executable, when
starting it. This behavior is already actively harnessed eg.\ for selecting
one of the several rendering engines.
\begin{figure}[!htb]
\centering
\includegraphics[scale=0.9, trim = 31mm 190mm 24mm 8mm, clip]
{ssr-networking.pdf}
\caption{A diagram displaying the SSR master/node setup with TCP/IP
socket connections over network (green lines), audio channels (red
dashed lines) and OSC connection (blue dashed line). Machines are
indicated as red dashed rectangles and connections to audio hardware
as outputs of SSR nodes as black lines below them.}
\label{fig:ssr-networking}
\end{figure}
While the SSR already has an internal logic to know which loudspeaker will
be used for what virtual audio source, this will have to be extended to be
able to know which renderer node has to render what source on which
loudspeaker (see Figure~\ref{fig:ssr-networking}).
To achieve the above features, the SSR's messaging (and thus also settings)
capabilities have to be extended alongside its internal logic concerning
the selection of output channels (and the master to node notification
thereof). To introduce as little redundant code as possible, most likely a
``the client knows all'' setup is desirable, in which each node knows about
the whole setup, but is also set to only serve its own subset of
loudspeakers in it. This will make sure that the rendering engine remains
functional also in a small scale WFS setup.\\
The lack of a direct OSC functionality, as provided by the two other
renderers, will not be problematic, as master and nodes can communicate
through their builtin TCP/IP sockets directly and the master can, if
needed, be controlled via OSC.
\subsection{Prelimenaries}
In preparation to the exposé I tried to implement a side-by-side
installation, using Arch Linux on a medium scale setup, facilitating the
WFS system of the Electronic Studio at TU Berlin. Unfortunately the
proprietary Dante driver, that is used in that system is very complex to be
built, as well as underdeveloped and thus keeps the system from being
easily updated, which is needed for testing purposes (finding a suitable
real-time, low-latency Linux kernel), trying out new software features,
building new software and keeping a system safe. The driver will most
likely require changes to the hardware due to implemention of hardware
branding by the vendor and dire testing before usage.\\
Although eventually using a proper WFS setup for testing will be necessary,
it is luckily not needed for implementing the features, as they can already
be worked out using two machines running Linux, JACK and the development
version
of SSR.\\
The hardware of the large scale setup at TU Berlin in H0104 is currently
about to be updated and therefore a valuable candidate for testing of the
sought after SSR features.
\subsection{Outline}
\subsubsection{Remote controlling a server}
\subsubsection{Remote controlling clients}
\subsubsection{Rendering only on dedicated speakers}
\subsection{Publisher/Subscriber interface}
\subsection{IP interface}
\subsubsection{PureData integration}
\subsection{OSC interface}
\subsubsection{liblo}
\subsubsection{Client-Server setup}
\subsubsection{Multi-layered clients}
\subsubsection{Message interface}
\section{Future Work}
\subsection{Stress testing the OSC interface}
\subsection{Implementing a NullRenderer}
\subsection{Implementing AlienLoudspeaker}
\subsection{Interpolation of moving sources}
\pagebreak
\listoffigures
\pagebreak
\listoftables
\pagebreak
\bibliographystyle{plainnat}
\bibliography{../bib/ssr-networking}
\end{document}
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