thesis/thesis.tex: Elaborating on Dynamic Binaural (Room) Synthesis and (Higher Order) Ambisonics Amplitude Panning and NFC-HOA.

1 files changed, 57 insertions, 8 deletions

diff --git a/thesis/thesis.tex b/thesis/thesis.tex
index a757ca9..a042e43 100644
--- a/thesis/thesis.tex
+++ b/thesis/thesis.tex
@@ -48,6 +48,7 @@ parskip=never]{paper}
 \newacronym{api}{API}{Application programming interface}
 \newacronym{asdf}{ASDF}{Audio Scene Description Format}
 \newacronym{bs}{BS}{Binaural Synthesis}
+\newacronym{brir}{BRIR}{Binaural Room Impulse Response}
 \newacronym{brs}{BRS}{Binaural Room Synthesis}
 \newacronym{cc}{CC}{Creative Commons}
 \newacronym{cicm}{CICM}{Centre de recherche Informatique et Création Musicale}
@@ -56,6 +57,8 @@ parskip=never]{paper}
 \newacronym{fdl}{FDL}{GNU Free Documentation License}
 \newacronym{gpl}{GPL}{GNU General Public License}
 \newacronym{gui}{GUI}{Graphical user interface}
+\newacronym{hrir}{HRIR}{Head Related Impulse Response}
+\newacronym{hrtf}{HRTF}{Head Related Transfer Function}
 \newacronym{ide}{IDE}{Integrated Development Environment}
 \newacronym{lgpl}{LGPL}{GNU Lesser General Public License}
 \newacronym{lts}{LTS}{Long Term Support}
@@ -63,7 +66,7 @@ parskip=never]{paper}
 \newacronym{ip}{IP}{Internet Protocol}
 \newacronym{jack}{JACK}{JACK Audio Connection Kit}
 \newacronym{madi}{MADI}{Multichannel Audio Digital Interface}
-\newacronym{nfc-hoa}{NFC-HOA}{Near-field-corrected Higher Order Ambisonics}
+\newacronym{nfc-hoa}{NFC-HOA}{Near-field-compensated Higher Order Ambisonics}
 \newacronym{oop}{OOP}{Object-oriented Programming}
 \newacronym{os}{OS}{Operating System}
 \newacronym{osc}{OSC}{Open Sound Control}
@@ -257,11 +260,59 @@ parskip=never]{paper}
     section about spatial audio renderer appliances and followed by one about
     free software and its pitfalls.
 
-    \subsection{Spatial audio renderers and their appliance}
+    \subsection{Spatial audio rendering algorithms and their appliances}
       \label{subsec:spatialaudiorenderersandtheirappliance}
+      In the following subsubsections several spatial audio rendering
+      algorithms are introduced briefly.
+      As they serve as a mere introductory, they are merged where applicable.
 
-      \subsubsection{Binaural (Room) Synthesis}
+      \subsubsection{Dynamic Binaural Synthesis and Dynamic Binaural Room
+      Synthesis}
         \label{subsubsec:binaural}
+        \gls{bs} describes a stereophonic audio reproduction, in which -
+        usually using headphones - acoustic signals are recreated at the ears
+        of the listener.\\
+        For humans, sound source localization and distance estimation takes
+        place according to auditory cues from each ear. The signals perceived
+        by inner and outer ear, are correlated by the brain, to account for
+        locations in all three dimensions and their distances from the
+        listener.\\
+        The differences between the cues perceived by each ear can be measured
+        as a \gls{hrir} for every human individually (as it is dependant on
+        physiology). Its Fourier transform, the \gls{hrtf}, can then be used
+        to modify audio signals to become a directional audio source, perceived
+        as in free field conditions.\\
+        \gls{brs} is a special form of \gls{bs}, in which \glspl{brir}, encode
+        all of the virtual source's characteristics, such as position,
+        alongside the room's acoustic characteristics.
+        This way, recordings from real rooms can be reproduced authentically.\\
+        \glspl{hrir} and \glspl{brir} are by default applied seperately for
+        each ear, therefore, if a resolution of 1\textdegree~is desired, it
+        can only be achieved by a set of 720 impulse responses.
+
+      \subsubsection{(Higher Order) Ambisonics Amplitude Panning and
+      Near-field-compensated Higher Order Ambisonics}
+        \label{subsubsec:aapandnfchoa}
+        \gls{aap} and \gls{hoa} are spatial rendering algorithms, that
+        reproduce audio on multi-speaker setups. Those are usually circular or
+        spherical.\\
+        Depending on a loudspeaker's position in the setup, relative to the
+        spheres's center (the listening area or \textit{sweet spot}), a linear
+        combination of all loudspeakers is used to achieve a localized
+        representation of a virtual sound source.\\
+        The relatively small listening area can be extended by using additional
+        sets of loudspeakers, which in turn lead to more spatial aliasing.\\
+        Due to the perceptebility of localization cues, mentioned in
+        \rer{subsubsec:binaural}, it is required to apply spatial equalization
+        for the rendered sources, to account for differences in low- and
+        high-frequency localization capabilities of the human ear.\\
+        For ambisonics, plane-wave sources are assumed. Due to the proximity
+        effect, this leads to a bass boost in the listening area. \gls{nfc-hoa}
+        accounts for this by a set of driving functions, applying a per speaker
+        near-field compensation.\\
+
+      \subsubsection{Vector Based Amplitude Panning}
+        \label{subsubsec:vbap}
 
       \subsubsection{Wave Field Synthesis}
         \label{subsubsec:wavefieldsynthesis}
@@ -269,13 +320,11 @@ parskip=never]{paper}
         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.\\
-        \gls{wfs} is typically implemented using a curved or linear loudspeaker
-        array surrounding the listening area.\\
+        \gls{wfs} is typically implemented using a circular, rectangular or
+        linear loudspeaker array surrounding or fronting the listening area.\\
         Several free and open-source renderer applications exist for \gls{wfs}
         environments, with varying stages of feature richness.\\
 
-      \subsubsection{Higher order ambisonics and vector based amplitude panning}
-        \label{subsubsec:hoaandvbap}
 
     \subsection{sWONDER}
       \label{subsec:swonder}
@@ -318,7 +367,7 @@ parskip=never]{paper}
       {https://puredata.info/downloads/mrpeach}} or \textit{IEMnet}\footnote{
         \href{https://puredata.info/downloads/iemnet}
       {https://puredata.info/downloads/iemnet}}.\\
-       
+
     \subsection{3Dj (SuperCollider Quark)}
       \label{subsec:3dj_supercollider_quark}
       3Dj is a \gls{supercollider} \gls{quark} conceived in the course of a Master