kicking off Codec 2 documentation

doc/codec2.tex

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+\documentclass{article}
+\usepackage{amsmath}
+\usepackage{hyperref}
+\usepackage{tikz}
+
+\usepackage{xstring}
+\usepackage{catchfile}
+
+\CatchFileDef{\headfull}{../.git/HEAD}{}
+\StrGobbleRight{\headfull}{1}[\head]
+\StrBehind[2]{\head}{/}[\branch]
+\IfFileExists{../.git/refs/heads/\branch}{%
+    \CatchFileDef{\commit}{../.git/refs/heads/\branch}{}}{%
+    \newcommand{\commit}{\dots~(in \emph{packed-refs})}}
+\newcommand{\gitrevision}{%
+  \StrLeft{\commit}{7}%
+}
+
+\title{Codec 2}
+\author{David Rowe\\ \\ Revision: {\gitrevision} on branch: {\branch}}
+
+\begin{document}
+\maketitle
+
+\section{Introduction}
+
+Codec 2 is an open source speech codec designed for communications quality speech between 700 and 3200 bit/s. The main application is low bandwidth HF/VHF digital radio. It fills a gap in open source voice codecs beneath 5000 bit/s and is released under the GNU Lesser General Public License (LGPL).  It is written in C99 standard C.
+
+The Codec 2 project was started in 2009 in response to the problem of closed source, patented, proprietary voice codecs in the sub-5 kbit/s range, in particular for use in the Amateur Radio service.
+
+This document describes Codec 2 at two levels.  Section \ref{sect:overview} is a high level overview aimed at the Radio Amateur, while Section \ref{sect:details} contains a more detailed description with math and signal processing theory. This document is not a concise algorithmic description, instead the algorithm is defined by the reference C99 source code and automated tests (ctests).
+
+This production of this document was kindly supported by an ARDC grant \cite{ardc2023}.  As an open source project, many people have contributed to Codec 2 over the years - we deeply appreciate all of your support.
+
+\section{Codec 2 for the Radio Amateur}
+\label{sect:overview}
+
+\section{Signal Processing Details}
+\label{sect:details}
+
+\section{Further Work}
+
+
+\cite{griffin1988multiband}
+
+\bibliographystyle{plain}
+\bibliography{codec2_refs}
+\end{document}

doc/codec2_refs.bib

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+@article{griffin1988multiband,
+  title={Multiband excitation vocoder},
+  author={Griffin, Daniel W and Lim, Jae S},
+  journal={IEEE Transactions on acoustics, speech, and signal processing},
+  volume={36},
+  number={8},
+  pages={1223--1235},
+  year={1988},
+  publisher={IEEE}
+}
+@book{rowe1997techniques,
+  title={Techniques for harmonic sinusoidal coding},
+  author={Rowe, David Grant},
+  year={1997},
+  publisher={Citeseer},
+  note = {\url{https://www.rowetel.com/downloads/1997_rowe_phd_thesis.pdf}}
+}
+
+@misc{ardc2023,
+  title = {{Enhancing HF Digital Voice with FreeDV}},
+  year = {2023}, 
+  note = {\url{https://www.ardc.net/apply/grants/2023-grants/enhancing-hf-digital-voice-with-freedv/}}
+}
+