Add some notes about resampling.

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+\documentclass{article}
+\begin{document}
+
+Here is what resampling we need to do.  Content video is at $C_V$ fps, audio at $C_A$.  
+
+\section{Easy case 1}
+
+$C_V$ and $C_A$ are both DCI rates, e.g.\ if $C_V = 24$, $C_A = 48\times{}10^3$.
+
+\medskip
+\textbf{Nothing to do.}
+
+\section{Easy case 2}
+
+$C_V$ is a DCI rate, $C_A$ is not.  e.g.\ if $C_V = 24$, $C_A = 44.1\times{}10^3$.
+
+\medskip
+\textbf{Resample $C_A$ to the DCI rate.}
+
+\section{Hard case 1}
+
+$C_V$ is not a DCI rate, $C_A$ is.  e.g.\ if $C_V = 25$, $C_A =
+48\times{}10^3$.  We will run the video at a nearby DCI rate $F_V$,
+meaning that it will run faster or slower than it should.  We resample
+the audio to $C_V C_A / F_V$ and mark it as $C_A$ so that it, too,
+runs faster or slower by the corresponding factor.
+
+e.g.\ if $C_V = 25$, $F_V = 24$ and $C_A = 48\times{}10^3$, we
+resample audio to $25 * 48\times{}10^3 / 24 = 50\times{}10^3$.
+
+\medskip
+\textbf{Resample $C_A$ to $C_V C_A / F_V$}
+
+
+\end{document}