Added doco for ratecv.
diff --git a/Doc/libaudioop.tex b/Doc/libaudioop.tex
index 6a74a0b..13a82b3 100644
--- a/Doc/libaudioop.tex
+++ b/Doc/libaudioop.tex
@@ -146,6 +146,17 @@
silently ignored.
\end{funcdesc}
+\begin{funcdesc}{ratecv}{fragment\, width\, nchannels\, inrate\, outrate\, state\optional{\, weightA\, weightB}}
+Convert the frame rate of the input fragment.
+
+\code{State} is a tuple containing the state of the converter. The
+converter returns a tupl \code{(\var{newfragment}, \var{newstate})},
+and \var{newstate} should be passed to the next call of ratecv.
+
+The \code{weightA} and \coden{weightB} arguments are parameters for a
+simple digital filter and default to 1 and 0 respectively.
+\end{funcdesc}
+
\begin{funcdesc}{reverse}{fragment\, width}
Reverse the samples in a fragment and returns the modified fragment.
\end{funcdesc}