+The <guilabel>Audio Channels</guilabel> control sets the number of
+audio channels that the DCP will have. If the DCP has any channels
+for which there is no content audio they will be replaced by silence.
+You can only set an even number of channels here, since that is
+required by the DCI standard. If you want an odd number of channels,
+set the DCP channel count to one greater than you need and the
+unused channel will be filled with silence.
+</para>
+
+<para>
+The <guilabel>Processor</guilabel> control allows you to select a
+process to apply to the audio before it goes into the DCP. Two processes are currently provided:
+</para>
+
+<itemizedlist>
+<listitem>Mid-side decode — this will take a L/R
+stereo input and extract the common part (corresponding to the
+‘Mid’ in a mid-side signal) into the DCP's centre channel.
+The remaining L/R parts will be kept in the L/R channels of the DCP.
+This may be useful to make near-field L/R mixes more compatible with
+cinema audio systems.</listitem>
+<listitem>Stereo to 5.1 up-mixer A — this will take a stereo input and up-mix it to ‘fake’ 5.1. The input L/R are treated as follows:
+<itemizedlist>
+<listitem>DCP L is input L bandpass-filtered between 1.9kHz and 4.8kHz.</listitem>
+<listitem>DCP R is input R bandpass-filtered between 1.9kHz and 4.8kHz.</listitem>
+<listitem>DCP C is input L mixed with input R, taken down by 3dB and then bandpass-filtered between 150Hz and 1.9kHz.</listitem>
+<listitem>DCP Lfe is input L mixed with input R, taken down by 3dB and then bandpass-filtered between 20Hz and 150Hz.</listitem>
+<listitem>DCP Ls is input L bandpass-filtered between 4.8kHz and 20kHz.</listitem>
+<listitem>DCP Rs is input R bandpass-filtered between 4.8kHz and 20kHz.</listitem>
+</itemizedlist>
+</listitem>
+</itemizedlist>
+
+<para>
+This upmixing algorithm is due to Gérald Maruccia.
+</para>
+
+
+<!-- ============================================================== -->
+<section>
+<title>Show audio</title>
+
+<para>
+The <guilabel>Show Audio</guilabel> button will instruct DCP-o-matic
+to examine the audio in your content and plot a graph of its level
+over time. This can be useful for getting a rough idea of how loud
+the sound will be in the cinema auditorium. A typical plot is shown
+in <xref linkend="fig-audio-plot"/>
+</para>
+
+<figure id="fig-audio-plot">
+ <title>Audio plot</title>
+ <mediaobject>
+ <imageobject>
+ <imagedata fileref="screenshots/audio-plot&scs;"/>
+ </imageobject>
+ </mediaobject>
+</figure>
+
+<para>
+The plot gives the audio level (vertical axis, in dB) with time
+(horizontal axis). 0dB represents full scale, so if there is anything
+near this you are in danger of clipping the projector's audio outputs.
+</para>
+
+<para>
+There are two plot types: the peak level and the RMS, which can be
+shown or hidden using the check-boxes on the right hand side of the
+window.
+</para>
+
+<para>
+The channel check-boxes will show or hide the plot(s) for
+the corresponding channels in the DCP.
+</para>
+
+<para>
+The smoothing slider applies a variable degree of temporal smoothing
+to the plots, which can make them easier to read in some cases.