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<refentry id="pvsmooth">
<indexterm id="Indexpvsmooth"><primary>pvsmooth</primary></indexterm>
<refentryinfo><title>Spectral Processing:Streaming</title></refentryinfo>
<refmeta>
<refentrytitle>pvsmooth</refentrytitle>
</refmeta>
<refnamediv>
<refname>pvsmooth</refname>
<refpurpose>
Smooth the amplitude and frequency time functions of a pv stream using parallel 1st order
lowpass IIR filters with time-varying cutoff frequency.
</refpurpose>
</refnamediv>
<refsect1>
<title>Description</title>
<para>
Smooth the amplitude and frequency time functions of a pv stream using a 1st order
lowpass IIR with time-varying cutoff frequency. This opcode uses the same filter
as the <emphasis>tone</emphasis> opcode, but this time acting separately on the amplitude and frequency
time functions that make up a pv stream. The cutoff frequency parameter runs at the
control-rate, but unlike <emphasis>tone</emphasis> and <emphasis>tonek</emphasis>, it is not specified in Hz, but as fractions
of 1/2 frame-rate (actually the pv stream sampling rate), which is easier to
understand. This means that the highest cutoff frequency is 1 and the lowest 0; the lower
the frequency the smoother the functions and more pronounced the effect will be.
</para>
<para>
These are filters applied to control signals so the effect is basically blurring the spectral evolution. The effects produced are more or less similar to <emphasis>pvsblur</emphasis>, but with two important
differences: 1.smoothing of amplitudes and frequencies use separate sets of filters; and 2. there is
no increase in computational cost when higher amounts of 'blurring' (smoothing) are desired.
</para>
</refsect1>
<refsect1>
<title>Syntax</title>
<synopsis>fsig <command>pvsmooth</command> fsigin, kacf, kfcf</synopsis>
</refsect1>
<refsect1>
<title>Performance</title>
<para>
<emphasis>fsig</emphasis> -- output pv stream
</para>
<para>
<emphasis>fsigin</emphasis> -- input pv stream.
</para>
<para>
<emphasis>kacf</emphasis> -- amount of cutoff frequency for amplitude function filtering, between 0 and 1,
in fractions of 1/2 frame-rate.
</para>
<para>
<emphasis>kfcf</emphasis> -- amount of cutoff frequency for frequency function filtering, between 0 and 1,
in fractions of 1/2 frame-rate.
</para>
<warning>
<para>
It is unsafe to use the same f-variable for both input and output of pvs opcodes. Using the same one might lead to undefined behavior on some opcodes. Use a different one on the left and right sides of the opcode.
</para>
</warning>
</refsect1>
<refsect1>
<title>Examples</title>
<para>
Here is an example of the pvsmooth opcode. It uses the file <ulink url="examples/pvsmooth.csd"><citetitle>pvsmooth.csd</citetitle></ulink>.
<example>
<title>Example of the pvsmooth opcode.</title>
<para>See the sections <link linkend="UsingRealTime"><citetitle>Real-time Audio</citetitle></link> and <link linkend="CommandFlags"><citetitle>Command Line Flags</citetitle></link> for more information on using command line flags.</para>
<xi:include href="examples-xml/pvsmooth.csd.xml" xmlns:xi="http://www.w3.org/2001/XInclude"/>
</example>
</para>
<para>
The formula for calculating the cutoff frequency of the filter: frame rate / hopsize = new frame starts per second (in Hz), then the percentage of half the framerate.
For example, looking at the first note in the example, the frame rate is 44100 / 256 = 172,265625 Hz (= 172 new frame starts per
second). half of the frame rate is about 86 Hz, and one percent of this is 0.86 Hz.
</para>
</refsect1>
<refsect1>
<title>Credits</title>
<para>
<simplelist>
<member>Author: &namevictor;</member>
<member>May 2006 </member>
</simplelist>
</para>
<para>New plugin in version 5</para>
<para>May 2006.</para>
</refsect1>
</refentry>
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