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<refentry id="pvstencil">
<indexterm id="IndexPvstencil"><primary>pvstencil</primary></indexterm>
<refentryinfo><title>Spectral Processing:Streaming</title></refentryinfo>
<refmeta>
<refentrytitle>pvstencil</refentrytitle>
</refmeta>
<refnamediv>
<refname>pvstencil</refname>
<refpurpose>
Transforms a pvoc stream according to a masking function table.
</refpurpose>
</refnamediv>
<refsect1>
<title>Description</title>
<para>
Transforms a pvoc stream according to a masking function table;
if the pvoc stream amplitude falls below the value of the function
for a specific pvoc channel, it applies a gain to that channel.
</para>
<para>
The pvoc stream amplitudes are compared to a masking table, if
the fall below the table values, they are scaled by kgain. Prior
to the operation, table values are scaled by klevel, which can be
used as masking depth control.
</para>
<para>
Tables have to be at least fftsize/2 in size; for most GENS it is
important to use an extended-guard point (size power-of-two plus
one), however this is not necessary with GEN43.
</para>
<para>
One of the typical uses of pvstencil would be in noise
reduction. A noise print can be analysed with pvanal into a PVOCEX
file and loaded in a table with GEN43. This then can be used as
the masking table for pvstencil and the amount of reduction would
be controlled by kgain. Skipping post-normalisation will keep the
original noise print average amplitudes. This would provide a good
starting point for a successful noise reduction (so that klevel
can be generally set to close to 1).
</para>
<para>
Other possible transformation effects are possible, such as
filtering and `inverse-masking'.
</para>
</refsect1>
<refsect1>
<title>Syntax</title>
<synopsis>fsig <command>pvstencil</command> fsigin, kgain, klevel, iftable</synopsis>
</refsect1>
<refsect1>
<title>Performance</title>
<para>
<emphasis>fsig</emphasis> -- output pv stream
</para>
<para>
<emphasis>fsigin</emphasis> -- input pv stream.
</para>
<para>
<emphasis>kgain</emphasis> -- `stencil' gain.
</para>
<para>
<emphasis>klevel</emphasis> -- masking function level (scales
the ftable prior to `stenciling') .
</para>
<para>
<emphasis>iftable</emphasis> -- masking function table.
</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>
<example>
<title>Example</title>
<programlisting>
fsig pvsanal asig, 1024, 256, 1024, 1
fclean pvstencil fsig, 0, 1, 1
aclean pvsynth fclean
</programlisting>
</example>
</para>
</refsect1>
<refsect1>
<title>Credits</title>
<para>
<simplelist>
<member>Author: &namevictor;</member>
<member>November 2004 </member>
</simplelist>
</para>
<para>New plugin in version 5</para>
<para>Nivember 2004.</para>
</refsect1>
</refentry>
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