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<refentry id="hrtfstat">
<indexterm id="IndexHrtfstat">
<primary>hrtfstat</primary>
</indexterm>
<refentryinfo><title>Signal Modifiers:Panning and Spatialization</title></refentryinfo>
<refmeta>
<refentrytitle>hrtfstat</refentrytitle>
</refmeta>
<refnamediv>
<refname>hrtfstat</refname>
<refpurpose>
Generates static 3d binaural audio for headphones using a
Woodworth based spherical head model with improved low frequency
phase accuracy.
</refpurpose>
</refnamediv>
<refsect1>
<title>Description</title>
<para>
This opcode takes a source signal and spatialises it in the 3 dimensional space around a listener using head related transfer function (HRTF) based filters. It produces a static output (azimuth and elevation parameters are i-rate), because a static source allows much more efficient processing than <link linkend="hrtfmove"><citetitle>hrtfmove</citetitle></link> and <link linkend="hrtfmove2"><citetitle>hrtfmove2</citetitle></link>,.
</para>
</refsect1>
<refsect1>
<title>Syntax</title>
<synopsis>
aleft, aright <command>hrtfstat</command> asrc, iAz, iElev, ifilel, ifiler [,iradius, isr]
</synopsis>
</refsect1>
<refsect1>
<title>Initialization</title>
<para>
<emphasis>iAz</emphasis> -- azimuth value in degrees. Positive
values represent position on the right, negative values are
positions on the left.
</para>
<para>
<emphasis>iElev</emphasis> -- elevation value in
degrees. Positive values represent position above horizontal,
negative values are positions below horizontal (min -40).
</para>
<para>
<emphasis>ifilel </emphasis> -- left HRTF spectral data file
</para>
<para>
<emphasis>ifiler </emphasis> -- right HRTF spectral data file
</para>
<note>
<para>
Spectral datafiles (based on the MIT
HRTF database) are available in 3 different sampling rates:
44.1, 48 and 96 khz and are labelled accordingly. Input and
processing sr should match datafile sr. Files should be in the
current directory or the SADIR (see <link linkend="CommandEnvironment"><citetitle>Environment Variables</citetitle></link>).
</para>
</note>
<note>
<para>
HRTF Data files for use with
<link linkend="hrtfmove"><citetitle>hrtfmove</citetitle></link>,
<link linkend="hrtfmove2"><citetitle>hrtfmove2</citetitle></link>,
<link linkend="hrtfstat"><citetitle>hrtfstat</citetitle></link>,
<link linkend="hrtfearly"><citetitle>hrtfearly</citetitle></link>,
<link linkend="hrtfreverb"><citetitle>hrtfreverb</citetitle></link>
were updated for Csound 5.15 and later (the code was updated and is more efficient). Old datafiles are now deprecated.
</para>
</note>
<para>
<emphasis>iradius</emphasis> -- optional, head radius used for
phase spectra calculation in centimeters (default 9.0)
</para>
<para>
<emphasis>isr</emphasis> - optional (default 44.1kHz). Legal
values are 44100, 48000 and 96000.
</para>
</refsect1>
<refsect1>
<title>Performance</title>
<para>
Artifact-free user-defined static spatialisation is made
possible using an interpolation algorithm based on spectral
magnitude interpolation and a derived phase based on the
Woodworth spherical head model.
Accuracy is increased for the data set provided by extracting
and applying a frequency dependent scaling factor to the phase
spectra, leading to a more precise low frequency interaural time
difference.
Users can control head radius for the phase derivation, allowing
a crude level of individualisation.
The static source version of the opcode uses overlap add
convolution (it does not need STFT processing, see <link linkend="hrtfmove2"><citetitle>hrtfmove2</citetitle></link>),
and is thus considerably more efficient than <link linkend="hrtfmove2"><citetitle>hrtfmove2</citetitle></link> or
<link linkend="hrtfmove"><citetitle>hrtfmove</citetitle></link>, but cannot generate moving sources.
</para>
</refsect1>
<refsect1>
<title>Examples</title>
<para>
Here is an example of the hrtfstat opcode. It uses the file <ulink url="examples/hrtfstat.csd"><citetitle>hrtfstat.csd</citetitle></ulink>.
</para>
<example>
<title>Example of the hrtfstat 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/hrtfstat.csd.xml" xmlns:xi="http://www.w3.org/2001/XInclude"/>
</example>
<para>
Here is another example of the hrtfstat opcode. It uses the file <ulink url="examples/hrtfstat-2.csd"><citetitle>htrfstat-2.csd</citetitle></ulink>, and <ulink url="examples/Church.wav"><citetitle>Church.wav</citetitle></ulink>, which is a looped sample.
<example>
<title>Example two of the hrtfstat opcode</title>
<xi:include href="examples-xml/hrtfstat-2.csd.xml" xmlns:xi="http://www.w3.org/2001/XInclude"/>
</example>
</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<link linkend="hrtfmove"><citetitle>hrtfmove</citetitle></link>,
<link linkend="hrtfmove2"><citetitle>hrtfmove2</citetitle></link>,
<link linkend="hrtfer"><citetitle>hrtfer</citetitle></link>.
</para>
<para> More information on this opcode: <ulink url="http://www.csounds.com/journal/issue9/newHRTFOpcodes.html"><citetitle>http://www.csounds.com/journal/issue9/newHRTFOpcodes.html</citetitle></ulink> , written by Brian Carty </para>
</refsect1>
<refsect1>
<title>Credits</title>
<para>
<simplelist>
<member>Author: Brian Carty</member>
<member>Maynooth</member>
<member>2008</member>
</simplelist>
</para>
</refsect1>
</refentry>
|
