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<refentry id="hetro">
<refentryinfo><title>Utilities</title></refentryinfo>
<refmeta>
<refentrytitle>hetro</refentrytitle>
</refmeta>
<refnamediv>
<refname>hetro</refname>
<refpurpose>
Decomposes an input soundfile into component sinusoids.
<indexterm id="IndexHetro"><primary>hetro</primary></indexterm>
</refpurpose>
</refnamediv>
<refsect1>
<title>Description</title>
<para>
Hetrodyne filter analysis for the Csound <link linkend="adsyn"><citetitle>adsyn</citetitle></link> generator.
</para>
</refsect1>
<refsect1>
<title>Syntax</title>
<synopsis><command>csound -U hetro</command> [flags] infilename outfilename</synopsis>
<synopsis><command>hetro</command> [flags] infilename outfilename</synopsis>
</refsect1>
<refsect1>
<title>Initialization</title>
<para>
<emphasis>hetro</emphasis> takes an input soundfile, decomposes it into component sinusoids, and outputs a description of the components in the form of breakpoint amplitude and frequency tracks. Analysis is conditioned by the control flags below. A space is optional between flag and value.
</para>
<para>
<emphasis>-s srate</emphasis> -- sampling rate of the audio input file. This will over-ride the srate of the soundfile header, which otherwise applies. If neither is present, the default is 10000. Note that for <emphasis>adsyn</emphasis> synthesis the srate of the source file and the generating orchestra need not be the same.
</para>
<para>
<emphasis>-c channel</emphasis> -- channel number sought. The default is 1.
</para>
<para>
<emphasis>-b begin</emphasis> -- beginning time (in seconds) of the audio segment to be analyzed. The default is 0.0
</para>
<para>
<emphasis>-d duration</emphasis> -- duration (in seconds) of the audio segment to be analyzed. The default of 0.0 means to the end of the file. Maximum length is 32.766 seconds.
</para>
<para>
<emphasis>-f begfreq</emphasis> -- estimated starting frequency of the fundamental, necessary to initialize the filter analysis. The default is 100 (cps).
</para>
<para>
<emphasis>-h partials</emphasis> -- number of harmonic partials sought in the audio file. Default is 10, maximum is a function of memory available.
</para>
<para>
<emphasis>-M maxamp</emphasis> -- maximum amplitude summed across all concurrent tracks. The default is 32767.
</para>
<para>
<emphasis>-m minamp</emphasis> -- amplitude threshold below which a single pair of amplitude/frequency tracks is considered dormant and will not contribute to output summation. Typical values: 128 (48 db down from full scale), 64 (54 db down), 32 (60 db down), 0 (no thresholding). The default threshold is 64 (54 db down).
</para>
<para>
<emphasis>-n brkpts</emphasis> -- initial number of analysis
breakpoints in each amplitude and frequency track, prior to
thresholding (<emphasis>-m</emphasis>) and linear breakpoint
consolidation. The initial points are spread evenly over the
duration. The default is 256.
</para>
<para>
<emphasis>-l cutfreq</emphasis> -- substitute a 3rd order
Butterworth low-pass filter with cutoff frequency
<emphasis>cutfreq</emphasis> (in Hz), in place of the default
averaging comb filter. The default is 0 (don't use).
</para>
</refsect1>
<refsect1>
<title>Performance</title>
<para>
As of Csound 4.08, <emphasis>hetro</emphasis> can write SDIF
output files if the output file name ends with
".sdif" or ".SDIF". See the <link
linkend="sdif2ad"><citetitle>sdif2ad utility</citetitle></link>
for more information about the Csound's SDIF support.
</para>
</refsect1>
<refsect1>
<title>Examples</title>
<para>
<!-- <informalexample> -->
<programlisting>
<emphasis>hetro</emphasis> -s44100 -b.5 -d2.5 -h16 -M24000 audiofile.test adsynfile7</programlisting>
<!-- </informalexample> -->
This will analyze 2.5 seconds of channel 1 of a file
"audiofile.test", recorded at 44.1 kHz, beginning .5
seconds from the start, and place the result in a file
"adsynfile7". We request just the first 16 harmonics of
the sound, with 256 initial breakpoint values per amplitude or
frequency track, and a peak summation amplitude of 24000. The
fundamental is estimated to begin at 100 Hz. Amplitude
thresholding is at 54 db down.
</para>
<para>
The Butterworth LPF is not enabled.
</para>
<refsect2 id="HetroFileFormat">
<title>File Format</title>
<para>
The output file contains time-sequenced amplitude and
frequency values for each partial of an additive complex audio
source. The information is in the form of breakpoints (time,
value, time, value, ....) using 16-bit integers in the range 0 -
32767. Time is given in milliseconds, and frequency in Hertz
(cps). The breakpoint data is exclusively non-negative, and the
values -1 and -2 uniquely signify the start of new amplitude and
frequency tracks. A track is terminated by the value
32767. Before being written out, each track is data-reduced by
amplitude thresholding and linear breakpoint consolidation.
</para>
<para>
A component partial is defined by two breakpoint sets: an
amplitude set, and a frequency set. Within a composite file
these sets may appear in any order (amplitude, frequency,
amplitude ....; or amplitude, amplitude..., then frequency,
frequency,...). During <link
linkend="adsyn"><citetitle>adsyn</citetitle></link> resynthesis
the sets are automatically paired (amplitude, frequency) from
the order in which they were found. There should be an equal
number of each.
</para>
<para>
A legal <emphasis>adsyn</emphasis> control file could have
following format:
<informalexample>
<programlisting>
-1 time1 value1 ... timeK valueK 32767 ; amplitude breakpoints for partial 1
-2 time1 value1 ... timeL valueL 32767 ; frequency breakpoints for partial 1
-1 time1 value1 ... timeM valueM 32767 ; amplitude breakpoints for partial 2
-2 time1 value1 ... timeN valueN 32767 ; frequency breakpoints for partial 2
-2 time1 value1 ..........
-2 time1 value1 .......... ; pairable tracks for partials 3 and 4
-1 time1 value1 ..........
-1 time2 value1 ..........</programlisting>
</informalexample>
</para>
</refsect2>
</refsect1>
<refsect1>
<title>Credits</title>
<para>
<simplelist>
<member>Author: Tom Sullivan</member>
<member>1992</member>
<member>Author: &namejohn;</member>
<member>1994</member>
<member>Author: Richard Dobson</member>
<member>2000</member>
</simplelist>
</para>
<para>
October 2002. Thanks to &namerasmus;, added a note about the SDIF format.
</para>
</refsect1>
</refentry>
|
