The heterodyne filter analysis window allows access to the hetro soundfile utility. This program (more fully documented in the Csound manual) analyzes a sound file, decomposes it into a set of component sinusoids, and outputs a description of the components which can be used by the adsyn opcode in Csound for resynthesis.

The following controls are present in the window:

Sound Input File

The name of the file containing the sound to be analyzed. For realtime input, enter either adc or devaudio.
NOTE: Realtime sound input is only available when the Csound Server is running.
This is a mandatory entry field.

Analysis Output File

The name of the generated file containing the resulting data.
This is a mandatory entry field.

Transcript

If this entry field contains a filename, all messages printed during analysis are logged and written to the named file.

Sample Rate

If present, indicates the sample rate of the sound input file. If omitted, the sample rate in the sound file's header is used. For headerless files, analysis assumes a default sample rate of 10000Hz.

Channel Number

Selects one of the channels in the sound input file. Default is channel 1.

Begin Time

Offset (in seconds) from the start of the input file to the start of the segment to be analyzed.

Duration

Length (in seconds) of the analyzed segment of the input file. If this parameter is omitted, analysis proceeds to the end of the file.
The maximum length of a segment to be analyzed is 32.766 seconds.

Starting Frequency

Estimated starting frequency of the fundamental (default 100Hz).

Harmonic Partials

Number of harmonic partials sought. A maximal number of 50 partials can be selected, the default being 10.

Maximum Amplitude

Maximum amplitude summed across all concurrent tracks (default 32767).

Amplitude Threshold

Amplitude threshold below which a single pair of tracks (amplitude and frequency) will not contribute to the output. The manual gives the following typical values:

Threshold value	Amplitude
128	-48dB
64	-54dB (default)
32	-60dB
0	No thresholding occurs.

Breakpoints

Initial number of analysis breakpoints in each track. Defaults to 256.

Low-Pass Filter Cutoff

If this field is left blank, the input signal is passed through an averaging comb filter; otherwise, the signal is filtered using a 3rd order low-pass Butterworth filter with the given cutoff frequency (in Hz).

Analyze

Clicking on this button (when enabled) starts analysis using the given parameters.

Abort

Clicking on this button (when enabled) causes a running analysis to be aborted.