247 lines
8.9 KiB
C
247 lines
8.9 KiB
C
/*
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* SpanDSP - a series of DSP components for telephony
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*
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* tone_detect.h - General telephony tone detection.
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*
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* Written by Steve Underwood <steveu@coppice.org>
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*
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* Copyright (C) 2001, 2005 Steve Underwood
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*
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* All rights reserved.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License version 2.1,
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* as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#if !defined(_SPANDSP_TONE_DETECT_H_)
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#define _SPANDSP_TONE_DETECT_H_
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/*!
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Goertzel filter descriptor.
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*/
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struct goertzel_descriptor_s
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{
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#if defined(SPANDSP_USE_FIXED_POINT)
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int16_t fac;
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#else
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float fac;
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#endif
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int samples;
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};
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/*!
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Goertzel filter state descriptor.
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*/
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struct goertzel_state_s
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{
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#if defined(SPANDSP_USE_FIXED_POINT)
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int16_t v2;
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int16_t v3;
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int16_t fac;
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#else
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float v2;
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float v3;
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float fac;
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#endif
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int samples;
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int current_sample;
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};
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/*!
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Goertzel filter descriptor.
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*/
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typedef struct goertzel_descriptor_s goertzel_descriptor_t;
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/*!
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Goertzel filter state descriptor.
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*/
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typedef struct goertzel_state_s goertzel_state_t;
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#if defined(__cplusplus)
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extern "C"
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{
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#endif
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/*! \brief Create a descriptor for use with either a Goertzel transform */
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SPAN_DECLARE(void) make_goertzel_descriptor(goertzel_descriptor_t *t,
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float freq,
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int samples);
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/*! \brief Initialise the state of a Goertzel transform.
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\param s The Goertzel context. If NULL, a context is allocated with malloc.
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\param t The Goertzel descriptor.
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\return A pointer to the Goertzel state. */
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SPAN_DECLARE(goertzel_state_t *) goertzel_init(goertzel_state_t *s,
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goertzel_descriptor_t *t);
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SPAN_DECLARE(int) goertzel_release(goertzel_state_t *s);
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SPAN_DECLARE(int) goertzel_free(goertzel_state_t *s);
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/*! \brief Reset the state of a Goertzel transform.
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\param s The Goertzel context. */
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SPAN_DECLARE(void) goertzel_reset(goertzel_state_t *s);
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/*! \brief Update the state of a Goertzel transform.
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\param s The Goertzel context.
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\param amp The samples to be transformed.
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\param samples The number of samples.
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\return The number of samples unprocessed */
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SPAN_DECLARE(int) goertzel_update(goertzel_state_t *s,
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const int16_t amp[],
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int samples);
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/*! \brief Evaluate the final result of a Goertzel transform.
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\param s The Goertzel context.
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\return The result of the transform. The expected result for a pure sine wave
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signal of level x dBm0, at the very centre of the bin is:
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[Floating point] ((samples_per_goertzel_block*32768.0/1.4142)*10^((x - DBM0_MAX_SINE_POWER)/20.0))^2
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[Fixed point] ((samples_per_goertzel_block*256.0/1.4142)*10^((x - DBM0_MAX_SINE_POWER)/20.0))^2 */
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#if defined(SPANDSP_USE_FIXED_POINT)
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SPAN_DECLARE(int32_t) goertzel_result(goertzel_state_t *s);
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#else
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SPAN_DECLARE(float) goertzel_result(goertzel_state_t *s);
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#endif
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/*! \brief Update the state of a Goertzel transform.
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\param s The Goertzel context.
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\param amp The sample to be transformed. */
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static __inline__ void goertzel_sample(goertzel_state_t *s, int16_t amp)
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{
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#if defined(SPANDSP_USE_FIXED_POINT)
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int16_t x;
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int16_t v1;
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#else
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float v1;
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#endif
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v1 = s->v2;
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s->v2 = s->v3;
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#if defined(SPANDSP_USE_FIXED_POINT)
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x = (((int32_t) s->fac*s->v2) >> 14);
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/* Scale down the input signal to avoid overflows. 9 bits is enough to
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monitor the signals of interest with adequate dynamic range and
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resolution. In telephony we generally only start with 13 or 14 bits,
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anyway. */
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s->v3 = x - v1 + (amp >> 7);
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#else
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s->v3 = s->fac*s->v2 - v1 + amp;
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#endif
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s->current_sample++;
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}
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/*- End of function --------------------------------------------------------*/
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/* Scale down the input signal to avoid overflows. 9 bits is enough to
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monitor the signals of interest with adequate dynamic range and
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resolution. In telephony we generally only start with 13 or 14 bits,
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anyway. This is sufficient for the longest Goertzel we currently use. */
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#if defined(SPANDSP_USE_FIXED_POINT)
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#define goertzel_preadjust_amp(amp) (((int16_t) amp) >> 7)
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#else
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#define goertzel_preadjust_amp(amp) ((float) amp)
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#endif
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/* Minimal update the state of a Goertzel transform. This is similar to
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goertzel_sample, but more suited to blocks of Goertzels. It assumes
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the amplitude is pre-shifted, and does not update the per-state sample
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count.
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\brief Update the state of a Goertzel transform.
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\param s The Goertzel context.
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\param amp The adjusted sample to be transformed. */
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#if defined(SPANDSP_USE_FIXED_POINT)
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static __inline__ void goertzel_samplex(goertzel_state_t *s, int16_t amp)
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#else
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static __inline__ void goertzel_samplex(goertzel_state_t *s, float amp)
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#endif
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{
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#if defined(SPANDSP_USE_FIXED_POINT)
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int16_t x;
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int16_t v1;
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#else
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float v1;
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#endif
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v1 = s->v2;
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s->v2 = s->v3;
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#if defined(SPANDSP_USE_FIXED_POINT)
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x = (((int32_t) s->fac*s->v2) >> 14);
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s->v3 = x - v1 + amp;
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#else
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s->v3 = s->fac*s->v2 - v1 + amp;
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#endif
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}
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/*- End of function --------------------------------------------------------*/
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/*! Generate a Hamming weighted coefficient set, to be used for a periodogram analysis.
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\param coeffs The generated coefficients.
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\param freq The frequency to be matched by the periodogram, in Hz.
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\param sample_rate The sample rate of the signal, in samples per second.
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\param window_len The length of the periodogram window. This must be an even number.
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\return The number of generated coefficients.
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*/
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SPAN_DECLARE(int) periodogram_generate_coeffs(complexf_t coeffs[], float freq, int sample_rate, int window_len);
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/*! Generate the phase offset to be expected between successive periodograms evaluated at the
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specified interval.
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\param offset A point to the generated phase offset.
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\param freq The frequency being matched by the periodogram, in Hz.
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\param sample_rate The sample rate of the signal, in samples per second.
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\param interval The interval between periodograms, in samples.
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\return The scaling factor.
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*/
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SPAN_DECLARE(float) periodogram_generate_phase_offset(complexf_t *offset, float freq, int sample_rate, int interval);
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/*! Evaluate a periodogram.
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\param coeffs A set of coefficients generated by periodogram_generate_coeffs().
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\param amp The complex amplitude of the signal.
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\param len The length of the periodogram, in samples. This must be an even number.
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\return The periodogram result.
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*/
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SPAN_DECLARE(complexf_t) periodogram(const complexf_t coeffs[], const complexf_t amp[], int len);
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/*! Prepare data for evaluating a set of periodograms.
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\param sum A vector of sums of pairs of signal samples. This will be half the length of len.
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\param diff A vector of differences between pairs of signal samples. This will be half the length of len.
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\param amp The complex amplitude of the signal.
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\param len The length of the periodogram, in samples. This must be an even number.
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\return The length of the vectors sum and diff.
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*/
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SPAN_DECLARE(int) periodogram_prepare(complexf_t sum[], complexf_t diff[], const complexf_t amp[], int len);
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/*! Evaluate a periodogram, based on data prepared by periodogram_prepare(). This is more efficient
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than using periodogram() when several periodograms are to be applied to the same signal.
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\param coeffs A set of coefficients generated by periodogram_generate_coeffs().
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\param sum A vector of sums produced by periodogram_prepare().
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\param diff A vector of differences produced by periodogram_prepare().
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\param len The length of the periodogram, in samples. This must be an even number.
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\return The periodogram result.
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*/
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SPAN_DECLARE(complexf_t) periodogram_apply(const complexf_t coeffs[], const complexf_t sum[], const complexf_t diff[], int len);
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/*! Apply a phase offset, to find the frequency error between periodogram evaluations.
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specified interval.
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\param phase_offset A point to the expected phase offset.
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\param scale The scaling factor to be used.
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\param last_result A pointer to the previous periodogram result.
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\param result A pointer to the current periodogram result.
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\return The frequency error, in Hz.
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*/
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SPAN_DECLARE(float) periodogram_freq_error(const complexf_t *phase_offset, float scale, const complexf_t *last_result, const complexf_t *result);
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#if defined(__cplusplus)
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}
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#endif
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#endif
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/*- End of file ------------------------------------------------------------*/
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