Further WIP

This commit is contained in:
Laurence Withers 2014-07-10 16:46:22 +00:00
parent 739ef26da3
commit 836fa2eb40
15 changed files with 581 additions and 5 deletions

5
python/.gitignore vendored Normal file
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.ipynb_checkpoints/
__pycache__/
build/
fir.py
pyfir_wrap.cxx

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1
python/fir++.h Symbolic link
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../obj/fir++.h

24
python/pyfir.i Normal file
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%module fir
%include <complex.i>
/*
* List conversion
*
* SWIG knows how to turn std::vector<T> func() into a function that returns a
* Python list. We do need to tell it about all <T> types with %template,
* however.
*/
%include <std_vector.i>
%template(vectord) std::vector<double>;
%{
#include "fir++.h"
%}
%include "fir++.h"
// vim: ts=4:sw=4

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python/setup.py Normal file
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#!/usr/bin/env python3
from distutils.core import setup, Extension
fir_module = Extension('_fir',
sources=['pyfir_wrap.cxx'],
libraries=['fir++'],
)
setup(name = 'fir',
version = '0.0.0',
author = 'Laurence Withers',
description = 'FIR filter',
ext_modules = [fir_module],
py_modules = ['fir'],
)

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@ -10,6 +10,7 @@
// standard includes, or includes needed for type declarations // standard includes, or includes needed for type declarations
#include <vector> #include <vector>
#include <complex>
// forward declares, allowing us to avoid including the C library header // forward declares, allowing us to avoid including the C library header
extern "C" { extern "C" {

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@ -32,6 +32,13 @@ Filter::Filter(const std::vector<double>& coeff, Symmetry symm)
Filter::Filter(struct fir_filter_t* fi)
{
fi_ = fi;
}
Filter::~Filter() Filter::~Filter()
{ {
fir_filter_free(fi_); fir_filter_free(fi_);
@ -71,6 +78,14 @@ Filter::coeff(int idx) const
std::complex<double>
Filter::response(double freq) const
{
return std::complex<double>(fir_filter_response(fi_, freq));
}
/* options for text editors /* options for text editors
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*/ */

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@ -39,7 +39,7 @@ enum Symmetry {
/*! \brief Basic FIR filter object. /*! \brief Basic %FIR filter object.
\ingroup libfirpp_fir \ingroup libfirpp_fir
@ -88,12 +88,25 @@ public:
/*! \brief Take ownership of underlying C filter object.
\param fi Filter.
This constructor may be used to build a filter object using an underlying C
library filter object. The new instance will take ownership of \a fi and
free it when the instance is deleted.
*/
explicit Filter(struct fir_filter_t* fi);
/*! \brief Destructor (frees underlying memory). */ /*! \brief Destructor (frees underlying memory). */
virtual ~Filter(); virtual ~Filter();
/*! \brief Filter a sample. /*! \brief %Filter a sample.
\param x Input sample. \param x Input sample.
\returns Filter output. \returns Filter output.
@ -141,6 +154,20 @@ public:
/*! \brief Evaluate response of filter at given frequency.
\param freq Frequency as a fraction of sampling rate.
\returns Complex response of filter at given frequency.
Performs Z-domain analysis of the filter to determine its complex response
(phase and magnitude) to a signal of the given frequency \a freq, which is
expressed as a fraction of the sampling rate being used with the filter.
*/
std::complex<double> response(double freq) const;
private: private:
struct fir_filter_t* fi_; struct fir_filter_t* fi_;

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/* libfir/src/libfir++/200_CommonFilters.cc
*
* Copyright: ©2014, Laurence Withers.
* Author: Laurence Withers <l@lwithers.me.uk>
* License: GPLv3
*/
Filter
SincLowpass(int npoints, double corner, double gain)
{
return Filter(fir_sinc_lowpass(npoints, corner, gain));
}
Filter
LanczosLowpass(int npoints, double corner, double gain, int a)
{
return Filter(fir_lanczos_lowpass(npoints, corner, gain, a));
}
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*/

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/* libfir/src/libfir++/200_CommonFilters.h
*
* Copyright: ©2014, Laurence Withers.
* Author: Laurence Withers <l@lwithers.me.uk>
* License: GPLv3
*/
/*! \defgroup libfirpp_common Common filter types
\ingroup libfirpp
*/
/*!@{*/
/*! \brief Brickwall low-pass linear phase: sinc filter.
\param npoints Number of points required (1).
\param corner Corner frequency as fraction of sample rate.
\param gain Gain of filter.
\returns Newly-allocated %FIR filter.
Builds a truncated-sinc filter which has a low-pass, brickwall effect (cutoff
at \a corner, which is a fraction of sampling rate, i.e. 0 &lt; \a corner &lt;
0.5).
The number of points \a npoints is a trade-off between accuracy of filter (an
ideal sinc filter would have an infinite number of points) and computation time.
\a npoints may be odd or even; symmetry will be exploited in either case.
The DC gain of the filter is normalised to \a gain, which is often 1.0.
*/
Filter SincLowpass(int npoints, double corner, double gain);
Filter LanczosLowpass(int npoints, double corner, double gain, int a);
/*!@}*/
/* options for text editors
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*/

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@ -8,14 +8,15 @@
#ifndef HEADER_libfir #ifndef HEADER_libfir
#define HEADER_libfir #define HEADER_libfir
/* standard includes, or includes needed for type declarations */
#include <complex.h>
#ifdef __cplusplus #ifdef __cplusplus
extern "C" { extern "C" {
#endif #endif
/*! \defgroup libfir C library */ /*! \defgroup libfir C library */
/* standard includes, or includes needed for type declarations */
/* options for text editors /* options for text editors
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*/ */

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@ -29,7 +29,7 @@ fir_sinc_lowpass(int npoints, double corner, double gain)
sum += 1; /* not 2, as we don't repeat this coeff */ sum += 1; /* not 2, as we don't repeat this coeff */
} else { } else {
t = i + 0.5 - npoints * 0.5; t = i + 0.5 - npoints * 0.5;
t *= corner * 2; t *= corner * 2 * M_PI;
coeff[i] = sin(t) / t; coeff[i] = sin(t) / t;
sum += coeff[i] * 2; sum += coeff[i] * 2;
} }
@ -47,6 +47,46 @@ fir_sinc_lowpass(int npoints, double corner, double gain)
struct fir_filter_t*
fir_lanczos_lowpass(int npoints, double corner, double gain, int a)
{
double* coeff, t, sum = 0;
int i, spoints;
if(npoints < 1) {
errno = EINVAL;
return 0;
}
/* find number of points after taking symmetry into account */
spoints = (npoints + 1) / 2;
coeff = alloca(sizeof(double) * spoints);
/* only fill out for t ≤ 0 */
for(i = 0; i < spoints; ++i) {
if((i * 2 + 1) == npoints) {
coeff[i] = 1;
sum += 1; /* not 2, as we don't repeat this coeff */
} else {
t = i + 0.5 - npoints * 0.5;
t *= corner * 2 * M_PI;
coeff[i] = (sin(t) / t) * sin(t / a) / (t / a);
sum += coeff[i] * 2;
}
}
/* normalise gain */
gain /= sum;
for(i = 0; i < spoints; ++i) {
coeff[i] *= gain;
}
return fir_filter_new(spoints, coeff,
(npoints & 1) ? fir_symmetry_odd : fir_symmetry_even);
}
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*/ */

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@ -41,6 +41,10 @@ struct fir_filter_t* fir_sinc_lowpass(int npoints, double corner, double gain);
struct fir_filter_t* fir_lanczos_lowpass(int npoints, double corner, double gain, int a);
/*!@}*/ /*!@}*/
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/* libfir/src/libfir/300_response.c
*
* Copyright: ©2014, Laurence Withers.
* Author: Laurence Withers <l@lwithers.me.uk>
* License: GPLv3
*/
double complex
fir_filter_response(const struct fir_filter_t* fi, double freq)
{
int i, ncoeff = fir_filter_get_ncoeff(fi);
double omega = 2 * M_PI * freq;
double complex resp = 0;
for(i = 0; i < ncoeff; ++i) {
resp += fir_filter_get_coeff(fi, i) * cexp(I * omega * i);
}
return resp;
}
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/* libfir/src/libfir/300_response.h
*
* Copyright: ©2014, Laurence Withers.
* Author: Laurence Withers <l@lwithers.me.uk>
* License: GPLv3
*/
/*! \defgroup libfir_response Response analysis
\ingroup libfir
Routines in this section allow the evaluation of the filter's response.
*/
/*!@{*/
/*! \brief Measure phase and frequency response of filter at frequency.
\param fi Filter to evaluate.
\param freq Frequency (as a ratio of sample rate).
\returns Complex response of filter at given frequency.
Performs Z-domain analysis of the filter to determine the magnitude and phase of
its response to a signal of the given frequency. \a freq is expressed as a
fraction of the sample rate to be used with the filter.
*/
double complex fir_filter_response(const struct fir_filter_t* fi, double freq);
/*!@}*/
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*/