window.c 6.81 KB
Newer Older
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
/*****************************************************************************
 * window.c : Implementation of FFT window routines
 *****************************************************************************
 * Copyright (C) 2014 Ronald Wright
 * $Id$
 *
 * Author: Ronald Wright <logiconcepts819@gmail.com>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
 *****************************************************************************/

#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include <math.h>
#include "window.h"
#include "window_presets.h"

32 33
#include <assert.h>

34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186
/* Flat top window coefficients */
#define FT_A0 1.000f
#define FT_A1 1.930f
#define FT_A2 1.290f
#define FT_A3 0.388f
#define FT_A4 0.028f

/* Blackman-Harris window coefficients */
#define BH_A0 0.35875f
#define BH_A1 0.48829f
#define BH_A2 0.14128f
#define BH_A3 0.01168f

/*
 * The modified Bessel function I0(x).  See Chapter 6 of the "Numerical Recipes
 * in C: The Art of Scientific Computing" book at
 * http://www.aip.de/groups/soe/local/numres/bookcpdf/c6-6.pdf
 */
static float bessi0( float x )
{
    float ax, ans;
    double y; /* Accumulate polynomials in double precision. */
    if( ( ax = fabsf( x ) ) < 3.75f ) /* Polynomial fit. */
    {
        y = x / 3.75;
        y *= y;
        ans = 1.0 + y * ( 3.5156229 + y * ( 3.0899424 + y * ( 1.2067492
                  + y * ( 0.2659732 + y * ( 0.360768e-1
                  + y * 0.45813e-2 ) ) ) ) );
    }
    else
    {
        y = 3.75 / ax;
        ans = ( exp( ax ) / sqrt( ax ) ) * ( 0.39894228 + y * ( 0.1328592e-1
            + y * ( 0.225319e-2 + y * ( -0.157565e-2 + y * ( 0.916281e-2
            + y * ( -0.2057706e-1 + y * ( 0.2635537e-1 + y * ( -0.1647633e-1
            + y * 0.392377e-2 ) ) ) ) ) ) ) );
    }
    return ans;
}

/*
 * Obtain the window type from the window type variable.
 */
void window_get_param( vlc_object_t * p_aout, window_param * p_param )
{
    /* Fetch Kaiser parameter */
    p_param->f_kaiser_alpha = var_InheritFloat( p_aout, "effect-kaiser-param" );

    /* Fetch window type */
    char * psz_preset = var_InheritString( p_aout, "effect-fft-window" );
    if( !psz_preset )
    {
        goto no_preset;
    }

    for( int i = 0; i < NB_WINDOWS; i++ )
    {
        if( !strcasecmp( psz_preset, window_list[i] ) )
        {
            p_param->wind_type = i;
            return;
        }
    }

no_preset:
    msg_Warn( p_aout, "No matching window preset found; using rectangular "
                      "window (i.e. no window)" );
    p_param->wind_type = NONE;
}

/*
 * Initialization routine - sets up a lookup table for scaling a sample of data
 * by window data.  If the lookup table is successfully allocated, its memory
 * location and its specified size are stored at the specified memory location
 * of the internal context.
 * Returns true if initialization succeeded and returns false otherwise.
 * The internal context should be freed when it is finished with, by
 * window_close().
 */
bool window_init( int i_buffer_size, window_param * p_param,
                  window_context * p_ctx )
{
    float * pf_table = NULL;
    window_type wind_type = p_param->wind_type;

    if( wind_type != HANN && wind_type != FLATTOP
                          && wind_type != BLACKMANHARRIS
                          && wind_type != KAISER )
    {
        /* Assume a rectangular window (i.e. no window) */
        i_buffer_size = 0;
        goto exit;
    }

    pf_table = malloc( i_buffer_size * sizeof( *pf_table ) );
    if( !pf_table )
    {
        /* Memory allocation failed */
        return false;
    }

    int i_buffer_size_minus_1 = i_buffer_size - 1;
    switch( wind_type )
    {
    case HANN:
        /* Hann window */
        for( int i = 0; i < i_buffer_size; i++ )
        {
            float f_val = (float) i / (float) i_buffer_size_minus_1;
            pf_table[i] = 0.5f - 0.5f * cosf( 2.0f * (float) M_PI * f_val );
        }
        break;
    case FLATTOP:
        /* Flat top window */
        for( int i = 0; i < i_buffer_size; i++ )
        {
            float f_val = (float) i / (float) i_buffer_size_minus_1;
            pf_table[i] = FT_A0
                        - FT_A1 * cosf( 2.0f * (float) M_PI * f_val )
                        + FT_A2 * cosf( 4.0f * (float) M_PI * f_val )
                        - FT_A3 * cosf( 6.0f * (float) M_PI * f_val )
                        + FT_A4 * cosf( 8.0f * (float) M_PI * f_val );
        }
        break;
    case BLACKMANHARRIS:
        /* Blackman-Harris window */
        for( int i = 0; i < i_buffer_size; i++ )
        {
            float f_val = (float) i / (float) i_buffer_size_minus_1;
            pf_table[i] = BH_A0
                        - BH_A1 * cosf( 2.0f * (float) M_PI * f_val )
                        + BH_A2 * cosf( 4.0f * (float) M_PI * f_val )
                        - BH_A3 * cosf( 6.0f * (float) M_PI * f_val );
        }
        break;
    case KAISER:
    {
        /* Kaiser window */
        float f_pialph = (float) M_PI * p_param->f_kaiser_alpha;
        float f_bessi0_pialph = bessi0( f_pialph );
        for( int i = 0; i < i_buffer_size; i++ )
        {
            float f_val = (float) i / (float) i_buffer_size_minus_1;
            float f_term_to_square = 2.0f * f_val - 1.0f;
            float f_sqd_term = f_term_to_square * f_term_to_square;
            float f_sqr_term = sqrtf( 1.0f - f_sqd_term );
            pf_table[i] = bessi0( f_pialph * f_sqr_term ) / f_bessi0_pialph;
        }
        break;
    }
    default:
        /* We should not reach here */
187
        vlc_assert_unreachable();
188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220
        break;
    }

exit:
    p_ctx->pf_window_table = pf_table;
    p_ctx->i_buffer_size = i_buffer_size;
    return true;
}

/*
 * Perform an in-place scaling of the input buffer by the window data
 * referenced from the specified context.
 */
void window_scale_in_place( int16_t * p_buffer, window_context * p_ctx )
{
    for( int i = 0; i < p_ctx->i_buffer_size; i++ )
    {
        p_buffer[i] *= p_ctx->pf_window_table[i];
    }
}

/*
 * Free the context.
 */
void window_close( window_context * p_ctx )
{
    if( p_ctx->pf_window_table )
    {
        free( p_ctx->pf_window_table );
        p_ctx->pf_window_table = NULL;
        p_ctx->i_buffer_size = 0;
    }
}