bandlimited.h

video linux conference

/*****************************************************************************
 * bandlimited.h : bandlimited interpolation resampler
 *****************************************************************************
 * Copyright (C) 2002 VideoLAN
 * $Id: bandlimited.h 10101 2005-03-02 16:47:31Z robux4 $
 *
 * Authors: Gildas Bazin <[e-mail]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111, USA.
 *****************************************************************************/

/* Conversion constants */
#define Nhc       8
#define Npc      (1<<Nhc)

/* Description of constants:
 *
 * Npc - is the number of look-up values available for the lowpass filter
 *    between the beginning of its impulse response and the "cutoff time"
 *    of the filter.  The cutoff time is defined as the reciprocal of the
 *    lowpass-filter cut off frequence in Hz.  For example, if the
 *    lowpass filter were a sinc function, Npc would be the index of the
 *    impulse-response lookup-table corresponding to the first zero-
 *    crossing of the sinc function.  (The inverse first zero-crossing
 *    time of a sinc function equals its nominal cutoff frequency in Hz.)
 *    Npc must be a power of 2 due to the details of the current
 *    implementation. The default value of 512 is sufficiently high that
 *    using linear interpolation to fill in between the table entries
 *    gives approximately 16-bit accuracy in filter coefficients.
 *
 * Nhc - is log base 2 of Npc.
 */

#define SMALL_FILTER_NMULT ((int16_t)13)
#define SMALL_FILTER_SCALE 13128 /* Unity-gain scale factor */
#define SMALL_FILTER_NWING 1536 /* Filter table length */
static float SMALL_FILTER_FLOAT_IMP[] /* Impulse response */ = {
0.900000,
0.899980,
0.899920,
0.899821,
0.899681,
0.899502,
0.899283,
0.899024,
0.898726,
0.898388,
0.898010,
0.897592,
0.897135,
0.896638,
0.896102,
0.895526,
0.894911,
0.894256,
0.893562,
0.892829,
0.892056,
0.891244,
0.890394,
0.889504,
0.888575,
0.887608,
0.886602,
0.885557,
0.884474,
0.883352,
0.882192,
0.880993,
0.879756,
0.878482,
0.877169,
0.875818,
0.874430,
0.873004,
0.871541,
0.870040,
0.868502,
0.866927,
0.865315,
0.863667,
0.861981,
0.860259,
0.858501,
0.856707,
0.854876,
0.853010,
0.851108,
0.849170,
0.847197,
0.845189,
0.843146,
0.841067,
0.838954,
0.836807,
0.834625,
0.832409,
0.830160,
0.827876,
0.825559,
0.823209,
0.820825,
0.818408,
0.815959,
0.813477,
0.810963,
0.808417,
0.805839,
0.803229,
0.800588,
0.797916,
0.795213,
0.792479,
0.789714,
0.786919,
0.784095,
0.781240,
0.778356,
0.775442,
0.772500,
0.769529,
0.766529,
0.763501,
0.760444,
0.757361,
0.754249,
0.751110,
0.747945,
0.744753,
0.741534,
0.738289,
0.735018,
0.731721,
0.728400,
0.725053,
0.721681,
0.718285,
0.714865,
0.711420,
0.707953,
0.704461,
0.700947,
0.697410,
0.693851,
0.690269,
0.686665,
0.683040,
0.679394,
0.675727,
0.672039,
0.668331,
0.664602,
0.660854,
0.657087,
0.653300,
0.649495,
0.645671,
0.641829,
0.637969,
0.634091,
0.630197,
0.626285,
0.622357,
0.618412,
0.614452,
0.610476,
0.606485,
0.602478,
0.598457,
0.594422,
0.590373,
0.586310,
0.582234,
0.578144,
0.574042,
0.569928,
0.565801,
0.561663,
0.557514,
0.553353,
0.549182,
0.545001,
0.540809,
0.536607,
0.532397,
0.528177,
0.523948,
0.519711,
0.515466,
0.511214,
0.506954,
0.502686,
0.498413,
0.494132,
0.489846,
0.485554,
0.481256,
0.476954,
0.472646,
0.468335,
0.464019,
0.459699,
0.455377,
0.451050,
0.446722,
0.442390,
0.438057,
0.433722,
0.429385,
0.425048,
0.420709,
0.416370,
0.412031,
0.407692,
0.403354,
0.399016,
0.394679,
0.390344,
0.386011,
0.381680,
0.377351,
0.373025,
0.368702,
0.364382,
0.360066,
0.355754,
0.351446,
0.347143,
0.342844,
0.338551,
0.334264,
0.329982,
0.325706,
0.321437,
0.317174,
0.312918,
0.308670,
0.304429,
0.300197,
0.295972,
0.291756,
0.287548,
0.283350,
0.279161,
0.274982,
0.270812,
0.266653,
0.262504,
0.258366,
0.254239,
0.250123,
0.246018,
0.241926,
0.237846,
0.233777,
0.229722,
0.225679,
0.221650,
0.217634,
0.213632,
0.209643,
0.205669,
0.201709,
0.197764,
0.193833,
0.189918,
0.186018,
0.182134,
0.178265,
0.174413,
0.170577,
0.166758,
0.162955,
0.159169,
0.155401,
0.151650,
0.147916,
0.144201,
0.140503,
0.136824,
0.133163,
0.129521,
0.125898,
0.122294,
0.118710,
0.115145,
0.111599,
0.108073,
0.104568,
0.101083,
0.097618,
0.094174,
0.090750,
0.087348,
0.083966,
0.080606,
0.077268,
0.073951,
0.070656,
0.067383,
0.064132,
0.060903,
0.057697,
0.054513,
0.051352,
0.048214,
0.045099,
0.042006,
0.038938,
0.035892,
0.032870,
0.029872,
0.026898,
0.023947,
0.021021,
0.018118,
0.015240,
0.012386,
0.009557,
0.006752,
0.003972,
0.001217,
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-0.100693,
-0.102173,
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-0.119042,
-0.120159,
-0.121251,
-0.122318,
-0.123360,
-0.124376,
-0.125368,
-0.126334,
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-0.128192,
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-0.130793,
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-0.133174,
-0.133919,
-0.134640,
-0.135337,
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-0.136659,
-0.137284,
-0.137886,
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-0.145008,
-0.145165,
-0.145301,
-0.145416,
-0.145511,
-0.145585,
-0.145639,
-0.145673,
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-0.063107,
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-0.060903,
-0.059802,
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-0.057600,
-0.056500,
-0.055401,
-0.054303,
-0.053206,
-0.052110,
-0.051015,
-0.049922,
-0.048831,
-0.047741,
-0.046654,
-0.045568,
-0.044485,
-0.043403,
-0.042325,
-0.041249,
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-0.039105,
-0.038037,
-0.036973,
-0.035912,
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-0.033799,
-0.032749,
-0.031701,
-0.030658,
-0.029619,
-0.028583,
-0.027552,
-0.026525,
-0.025502,
-0.024484,
-0.023471,
-0.022462,
-0.021458,
-0.020459,
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-0.000772,
0.000096,
0.000958,
0.001813,
0.002660,
0.003501,
0.004335,
0.005161,
0.005980,
0.006792,
0.007597,
0.008394,
0.009183,
0.009965,
0.010740,
0.011507,
0.012266,
0.013018,
0.013762,
0.014498,
0.015226,
0.015946,
0.016658,
0.017363,
0.018059,
0.018747,
0.019428,
0.020100,
0.020764,
0.021420,
0.022067,
0.022707,
0.023338,
0.023961,
0.024575,
0.025181,
0.025779,
0.026369,
0.026950,
0.027523,
0.028087,
0.028643,
0.029191,
0.029730,
0.030260,
0.030782,
0.031296,
0.031801,
0.032297,
0.032785,
0.033265,
0.033736,
0.034199,
0.034653,
0.035098,
0.035536,
0.035964,
0.036384,
0.036796,
0.037199,
0.037594,
0.037980,
0.038358,
0.038727,
0.039088,
0.039441,
0.039785,
0.040121,
0.040448,
0.040768,
0.041078,
0.041381,
0.041675,
0.041961,
0.042239,
0.042509,
0.042770,
0.043024,
0.043269,
0.043506,
0.043735,
0.043956,
0.044169,
0.044375,
0.044572,
0.044761,
0.044943,
0.045116,
0.045282,
0.045440,
0.045591,
0.045734,
0.045869,
0.045996,
0.046117,
0.046229,
0.046334,
0.046432,
0.046522,
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0.046681,
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0.047012,
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0.033967,
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0.032686,
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