32a595222d
Made the OpenMPT / legacy OpenMPT and mpg123 libraries pre-built. Changed the OpenMPT and vgmstream plugins to import the libraries as they are now. Made mpg123 embedded and imported by the main binary, since it's now shared by two plugins. Signed-off-by: Christopher Snowhill <kode54@gmail.com>
119 lines
3.1 KiB
C
119 lines
3.1 KiB
C
/*
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dither: Generate shaped noise for dithering
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copyright 2009 by the mpg123 project - free software under the terms of the LGPL 2.1
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see COPYING and AUTHORS files in distribution or http://mpg123.org
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initially written by Taihei Monma
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*/
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#include "config.h"
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#include "compat.h"
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#include "dither.h"
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static const uint32_t init_seed = 2463534242UL;
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#define LAP 100
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/*
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xorshift random number generator, with output scaling to [-0.5, 0.5]
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This is the white noise...
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See http://www.jstatsoft.org/v08/i14/paper on XOR shift random number generators.
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*/
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static float rand_xorshift32(uint32_t *seed)
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{
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union
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{
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uint32_t i;
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float f;
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} fi;
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fi.i = *seed;
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fi.i ^= (fi.i<<13);
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fi.i ^= (fi.i>>17);
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fi.i ^= (fi.i<<5);
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*seed = fi.i;
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/* scale the number to [-0.5, 0.5] */
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#ifdef IEEE_FLOAT
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fi.i = (fi.i>>9)|0x3f800000;
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fi.f -= 1.5f;
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#else
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fi.f = (double)fi.i / 4294967295.0;
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fi.f -= 0.5f;
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#endif
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return fi.f;
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}
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static void white_noise(float *table, size_t count)
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{
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size_t i;
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uint32_t seed = init_seed;
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for(i=0; i<count; ++i)
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table[i] = rand_xorshift32(&seed);
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}
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static void tpdf_noise(float *table, size_t count)
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{
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size_t i;
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uint32_t seed = init_seed;
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for(i=0; i<count; ++i)
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table[i] = rand_xorshift32(&seed) + rand_xorshift32(&seed);
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}
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static void highpass_tpdf_noise(float *table, size_t count)
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{
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size_t i;
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uint32_t seed = init_seed;
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/* Ensure some minimum lap for keeping the high-pass filter circular. */
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size_t lap = count > 2*LAP ? LAP : count/2;
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float input_noise;
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float xv[9], yv[9];
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for(i=0;i<9;i++)
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{
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xv[i] = yv[i] = 0.0f;
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}
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for(i=0;i<count+lap;i++)
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{
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if(i==count) seed=init_seed;
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/* generate and add 2 random numbers, to make a TPDF noise distribution */
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input_noise = rand_xorshift32(&seed) + rand_xorshift32(&seed);
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/* apply 8th order Chebyshev high-pass IIR filter */
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/* Coefficients are from http://www-users.cs.york.ac.uk/~fisher/mkfilter/trad.html
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Given parameters are: Chebyshev, Highpass, ripple=-1, order=8, samplerate=44100, corner1=19000 */
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xv[0] = xv[1]; xv[1] = xv[2]; xv[2] = xv[3]; xv[3] = xv[4]; xv[4] = xv[5]; xv[5] = xv[6]; xv[6] = xv[7]; xv[7] = xv[8];
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xv[8] = input_noise / 1.382814179e+07;
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yv[0] = yv[1]; yv[1] = yv[2]; yv[2] = yv[3]; yv[3] = yv[4]; yv[4] = yv[5]; yv[5] = yv[6]; yv[6] = yv[7]; yv[7] = yv[8];
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yv[8] = (xv[0] + xv[8]) - 8 * (xv[1] + xv[7]) + 28 * (xv[2] + xv[6])
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- 56 * (xv[3] + xv[5]) + 70 * xv[4]
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+ ( -0.6706204984 * yv[0]) + ( -5.3720827038 * yv[1])
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+ (-19.0865382480 * yv[2]) + (-39.2831607860 * yv[3])
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+ (-51.2308985070 * yv[4]) + (-43.3590135780 * yv[5])
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+ (-23.2632305320 * yv[6]) + ( -7.2370122050 * yv[7]);
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if(i>=lap) table[i-lap] = yv[8] * 3.0f;
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}
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}
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void mpg123_noise(float* table, size_t count, enum mpg123_noise_type noisetype)
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{
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switch(noisetype)
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{
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case mpg123_white_noise: white_noise(table, count); break;
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case mpg123_tpdf_noise: tpdf_noise(table, count); break;
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case mpg123_highpass_tpdf_noise:
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highpass_tpdf_noise(table, count);
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break;
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}
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}
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/* Generate white noise and shape it with a high pass filter. */
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void dither_table_init(float *dithertable)
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{
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highpass_tpdf_noise(dithertable, DITHERSIZE);
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}
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