123 lines
3.3 KiB
C
123 lines
3.3 KiB
C
/*
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SDL_mixer: An audio mixer library based on the SDL library
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Copyright (C) 1997-2009 Sam Lantinga
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public
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License as published by the Free Software Foundation; either
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version 2 of the License, or (at your option) any later version.
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This library 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 GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with this library; if not, write to the Free
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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This file by Ryan C. Gordon (icculus@icculus.org)
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These are some helper functions for the internal mixer special effects.
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*/
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/* $Id: effects_internal.c 4211 2008-12-08 00:27:32Z slouken $ */
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/* ------ These are used internally only. Don't touch. ------ */
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#include <stdio.h>
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#include <stdlib.h>
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#include "SDL_mixer.h"
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#define __MIX_INTERNAL_EFFECT__
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#include "effects_internal.h"
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/* Should we favor speed over memory usage and/or quality of output? */
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int _Mix_effects_max_speed = 0;
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void _Mix_InitEffects(void)
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{
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_Mix_effects_max_speed = (getenv(MIX_EFFECTSMAXSPEED) != NULL);
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}
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void _Mix_DeinitEffects(void)
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{
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_Eff_PositionDeinit();
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}
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void *_Eff_volume_table = NULL;
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/* Build the volume table for Uint8-format samples.
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*
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* Each column of the table is a possible sample, while each row of the
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* table is a volume. Volume is a Uint8, where 0 is silence and 255 is full
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* volume. So _Eff_volume_table[128][mysample] would be the value of
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* mysample, at half volume.
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*/
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void *_Eff_build_volume_table_u8(void)
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{
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int volume;
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int sample;
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Uint8 *rc;
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if (!_Mix_effects_max_speed) {
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return(NULL);
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}
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if (!_Eff_volume_table) {
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rc = malloc(256 * 256);
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if (rc) {
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_Eff_volume_table = (void *) rc;
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for (volume = 0; volume < 256; volume++) {
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for (sample = -128; sample < 128; sample ++) {
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*rc = (Uint8)(((float) sample) * ((float) volume / 255.0))
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+ 128;
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rc++;
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}
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}
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}
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}
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return(_Eff_volume_table);
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}
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/* Build the volume table for Sint8-format samples.
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*
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* Each column of the table is a possible sample, while each row of the
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* table is a volume. Volume is a Uint8, where 0 is silence and 255 is full
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* volume. So _Eff_volume_table[128][mysample+128] would be the value of
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* mysample, at half volume.
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*/
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void *_Eff_build_volume_table_s8(void)
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{
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int volume;
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int sample;
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Sint8 *rc;
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if (!_Eff_volume_table) {
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rc = malloc(256 * 256);
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if (rc) {
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_Eff_volume_table = (void *) rc;
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for (volume = 0; volume < 256; volume++) {
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for (sample = -128; sample < 128; sample ++) {
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*rc = (Sint8)(((float) sample) * ((float) volume / 255.0));
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rc++;
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}
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}
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}
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}
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return(_Eff_volume_table);
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}
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/* end of effects.c ... */
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