effects_internal.c
author Ozkan Sezer <sezeroz@gmail.com>
Sun, 07 Oct 2018 03:07:33 +0300
branchSDL-1.2
changeset 885 dd251a0ec666
parent 561 87bdb4c81c0b
child 601 05123263dab3
permissions -rw-r--r--
backport fix for bug #2795. (from 2.0 branch commit b28b41b93ba7).
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/*
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  SDL_mixer:  An audio mixer library based on the SDL library
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  Copyright (C) 1997-2012 Sam Lantinga <slouken@libsdl.org>
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  This software is provided 'as-is', without any express or implied
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  warranty.  In no event will the authors be held liable for any damages
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  arising from the use of this software.
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  Permission is granted to anyone to use this software for any purpose,
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  including commercial applications, and to alter it and redistribute it
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  freely, subject to the following restrictions:
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  1. The origin of this software must not be misrepresented; you must not
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     claim that you wrote the original software. If you use this software
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     in a product, an acknowledgment in the product documentation would be
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     appreciated but is not required.
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  2. Altered source versions must be plainly marked as such, and must not be
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     misrepresented as being the original software.
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  3. This notice may not be removed or altered from any source distribution.
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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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/* $Id$ */
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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 = (SDL_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 = SDL_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 = SDL_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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