121 lines
3.2 KiB
C
121 lines
3.2 KiB
C
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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 internally supported special effects that use SDL_mixer's
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effect callback API. They are meant for speed over quality. :)
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*/
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/* $Id$ */
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#include <stdio.h>
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#include <stdlib.h>
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#include "SDL.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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/* profile code:
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#include <sys/time.h>
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#include <unistd.h>
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struct timeval tv1;
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struct timeval tv2;
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gettimeofday(&tv1, NULL);
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... do your thing here ...
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gettimeofday(&tv2, NULL);
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printf("%ld\n", tv2.tv_usec - tv1.tv_usec);
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*/
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/*
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* Stereo reversal effect...this one's pretty straightforward...
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*/
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static void _Eff_reversestereo16(int chan, void *stream, int len, void *udata)
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{
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/* 16 bits * 2 channels. */
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Uint32 *ptr = (Uint32 *) stream;
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int i;
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for (i = 0; i < len; i += sizeof (Uint32), ptr++) {
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*ptr = (((*ptr) & 0xFFFF0000) >> 16) | (((*ptr) & 0x0000FFFF) << 16);
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}
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}
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static void _Eff_reversestereo8(int chan, void *stream, int len, void *udata)
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{
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/* 8 bits * 2 channels. */
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Uint32 *ptr = (Uint32 *) stream;
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int i;
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/* get the last two bytes if len is not divisible by four... */
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if (len % sizeof (Uint32) != 0) {
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Uint16 *p = (Uint16 *) (((Uint8 *) stream) + (len - 2));
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*p = (Uint16)((((*p) & 0xFF00) >> 8) | (((*ptr) & 0x00FF) << 8));
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len -= 2;
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}
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for (i = 0; i < len; i += sizeof (Uint32), ptr++) {
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*ptr = (((*ptr) & 0x0000FF00) >> 8) | (((*ptr) & 0x000000FF) << 8) |
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(((*ptr) & 0xFF000000) >> 8) | (((*ptr) & 0x00FF0000) << 8);
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}
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}
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int Mix_SetReverseStereo(int channel, int flip)
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{
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Mix_EffectFunc_t f = NULL;
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int channels;
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Uint16 format;
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Mix_QuerySpec(NULL, &format, &channels);
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if (channels == 2) {
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if ((format & 0xFF) == 16)
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f = _Eff_reversestereo16;
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else if ((format & 0xFF) == 8)
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f = _Eff_reversestereo8;
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else {
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Mix_SetError("Unsupported audio format");
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return(0);
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}
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if (!flip) {
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return(Mix_UnregisterEffect(channel, f));
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} else {
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return(Mix_RegisterEffect(channel, f, NULL, NULL));
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}
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}
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return(1);
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}
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/* end of effect_stereoreverse.c ... */
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