effect_stereoreverse.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
modify it under the terms of the GNU Library General Public
License as published by the Free Software Foundation; either
version 2 of the License, or (at your option) any later version.
This library 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
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with this library; if not, write to the Free
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 internally supported special effects that use SDL_mixer's
effect callback API. They are meant for speed over quality. :)
*/
/* $Id$ */
#include <stdio.h>
#include <stdlib.h>
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#include "SDL.h"
#include "SDL_mixer.h"
#define __MIX_INTERNAL_EFFECT__
#include "effects_internal.h"
/* profile code:
#include <sys/time.h>
#include <unistd.h>
struct timeval tv1;
struct timeval tv2;
gettimeofday(&tv1, NULL);
... do your thing here ...
gettimeofday(&tv2, NULL);
printf("%ld\n", tv2.tv_usec - tv1.tv_usec);
*/
/*
* Stereo reversal effect...this one's pretty straightforward...
*/
static void _Eff_reversestereo16(int chan, void *stream, int len, void *udata)
{
/* 16 bits * 2 channels. */
Uint32 *ptr = (Uint32 *) stream;
int i;
for (i = 0; i < len; i += sizeof (Uint32), ptr++) {
*ptr = (((*ptr) & 0xFFFF0000) >> 16) | (((*ptr) & 0x0000FFFF) << 16);
}
}
static void _Eff_reversestereo8(int chan, void *stream, int len, void *udata)
{
/* 8 bits * 2 channels. */
Uint32 *ptr = (Uint32 *) stream;
int i;
/* get the last two bytes if len is not divisible by four... */
if (len % sizeof (Uint32) != 0) {
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;
}
for (i = 0; i < len; i += sizeof (Uint32), ptr++) {
*ptr = (((*ptr) & 0x0000FF00) >> 8) | (((*ptr) & 0x000000FF) << 8) |
(((*ptr) & 0xFF000000) >> 8) | (((*ptr) & 0x00FF0000) << 8);
}
}
int Mix_SetReverseStereo(int channel, int flip)
{
Mix_EffectFunc_t f = NULL;
int channels;
Uint16 format;
Mix_QuerySpec(NULL, &format, &channels);
if (channels == 2) {
if ((format & 0xFF) == 16)
f = _Eff_reversestereo16;
else if ((format & 0xFF) == 8)
f = _Eff_reversestereo8;
else {
Mix_SetError("Unsupported audio format");
return(0);
}
if (!flip) {
return(Mix_UnregisterEffect(channel, f));
} else {
return(Mix_RegisterEffect(channel, f, NULL, NULL));
}
}
return(1);
}
/* end of effect_stereoreverse.c ... */