/*
    SDL_mixer:  An audio mixer library based on the SDL library
    Copyright (C) 1997-2009 Sam Lantinga

    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

    This file by Ryan C. Gordon (icculus@icculus.org)

    These are some internally supported special effects that use SDL_mixer's
    effect callback API. They are meant for speed over quality.  :)
*/

/* $Id: effect_position.c 5045 2009-10-11 02:59:12Z icculus $ */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "SDL.h"
#include "SDL_mixer.h"
#include "SDL_endian.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);
*/


/*
 * Positional effects...panning, distance attenuation, etc.
 */

typedef struct _Eff_positionargs
{
    volatile float left_f;
    volatile float right_f;
    volatile Uint8 left_u8;
    volatile Uint8 right_u8;
    volatile float left_rear_f;
    volatile float right_rear_f;
    volatile float center_f;
    volatile float lfe_f;
    volatile Uint8 left_rear_u8;
    volatile Uint8 right_rear_u8;
    volatile Uint8 center_u8;
    volatile Uint8 lfe_u8;
    volatile float distance_f;
    volatile Uint8 distance_u8;
    volatile Sint16 room_angle;
    volatile int in_use;
    volatile int channels;
} position_args;

static position_args **pos_args_array = NULL;
static position_args *pos_args_global = NULL;
static int position_channels = 0;

void _Eff_PositionDeinit(void)
{
    int i;
    for (i = 0; i < position_channels; i++) {
        free(pos_args_array[i]);
    }

    position_channels = 0;

    free(pos_args_global);
    pos_args_global = NULL;
    free(pos_args_array);
    pos_args_array = NULL;
}


/* This just frees up the callback-specific data. */
static void _Eff_PositionDone(int channel, void *udata)
{
    if (channel < 0) {
        if (pos_args_global != NULL) {
            free(pos_args_global);
            pos_args_global = NULL;
        }
    }

    else if (pos_args_array[channel] != NULL) {
        free(pos_args_array[channel]);
        pos_args_array[channel] = NULL;
    }
}


static void _Eff_position_u8(int chan, void *stream, int len, void *udata)
{
    volatile position_args *args = (volatile position_args *) udata;
    Uint8 *ptr = (Uint8 *) stream;
    int i;

        /*
         * if there's only a mono channnel (the only way we wouldn't have
         *  a len divisible by 2 here), then left_f and right_f are always
         *  1.0, and are therefore throwaways.
         */
    if (len % sizeof (Uint16) != 0) {
        *ptr = (Uint8) (((float) *ptr) * args->distance_f);
        ptr++;
        len--;
    }

    if (args->room_angle == 180)
    for (i = 0; i < len; i += sizeof (Uint8) * 2) {
        /* must adjust the sample so that 0 is the center */
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->right_f) * args->distance_f) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->left_f) * args->distance_f) + 128);
        ptr++;
    }
    else for (i = 0; i < len; i += sizeof (Uint8) * 2) {
        /* must adjust the sample so that 0 is the center */
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->left_f) * args->distance_f) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->right_f) * args->distance_f) + 128);
        ptr++;
    }
}
static void _Eff_position_u8_c4(int chan, void *stream, int len, void *udata)
{
    volatile position_args *args = (volatile position_args *) udata;
    Uint8 *ptr = (Uint8 *) stream;
    int i;

        /*
         * if there's only a mono channnel (the only way we wouldn't have
         *  a len divisible by 2 here), then left_f and right_f are always
         *  1.0, and are therefore throwaways.
         */
    if (len % sizeof (Uint16) != 0) {
        *ptr = (Uint8) (((float) *ptr) * args->distance_f);
        ptr++;
        len--;
    }

    if (args->room_angle == 0)
    for (i = 0; i < len; i += sizeof (Uint8) * 6) {
        /* must adjust the sample so that 0 is the center */
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->left_f) * args->distance_f) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->right_f) * args->distance_f) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->left_rear_f) * args->distance_f) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->right_rear_f) * args->distance_f) + 128);
        ptr++;
    }
    else if (args->room_angle == 90)
    for (i = 0; i < len; i += sizeof (Uint8) * 6) {
        /* must adjust the sample so that 0 is the center */
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->right_f) * args->distance_f) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->right_rear_f) * args->distance_f) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->left_f) * args->distance_f) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->left_rear_f) * args->distance_f) + 128);
        ptr++;
    }
    else if (args->room_angle == 180)
    for (i = 0; i < len; i += sizeof (Uint8) * 6) {
        /* must adjust the sample so that 0 is the center */
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->right_rear_f) * args->distance_f) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->left_rear_f) * args->distance_f) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->right_f) * args->distance_f) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->left_f) * args->distance_f) + 128);
        ptr++;
    }
    else if (args->room_angle == 270)
    for (i = 0; i < len; i += sizeof (Uint8) * 6) {
        /* must adjust the sample so that 0 is the center */
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->left_rear_f) * args->distance_f) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->left_f) * args->distance_f) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->right_rear_f) * args->distance_f) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->right_f) * args->distance_f) + 128);
        ptr++;
    }
}


static void _Eff_position_u8_c6(int chan, void *stream, int len, void *udata)
{
    volatile position_args *args = (volatile position_args *) udata;
    Uint8 *ptr = (Uint8 *) stream;
    int i;

        /*
         * if there's only a mono channnel (the only way we wouldn't have
         *  a len divisible by 2 here), then left_f and right_f are always
         *  1.0, and are therefore throwaways.
         */
    if (len % sizeof (Uint16) != 0) {
        *ptr = (Uint8) (((float) *ptr) * args->distance_f);
        ptr++;
        len--;
    }

    if (args->room_angle == 0)
    for (i = 0; i < len; i += sizeof (Uint8) * 6) {
        /* must adjust the sample so that 0 is the center */
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->left_f) * args->distance_f) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->right_f) * args->distance_f) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->left_rear_f) * args->distance_f) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->right_rear_f) * args->distance_f) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->center_f) * args->distance_f) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->lfe_f) * args->distance_f) + 128);
        ptr++;
    }
    else if (args->room_angle == 90)
    for (i = 0; i < len; i += sizeof (Uint8) * 6) {
        /* must adjust the sample so that 0 is the center */
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->right_f) * args->distance_f) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->right_rear_f) * args->distance_f) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->left_f) * args->distance_f) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->left_rear_f) * args->distance_f) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->right_rear_f) * args->distance_f/2) + 128)
            + (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->right_f) * args->distance_f/2) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->lfe_f) * args->distance_f) + 128);
        ptr++;
    }
    else if (args->room_angle == 180)
    for (i = 0; i < len; i += sizeof (Uint8) * 6) {
        /* must adjust the sample so that 0 is the center */
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->right_rear_f) * args->distance_f) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->left_rear_f) * args->distance_f) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->right_f) * args->distance_f) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->left_f) * args->distance_f) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->right_rear_f) * args->distance_f/2) + 128)
            + (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->left_rear_f) * args->distance_f/2) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->lfe_f) * args->distance_f) + 128);
        ptr++;
    }
    else if (args->room_angle == 270)
    for (i = 0; i < len; i += sizeof (Uint8) * 6) {
        /* must adjust the sample so that 0 is the center */
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->left_rear_f) * args->distance_f) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->left_f) * args->distance_f) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->right_rear_f) * args->distance_f) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->right_f) * args->distance_f) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->left_f) * args->distance_f/2) + 128)
            + (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->left_rear_f) * args->distance_f/2) + 128);
        ptr++;
        *ptr = (Uint8) ((Sint8) ((((float) (Sint8) (*ptr - 128)) 
            * args->lfe_f) * args->distance_f) + 128);
        ptr++;
    }
}


/*
 * This one runs about 10.1 times faster than the non-table version, with
 *  no loss in quality. It does, however, require 64k of memory for the
 *  lookup table. Also, this will only update position information once per
 *  call; the non-table version always checks the arguments for each sample,
 *  in case the user has called Mix_SetPanning() or whatnot again while this
 *  callback is running.
 */
static void _Eff_position_table_u8(int chan, void *stream, int len, void *udata)
{
    volatile position_args *args = (volatile position_args *) udata;
    Uint8 *ptr = (Uint8 *) stream;
    Uint32 *p;
    int i;
    Uint8 *l = ((Uint8 *) _Eff_volume_table) + (256 * args->left_u8);
    Uint8 *r = ((Uint8 *) _Eff_volume_table) + (256 * args->right_u8);
    Uint8 *d = ((Uint8 *) _Eff_volume_table) + (256 * args->distance_u8);

    if (args->room_angle == 180) {
	    Uint8 *temp = l;
	    l = r;
	    r = temp;
    }
        /*
         * if there's only a mono channnel, then l[] and r[] are always
         *  volume 255, and are therefore throwaways. Still, we have to
         *  be sure not to overrun the audio buffer...
         */
    while (len % sizeof (Uint32) != 0) {
        *ptr = d[l[*ptr]];
        ptr++;
        if (args->channels > 1) {
            *ptr = d[r[*ptr]];
            ptr++;
        }
        len -= args->channels;
    }

    p = (Uint32 *) ptr;

    for (i = 0; i < len; i += sizeof (Uint32)) {
#if (SDL_BYTEORDER == SDL_BIG_ENDIAN)
        *p = (d[l[(*p & 0xFF000000) >> 24]] << 24) |
             (d[r[(*p & 0x00FF0000) >> 16]] << 16) |
             (d[l[(*p & 0x0000FF00) >>  8]] <<  8) |
             (d[r[(*p & 0x000000FF)      ]]      ) ;
#else
        *p = (d[r[(*p & 0xFF000000) >> 24]] << 24) |
             (d[l[(*p & 0x00FF0000) >> 16]] << 16) |
             (d[r[(*p & 0x0000FF00) >>  8]] <<  8) |
             (d[l[(*p & 0x000000FF)      ]]      ) ;
#endif
        ++p;
    }
}


static void _Eff_position_s8(int chan, void *stream, int len, void *udata)
{
    volatile position_args *args = (volatile position_args *) udata;
    Sint8 *ptr = (Sint8 *) stream;
    int i;

        /*
         * if there's only a mono channnel (the only way we wouldn't have
         *  a len divisible by 2 here), then left_f and right_f are always
         *  1.0, and are therefore throwaways.
         */
    if (len % sizeof (Sint16) != 0) {
        *ptr = (Sint8) (((float) *ptr) * args->distance_f);
        ptr++;
        len--;
    }

    if (args->room_angle == 180)
    for (i = 0; i < len; i += sizeof (Sint8) * 2) {
        *ptr = (Sint8)((((float) *ptr) * args->right_f) * args->distance_f);
        ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->left_f) * args->distance_f);
        ptr++;
    }
    else
    for (i = 0; i < len; i += sizeof (Sint8) * 2) {
        *ptr = (Sint8)((((float) *ptr) * args->left_f) * args->distance_f);
        ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->right_f) * args->distance_f);
        ptr++;
    }
}
static void _Eff_position_s8_c4(int chan, void *stream, int len, void *udata)
{
    volatile position_args *args = (volatile position_args *) udata;
    Sint8 *ptr = (Sint8 *) stream;
    int i;

        /*
         * if there's only a mono channnel (the only way we wouldn't have
         *  a len divisible by 2 here), then left_f and right_f are always
         *  1.0, and are therefore throwaways.
         */
    if (len % sizeof (Sint16) != 0) {
        *ptr = (Sint8) (((float) *ptr) * args->distance_f);
        ptr++;
        len--;
    }

    for (i = 0; i < len; i += sizeof (Sint8) * 4) {
      switch (args->room_angle) {
       case 0:
        *ptr = (Sint8)((((float) *ptr) * args->left_f) * args->distance_f); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->right_f) * args->distance_f); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->left_rear_f) * args->distance_f); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->right_rear_f) * args->distance_f); ptr++;
	break;
       case 90:
        *ptr = (Sint8)((((float) *ptr) * args->right_f) * args->distance_f); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->right_rear_f) * args->distance_f); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->left_f) * args->distance_f); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->left_rear_f) * args->distance_f); ptr++;
	break;
       case 180:
        *ptr = (Sint8)((((float) *ptr) * args->right_rear_f) * args->distance_f); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->left_rear_f) * args->distance_f); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->right_f) * args->distance_f); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->left_f) * args->distance_f); ptr++;
	break;
       case 270:
        *ptr = (Sint8)((((float) *ptr) * args->left_rear_f) * args->distance_f); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->left_f) * args->distance_f); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->right_rear_f) * args->distance_f); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->right_f) * args->distance_f); ptr++;
	break;
      }
    }
}
static void _Eff_position_s8_c6(int chan, void *stream, int len, void *udata)
{
    volatile position_args *args = (volatile position_args *) udata;
    Sint8 *ptr = (Sint8 *) stream;
    int i;

        /*
         * if there's only a mono channnel (the only way we wouldn't have
         *  a len divisible by 2 here), then left_f and right_f are always
         *  1.0, and are therefore throwaways.
         */
    if (len % sizeof (Sint16) != 0) {
        *ptr = (Sint8) (((float) *ptr) * args->distance_f);
        ptr++;
        len--;
    }

    for (i = 0; i < len; i += sizeof (Sint8) * 6) {
      switch (args->room_angle) {
       case 0:
        *ptr = (Sint8)((((float) *ptr) * args->left_f) * args->distance_f); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->right_f) * args->distance_f); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->left_rear_f) * args->distance_f); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->right_rear_f) * args->distance_f); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->center_f) * args->distance_f); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->lfe_f) * args->distance_f); ptr++;
	break;
       case 90:
        *ptr = (Sint8)((((float) *ptr) * args->right_f) * args->distance_f); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->right_rear_f) * args->distance_f); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->left_f) * args->distance_f); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->left_rear_f) * args->distance_f); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->right_rear_f) * args->distance_f / 2)
           + (Sint8)((((float) *ptr) * args->right_f) * args->distance_f / 2); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->lfe_f) * args->distance_f); ptr++;
	break;
       case 180:
        *ptr = (Sint8)((((float) *ptr) * args->right_rear_f) * args->distance_f); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->left_rear_f) * args->distance_f); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->right_f) * args->distance_f); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->left_f) * args->distance_f); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->right_rear_f) * args->distance_f / 2)
           + (Sint8)((((float) *ptr) * args->left_rear_f) * args->distance_f / 2); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->lfe_f) * args->distance_f); ptr++;
	break;
       case 270:
        *ptr = (Sint8)((((float) *ptr) * args->left_rear_f) * args->distance_f); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->left_f) * args->distance_f); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->right_rear_f) * args->distance_f); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->right_f) * args->distance_f); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->left_f) * args->distance_f / 2)
           + (Sint8)((((float) *ptr) * args->left_rear_f) * args->distance_f / 2); ptr++;
        *ptr = (Sint8)((((float) *ptr) * args->lfe_f) * args->distance_f); ptr++;
	break;
      }
    }
}


/*
 * This one runs about 10.1 times faster than the non-table version, with
 *  no loss in quality. It does, however, require 64k of memory for the
 *  lookup table. Also, this will only update position information once per
 *  call; the non-table version always checks the arguments for each sample,
 *  in case the user has called Mix_SetPanning() or whatnot again while this
 *  callback is running.
 */
static void _Eff_position_table_s8(int chan, void *stream, int len, void *udata)
{
    volatile position_args *args = (volatile position_args *) udata;
    Sint8 *ptr = (Sint8 *) stream;
    Uint32 *p;
    int i;
    Sint8 *l = ((Sint8 *) _Eff_volume_table) + (256 * args->left_u8);
    Sint8 *r = ((Sint8 *) _Eff_volume_table) + (256 * args->right_u8);
    Sint8 *d = ((Sint8 *) _Eff_volume_table) + (256 * args->distance_u8);

    if (args->room_angle == 180) {
	    Sint8 *temp = l;
	    l = r;
	    r = temp;
    }


    while (len % sizeof (Uint32) != 0) {
        *ptr = d[l[*ptr]];
        ptr++;
        if (args->channels > 1) {
            *ptr = d[r[*ptr]];
            ptr++;
        }
        len -= args->channels;
    }

    p = (Uint32 *) ptr;

    for (i = 0; i < len; i += sizeof (Uint32)) {
#if (SDL_BYTEORDER == SDL_BIG_ENDIAN)
        *p = (d[l[((Sint16)(Sint8)((*p & 0xFF000000) >> 24))+128]] << 24) |
             (d[r[((Sint16)(Sint8)((*p & 0x00FF0000) >> 16))+128]] << 16) |
             (d[l[((Sint16)(Sint8)((*p & 0x0000FF00) >>  8))+128]] <<  8) |
             (d[r[((Sint16)(Sint8)((*p & 0x000000FF)      ))+128]]      ) ;
#else
        *p = (d[r[((Sint16)(Sint8)((*p & 0xFF000000) >> 24))+128]] << 24) |
             (d[l[((Sint16)(Sint8)((*p & 0x00FF0000) >> 16))+128]] << 16) |
             (d[r[((Sint16)(Sint8)((*p & 0x0000FF00) >>  8))+128]] <<  8) |
             (d[l[((Sint16)(Sint8)((*p & 0x000000FF)      ))+128]]      ) ;
#endif
        ++p;
    }


}


/* !!! FIXME : Optimize the code for 16-bit samples? */

static void _Eff_position_u16lsb(int chan, void *stream, int len, void *udata)
{
    volatile position_args *args = (volatile position_args *) udata;
    Uint16 *ptr = (Uint16 *) stream;
    int i;

    for (i = 0; i < len; i += sizeof (Uint16) * 2) {
        Sint16 sampl = (Sint16) (SDL_SwapLE16(*(ptr+0)) - 32768);
        Sint16 sampr = (Sint16) (SDL_SwapLE16(*(ptr+1)) - 32768);
        
        Uint16 swapl = (Uint16) ((Sint16) (((float) sampl * args->left_f)
                                    * args->distance_f) + 32768);
        Uint16 swapr = (Uint16) ((Sint16) (((float) sampr * args->right_f)
                                    * args->distance_f) + 32768);

	if (args->room_angle == 180) {
        	*(ptr++) = (Uint16) SDL_SwapLE16(swapr);
        	*(ptr++) = (Uint16) SDL_SwapLE16(swapl);
	}
	else {
        	*(ptr++) = (Uint16) SDL_SwapLE16(swapl);
        	*(ptr++) = (Uint16) SDL_SwapLE16(swapr);
	}
    }
}
static void _Eff_position_u16lsb_c4(int chan, void *stream, int len, void *udata)
{
    volatile position_args *args = (volatile position_args *) udata;
    Uint16 *ptr = (Uint16 *) stream;
    int i;

    for (i = 0; i < len; i += sizeof (Uint16) * 4) {
        Sint16 sampl = (Sint16) (SDL_SwapLE16(*(ptr+0)) - 32768);
        Sint16 sampr = (Sint16) (SDL_SwapLE16(*(ptr+1)) - 32768);
        Sint16 samplr = (Sint16) (SDL_SwapLE16(*(ptr+2)) - 32768);
        Sint16 samprr = (Sint16) (SDL_SwapLE16(*(ptr+3)) - 32768);
        
        Uint16 swapl = (Uint16) ((Sint16) (((float) sampl * args->left_f)
                                    * args->distance_f) + 32768);
        Uint16 swapr = (Uint16) ((Sint16) (((float) sampr * args->right_f)
                                    * args->distance_f) + 32768);
        Uint16 swaplr = (Uint16) ((Sint16) (((float) samplr * args->left_rear_f)
                                    * args->distance_f) + 32768);
        Uint16 swaprr = (Uint16) ((Sint16) (((float) samprr * args->right_rear_f)
                                    * args->distance_f) + 32768);

	switch (args->room_angle) {
		case 0:
        		*(ptr++) = (Uint16) SDL_SwapLE16(swapl);
        		*(ptr++) = (Uint16) SDL_SwapLE16(swapr);
        		*(ptr++) = (Uint16) SDL_SwapLE16(swaplr);
        		*(ptr++) = (Uint16) SDL_SwapLE16(swaprr);
			break;
		case 90:
        		*(ptr++) = (Uint16) SDL_SwapLE16(swapr);
        		*(ptr++) = (Uint16) SDL_SwapLE16(swaprr);
        		*(ptr++) = (Uint16) SDL_SwapLE16(swapl);
        		*(ptr++) = (Uint16) SDL_SwapLE16(swaplr);
			break;
		case 180:
        		*(ptr++) = (Uint16) SDL_SwapLE16(swaprr);
        		*(ptr++) = (Uint16) SDL_SwapLE16(swaplr);
        		*(ptr++) = (Uint16) SDL_SwapLE16(swapr);
        		*(ptr++) = (Uint16) SDL_SwapLE16(swapl);
			break;
		case 270:
        		*(ptr++) = (Uint16) SDL_SwapLE16(swaplr);
        		*(ptr++) = (Uint16) SDL_SwapLE16(swapl);
        		*(ptr++) = (Uint16) SDL_SwapLE16(swaprr);
        		*(ptr++) = (Uint16) SDL_SwapLE16(swapr);
			break;
	}
    }
}
static void _Eff_position_u16lsb_c6(int chan, void *stream, int len, void *udata)
{
    volatile position_args *args = (volatile position_args *) udata;
    Uint16 *ptr = (Uint16 *) stream;
    int i;

    for (i = 0; i < len; i += sizeof (Uint16) * 6) {
        Sint16 sampl = (Sint16) (SDL_SwapLE16(*(ptr+0)) - 32768);
        Sint16 sampr = (Sint16) (SDL_SwapLE16(*(ptr+1)) - 32768);
        Sint16 samplr = (Sint16) (SDL_SwapLE16(*(ptr+2)) - 32768);
        Sint16 samprr = (Sint16) (SDL_SwapLE16(*(ptr+3)) - 32768);
        Sint16 sampce = (Sint16) (SDL_SwapLE16(*(ptr+4)) - 32768);
        Sint16 sampwf = (Sint16) (SDL_SwapLE16(*(ptr+5)) - 32768);

        Uint16 swapl = (Uint16) ((Sint16) (((float) sampl * args->left_f)
                                    * args->distance_f) + 32768);
        Uint16 swapr = (Uint16) ((Sint16) (((float) sampr * args->right_f)
                                    * args->distance_f) + 32768);
        Uint16 swaplr = (Uint16) ((Sint16) (((float) samplr * args->left_rear_f)
                                    * args->distance_f) + 32768);
        Uint16 swaprr = (Uint16) ((Sint16) (((float) samprr * args->right_rear_f)
                                    * args->distance_f) + 32768);
        Uint16 swapce = (Uint16) ((Sint16) (((float) sampce * args->center_f)
                                    * args->distance_f) + 32768);
        Uint16 swapwf = (Uint16) ((Sint16) (((float) sampwf * args->lfe_f)
                                    * args->distance_f) + 32768);

	switch (args->room_angle) {
		case 0:
        		*(ptr++) = (Uint16) SDL_SwapLE16(swapl);
        		*(ptr++) = (Uint16) SDL_SwapLE16(swapr);
        		*(ptr++) = (Uint16) SDL_SwapLE16(swaplr);
        		*(ptr++) = (Uint16) SDL_SwapLE16(swaprr);
        		*(ptr++) = (Uint16) SDL_SwapLE16(swapce);
        		*(ptr++) = (Uint16) SDL_SwapLE16(swapwf);
			break;
		case 90:
        		*(ptr++) = (Uint16) SDL_SwapLE16(swapr);
        		*(ptr++) = (Uint16) SDL_SwapLE16(swaprr);
        		*(ptr++) = (Uint16) SDL_SwapLE16(swapl);
        		*(ptr++) = (Uint16) SDL_SwapLE16(swaplr);
        		*(ptr++) = (Uint16) SDL_SwapLE16(swapr)/2 + (Uint16) SDL_SwapLE16(swaprr)/2;
        		*(ptr++) = (Uint16) SDL_SwapLE16(swapwf);
			break;
		case 180:
        		*(ptr++) = (Uint16) SDL_SwapLE16(swaprr);
        		*(ptr++) = (Uint16) SDL_SwapLE16(swaplr);
        		*(ptr++) = (Uint16) SDL_SwapLE16(swapr);
        		*(ptr++) = (Uint16) SDL_SwapLE16(swapl);
        		*(ptr++) = (Uint16) SDL_SwapLE16(swaprr)/2 + (Uint16) SDL_SwapLE16(swaplr)/2;
        		*(ptr++) = (Uint16) SDL_SwapLE16(swapwf);
			break;
		case 270:
        		*(ptr++) = (Uint16) SDL_SwapLE16(swaplr);
        		*(ptr++) = (Uint16) SDL_SwapLE16(swapl);
        		*(ptr++) = (Uint16) SDL_SwapLE16(swaprr);
        		*(ptr++) = (Uint16) SDL_SwapLE16(swapr);
        		*(ptr++) = (Uint16) SDL_SwapLE16(swapl)/2 + (Uint16) SDL_SwapLE16(swaplr)/2;
        		*(ptr++) = (Uint16) SDL_SwapLE16(swapwf);
			break;
	}
    }
}

static void _Eff_position_s16lsb(int chan, void *stream, int len, void *udata)
{
    /* 16 signed bits (lsb) * 2 channels. */
    volatile position_args *args = (volatile position_args *) udata;
    Sint16 *ptr = (Sint16 *) stream;
    int i;

#if 0
    if (len % (sizeof(Sint16) * 2)) {
	    fprintf(stderr,"Not an even number of frames! len=%d\n", len);
	    return;
    }
#endif

    for (i = 0; i < len; i += sizeof (Sint16) * 2) {
        Sint16 swapl = (Sint16) ((((float) (Sint16) SDL_SwapLE16(*(ptr+0))) *
                                    args->left_f) * args->distance_f);
        Sint16 swapr = (Sint16) ((((float) (Sint16) SDL_SwapLE16(*(ptr+1))) *
                                    args->right_f) * args->distance_f);
	if (args->room_angle == 180) {
        	*(ptr++) = (Sint16) SDL_SwapLE16(swapr);
        	*(ptr++) = (Sint16) SDL_SwapLE16(swapl);
	}
	else {
        	*(ptr++) = (Sint16) SDL_SwapLE16(swapl);
        	*(ptr++) = (Sint16) SDL_SwapLE16(swapr);
	}
    }
}
static void _Eff_position_s16lsb_c4(int chan, void *stream, int len, void *udata)
{
    /* 16 signed bits (lsb) * 4 channels. */
    volatile position_args *args = (volatile position_args *) udata;
    Sint16 *ptr = (Sint16 *) stream;
    int i;

    for (i = 0; i < len; i += sizeof (Sint16) * 4) {
        Sint16 swapl = (Sint16) ((((float) (Sint16) SDL_SwapLE16(*(ptr+0))) *
                                    args->left_f) * args->distance_f);
        Sint16 swapr = (Sint16) ((((float) (Sint16) SDL_SwapLE16(*(ptr+1))) *
                                    args->right_f) * args->distance_f);
        Sint16 swaplr = (Sint16) ((((float) (Sint16) SDL_SwapLE16(*(ptr+1))) *
                                    args->left_rear_f) * args->distance_f);
        Sint16 swaprr = (Sint16) ((((float) (Sint16) SDL_SwapLE16(*(ptr+2))) *
                                    args->right_rear_f) * args->distance_f);
	switch (args->room_angle) {
		case 0:
        		*(ptr++) = (Sint16) SDL_SwapLE16(swapl);
        		*(ptr++) = (Sint16) SDL_SwapLE16(swapr);
        		*(ptr++) = (Sint16) SDL_SwapLE16(swaplr);
        		*(ptr++) = (Sint16) SDL_SwapLE16(swaprr);
			break;
		case 90:
        		*(ptr++) = (Sint16) SDL_SwapLE16(swapr);
        		*(ptr++) = (Sint16) SDL_SwapLE16(swaprr);
        		*(ptr++) = (Sint16) SDL_SwapLE16(swapl);
        		*(ptr++) = (Sint16) SDL_SwapLE16(swaplr);
			break;
		case 180:
        		*(ptr++) = (Sint16) SDL_SwapLE16(swaprr);
        		*(ptr++) = (Sint16) SDL_SwapLE16(swaplr);
        		*(ptr++) = (Sint16) SDL_SwapLE16(swapr);
        		*(ptr++) = (Sint16) SDL_SwapLE16(swapl);
			break;
		case 270:
        		*(ptr++) = (Sint16) SDL_SwapLE16(swaplr);
        		*(ptr++) = (Sint16) SDL_SwapLE16(swapl);
        		*(ptr++) = (Sint16) SDL_SwapLE16(swaprr);
        		*(ptr++) = (Sint16) SDL_SwapLE16(swapr);
			break;
	}
    }
}

static void _Eff_position_s16lsb_c6(int chan, void *stream, int len, void *udata)
{
    /* 16 signed bits (lsb) * 6 channels. */
    volatile position_args *args = (volatile position_args *) udata;
    Sint16 *ptr = (Sint16 *) stream;
    int i;

    for (i = 0; i < len; i += sizeof (Sint16) * 6) {
        Sint16 swapl = (Sint16) ((((float) (Sint16) SDL_SwapLE16(*(ptr+0))) *
                                    args->left_f) * args->distance_f);
        Sint16 swapr = (Sint16) ((((float) (Sint16) SDL_SwapLE16(*(ptr+1))) *
                                    args->right_f) * args->distance_f);
        Sint16 swaplr = (Sint16) ((((float) (Sint16) SDL_SwapLE16(*(ptr+2))) *
                                    args->left_rear_f) * args->distance_f);
        Sint16 swaprr = (Sint16) ((((float) (Sint16) SDL_SwapLE16(*(ptr+3))) *
                                    args->right_rear_f) * args->distance_f);
        Sint16 swapce = (Sint16) ((((float) (Sint16) SDL_SwapLE16(*(ptr+4))) *
                                    args->center_f) * args->distance_f);
        Sint16 swapwf = (Sint16) ((((float) (Sint16) SDL_SwapLE16(*(ptr+5))) *
                                    args->lfe_f) * args->distance_f);
	switch (args->room_angle) {
		case 0:
        		*(ptr++) = (Sint16) SDL_SwapLE16(swapl);
        		*(ptr++) = (Sint16) SDL_SwapLE16(swapr);
        		*(ptr++) = (Sint16) SDL_SwapLE16(swaplr);
        		*(ptr++) = (Sint16) SDL_SwapLE16(swaprr);
        		*(ptr++) = (Sint16) SDL_SwapLE16(swapce);
        		*(ptr++) = (Sint16) SDL_SwapLE16(swapwf);
			break;
		case 90:
        		*(ptr++) = (Sint16) SDL_SwapLE16(swapr);
        		*(ptr++) = (Sint16) SDL_SwapLE16(swaprr);
        		*(ptr++) = (Sint16) SDL_SwapLE16(swapl);
        		*(ptr++) = (Sint16) SDL_SwapLE16(swaplr);
        		*(ptr++) = (Sint16) SDL_SwapLE16(swapr)/2 + (Sint16) SDL_SwapLE16(swaprr)/2;
        		*(ptr++) = (Sint16) SDL_SwapLE16(swapwf);
			break;
		case 180:
        		*(ptr++) = (Sint16) SDL_SwapLE16(swaprr);
        		*(ptr++) = (Sint16) SDL_SwapLE16(swaplr);
        		*(ptr++) = (Sint16) SDL_SwapLE16(swapr);
        		*(ptr++) = (Sint16) SDL_SwapLE16(swapl);
        		*(ptr++) = (Sint16) SDL_SwapLE16(swaprr)/2 + (Sint16) SDL_SwapLE16(swaplr)/2;
        		*(ptr++) = (Sint16) SDL_SwapLE16(swapwf);
			break;
		case 270:
        		*(ptr++) = (Sint16) SDL_SwapLE16(swaplr);
        		*(ptr++) = (Sint16) SDL_SwapLE16(swapl);
        		*(ptr++) = (Sint16) SDL_SwapLE16(swaprr);
        		*(ptr++) = (Sint16) SDL_SwapLE16(swapr);
        		*(ptr++) = (Sint16) SDL_SwapLE16(swapl)/2 + (Sint16) SDL_SwapLE16(swaplr)/2;
        		*(ptr++) = (Sint16) SDL_SwapLE16(swapwf);
			break;
	}
    }
}

static void _Eff_position_u16msb(int chan, void *stream, int len, void *udata)
{
    /* 16 signed bits (lsb) * 2 channels. */
    volatile position_args *args = (volatile position_args *) udata;
    Uint16 *ptr = (Uint16 *) stream;
    int i;

    for (i = 0; i < len; i += sizeof (Sint16) * 2) {
        Sint16 sampl = (Sint16) (SDL_SwapBE16(*(ptr+0)) - 32768);
        Sint16 sampr = (Sint16) (SDL_SwapBE16(*(ptr+1)) - 32768);
        
        Uint16 swapl = (Uint16) ((Sint16) (((float) sampl * args->left_f)
                                    * args->distance_f) + 32768);
        Uint16 swapr = (Uint16) ((Sint16) (((float) sampr * args->right_f)
                                    * args->distance_f) + 32768);

	if (args->room_angle == 180) {
        	*(ptr++) = (Uint16) SDL_SwapBE16(swapr);
        	*(ptr++) = (Uint16) SDL_SwapBE16(swapl);
	}
	else {
        	*(ptr++) = (Uint16) SDL_SwapBE16(swapl);
        	*(ptr++) = (Uint16) SDL_SwapBE16(swapr);
	}
    }
}
static void _Eff_position_u16msb_c4(int chan, void *stream, int len, void *udata)
{
    /* 16 signed bits (lsb) * 4 channels. */
    volatile position_args *args = (volatile position_args *) udata;
    Uint16 *ptr = (Uint16 *) stream;
    int i;

    for (i = 0; i < len; i += sizeof (Sint16) * 4) {
        Sint16 sampl = (Sint16) (SDL_SwapBE16(*(ptr+0)) - 32768);
        Sint16 sampr = (Sint16) (SDL_SwapBE16(*(ptr+1)) - 32768);
        Sint16 samplr = (Sint16) (SDL_SwapBE16(*(ptr+2)) - 32768);
        Sint16 samprr = (Sint16) (SDL_SwapBE16(*(ptr+3)) - 32768);
        
        Uint16 swapl = (Uint16) ((Sint16) (((float) sampl * args->left_f)
                                    * args->distance_f) + 32768);
        Uint16 swapr = (Uint16) ((Sint16) (((float) sampr * args->right_f)
                                    * args->distance_f) + 32768);
        Uint16 swaplr = (Uint16) ((Sint16) (((float) samplr * args->left_rear_f)
                                    * args->distance_f) + 32768);
        Uint16 swaprr = (Uint16) ((Sint16) (((float) samprr * args->right_rear_f)
                                    * args->distance_f) + 32768);

	switch (args->room_angle) {
		case 0:
        		*(ptr++) = (Uint16) SDL_SwapBE16(swapl);
        		*(ptr++) = (Uint16) SDL_SwapBE16(swapr);
        		*(ptr++) = (Uint16) SDL_SwapBE16(swaplr);
        		*(ptr++) = (Uint16) SDL_SwapBE16(swaprr);
			break;
		case 90:
        		*(ptr++) = (Uint16) SDL_SwapBE16(swapr);
        		*(ptr++) = (Uint16) SDL_SwapBE16(swaprr);
        		*(ptr++) = (Uint16) SDL_SwapBE16(swapl);
        		*(ptr++) = (Uint16) SDL_SwapBE16(swaplr);
			break;
		case 180:
        		*(ptr++) = (Uint16) SDL_SwapBE16(swaprr);
        		*(ptr++) = (Uint16) SDL_SwapBE16(swaplr);
        		*(ptr++) = (Uint16) SDL_SwapBE16(swapr);
        		*(ptr++) = (Uint16) SDL_SwapBE16(swapl);
			break;
		case 270:
        		*(ptr++) = (Uint16) SDL_SwapBE16(swaplr);
        		*(ptr++) = (Uint16) SDL_SwapBE16(swapl);
        		*(ptr++) = (Uint16) SDL_SwapBE16(swaprr);
        		*(ptr++) = (Uint16) SDL_SwapBE16(swapr);
			break;
	}
    }
}
static void _Eff_position_u16msb_c6(int chan, void *stream, int len, void *udata)
{
    /* 16 signed bits (lsb) * 6 channels. */
    volatile position_args *args = (volatile position_args *) udata;
    Uint16 *ptr = (Uint16 *) stream;
    int i;

    for (i = 0; i < len; i += sizeof (Sint16) * 6) {
        Sint16 sampl = (Sint16) (SDL_SwapBE16(*(ptr+0)) - 32768);
        Sint16 sampr = (Sint16) (SDL_SwapBE16(*(ptr+1)) - 32768);
        Sint16 samplr = (Sint16) (SDL_SwapBE16(*(ptr+2)) - 32768);
        Sint16 samprr = (Sint16) (SDL_SwapBE16(*(ptr+3)) - 32768);
        Sint16 sampce = (Sint16) (SDL_SwapBE16(*(ptr+4)) - 32768);
        Sint16 sampwf = (Sint16) (SDL_SwapBE16(*(ptr+5)) - 32768);
        
        Uint16 swapl = (Uint16) ((Sint16) (((float) sampl * args->left_f)
                                    * args->distance_f) + 32768);
        Uint16 swapr = (Uint16) ((Sint16) (((float) sampr * args->right_f)
                                    * args->distance_f) + 32768);
        Uint16 swaplr = (Uint16) ((Sint16) (((float) samplr * args->left_rear_f)
                                    * args->distance_f) + 32768);
        Uint16 swaprr = (Uint16) ((Sint16) (((float) samprr * args->right_rear_f)
                                    * args->distance_f) + 32768);
        Uint16 swapce = (Uint16) ((Sint16) (((float) sampce * args->center_f)
                                    * args->distance_f) + 32768);
        Uint16 swapwf = (Uint16) ((Sint16) (((float) sampwf * args->lfe_f)
                                    * args->distance_f) + 32768);

	switch (args->room_angle) {
		case 0:
        		*(ptr++) = (Uint16) SDL_SwapBE16(swapl);
        		*(ptr++) = (Uint16) SDL_SwapBE16(swapr);
        		*(ptr++) = (Uint16) SDL_SwapBE16(swaplr);
        		*(ptr++) = (Uint16) SDL_SwapBE16(swaprr);
        		*(ptr++) = (Uint16) SDL_SwapBE16(swapce);
        		*(ptr++) = (Uint16) SDL_SwapBE16(swapwf);
			break;
		case 90:
        		*(ptr++) = (Uint16) SDL_SwapBE16(swapr);
        		*(ptr++) = (Uint16) SDL_SwapBE16(swaprr);
        		*(ptr++) = (Uint16) SDL_SwapBE16(swapl);
        		*(ptr++) = (Uint16) SDL_SwapBE16(swaplr);
        		*(ptr++) = (Uint16) SDL_SwapBE16(swapr)/2 + (Uint16) SDL_SwapBE16(swaprr)/2;
        		*(ptr++) = (Uint16) SDL_SwapBE16(swapwf);
			break;
		case 180:
        		*(ptr++) = (Uint16) SDL_SwapBE16(swaprr);
        		*(ptr++) = (Uint16) SDL_SwapBE16(swaplr);
        		*(ptr++) = (Uint16) SDL_SwapBE16(swapr);
        		*(ptr++) = (Uint16) SDL_SwapBE16(swapl);
        		*(ptr++) = (Uint16) SDL_SwapBE16(swaprr)/2 + (Uint16) SDL_SwapBE16(swaplr)/2;
        		*(ptr++) = (Uint16) SDL_SwapBE16(swapwf);
			break;
		case 270:
        		*(ptr++) = (Uint16) SDL_SwapBE16(swaplr);
        		*(ptr++) = (Uint16) SDL_SwapBE16(swapl);
        		*(ptr++) = (Uint16) SDL_SwapBE16(swaprr);
        		*(ptr++) = (Uint16) SDL_SwapBE16(swapr);
        		*(ptr++) = (Uint16) SDL_SwapBE16(swapl)/2 + (Uint16) SDL_SwapBE16(swaplr)/2;
        		*(ptr++) = (Uint16) SDL_SwapBE16(swapwf);
			break;
	}
    }
}

static void _Eff_position_s16msb(int chan, void *stream, int len, void *udata)
{
    /* 16 signed bits (lsb) * 2 channels. */
    volatile position_args *args = (volatile position_args *) udata;
    Sint16 *ptr = (Sint16 *) stream;
    int i;

    for (i = 0; i < len; i += sizeof (Sint16) * 2) {
        Sint16 swapl = (Sint16) ((((float) (Sint16) SDL_SwapBE16(*(ptr+0))) *
                                    args->left_f) * args->distance_f);
        Sint16 swapr = (Sint16) ((((float) (Sint16) SDL_SwapBE16(*(ptr+1))) *
                                    args->right_f) * args->distance_f);
        *(ptr++) = (Sint16) SDL_SwapBE16(swapl);
        *(ptr++) = (Sint16) SDL_SwapBE16(swapr);
    }
}
static void _Eff_position_s16msb_c4(int chan, void *stream, int len, void *udata)
{
    /* 16 signed bits (lsb) * 4 channels. */
    volatile position_args *args = (volatile position_args *) udata;
    Sint16 *ptr = (Sint16 *) stream;
    int i;

    for (i = 0; i < len; i += sizeof (Sint16) * 4) {
        Sint16 swapl = (Sint16) ((((float) (Sint16) SDL_SwapBE16(*(ptr+0))) *
                                    args->left_f) * args->distance_f);
        Sint16 swapr = (Sint16) ((((float) (Sint16) SDL_SwapBE16(*(ptr+1))) *
                                    args->right_f) * args->distance_f);
        Sint16 swaplr = (Sint16) ((((float) (Sint16) SDL_SwapBE16(*(ptr+2))) *
                                    args->left_rear_f) * args->distance_f);
        Sint16 swaprr = (Sint16) ((((float) (Sint16) SDL_SwapBE16(*(ptr+3))) *
                                    args->right_rear_f) * args->distance_f);
	switch (args->room_angle) {
		case 0:
        		*(ptr++) = (Sint16) SDL_SwapBE16(swapl);
        		*(ptr++) = (Sint16) SDL_SwapBE16(swapr);
        		*(ptr++) = (Sint16) SDL_SwapBE16(swaplr);
        		*(ptr++) = (Sint16) SDL_SwapBE16(swaprr);
			break;
		case 90:
        		*(ptr++) = (Sint16) SDL_SwapBE16(swapr);
        		*(ptr++) = (Sint16) SDL_SwapBE16(swaprr);
        		*(ptr++) = (Sint16) SDL_SwapBE16(swapl);
        		*(ptr++) = (Sint16) SDL_SwapBE16(swaplr);
			break;
		case 180:
        		*(ptr++) = (Sint16) SDL_SwapBE16(swaprr);
        		*(ptr++) = (Sint16) SDL_SwapBE16(swaplr);
        		*(ptr++) = (Sint16) SDL_SwapBE16(swapr);
        		*(ptr++) = (Sint16) SDL_SwapBE16(swapl);
			break;
		case 270:
        		*(ptr++) = (Sint16) SDL_SwapBE16(swaplr);
        		*(ptr++) = (Sint16) SDL_SwapBE16(swapl);
        		*(ptr++) = (Sint16) SDL_SwapBE16(swaprr);
        		*(ptr++) = (Sint16) SDL_SwapBE16(swapr);
			break;
	}
    }
}
static void _Eff_position_s16msb_c6(int chan, void *stream, int len, void *udata)
{
    /* 16 signed bits (lsb) * 6 channels. */
    volatile position_args *args = (volatile position_args *) udata;
    Sint16 *ptr = (Sint16 *) stream;
    int i;

    for (i = 0; i < len; i += sizeof (Sint16) * 6) {
        Sint16 swapl = (Sint16) ((((float) (Sint16) SDL_SwapBE16(*(ptr+0))) *
                                    args->left_f) * args->distance_f);
        Sint16 swapr = (Sint16) ((((float) (Sint16) SDL_SwapBE16(*(ptr+1))) *
                                    args->right_f) * args->distance_f);
        Sint16 swaplr = (Sint16) ((((float) (Sint16) SDL_SwapBE16(*(ptr+2))) *
                                    args->left_rear_f) * args->distance_f);
        Sint16 swaprr = (Sint16) ((((float) (Sint16) SDL_SwapBE16(*(ptr+3))) *
                                    args->right_rear_f) * args->distance_f);
        Sint16 swapce = (Sint16) ((((float) (Sint16) SDL_SwapBE16(*(ptr+4))) *
                                    args->center_f) * args->distance_f);
        Sint16 swapwf = (Sint16) ((((float) (Sint16) SDL_SwapBE16(*(ptr+5))) *
                                    args->lfe_f) * args->distance_f);

	switch (args->room_angle) {
		case 0:
        		*(ptr++) = (Sint16) SDL_SwapBE16(swapl);
        		*(ptr++) = (Sint16) SDL_SwapBE16(swapr);
        		*(ptr++) = (Sint16) SDL_SwapBE16(swaplr);
        		*(ptr++) = (Sint16) SDL_SwapBE16(swaprr);
        		*(ptr++) = (Sint16) SDL_SwapBE16(swapce);
        		*(ptr++) = (Sint16) SDL_SwapBE16(swapwf);
			break;
		case 90:
        		*(ptr++) = (Sint16) SDL_SwapBE16(swapr);
        		*(ptr++) = (Sint16) SDL_SwapBE16(swaprr);
        		*(ptr++) = (Sint16) SDL_SwapBE16(swapl);
        		*(ptr++) = (Sint16) SDL_SwapBE16(swaplr);
        		*(ptr++) = (Sint16) SDL_SwapBE16(swapr)/2 + (Sint16) SDL_SwapBE16(swaprr)/2;
        		*(ptr++) = (Sint16) SDL_SwapBE16(swapwf);
			break;
		case 180:
        		*(ptr++) = (Sint16) SDL_SwapBE16(swaprr);
        		*(ptr++) = (Sint16) SDL_SwapBE16(swaplr);
        		*(ptr++) = (Sint16) SDL_SwapBE16(swapr);
        		*(ptr++) = (Sint16) SDL_SwapBE16(swapl);
        		*(ptr++) = (Sint16) SDL_SwapBE16(swaprr)/2 + (Sint16) SDL_SwapBE16(swaplr)/2;
        		*(ptr++) = (Sint16) SDL_SwapBE16(swapwf);
			break;
		case 270:
        		*(ptr++) = (Sint16) SDL_SwapBE16(swaplr);
        		*(ptr++) = (Sint16) SDL_SwapBE16(swapl);
        		*(ptr++) = (Sint16) SDL_SwapBE16(swaprr);
        		*(ptr++) = (Sint16) SDL_SwapBE16(swapr);
        		*(ptr++) = (Sint16) SDL_SwapBE16(swapl)/2 + (Sint16) SDL_SwapBE16(swaplr)/2;
        		*(ptr++) = (Sint16) SDL_SwapBE16(swapwf);
			break;
	}
    }
}

static void init_position_args(position_args *args)
{
    memset(args, '\0', sizeof (position_args));
    args->in_use = 0;
    args->room_angle = 0;
    args->left_u8 = args->right_u8 = args->distance_u8 = 255;
    args->left_f  = args->right_f  = args->distance_f  = 1.0f;
    args->left_rear_u8 = args->right_rear_u8 = args->center_u8 = args->lfe_u8 = 255;
    args->left_rear_f = args->right_rear_f = args->center_f = args->lfe_f = 1.0f;
    Mix_QuerySpec(NULL, NULL, (int *) &args->channels);
}


static position_args *get_position_arg(int channel)
{
    void *rc;
    int i;

    if (channel < 0) {
        if (pos_args_global == NULL) {
            pos_args_global = malloc(sizeof (position_args));
            if (pos_args_global == NULL) {
                Mix_SetError("Out of memory");
                return(NULL);
            }
            init_position_args(pos_args_global);
        }

        return(pos_args_global);
    }

    if (channel >= position_channels) {
        rc = realloc(pos_args_array, (channel + 1) * sizeof (position_args *));
        if (rc == NULL) {
            Mix_SetError("Out of memory");
            return(NULL);
        }
        pos_args_array = (position_args **) rc;
        for (i = position_channels; i <= channel; i++) {
            pos_args_array[i] = NULL;
        }
        position_channels = channel + 1;
    }

    if (pos_args_array[channel] == NULL) {
        pos_args_array[channel] = (position_args *)malloc(sizeof(position_args));
        if (pos_args_array[channel] == NULL) {
            Mix_SetError("Out of memory");
            return(NULL);
        }
        init_position_args(pos_args_array[channel]);
    }

    return(pos_args_array[channel]);
}


static Mix_EffectFunc_t get_position_effect_func(Uint16 format, int channels)
{
    Mix_EffectFunc_t f = NULL;

    switch (format) {
        case AUDIO_U8:
	    switch (channels) {
		    case 1:
		    case 2:
            		f = (_Eff_build_volume_table_u8()) ? _Eff_position_table_u8 :
                                                 		_Eff_position_u8;
	    		break;
	    	    case 4:
                        f = _Eff_position_u8_c4;
	    		break;
	    	    case 6:
                        f = _Eff_position_u8_c6;
	    		break;
	    }
            break;

        case AUDIO_S8:
	    switch (channels) {
		    case 1:
		    case 2:
            		f = (_Eff_build_volume_table_s8()) ? _Eff_position_table_s8 :
                                                 		_Eff_position_s8;
	    		break;
	    	    case 4:
                        f = _Eff_position_s8_c4;
	    		break;
	    	    case 6:
                        f = _Eff_position_s8_c6;
	    		break;
	    }
            break;

        case AUDIO_U16LSB:
	    switch (channels) {
		    case 1:
		    case 2:
            		f = _Eff_position_u16lsb;
	    		break;
	    	    case 4:
            		f = _Eff_position_u16lsb_c4;
	    		break;
	    	    case 6:
            		f = _Eff_position_u16lsb_c6;
	    		break;
	    }
            break;

        case AUDIO_S16LSB:
	    switch (channels) {
		    case 1:
		    case 2:
            		f = _Eff_position_s16lsb;
	    		break;
	    	    case 4:
            		f = _Eff_position_s16lsb_c4;
	    		break;
	    	    case 6:
            		f = _Eff_position_s16lsb_c6;
	    		break;
	    }
            break;

        case AUDIO_U16MSB:
	    switch (channels) {
		    case 1:
		    case 2:
            		f = _Eff_position_u16msb;
	    		break;
	    	    case 4:
            		f = _Eff_position_u16msb_c4;
	    		break;
	    	    case 6:
            		f = _Eff_position_u16msb_c6;
	    		break;
	    }
            break;

        case AUDIO_S16MSB:
	    switch (channels) {
		    case 1:
		    case 2:
            		f = _Eff_position_s16msb;
	    		break;
	    	    case 4:
            		f = _Eff_position_s16msb_c4;
	    		break;
	    	    case 6:
            		f = _Eff_position_s16msb_c6;
	    		break;
	    }
            break;

        default:
            Mix_SetError("Unsupported audio format");
    }

    return(f);
}

static Uint8 speaker_amplitude[6];

static void set_amplitudes(int channels, int angle, int room_angle)
{
    int left = 255, right = 255;
    int left_rear = 255, right_rear = 255, center = 255;

    angle = SDL_abs(angle) % 360;  /* make angle between 0 an…