src/audio/SDL_mixer.c
author Sam Lantinga <slouken@libsdl.org>
Fri, 14 Dec 2001 12:38:15 +0000
changeset 252 e8157fcb3114
parent 1 cf2af46e9e2a
child 297 f6ffac90895c
permissions -rw-r--r--
Updated the source with the correct e-mail address
     1 /*
     2     SDL - Simple DirectMedia Layer
     3     Copyright (C) 1997, 1998, 1999, 2000, 2001  Sam Lantinga
     4 
     5     This library is free software; you can redistribute it and/or
     6     modify it under the terms of the GNU Library General Public
     7     License as published by the Free Software Foundation; either
     8     version 2 of the License, or (at your option) any later version.
     9 
    10     This library is distributed in the hope that it will be useful,
    11     but WITHOUT ANY WARRANTY; without even the implied warranty of
    12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    13     Library General Public License for more details.
    14 
    15     You should have received a copy of the GNU Library General Public
    16     License along with this library; if not, write to the Free
    17     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
    18 
    19     Sam Lantinga
    20     slouken@libsdl.org
    21 */
    22 
    23 #ifdef SAVE_RCSID
    24 static char rcsid =
    25  "@(#) $Id$";
    26 #endif
    27 
    28 /* This provides the default mixing callback for the SDL audio routines */
    29 
    30 #include <stdio.h>
    31 #include <stdlib.h>
    32 #include <string.h>
    33 
    34 #include "SDL_audio.h"
    35 #include "SDL_mutex.h"
    36 #include "SDL_timer.h"
    37 #include "SDL_sysaudio.h"
    38 
    39 
    40 /* This table is used to add two sound values together and pin
    41  * the value to avoid overflow.  (used with permission from ARDI)
    42  * Changed to use 0xFE instead of 0xFF for better sound quality.
    43  */
    44 static const Uint8 mix8[] =
    45 {
    46   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    47   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    48   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    49   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    50   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    51   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    52   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    53   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    54   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    55   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    56   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    57   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x02, 0x03,
    58   0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E,
    59   0x0F, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19,
    60   0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20, 0x21, 0x22, 0x23, 0x24,
    61   0x25, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C, 0x2D, 0x2E, 0x2F,
    62   0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3A,
    63   0x3B, 0x3C, 0x3D, 0x3E, 0x3F, 0x40, 0x41, 0x42, 0x43, 0x44, 0x45,
    64   0x46, 0x47, 0x48, 0x49, 0x4A, 0x4B, 0x4C, 0x4D, 0x4E, 0x4F, 0x50,
    65   0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59, 0x5A, 0x5B,
    66   0x5C, 0x5D, 0x5E, 0x5F, 0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66,
    67   0x67, 0x68, 0x69, 0x6A, 0x6B, 0x6C, 0x6D, 0x6E, 0x6F, 0x70, 0x71,
    68   0x72, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79, 0x7A, 0x7B, 0x7C,
    69   0x7D, 0x7E, 0x7F, 0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
    70   0x88, 0x89, 0x8A, 0x8B, 0x8C, 0x8D, 0x8E, 0x8F, 0x90, 0x91, 0x92,
    71   0x93, 0x94, 0x95, 0x96, 0x97, 0x98, 0x99, 0x9A, 0x9B, 0x9C, 0x9D,
    72   0x9E, 0x9F, 0xA0, 0xA1, 0xA2, 0xA3, 0xA4, 0xA5, 0xA6, 0xA7, 0xA8,
    73   0xA9, 0xAA, 0xAB, 0xAC, 0xAD, 0xAE, 0xAF, 0xB0, 0xB1, 0xB2, 0xB3,
    74   0xB4, 0xB5, 0xB6, 0xB7, 0xB8, 0xB9, 0xBA, 0xBB, 0xBC, 0xBD, 0xBE,
    75   0xBF, 0xC0, 0xC1, 0xC2, 0xC3, 0xC4, 0xC5, 0xC6, 0xC7, 0xC8, 0xC9,
    76   0xCA, 0xCB, 0xCC, 0xCD, 0xCE, 0xCF, 0xD0, 0xD1, 0xD2, 0xD3, 0xD4,
    77   0xD5, 0xD6, 0xD7, 0xD8, 0xD9, 0xDA, 0xDB, 0xDC, 0xDD, 0xDE, 0xDF,
    78   0xE0, 0xE1, 0xE2, 0xE3, 0xE4, 0xE5, 0xE6, 0xE7, 0xE8, 0xE9, 0xEA,
    79   0xEB, 0xEC, 0xED, 0xEE, 0xEF, 0xF0, 0xF1, 0xF2, 0xF3, 0xF4, 0xF5,
    80   0xF6, 0xF7, 0xF8, 0xF9, 0xFA, 0xFB, 0xFC, 0xFD, 0xFE, 0xFE, 0xFE,
    81   0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE,
    82   0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE,
    83   0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE,
    84   0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE,
    85   0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE,
    86   0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE,
    87   0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE,
    88   0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE,
    89   0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE,
    90   0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE,
    91   0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE,
    92   0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE
    93 };
    94 
    95 /* The volume ranges from 0 - 128 */
    96 #define ADJUST_VOLUME(s, v)	(s = (s*v)/SDL_MIX_MAXVOLUME)
    97 #define ADJUST_VOLUME_U8(s, v)	(s = (((s-128)*v)/SDL_MIX_MAXVOLUME)+128)
    98 
    99 void SDL_MixAudio (Uint8 *dst, const Uint8 *src, Uint32 len, int volume)
   100 {
   101 	Uint16 format;
   102 
   103 	if ( volume == 0 ) {
   104 		return;
   105 	}
   106 	/* Mix the user-level audio format */
   107 	if ( current_audio ) {
   108 		if ( current_audio->convert.needed ) {
   109 			format = current_audio->convert.src_format;
   110 		} else {
   111 			format = current_audio->spec.format;
   112 		}
   113 	} else {
   114   		/* HACK HACK HACK */
   115 		format = AUDIO_S16;
   116 	}
   117 	switch (format) {
   118 
   119 		case AUDIO_U8: {
   120 			Uint8 src_sample;
   121 
   122 			while ( len-- ) {
   123 				src_sample = *src;
   124 				ADJUST_VOLUME_U8(src_sample, volume);
   125 				*dst = mix8[*dst+src_sample];
   126 				++dst;
   127 				++src;
   128 			}
   129 		}
   130 		break;
   131 
   132 		case AUDIO_S8: {
   133 			Sint8 *dst8, *src8;
   134 			Sint8 src_sample;
   135 			int dst_sample;
   136 			const int max_audioval = ((1<<(8-1))-1);
   137 			const int min_audioval = -(1<<(8-1));
   138 
   139 			src8 = (Sint8 *)src;
   140 			dst8 = (Sint8 *)dst;
   141 			while ( len-- ) {
   142 				src_sample = *src8;
   143 				ADJUST_VOLUME(src_sample, volume);
   144 				dst_sample = *dst8 + src_sample;
   145 				if ( dst_sample > max_audioval ) {
   146 					*dst8 = max_audioval;
   147 				} else
   148 				if ( dst_sample < min_audioval ) {
   149 					*dst8 = min_audioval;
   150 				} else {
   151 					*dst8 = dst_sample;
   152 				}
   153 				++dst8;
   154 				++src8;
   155 			}
   156 		}
   157 		break;
   158 
   159 		case AUDIO_S16LSB: {
   160 			Sint16 src1, src2;
   161 			int dst_sample;
   162 			const int max_audioval = ((1<<(16-1))-1);
   163 			const int min_audioval = -(1<<(16-1));
   164 
   165 			len /= 2;
   166 			while ( len-- ) {
   167 				src1 = ((src[1])<<8|src[0]);
   168 				ADJUST_VOLUME(src1, volume);
   169 				src2 = ((dst[1])<<8|dst[0]);
   170 				src += 2;
   171 				dst_sample = src1+src2;
   172 				if ( dst_sample > max_audioval ) {
   173 					dst_sample = max_audioval;
   174 				} else
   175 				if ( dst_sample < min_audioval ) {
   176 					dst_sample = min_audioval;
   177 				}
   178 				dst[0] = dst_sample&0xFF;
   179 				dst_sample >>= 8;
   180 				dst[1] = dst_sample&0xFF;
   181 				dst += 2;
   182 			}
   183 		}
   184 		break;
   185 
   186 		case AUDIO_S16MSB: {
   187 			Sint16 src1, src2;
   188 			int dst_sample;
   189 			const int max_audioval = ((1<<(16-1))-1);
   190 			const int min_audioval = -(1<<(16-1));
   191 
   192 			len /= 2;
   193 			while ( len-- ) {
   194 				src1 = ((src[0])<<8|src[1]);
   195 				ADJUST_VOLUME(src1, volume);
   196 				src2 = ((dst[0])<<8|dst[1]);
   197 				src += 2;
   198 				dst_sample = src1+src2;
   199 				if ( dst_sample > max_audioval ) {
   200 					dst_sample = max_audioval;
   201 				} else
   202 				if ( dst_sample < min_audioval ) {
   203 					dst_sample = min_audioval;
   204 				}
   205 				dst[1] = dst_sample&0xFF;
   206 				dst_sample >>= 8;
   207 				dst[0] = dst_sample&0xFF;
   208 				dst += 2;
   209 			}
   210 		}
   211 		break;
   212 
   213 		default: /* If this happens... FIXME! */
   214 			SDL_SetError("SDL_MixAudio(): unknown audio format");
   215 			return;
   216 	}
   217 }