src/audio/SDL_mixer.c
/* [<][>][^][v][top][bottom][index][help] */
FUNCTIONS
This source file includes following functions.
- ADJUST_VOLUME
- ADJUST_VOLUME_U8
- SDL_MixAudio
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@devolution.com
21 */
22
23 #ifdef SAVE_RCSID
24 static char rcsid =
25 "@(#) $Id: SDL_mixer.c,v 1.4.2.5 2001/02/10 07:20:03 hercules Exp $";
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)
/* [<][>][^][v][top][bottom][index][help] */
97 #define ADJUST_VOLUME_U8(s, v) (s = (((s-128)*v)/SDL_MIX_MAXVOLUME)+128)
/* [<][>][^][v][top][bottom][index][help] */
98
99 void SDL_MixAudio (Uint8 *dst, Uint8 *src, Uint32 len, int volume)
/* [<][>][^][v][top][bottom][index][help] */
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 }