1 /* 2 SDL - Simple DirectMedia Layer 3 Copyright (C) 1997-2004 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 (at) libsdl.org 21 */ 22 23 #ifdef SAVE_RCSID 24 static char rcsid = 25 "@(#) $Id: SDL_audio.h,v 1.9 2004/08/20 18:57:01 slouken Exp $"; 26 #endif 27 28 /* Access to the raw audio mixing buffer for the SDL library */ 29 30 #ifndef _SDL_audio_h 31 #define _SDL_audio_h 32 33 #include <stdio.h> 34 35 #include "SDL_main.h" 36 #include "SDL_types.h" 37 #include "SDL_error.h" 38 #include "SDL_rwops.h" 39 #include "SDL_byteorder.h" 40 41 #include "begin_code.h" 42 /* Set up for C function definitions, even when using C++ */ 43 #ifdef __cplusplus 44 extern "C" { 45 #endif 46 47 /* The calculated values in this structure are calculated by SDL_OpenAudio() */ 48 typedef struct SDL_AudioSpec { 49 int freq; /* DSP frequency -- samples per second */ 50 Uint16 format; /* Audio data format */ 51 Uint8 channels; /* Number of channels: 1 mono, 2 stereo */ 52 Uint8 silence; /* Audio buffer silence value (calculated) */ 53 Uint16 samples; /* Audio buffer size in samples (power of 2) */ 54 Uint16 padding; /* Necessary for some compile environments */ 55 Uint32 size; /* Audio buffer size in bytes (calculated) */ 56 /* This function is called when the audio device needs more data. 57 'stream' is a pointer to the audio data buffer 58 'len' is the length of that buffer in bytes. 59 Once the callback returns, the buffer will no longer be valid. 60 Stereo samples are stored in a LRLRLR ordering. 61 */ 62 void (SDLCALL *callback)(void *userdata, Uint8 *stream, int len); 63 void *userdata; 64 } SDL_AudioSpec; 65 66 /* Audio format flags (defaults to LSB byte order) */ 67 #define AUDIO_U8 0x0008 /* Unsigned 8-bit samples */ 68 #define AUDIO_S8 0x8008 /* Signed 8-bit samples */ 69 #define AUDIO_U16LSB 0x0010 /* Unsigned 16-bit samples */ 70 #define AUDIO_S16LSB 0x8010 /* Signed 16-bit samples */ 71 #define AUDIO_U16MSB 0x1010 /* As above, but big-endian byte order */ 72 #define AUDIO_S16MSB 0x9010 /* As above, but big-endian byte order */ 73 #define AUDIO_U16 AUDIO_U16LSB 74 #define AUDIO_S16 AUDIO_S16LSB 75 76 /* Native audio byte ordering */ 77 #if SDL_BYTEORDER == SDL_LIL_ENDIAN 78 #define AUDIO_U16SYS AUDIO_U16LSB 79 #define AUDIO_S16SYS AUDIO_S16LSB 80 #else 81 #define AUDIO_U16SYS AUDIO_U16MSB 82 #define AUDIO_S16SYS AUDIO_S16MSB 83 #endif 84 85 86 /* A structure to hold a set of audio conversion filters and buffers */ 87 typedef struct SDL_AudioCVT { 88 int needed; /* Set to 1 if conversion possible */ 89 Uint16 src_format; /* Source audio format */ 90 Uint16 dst_format; /* Target audio format */ 91 double rate_incr; /* Rate conversion increment */ 92 Uint8 *buf; /* Buffer to hold entire audio data */ 93 int len; /* Length of original audio buffer */ 94 int len_cvt; /* Length of converted audio buffer */ 95 int len_mult; /* buffer must be len*len_mult big */ 96 double len_ratio; /* Given len, final size is len*len_ratio */ 97 void (SDLCALL *filters[10])(struct SDL_AudioCVT *cvt, Uint16 format); 98 int filter_index; /* Current audio conversion function */ 99 } SDL_AudioCVT; 100 101 102 /* Function prototypes */ 103 104 /* These functions are used internally, and should not be used unless you 105 * have a specific need to specify the audio driver you want to use. 106 * You should normally use SDL_Init() or SDL_InitSubSystem(). 107 */ 108 extern DECLSPEC int SDLCALL SDL_AudioInit(const char *driver_name); 109 extern DECLSPEC void SDLCALL SDL_AudioQuit(void); 110 111 /* This function fills the given character buffer with the name of the 112 * current audio driver, and returns a pointer to it if the audio driver has 113 * been initialized. It returns NULL if no driver has been initialized. 114 */ 115 extern DECLSPEC char * SDLCALL SDL_AudioDriverName(char *namebuf, int maxlen); 116 117 /* 118 * This function opens the audio device with the desired parameters, and 119 * returns 0 if successful, placing the actual hardware parameters in the 120 * structure pointed to by 'obtained'. If 'obtained' is NULL, the audio 121 * data passed to the callback function will be guaranteed to be in the 122 * requested format, and will be automatically converted to the hardware 123 * audio format if necessary. This function returns -1 if it failed 124 * to open the audio device, or couldn't set up the audio thread. 125 * 126 * When filling in the desired audio spec structure, 127 * 'desired->freq' should be the desired audio frequency in samples-per-second. 128 * 'desired->format' should be the desired audio format. 129 * 'desired->samples' is the desired size of the audio buffer, in samples. 130 * This number should be a power of two, and may be adjusted by the audio 131 * driver to a value more suitable for the hardware. Good values seem to 132 * range between 512 and 8096 inclusive, depending on the application and 133 * CPU speed. Smaller values yield faster response time, but can lead 134 * to underflow if the application is doing heavy processing and cannot 135 * fill the audio buffer in time. A stereo sample consists of both right 136 * and left channels in LR ordering. 137 * Note that the number of samples is directly related to time by the 138 * following formula: ms = (samples*1000)/freq 139 * 'desired->size' is the size in bytes of the audio buffer, and is 140 * calculated by SDL_OpenAudio(). 141 * 'desired->silence' is the value used to set the buffer to silence, 142 * and is calculated by SDL_OpenAudio(). 143 * 'desired->callback' should be set to a function that will be called 144 * when the audio device is ready for more data. It is passed a pointer 145 * to the audio buffer, and the length in bytes of the audio buffer. 146 * This function usually runs in a separate thread, and so you should 147 * protect data structures that it accesses by calling SDL_LockAudio() 148 * and SDL_UnlockAudio() in your code. 149 * 'desired->userdata' is passed as the first parameter to your callback 150 * function. 151 * 152 * The audio device starts out playing silence when it's opened, and should 153 * be enabled for playing by calling SDL_PauseAudio(0) when you are ready 154 * for your audio callback function to be called. Since the audio driver 155 * may modify the requested size of the audio buffer, you should allocate 156 * any local mixing buffers after you open the audio device. 157 */ 158 extern DECLSPEC int SDLCALL SDL_OpenAudio(SDL_AudioSpec *desired, SDL_AudioSpec *obtained); 159 160 /* 161 * Get the current audio state: 162 */ 163 typedef enum { 164 SDL_AUDIO_STOPPED = 0, 165 SDL_AUDIO_PLAYING, 166 SDL_AUDIO_PAUSED 167 } SDL_audiostatus; 168 extern DECLSPEC SDL_audiostatus SDLCALL SDL_GetAudioStatus(void); 169 170 /* 171 * This function pauses and unpauses the audio callback processing. 172 * It should be called with a parameter of 0 after opening the audio 173 * device to start playing sound. This is so you can safely initialize 174 * data for your callback function after opening the audio device. 175 * Silence will be written to the audio device during the pause. 176 */ 177 extern DECLSPEC void SDLCALL SDL_PauseAudio(int pause_on); 178 179 /* 180 * This function loads a WAVE from the data source, automatically freeing 181 * that source if 'freesrc' is non-zero. For example, to load a WAVE file, 182 * you could do: 183 * SDL_LoadWAV_RW(SDL_RWFromFile("sample.wav", "rb"), 1, ...); 184 * 185 * If this function succeeds, it returns the given SDL_AudioSpec, 186 * filled with the audio data format of the wave data, and sets 187 * 'audio_buf' to a malloc()'d buffer containing the audio data, 188 * and sets 'audio_len' to the length of that audio buffer, in bytes. 189 * You need to free the audio buffer with SDL_FreeWAV() when you are 190 * done with it. 191 * 192 * This function returns NULL and sets the SDL error message if the 193 * wave file cannot be opened, uses an unknown data format, or is 194 * corrupt. Currently raw and MS-ADPCM WAVE files are supported. 195 */ 196 extern DECLSPEC SDL_AudioSpec * SDLCALL SDL_LoadWAV_RW(SDL_RWops *src, int freesrc, SDL_AudioSpec *spec, Uint8 **audio_buf, Uint32 *audio_len); 197 198 /* Compatibility convenience function -- loads a WAV from a file */ 199 #define SDL_LoadWAV(file, spec, audio_buf, audio_len) \ 200 SDL_LoadWAV_RW(SDL_RWFromFile(file, "rb"),1, spec,audio_buf,audio_len) 201 202 /* 203 * This function frees data previously allocated with SDL_LoadWAV_RW() 204 */ 205 extern DECLSPEC void SDLCALL SDL_FreeWAV(Uint8 *audio_buf); 206 207 /* 208 * This function takes a source format and rate and a destination format 209 * and rate, and initializes the 'cvt' structure with information needed 210 * by SDL_ConvertAudio() to convert a buffer of audio data from one format 211 * to the other. 212 * This function returns 0, or -1 if there was an error. 213 */ 214 extern DECLSPEC int SDLCALL SDL_BuildAudioCVT(SDL_AudioCVT *cvt, 215 Uint16 src_format, Uint8 src_channels, int src_rate, 216 Uint16 dst_format, Uint8 dst_channels, int dst_rate); 217 218 /* Once you have initialized the 'cvt' structure using SDL_BuildAudioCVT(), 219 * created an audio buffer cvt->buf, and filled it with cvt->len bytes of 220 * audio data in the source format, this function will convert it in-place 221 * to the desired format. 222 * The data conversion may expand the size of the audio data, so the buffer 223 * cvt->buf should be allocated after the cvt structure is initialized by 224 * SDL_BuildAudioCVT(), and should be cvt->len*cvt->len_mult bytes long. 225 */ 226 extern DECLSPEC int SDLCALL SDL_ConvertAudio(SDL_AudioCVT *cvt); 227 228 /* 229 * This takes two audio buffers of the playing audio format and mixes 230 * them, performing addition, volume adjustment, and overflow clipping. 231 * The volume ranges from 0 - 128, and should be set to SDL_MIX_MAXVOLUME 232 * for full audio volume. Note this does not change hardware volume. 233 * This is provided for convenience -- you can mix your own audio data. 234 */ 235 #define SDL_MIX_MAXVOLUME 128 236 extern DECLSPEC void SDLCALL SDL_MixAudio(Uint8 *dst, const Uint8 *src, Uint32 len, int volume); 237 238 /* 239 * The lock manipulated by these functions protects the callback function. 240 * During a LockAudio/UnlockAudio pair, you can be guaranteed that the 241 * callback function is not running. Do not call these from the callback 242 * function or you will cause deadlock. 243 */ 244 extern DECLSPEC void SDLCALL SDL_LockAudio(void); 245 extern DECLSPEC void SDLCALL SDL_UnlockAudio(void); 246 247 /* 248 * This function shuts down audio processing and closes the audio device. 249 */ 250 extern DECLSPEC void SDLCALL SDL_CloseAudio(void); 251 252 253 /* Ends C function definitions when using C++ */ 254 #ifdef __cplusplus 255 } 256 #endif 257 #include "close_code.h" 258 259 #endif /* _SDL_audio_h */ 260
