1 /* 2 SDL - Simple DirectMedia Layer 3 Copyright (C) 1997-2009 Sam Lantinga 4 5 This library is free software; you can redistribute it and/or 6 modify it under the terms of the GNU Lesser General Public 7 License as published by the Free Software Foundation; either 8 version 2.1 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 Lesser General Public License for more details. 14 15 You should have received a copy of the GNU Lesser General Public 16 License along with this library; if not, write to the Free Software 17 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA 18 19 Sam Lantinga 20 slouken@libsdl.org 21 */ 22 23 /** 24 * @file SDL_audio.h 25 * Access to the raw audio mixing buffer for the SDL library 26 */ 27 28 #ifndef _SDL_audio_h 29 #define _SDL_audio_h 30 31 #include "SDL_stdinc.h" 32 #include "SDL_error.h" 33 #include "SDL_endian.h" 34 #include "SDL_mutex.h" 35 #include "SDL_thread.h" 36 #include "SDL_rwops.h" 37 38 #include "begin_code.h" 39 /* Set up for C function definitions, even when using C++ */ 40 #ifdef __cplusplus 41 extern "C" { 42 #endif 43 44 /** 45 * When filling in the desired audio spec structure, 46 * - 'desired->freq' should be the desired audio frequency in samples-per-second. 47 * - 'desired->format' should be the desired audio format. 48 * - 'desired->samples' is the desired size of the audio buffer, in samples. 49 * This number should be a power of two, and may be adjusted by the audio 50 * driver to a value more suitable for the hardware. Good values seem to 51 * range between 512 and 8096 inclusive, depending on the application and 52 * CPU speed. Smaller values yield faster response time, but can lead 53 * to underflow if the application is doing heavy processing and cannot 54 * fill the audio buffer in time. A stereo sample consists of both right 55 * and left channels in LR ordering. 56 * Note that the number of samples is directly related to time by the 57 * following formula: ms = (samples*1000)/freq 58 * - 'desired->size' is the size in bytes of the audio buffer, and is 59 * calculated by SDL_OpenAudio(). 60 * - 'desired->silence' is the value used to set the buffer to silence, 61 * and is calculated by SDL_OpenAudio(). 62 * - 'desired->callback' should be set to a function that will be called 63 * when the audio device is ready for more data. It is passed a pointer 64 * to the audio buffer, and the length in bytes of the audio buffer. 65 * This function usually runs in a separate thread, and so you should 66 * protect data structures that it accesses by calling SDL_LockAudio() 67 * and SDL_UnlockAudio() in your code. 68 * - 'desired->userdata' is passed as the first parameter to your callback 69 * function. 70 * 71 * @note The calculated values in this structure are calculated by SDL_OpenAudio() 72 * 73 */ 74 typedef struct SDL_AudioSpec { 75 int freq; /**< DSP frequency -- samples per second */ 76 Uint16 format; /**< Audio data format */ 77 Uint8 channels; /**< Number of channels: 1 mono, 2 stereo */ 78 Uint8 silence; /**< Audio buffer silence value (calculated) */ 79 Uint16 samples; /**< Audio buffer size in samples (power of 2) */ 80 Uint16 padding; /**< Necessary for some compile environments */ 81 Uint32 size; /**< Audio buffer size in bytes (calculated) */ 82 /** 83 * This function is called when the audio device needs more data. 84 * 85 * @param[out] stream A pointer to the audio data buffer 86 * @param[in] len The length of the audio buffer in bytes. 87 * 88 * Once the callback returns, the buffer will no longer be valid. 89 * Stereo samples are stored in a LRLRLR ordering. 90 */ 91 void (SDLCALL *callback)(void *userdata, Uint8 *stream, int len); 92 void *userdata; 93 } SDL_AudioSpec; 94 95 /** 96 * @name Audio format flags 97 * defaults to LSB byte order 98 */ 99 /*@{*/ 100 #define AUDIO_U8 0x0008 /**< Unsigned 8-bit samples */ 101 #define AUDIO_S8 0x8008 /**< Signed 8-bit samples */ 102 #define AUDIO_U16LSB 0x0010 /**< Unsigned 16-bit samples */ 103 #define AUDIO_S16LSB 0x8010 /**< Signed 16-bit samples */ 104 #define AUDIO_U16MSB 0x1010 /**< As above, but big-endian byte order */ 105 #define AUDIO_S16MSB 0x9010 /**< As above, but big-endian byte order */ 106 #define AUDIO_U16 AUDIO_U16LSB 107 #define AUDIO_S16 AUDIO_S16LSB 108 109 /** 110 * @name Native audio byte ordering 111 */ 112 /*@{*/ 113 #if SDL_BYTEORDER == SDL_LIL_ENDIAN 114 #define AUDIO_U16SYS AUDIO_U16LSB 115 #define AUDIO_S16SYS AUDIO_S16LSB 116 #else 117 #define AUDIO_U16SYS AUDIO_U16MSB 118 #define AUDIO_S16SYS AUDIO_S16MSB 119 #endif 120 /*@}*/ 121 122 /*@}*/ 123 124 125 /** A structure to hold a set of audio conversion filters and buffers */ 126 typedef struct SDL_AudioCVT { 127 int needed; /**< Set to 1 if conversion possible */ 128 Uint16 src_format; /**< Source audio format */ 129 Uint16 dst_format; /**< Target audio format */ 130 double rate_incr; /**< Rate conversion increment */ 131 Uint8 *buf; /**< Buffer to hold entire audio data */ 132 int len; /**< Length of original audio buffer */ 133 int len_cvt; /**< Length of converted audio buffer */ 134 int len_mult; /**< buffer must be len*len_mult big */ 135 double len_ratio; /**< Given len, final size is len*len_ratio */ 136 void (SDLCALL *filters[10])(struct SDL_AudioCVT *cvt, Uint16 format); 137 int filter_index; /**< Current audio conversion function */ 138 } SDL_AudioCVT; 139 140 141 /* Function prototypes */ 142 143 /** 144 * @name Audio Init and Quit 145 * These functions are used internally, and should not be used unless you 146 * have a specific need to specify the audio driver you want to use. 147 * You should normally use SDL_Init() or SDL_InitSubSystem(). 148 */ 149 /*@{*/ 150 extern DECLSPEC int SDLCALL SDL_AudioInit(const char *driver_name); 151 extern DECLSPEC void SDLCALL SDL_AudioQuit(void); 152 /*@}*/ 153 154 /** 155 * This function fills the given character buffer with the name of the 156 * current audio driver, and returns a pointer to it if the audio driver has 157 * been initialized. It returns NULL if no driver has been initialized. 158 */ 159 extern DECLSPEC char * SDLCALL SDL_AudioDriverName(char *namebuf, int maxlen); 160 161 /** 162 * This function opens the audio device with the desired parameters, and 163 * returns 0 if successful, placing the actual hardware parameters in the 164 * structure pointed to by 'obtained'. If 'obtained' is NULL, the audio 165 * data passed to the callback function will be guaranteed to be in the 166 * requested format, and will be automatically converted to the hardware 167 * audio format if necessary. This function returns -1 if it failed 168 * to open the audio device, or couldn't set up the audio thread. 169 * 170 * The audio device starts out playing silence when it's opened, and should 171 * be enabled for playing by calling SDL_PauseAudio(0) when you are ready 172 * for your audio callback function to be called. Since the audio driver 173 * may modify the requested size of the audio buffer, you should allocate 174 * any local mixing buffers after you open the audio device. 175 * 176 * @sa SDL_AudioSpec 177 */ 178 extern DECLSPEC int SDLCALL SDL_OpenAudio(SDL_AudioSpec *desired, SDL_AudioSpec *obtained); 179 180 typedef enum { 181 SDL_AUDIO_STOPPED = 0, 182 SDL_AUDIO_PLAYING, 183 SDL_AUDIO_PAUSED 184 } SDL_audiostatus; 185 186 /** Get the current audio state */ 187 extern DECLSPEC SDL_audiostatus SDLCALL SDL_GetAudioStatus(void); 188 189 /** 190 * This function pauses and unpauses the audio callback processing. 191 * It should be called with a parameter of 0 after opening the audio 192 * device to start playing sound. This is so you can safely initialize 193 * data for your callback function after opening the audio device. 194 * Silence will be written to the audio device during the pause. 195 */ 196 extern DECLSPEC void SDLCALL SDL_PauseAudio(int pause_on); 197 198 /** 199 * This function loads a WAVE from the data source, automatically freeing 200 * that source if 'freesrc' is non-zero. For example, to load a WAVE file, 201 * you could do: 202 * @code SDL_LoadWAV_RW(SDL_RWFromFile("sample.wav", "rb"), 1, ...); @endcode 203 * 204 * If this function succeeds, it returns the given SDL_AudioSpec, 205 * filled with the audio data format of the wave data, and sets 206 * 'audio_buf' to a malloc()'d buffer containing the audio data, 207 * and sets 'audio_len' to the length of that audio buffer, in bytes. 208 * You need to free the audio buffer with SDL_FreeWAV() when you are 209 * done with it. 210 * 211 * This function returns NULL and sets the SDL error message if the 212 * wave file cannot be opened, uses an unknown data format, or is 213 * corrupt. Currently raw and MS-ADPCM WAVE files are supported. 214 */ 215 extern DECLSPEC SDL_AudioSpec * SDLCALL SDL_LoadWAV_RW(SDL_RWops *src, int freesrc, SDL_AudioSpec *spec, Uint8 **audio_buf, Uint32 *audio_len); 216 217 /** Compatibility convenience function -- loads a WAV from a file */ 218 #define SDL_LoadWAV(file, spec, audio_buf, audio_len) \ 219 SDL_LoadWAV_RW(SDL_RWFromFile(file, "rb"),1, spec,audio_buf,audio_len) 220 221 /** 222 * This function frees data previously allocated with SDL_LoadWAV_RW() 223 */ 224 extern DECLSPEC void SDLCALL SDL_FreeWAV(Uint8 *audio_buf); 225 226 /** 227 * This function takes a source format and rate and a destination format 228 * and rate, and initializes the 'cvt' structure with information needed 229 * by SDL_ConvertAudio() to convert a buffer of audio data from one format 230 * to the other. 231 * 232 * @return This function returns 0, or -1 if there was an error. 233 */ 234 extern DECLSPEC int SDLCALL SDL_BuildAudioCVT(SDL_AudioCVT *cvt, 235 Uint16 src_format, Uint8 src_channels, int src_rate, 236 Uint16 dst_format, Uint8 dst_channels, int dst_rate); 237 238 /** 239 * Once you have initialized the 'cvt' structure using SDL_BuildAudioCVT(), 240 * created an audio buffer cvt->buf, and filled it with cvt->len bytes of 241 * audio data in the source format, this function will convert it in-place 242 * to the desired format. 243 * The data conversion may expand the size of the audio data, so the buffer 244 * cvt->buf should be allocated after the cvt structure is initialized by 245 * SDL_BuildAudioCVT(), and should be cvt->len*cvt->len_mult bytes long. 246 */ 247 extern DECLSPEC int SDLCALL SDL_ConvertAudio(SDL_AudioCVT *cvt); 248 249 250 #define SDL_MIX_MAXVOLUME 128 251 /** 252 * This takes two audio buffers of the playing audio format and mixes 253 * them, performing addition, volume adjustment, and overflow clipping. 254 * The volume ranges from 0 - 128, and should be set to SDL_MIX_MAXVOLUME 255 * for full audio volume. Note this does not change hardware volume. 256 * This is provided for convenience -- you can mix your own audio data. 257 */ 258 extern DECLSPEC void SDLCALL SDL_MixAudio(Uint8 *dst, const Uint8 *src, Uint32 len, int volume); 259 260 /** 261 * @name Audio Locks 262 * The lock manipulated by these functions protects the callback function. 263 * During a LockAudio/UnlockAudio pair, you can be guaranteed that the 264 * callback function is not running. Do not call these from the callback 265 * function or you will cause deadlock. 266 */ 267 /*@{*/ 268 extern DECLSPEC void SDLCALL SDL_LockAudio(void); 269 extern DECLSPEC void SDLCALL SDL_UnlockAudio(void); 270 /*@}*/ 271 272 /** 273 * This function shuts down audio processing and closes the audio device. 274 */ 275 extern DECLSPEC void SDLCALL SDL_CloseAudio(void); 276 277 278 /* Ends C function definitions when using C++ */ 279 #ifdef __cplusplus 280 } 281 #endif 282 #include "close_code.h" 283 284 #endif /* _SDL_audio_h */ 285