Name the audio callback for documentation clarity.
2 SDL - Simple DirectMedia Layer
3 Copyright (C) 1997-2009 Sam Lantinga
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.
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.
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
26 * Access to the raw audio mixing buffer for the SDL library.
32 #include "SDL_stdinc.h"
33 #include "SDL_error.h"
34 #include "SDL_endian.h"
35 #include "SDL_mutex.h"
36 #include "SDL_thread.h"
37 #include "SDL_rwops.h"
39 #include "begin_code.h"
40 /* Set up for C function definitions, even when using C++ */
48 * \brief Audio format flags.
50 * These are what the 16 bits in SDL_AudioFormat currently mean...
51 * (Unspecified bits are always zero).
54 ++-----------------------sample is signed if set
56 || ++-----------sample is bigendian if set
58 || || ++---sample is float if set
60 || || || +---sample bit size---+
62 15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00
65 * There are macros in SDL 1.3 and later to query these bits.
67 typedef Uint16 SDL_AudioFormat;
74 #define SDL_AUDIO_MASK_BITSIZE (0xFF)
75 #define SDL_AUDIO_MASK_DATATYPE (1<<8)
76 #define SDL_AUDIO_MASK_ENDIAN (1<<12)
77 #define SDL_AUDIO_MASK_SIGNED (1<<15)
78 #define SDL_AUDIO_BITSIZE(x) (x & SDL_AUDIO_MASK_BITSIZE)
79 #define SDL_AUDIO_ISFLOAT(x) (x & SDL_AUDIO_MASK_DATATYPE)
80 #define SDL_AUDIO_ISBIGENDIAN(x) (x & SDL_AUDIO_MASK_ENDIAN)
81 #define SDL_AUDIO_ISSIGNED(x) (x & SDL_AUDIO_MASK_SIGNED)
82 #define SDL_AUDIO_ISINT(x) (!SDL_AUDIO_ISFLOAT(x))
83 #define SDL_AUDIO_ISLITTLEENDIAN(x) (!SDL_AUDIO_ISBIGENDIAN(x))
84 #define SDL_AUDIO_ISUNSIGNED(x) (!SDL_AUDIO_ISSIGNED(x))
87 * \name Audio format flags
89 * Defaults to LSB byte order.
92 #define AUDIO_U8 0x0008 /**< Unsigned 8-bit samples */
93 #define AUDIO_S8 0x8008 /**< Signed 8-bit samples */
94 #define AUDIO_U16LSB 0x0010 /**< Unsigned 16-bit samples */
95 #define AUDIO_S16LSB 0x8010 /**< Signed 16-bit samples */
96 #define AUDIO_U16MSB 0x1010 /**< As above, but big-endian byte order */
97 #define AUDIO_S16MSB 0x9010 /**< As above, but big-endian byte order */
98 #define AUDIO_U16 AUDIO_U16LSB
99 #define AUDIO_S16 AUDIO_S16LSB
103 * \name int32 support
108 #define AUDIO_S32LSB 0x8020 /**< 32-bit integer samples */
109 #define AUDIO_S32MSB 0x9020 /**< As above, but big-endian byte order */
110 #define AUDIO_S32 AUDIO_S32LSB
114 * \name float32 support
119 #define AUDIO_F32LSB 0x8120 /**< 32-bit floating point samples */
120 #define AUDIO_F32MSB 0x9120 /**< As above, but big-endian byte order */
121 #define AUDIO_F32 AUDIO_F32LSB
125 * \name Native audio byte ordering
128 #if SDL_BYTEORDER == SDL_LIL_ENDIAN
129 #define AUDIO_U16SYS AUDIO_U16LSB
130 #define AUDIO_S16SYS AUDIO_S16LSB
131 #define AUDIO_S32SYS AUDIO_S32LSB
132 #define AUDIO_F32SYS AUDIO_F32LSB
134 #define AUDIO_U16SYS AUDIO_U16MSB
135 #define AUDIO_S16SYS AUDIO_S16MSB
136 #define AUDIO_S32SYS AUDIO_S32MSB
137 #define AUDIO_F32SYS AUDIO_F32MSB
142 * \name Allow change flags
144 * Which audio format changes are allowed when opening a device.
147 #define SDL_AUDIO_ALLOW_FREQUENCY_CHANGE 0x00000001
148 #define SDL_AUDIO_ALLOW_FORMAT_CHANGE 0x00000002
149 #define SDL_AUDIO_ALLOW_CHANNELS_CHANGE 0x00000004
150 #define SDL_AUDIO_ALLOW_ANY_CHANGE (SDL_AUDIO_ALLOW_FREQUENCY_CHANGE|SDL_AUDIO_ALLOW_FORMAT_CHANGE|SDL_AUDIO_ALLOW_CHANNELS_CHANGE)
153 /*@}*//*Audio flags*/
156 * This function is called when the audio device needs more data.
158 * \param userdata An application-specific parameter saved in
159 * the SDL_AudioSpec structure
160 * \param stream A pointer to the audio data buffer.
161 * \param len The length of that buffer in bytes.
163 * Once the callback returns, the buffer will no longer be valid.
164 * Stereo samples are stored in a LRLRLR ordering.
166 typedef void (SDLCALL * SDL_AudioCallback) (void *userdata, Uint8 * stream,
170 * The calculated values in this structure are calculated by SDL_OpenAudio().
172 typedef struct SDL_AudioSpec
174 int freq; /**< DSP frequency -- samples per second */
175 SDL_AudioFormat format; /**< Audio data format */
176 Uint8 channels; /**< Number of channels: 1 mono, 2 stereo */
177 Uint8 silence; /**< Audio buffer silence value (calculated) */
178 Uint16 samples; /**< Audio buffer size in samples (power of 2) */
179 Uint16 padding; /**< Necessary for some compile environments */
180 Uint32 size; /**< Audio buffer size in bytes (calculated) */
181 SDL_AudioCallback callback;
187 typedef void (SDLCALL * SDL_AudioFilter) (struct SDL_AudioCVT * cvt,
188 SDL_AudioFormat format);
191 * A structure to hold a set of audio conversion filters and buffers.
193 typedef struct SDL_AudioCVT
195 int needed; /**< Set to 1 if conversion possible */
196 SDL_AudioFormat src_format; /**< Source audio format */
197 SDL_AudioFormat dst_format; /**< Target audio format */
198 double rate_incr; /**< Rate conversion increment */
199 Uint8 *buf; /**< Buffer to hold entire audio data */
200 int len; /**< Length of original audio buffer */
201 int len_cvt; /**< Length of converted audio buffer */
202 int len_mult; /**< buffer must be len*len_mult big */
203 double len_ratio; /**< Given len, final size is len*len_ratio */
204 SDL_AudioFilter filters[10]; /**< Filter list */
205 int filter_index; /**< Current audio conversion function */
209 /* Function prototypes */
212 * \name Driver discovery functions
214 * These functions return the list of built in audio drivers, in the
215 * order that they are normally initialized by default.
218 extern DECLSPEC int SDLCALL SDL_GetNumAudioDrivers(void);
219 extern DECLSPEC const char *SDLCALL SDL_GetAudioDriver(int index);
223 * \name Initialization and cleanup
225 * \internal These functions are used internally, and should not be used unless
226 * you have a specific need to specify the audio driver you want to
227 * use. You should normally use SDL_Init() or SDL_InitSubSystem().
230 extern DECLSPEC int SDLCALL SDL_AudioInit(const char *driver_name);
231 extern DECLSPEC void SDLCALL SDL_AudioQuit(void);
235 * This function returns the name of the current audio driver, or NULL
236 * if no driver has been initialized.
238 extern DECLSPEC const char *SDLCALL SDL_GetCurrentAudioDriver(void);
241 * This function opens the audio device with the desired parameters, and
242 * returns 0 if successful, placing the actual hardware parameters in the
243 * structure pointed to by \c obtained. If \c obtained is NULL, the audio
244 * data passed to the callback function will be guaranteed to be in the
245 * requested format, and will be automatically converted to the hardware
246 * audio format if necessary. This function returns -1 if it failed
247 * to open the audio device, or couldn't set up the audio thread.
249 * When filling in the desired audio spec structure,
250 * - \c desired->freq should be the desired audio frequency in samples-per-
252 * - \c desired->format should be the desired audio format.
253 * - \c desired->samples is the desired size of the audio buffer, in
254 * samples. This number should be a power of two, and may be adjusted by
255 * the audio driver to a value more suitable for the hardware. Good values
256 * seem to range between 512 and 8096 inclusive, depending on the
257 * application and CPU speed. Smaller values yield faster response time,
258 * but can lead to underflow if the application is doing heavy processing
259 * and cannot fill the audio buffer in time. A stereo sample consists of
260 * both right and left channels in LR ordering.
261 * Note that the number of samples is directly related to time by the
262 * following formula: \code ms = (samples*1000)/freq \endcode
263 * - \c desired->size is the size in bytes of the audio buffer, and is
264 * calculated by SDL_OpenAudio().
265 * - \c desired->silence is the value used to set the buffer to silence,
266 * and is calculated by SDL_OpenAudio().
267 * - \c desired->callback should be set to a function that will be called
268 * when the audio device is ready for more data. It is passed a pointer
269 * to the audio buffer, and the length in bytes of the audio buffer.
270 * This function usually runs in a separate thread, and so you should
271 * protect data structures that it accesses by calling SDL_LockAudio()
272 * and SDL_UnlockAudio() in your code.
273 * - \c desired->userdata is passed as the first parameter to your callback
276 * The audio device starts out playing silence when it's opened, and should
277 * be enabled for playing by calling \c SDL_PauseAudio(0) when you are ready
278 * for your audio callback function to be called. Since the audio driver
279 * may modify the requested size of the audio buffer, you should allocate
280 * any local mixing buffers after you open the audio device.
282 extern DECLSPEC int SDLCALL SDL_OpenAudio(SDL_AudioSpec * desired,
283 SDL_AudioSpec * obtained);
286 * SDL Audio Device IDs.
288 * A successful call to SDL_OpenAudio() is always device id 1, and legacy
289 * SDL audio APIs assume you want this device ID. SDL_OpenAudioDevice() calls
290 * always returns devices >= 2 on success. The legacy calls are good both
291 * for backwards compatibility and when you don't care about multiple,
292 * specific, or capture devices.
294 typedef Uint32 SDL_AudioDeviceID;
297 * Get the number of available devices exposed by the current driver.
298 * Only valid after a successfully initializing the audio subsystem.
299 * Returns -1 if an explicit list of devices can't be determined; this is
300 * not an error. For example, if SDL is set up to talk to a remote audio
301 * server, it can't list every one available on the Internet, but it will
302 * still allow a specific host to be specified to SDL_OpenAudioDevice().
304 * In many common cases, when this function returns a value <= 0, it can still
305 * successfully open the default device (NULL for first argument of
306 * SDL_OpenAudioDevice()).
308 extern DECLSPEC int SDLCALL SDL_GetNumAudioDevices(int iscapture);
311 * Get the human-readable name of a specific audio device.
312 * Must be a value between 0 and (number of audio devices-1).
313 * Only valid after a successfully initializing the audio subsystem.
314 * The values returned by this function reflect the latest call to
315 * SDL_GetNumAudioDevices(); recall that function to redetect available
318 * The string returned by this function is UTF-8 encoded, read-only, and
319 * managed internally. You are not to free it. If you need to keep the
320 * string for any length of time, you should make your own copy of it, as it
321 * will be invalid next time any of several other SDL functions is called.
323 extern DECLSPEC const char *SDLCALL SDL_GetAudioDeviceName(int index,
328 * Open a specific audio device. Passing in a device name of NULL requests
329 * the most reasonable default (and is equivalent to calling SDL_OpenAudio()).
331 * The device name is a UTF-8 string reported by SDL_GetAudioDeviceName(), but
332 * some drivers allow arbitrary and driver-specific strings, such as a
333 * hostname/IP address for a remote audio server, or a filename in the
336 * \return 0 on error, a valid device ID that is >= 2 on success.
338 * SDL_OpenAudio(), unlike this function, always acts on device ID 1.
340 extern DECLSPEC SDL_AudioDeviceID SDLCALL SDL_OpenAudioDevice(const char
356 * Get the current audio state.
361 SDL_AUDIO_STOPPED = 0,
365 extern DECLSPEC SDL_AudioStatus SDLCALL SDL_GetAudioStatus(void);
367 extern DECLSPEC SDL_AudioStatus SDLCALL
368 SDL_GetAudioDeviceStatus(SDL_AudioDeviceID dev);
369 /*@}*//*Audio State*/
372 * \name Pause audio functions
374 * These functions pause and unpause the audio callback processing.
375 * They should be called with a parameter of 0 after opening the audio
376 * device to start playing sound. This is so you can safely initialize
377 * data for your callback function after opening the audio device.
378 * Silence will be written to the audio device during the pause.
381 extern DECLSPEC void SDLCALL SDL_PauseAudio(int pause_on);
382 extern DECLSPEC void SDLCALL SDL_PauseAudioDevice(SDL_AudioDeviceID dev,
384 /*@}*//*Pause audio functions*/
387 * This function loads a WAVE from the data source, automatically freeing
388 * that source if \c freesrc is non-zero. For example, to load a WAVE file,
391 * SDL_LoadWAV_RW(SDL_RWFromFile("sample.wav", "rb"), 1, ...);
394 * If this function succeeds, it returns the given SDL_AudioSpec,
395 * filled with the audio data format of the wave data, and sets
396 * \c *audio_buf to a malloc()'d buffer containing the audio data,
397 * and sets \c *audio_len to the length of that audio buffer, in bytes.
398 * You need to free the audio buffer with SDL_FreeWAV() when you are
401 * This function returns NULL and sets the SDL error message if the
402 * wave file cannot be opened, uses an unknown data format, or is
403 * corrupt. Currently raw and MS-ADPCM WAVE files are supported.
405 extern DECLSPEC SDL_AudioSpec *SDLCALL SDL_LoadWAV_RW(SDL_RWops * src,
407 SDL_AudioSpec * spec,
412 * Loads a WAV from a file.
413 * Compatibility convenience function.
415 #define SDL_LoadWAV(file, spec, audio_buf, audio_len) \
416 SDL_LoadWAV_RW(SDL_RWFromFile(file, "rb"),1, spec,audio_buf,audio_len)
419 * This function frees data previously allocated with SDL_LoadWAV_RW()
421 extern DECLSPEC void SDLCALL SDL_FreeWAV(Uint8 * audio_buf);
424 * This function takes a source format and rate and a destination format
425 * and rate, and initializes the \c cvt structure with information needed
426 * by SDL_ConvertAudio() to convert a buffer of audio data from one format
429 * \return -1 if the format conversion is not supported, 0 if there's
430 * no conversion needed, or 1 if the audio filter is set up.
432 extern DECLSPEC int SDLCALL SDL_BuildAudioCVT(SDL_AudioCVT * cvt,
433 SDL_AudioFormat src_format,
436 SDL_AudioFormat dst_format,
441 * Once you have initialized the \c cvt structure using SDL_BuildAudioCVT(),
442 * created an audio buffer \c cvt->buf, and filled it with \c cvt->len bytes of
443 * audio data in the source format, this function will convert it in-place
444 * to the desired format.
446 * The data conversion may expand the size of the audio data, so the buffer
447 * \c cvt->buf should be allocated after the \c cvt structure is initialized by
448 * SDL_BuildAudioCVT(), and should be \c cvt->len*cvt->len_mult bytes long.
450 extern DECLSPEC int SDLCALL SDL_ConvertAudio(SDL_AudioCVT * cvt);
452 #define SDL_MIX_MAXVOLUME 128
454 * This takes two audio buffers of the playing audio format and mixes
455 * them, performing addition, volume adjustment, and overflow clipping.
456 * The volume ranges from 0 - 128, and should be set to ::SDL_MIX_MAXVOLUME
457 * for full audio volume. Note this does not change hardware volume.
458 * This is provided for convenience -- you can mix your own audio data.
460 extern DECLSPEC void SDLCALL SDL_MixAudio(Uint8 * dst, const Uint8 * src,
461 Uint32 len, int volume);
464 * This works like SDL_MixAudio(), but you specify the audio format instead of
465 * using the format of audio device 1. Thus it can be used when no audio
466 * device is open at all.
468 extern DECLSPEC void SDLCALL SDL_MixAudioFormat(Uint8 * dst,
470 SDL_AudioFormat format,
471 Uint32 len, int volume);
474 * \name Audio lock functions
476 * The lock manipulated by these functions protects the callback function.
477 * During a SDL_LockAudio()/SDL_UnlockAudio() pair, you can be guaranteed that
478 * the callback function is not running. Do not call these from the callback
479 * function or you will cause deadlock.
482 extern DECLSPEC void SDLCALL SDL_LockAudio(void);
483 extern DECLSPEC void SDLCALL SDL_LockAudioDevice(SDL_AudioDeviceID dev);
484 extern DECLSPEC void SDLCALL SDL_UnlockAudio(void);
485 extern DECLSPEC void SDLCALL SDL_UnlockAudioDevice(SDL_AudioDeviceID dev);
486 /*@}*//*Audio lock functions*/
489 * This function shuts down audio processing and closes the audio device.
491 extern DECLSPEC void SDLCALL SDL_CloseAudio(void);
492 extern DECLSPEC void SDLCALL SDL_CloseAudioDevice(SDL_AudioDeviceID dev);
495 * \return 1 if audio device is still functioning, zero if not, -1 on error.
497 extern DECLSPEC int SDLCALL SDL_AudioDeviceConnected(SDL_AudioDeviceID dev);
500 /* Ends C function definitions when using C++ */
506 #include "close_code.h"
508 #endif /* _SDL_audio_h */
510 /* vi: set ts=4 sw=4 expandtab: */