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 */