include/SDL_audio.h
author Sam Lantinga <slouken@libsdl.org>
Sat, 26 Sep 2009 23:17:08 +0000
branchSDL-1.2
changeset 4246 8b8314cc34a6
parent 4217 4c4113c2162c
child 6137 4720145f848b
permissions -rw-r--r--
Fixed bug #810

Lauri Kenttä 2009-09-26 06:42:23 PDT

Support for disabling stdio redirect with environment variables.
     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 */