include/SDL_audio.h
author Sam Lantinga <slouken@libsdl.org>
Mon, 06 Feb 2006 08:28:51 +0000
changeset 1330 450721ad5436
parent 1312 c9b51268668f
child 1353 7ba544e2888d
permissions -rw-r--r--
It's now possible to build SDL without any C runtime at all on Windows,
using Visual C++ 2005
     1 /*
     2     SDL - Simple DirectMedia Layer
     3     Copyright (C) 1997-2006 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 /* Access to the raw audio mixing buffer for the SDL library */
    24 
    25 #ifndef _SDL_audio_h
    26 #define _SDL_audio_h
    27 
    28 #include "SDL_main.h"
    29 #include "SDL_types.h"
    30 #include "SDL_error.h"
    31 #include "SDL_rwops.h"
    32 #include "SDL_byteorder.h"
    33 
    34 #include "begin_code.h"
    35 /* Set up for C function definitions, even when using C++ */
    36 #ifdef __cplusplus
    37 extern "C" {
    38 #endif
    39 
    40 /* The calculated values in this structure are calculated by SDL_OpenAudio() */
    41 typedef struct SDL_AudioSpec {
    42 	int freq;		/* DSP frequency -- samples per second */
    43 	Uint16 format;		/* Audio data format */
    44 	Uint8  channels;	/* Number of channels: 1 mono, 2 stereo */
    45 	Uint8  silence;		/* Audio buffer silence value (calculated) */
    46 	Uint16 samples;		/* Audio buffer size in samples (power of 2) */
    47 	Uint16 padding;		/* Necessary for some compile environments */
    48 	Uint32 size;		/* Audio buffer size in bytes (calculated) */
    49 	/* This function is called when the audio device needs more data.
    50 	   'stream' is a pointer to the audio data buffer
    51 	   'len' is the length of that buffer in bytes.
    52 	   Once the callback returns, the buffer will no longer be valid.
    53 	   Stereo samples are stored in a LRLRLR ordering.
    54 	*/
    55 	void (SDLCALL *callback)(void *userdata, Uint8 *stream, int len);
    56 	void  *userdata;
    57 } SDL_AudioSpec;
    58 
    59 /* Audio format flags (defaults to LSB byte order) */
    60 #define AUDIO_U8	0x0008	/* Unsigned 8-bit samples */
    61 #define AUDIO_S8	0x8008	/* Signed 8-bit samples */
    62 #define AUDIO_U16LSB	0x0010	/* Unsigned 16-bit samples */
    63 #define AUDIO_S16LSB	0x8010	/* Signed 16-bit samples */
    64 #define AUDIO_U16MSB	0x1010	/* As above, but big-endian byte order */
    65 #define AUDIO_S16MSB	0x9010	/* As above, but big-endian byte order */
    66 #define AUDIO_U16	AUDIO_U16LSB
    67 #define AUDIO_S16	AUDIO_S16LSB
    68 
    69 /* Native audio byte ordering */
    70 #if SDL_BYTEORDER == SDL_LIL_ENDIAN
    71 #define AUDIO_U16SYS	AUDIO_U16LSB
    72 #define AUDIO_S16SYS	AUDIO_S16LSB
    73 #else
    74 #define AUDIO_U16SYS	AUDIO_U16MSB
    75 #define AUDIO_S16SYS	AUDIO_S16MSB
    76 #endif
    77 
    78 
    79 /* A structure to hold a set of audio conversion filters and buffers */
    80 typedef struct SDL_AudioCVT {
    81 	int needed;			/* Set to 1 if conversion possible */
    82 	Uint16 src_format;		/* Source audio format */
    83 	Uint16 dst_format;		/* Target audio format */
    84 	double rate_incr;		/* Rate conversion increment */
    85 	Uint8 *buf;			/* Buffer to hold entire audio data */
    86 	int    len;			/* Length of original audio buffer */
    87 	int    len_cvt;			/* Length of converted audio buffer */
    88 	int    len_mult;		/* buffer must be len*len_mult big */
    89 	double len_ratio; 	/* Given len, final size is len*len_ratio */
    90 	void (SDLCALL *filters[10])(struct SDL_AudioCVT *cvt, Uint16 format);
    91 	int filter_index;		/* Current audio conversion function */
    92 } SDL_AudioCVT;
    93 
    94 
    95 /* Function prototypes */
    96 
    97 /* These functions are used internally, and should not be used unless you
    98  * have a specific need to specify the audio driver you want to use.
    99  * You should normally use SDL_Init() or SDL_InitSubSystem().
   100  */
   101 extern DECLSPEC int SDLCALL SDL_AudioInit(const char *driver_name);
   102 extern DECLSPEC void SDLCALL SDL_AudioQuit(void);
   103 
   104 /* This function fills the given character buffer with the name of the
   105  * current audio driver, and returns a pointer to it if the audio driver has
   106  * been initialized.  It returns NULL if no driver has been initialized.
   107  */
   108 extern DECLSPEC char * SDLCALL SDL_AudioDriverName(char *namebuf, int maxlen);
   109 
   110 /*
   111  * This function opens the audio device with the desired parameters, and
   112  * returns 0 if successful, placing the actual hardware parameters in the
   113  * structure pointed to by 'obtained'.  If 'obtained' is NULL, the audio
   114  * data passed to the callback function will be guaranteed to be in the
   115  * requested format, and will be automatically converted to the hardware
   116  * audio format if necessary.  This function returns -1 if it failed 
   117  * to open the audio device, or couldn't set up the audio thread.
   118  *
   119  * When filling in the desired audio spec structure,
   120  *  'desired->freq' should be the desired audio frequency in samples-per-second.
   121  *  'desired->format' should be the desired audio format.
   122  *  'desired->samples' is the desired size of the audio buffer, in samples.
   123  *     This number should be a power of two, and may be adjusted by the audio
   124  *     driver to a value more suitable for the hardware.  Good values seem to
   125  *     range between 512 and 8096 inclusive, depending on the application and
   126  *     CPU speed.  Smaller values yield faster response time, but can lead
   127  *     to underflow if the application is doing heavy processing and cannot
   128  *     fill the audio buffer in time.  A stereo sample consists of both right
   129  *     and left channels in LR ordering.
   130  *     Note that the number of samples is directly related to time by the
   131  *     following formula:  ms = (samples*1000)/freq
   132  *  'desired->size' is the size in bytes of the audio buffer, and is
   133  *     calculated by SDL_OpenAudio().
   134  *  'desired->silence' is the value used to set the buffer to silence,
   135  *     and is calculated by SDL_OpenAudio().
   136  *  'desired->callback' should be set to a function that will be called
   137  *     when the audio device is ready for more data.  It is passed a pointer
   138  *     to the audio buffer, and the length in bytes of the audio buffer.
   139  *     This function usually runs in a separate thread, and so you should
   140  *     protect data structures that it accesses by calling SDL_LockAudio()
   141  *     and SDL_UnlockAudio() in your code.
   142  *  'desired->userdata' is passed as the first parameter to your callback
   143  *     function.
   144  *
   145  * The audio device starts out playing silence when it's opened, and should
   146  * be enabled for playing by calling SDL_PauseAudio(0) when you are ready
   147  * for your audio callback function to be called.  Since the audio driver
   148  * may modify the requested size of the audio buffer, you should allocate
   149  * any local mixing buffers after you open the audio device.
   150  */
   151 extern DECLSPEC int SDLCALL SDL_OpenAudio(SDL_AudioSpec *desired, SDL_AudioSpec *obtained);
   152 
   153 /*
   154  * Get the current audio state:
   155  */
   156 typedef enum {
   157 	SDL_AUDIO_STOPPED = 0,
   158 	SDL_AUDIO_PLAYING,
   159 	SDL_AUDIO_PAUSED
   160 } SDL_audiostatus;
   161 extern DECLSPEC SDL_audiostatus SDLCALL SDL_GetAudioStatus(void);
   162 
   163 /*
   164  * This function pauses and unpauses the audio callback processing.
   165  * It should be called with a parameter of 0 after opening the audio
   166  * device to start playing sound.  This is so you can safely initialize
   167  * data for your callback function after opening the audio device.
   168  * Silence will be written to the audio device during the pause.
   169  */
   170 extern DECLSPEC void SDLCALL SDL_PauseAudio(int pause_on);
   171 
   172 /*
   173  * This function loads a WAVE from the data source, automatically freeing
   174  * that source if 'freesrc' is non-zero.  For example, to load a WAVE file,
   175  * you could do:
   176  *	SDL_LoadWAV_RW(SDL_RWFromFile("sample.wav", "rb"), 1, ...);
   177  *
   178  * If this function succeeds, it returns the given SDL_AudioSpec,
   179  * filled with the audio data format of the wave data, and sets
   180  * 'audio_buf' to a malloc()'d buffer containing the audio data,
   181  * and sets 'audio_len' to the length of that audio buffer, in bytes.
   182  * You need to free the audio buffer with SDL_FreeWAV() when you are 
   183  * done with it.
   184  *
   185  * This function returns NULL and sets the SDL error message if the 
   186  * wave file cannot be opened, uses an unknown data format, or is 
   187  * corrupt.  Currently raw and MS-ADPCM WAVE files are supported.
   188  */
   189 extern DECLSPEC SDL_AudioSpec * SDLCALL SDL_LoadWAV_RW(SDL_RWops *src, int freesrc, SDL_AudioSpec *spec, Uint8 **audio_buf, Uint32 *audio_len);
   190 
   191 /* Compatibility convenience function -- loads a WAV from a file */
   192 #define SDL_LoadWAV(file, spec, audio_buf, audio_len) \
   193 	SDL_LoadWAV_RW(SDL_RWFromFile(file, "rb"),1, spec,audio_buf,audio_len)
   194 
   195 /*
   196  * This function frees data previously allocated with SDL_LoadWAV_RW()
   197  */
   198 extern DECLSPEC void SDLCALL SDL_FreeWAV(Uint8 *audio_buf);
   199 
   200 /*
   201  * This function takes a source format and rate and a destination format
   202  * and rate, and initializes the 'cvt' structure with information needed
   203  * by SDL_ConvertAudio() to convert a buffer of audio data from one format
   204  * to the other.
   205  * This function returns 0, or -1 if there was an error.
   206  */
   207 extern DECLSPEC int SDLCALL SDL_BuildAudioCVT(SDL_AudioCVT *cvt,
   208 		Uint16 src_format, Uint8 src_channels, int src_rate,
   209 		Uint16 dst_format, Uint8 dst_channels, int dst_rate);
   210 
   211 /* Once you have initialized the 'cvt' structure using SDL_BuildAudioCVT(),
   212  * created an audio buffer cvt->buf, and filled it with cvt->len bytes of
   213  * audio data in the source format, this function will convert it in-place
   214  * to the desired format.
   215  * The data conversion may expand the size of the audio data, so the buffer
   216  * cvt->buf should be allocated after the cvt structure is initialized by
   217  * SDL_BuildAudioCVT(), and should be cvt->len*cvt->len_mult bytes long.
   218  */
   219 extern DECLSPEC int SDLCALL SDL_ConvertAudio(SDL_AudioCVT *cvt);
   220 
   221 /*
   222  * This takes two audio buffers of the playing audio format and mixes
   223  * them, performing addition, volume adjustment, and overflow clipping.
   224  * The volume ranges from 0 - 128, and should be set to SDL_MIX_MAXVOLUME
   225  * for full audio volume.  Note this does not change hardware volume.
   226  * This is provided for convenience -- you can mix your own audio data.
   227  */
   228 #define SDL_MIX_MAXVOLUME 128
   229 extern DECLSPEC void SDLCALL SDL_MixAudio(Uint8 *dst, const Uint8 *src, Uint32 len, int volume);
   230 
   231 /*
   232  * The lock manipulated by these functions protects the callback function.
   233  * During a LockAudio/UnlockAudio pair, you can be guaranteed that the
   234  * callback function is not running.  Do not call these from the callback
   235  * function or you will cause deadlock.
   236  */
   237 extern DECLSPEC void SDLCALL SDL_LockAudio(void);
   238 extern DECLSPEC void SDLCALL SDL_UnlockAudio(void);
   239 
   240 /*
   241  * This function shuts down audio processing and closes the audio device.
   242  */
   243 extern DECLSPEC void SDLCALL SDL_CloseAudio(void);
   244 
   245 
   246 /* Ends C function definitions when using C++ */
   247 #ifdef __cplusplus
   248 }
   249 #endif
   250 #include "close_code.h"
   251 
   252 #endif /* _SDL_audio_h */