include/SDL_audio.h
author Sam Lantinga <slouken@libsdl.org>
Wed, 17 May 2006 08:18:28 +0000
branchSDL-1.3
changeset 1659 14717b52abc0
parent 1358 c71e05b4dc2e
child 1660 8b9d79e7eacf
child 1895 c121d94672cb
child 4159 a1b03ba2fcd0
permissions -rw-r--r--
Merge trunk-1.3-3
     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_stdinc.h"
    29 #include "SDL_error.h"
    30 #include "SDL_endian.h"
    31 #include "SDL_mutex.h"
    32 #include "SDL_thread.h"
    33 #include "SDL_rwops.h"
    34 
    35 #include "begin_code.h"
    36 /* Set up for C function definitions, even when using C++ */
    37 #ifdef __cplusplus
    38 extern "C" {
    39 #endif
    40 
    41 /* The calculated values in this structure are calculated by SDL_OpenAudio() */
    42 typedef struct SDL_AudioSpec {
    43 	int freq;		/* DSP frequency -- samples per second */
    44 	Uint16 format;		/* Audio data format */
    45 	Uint8  channels;	/* Number of channels: 1 mono, 2 stereo */
    46 	Uint8  silence;		/* Audio buffer silence value (calculated) */
    47 	Uint16 samples;		/* Audio buffer size in samples (power of 2) */
    48 	Uint16 padding;		/* Necessary for some compile environments */
    49 	Uint32 size;		/* Audio buffer size in bytes (calculated) */
    50 	/* This function is called when the audio device needs more data.
    51 	   'stream' is a pointer to the audio data buffer
    52 	   'len' is the length of that buffer in bytes.
    53 	   Once the callback returns, the buffer will no longer be valid.
    54 	   Stereo samples are stored in a LRLRLR ordering.
    55 	*/
    56 	void (SDLCALL *callback)(void *userdata, Uint8 *stream, int len);
    57 	void  *userdata;
    58 } SDL_AudioSpec;
    59 
    60 /* Audio format flags (defaults to LSB byte order) */
    61 #define AUDIO_U8	0x0008	/* Unsigned 8-bit samples */
    62 #define AUDIO_S8	0x8008	/* Signed 8-bit samples */
    63 #define AUDIO_U16LSB	0x0010	/* Unsigned 16-bit samples */
    64 #define AUDIO_S16LSB	0x8010	/* Signed 16-bit samples */
    65 #define AUDIO_U16MSB	0x1010	/* As above, but big-endian byte order */
    66 #define AUDIO_S16MSB	0x9010	/* As above, but big-endian byte order */
    67 #define AUDIO_U16	AUDIO_U16LSB
    68 #define AUDIO_S16	AUDIO_S16LSB
    69 
    70 /* Native audio byte ordering */
    71 #if SDL_BYTEORDER == SDL_LIL_ENDIAN
    72 #define AUDIO_U16SYS	AUDIO_U16LSB
    73 #define AUDIO_S16SYS	AUDIO_S16LSB
    74 #else
    75 #define AUDIO_U16SYS	AUDIO_U16MSB
    76 #define AUDIO_S16SYS	AUDIO_S16MSB
    77 #endif
    78 
    79 
    80 /* A structure to hold a set of audio conversion filters and buffers */
    81 typedef struct SDL_AudioCVT {
    82 	int needed;			/* Set to 1 if conversion possible */
    83 	Uint16 src_format;		/* Source audio format */
    84 	Uint16 dst_format;		/* Target audio format */
    85 	double rate_incr;		/* Rate conversion increment */
    86 	Uint8 *buf;			/* Buffer to hold entire audio data */
    87 	int    len;			/* Length of original audio buffer */
    88 	int    len_cvt;			/* Length of converted audio buffer */
    89 	int    len_mult;		/* buffer must be len*len_mult big */
    90 	double len_ratio; 	/* Given len, final size is len*len_ratio */
    91 	void (SDLCALL *filters[10])(struct SDL_AudioCVT *cvt, Uint16 format);
    92 	int filter_index;		/* Current audio conversion function */
    93 } SDL_AudioCVT;
    94 
    95 
    96 /* Function prototypes */
    97 
    98 /* These functions are used internally, and should not be used unless you
    99  * have a specific need to specify the audio driver you want to use.
   100  * You should normally use SDL_Init() or SDL_InitSubSystem().
   101  */
   102 extern DECLSPEC int SDLCALL SDL_AudioInit(const char *driver_name);
   103 extern DECLSPEC void SDLCALL SDL_AudioQuit(void);
   104 
   105 /* This function fills the given character buffer with the name of the
   106  * current audio driver, and returns a pointer to it if the audio driver has
   107  * been initialized.  It returns NULL if no driver has been initialized.
   108  */
   109 extern DECLSPEC char * SDLCALL SDL_AudioDriverName(char *namebuf, int maxlen);
   110 
   111 /*
   112  * This function opens the audio device with the desired parameters, and
   113  * returns 0 if successful, placing the actual hardware parameters in the
   114  * structure pointed to by 'obtained'.  If 'obtained' is NULL, the audio
   115  * data passed to the callback function will be guaranteed to be in the
   116  * requested format, and will be automatically converted to the hardware
   117  * audio format if necessary.  This function returns -1 if it failed 
   118  * to open the audio device, or couldn't set up the audio thread.
   119  *
   120  * When filling in the desired audio spec structure,
   121  *  'desired->freq' should be the desired audio frequency in samples-per-second.
   122  *  'desired->format' should be the desired audio format.
   123  *  'desired->samples' is the desired size of the audio buffer, in samples.
   124  *     This number should be a power of two, and may be adjusted by the audio
   125  *     driver to a value more suitable for the hardware.  Good values seem to
   126  *     range between 512 and 8096 inclusive, depending on the application and
   127  *     CPU speed.  Smaller values yield faster response time, but can lead
   128  *     to underflow if the application is doing heavy processing and cannot
   129  *     fill the audio buffer in time.  A stereo sample consists of both right
   130  *     and left channels in LR ordering.
   131  *     Note that the number of samples is directly related to time by the
   132  *     following formula:  ms = (samples*1000)/freq
   133  *  'desired->size' is the size in bytes of the audio buffer, and is
   134  *     calculated by SDL_OpenAudio().
   135  *  'desired->silence' is the value used to set the buffer to silence,
   136  *     and is calculated by SDL_OpenAudio().
   137  *  'desired->callback' should be set to a function that will be called
   138  *     when the audio device is ready for more data.  It is passed a pointer
   139  *     to the audio buffer, and the length in bytes of the audio buffer.
   140  *     This function usually runs in a separate thread, and so you should
   141  *     protect data structures that it accesses by calling SDL_LockAudio()
   142  *     and SDL_UnlockAudio() in your code.
   143  *  'desired->userdata' is passed as the first parameter to your callback
   144  *     function.
   145  *
   146  * The audio device starts out playing silence when it's opened, and should
   147  * be enabled for playing by calling SDL_PauseAudio(0) when you are ready
   148  * for your audio callback function to be called.  Since the audio driver
   149  * may modify the requested size of the audio buffer, you should allocate
   150  * any local mixing buffers after you open the audio device.
   151  */
   152 extern DECLSPEC int SDLCALL SDL_OpenAudio(SDL_AudioSpec *desired, SDL_AudioSpec *obtained);
   153 
   154 /*
   155  * Get the current audio state:
   156  */
   157 typedef enum {
   158 	SDL_AUDIO_STOPPED = 0,
   159 	SDL_AUDIO_PLAYING,
   160 	SDL_AUDIO_PAUSED
   161 } SDL_audiostatus;
   162 extern DECLSPEC SDL_audiostatus SDLCALL SDL_GetAudioStatus(void);
   163 
   164 /*
   165  * This function pauses and unpauses the audio callback processing.
   166  * It should be called with a parameter of 0 after opening the audio
   167  * device to start playing sound.  This is so you can safely initialize
   168  * data for your callback function after opening the audio device.
   169  * Silence will be written to the audio device during the pause.
   170  */
   171 extern DECLSPEC void SDLCALL SDL_PauseAudio(int pause_on);
   172 
   173 /*
   174  * This function loads a WAVE from the data source, automatically freeing
   175  * that source if 'freesrc' is non-zero.  For example, to load a WAVE file,
   176  * you could do:
   177  *	SDL_LoadWAV_RW(SDL_RWFromFile("sample.wav", "rb"), 1, ...);
   178  *
   179  * If this function succeeds, it returns the given SDL_AudioSpec,
   180  * filled with the audio data format of the wave data, and sets
   181  * 'audio_buf' to a malloc()'d buffer containing the audio data,
   182  * and sets 'audio_len' to the length of that audio buffer, in bytes.
   183  * You need to free the audio buffer with SDL_FreeWAV() when you are 
   184  * done with it.
   185  *
   186  * This function returns NULL and sets the SDL error message if the 
   187  * wave file cannot be opened, uses an unknown data format, or is 
   188  * corrupt.  Currently raw and MS-ADPCM WAVE files are supported.
   189  */
   190 extern DECLSPEC SDL_AudioSpec * SDLCALL SDL_LoadWAV_RW(SDL_RWops *src, int freesrc, SDL_AudioSpec *spec, Uint8 **audio_buf, Uint32 *audio_len);
   191 
   192 /* Compatibility convenience function -- loads a WAV from a file */
   193 #define SDL_LoadWAV(file, spec, audio_buf, audio_len) \
   194 	SDL_LoadWAV_RW(SDL_RWFromFile(file, "rb"),1, spec,audio_buf,audio_len)
   195 
   196 /*
   197  * This function frees data previously allocated with SDL_LoadWAV_RW()
   198  */
   199 extern DECLSPEC void SDLCALL SDL_FreeWAV(Uint8 *audio_buf);
   200 
   201 /*
   202  * This function takes a source format and rate and a destination format
   203  * and rate, and initializes the 'cvt' structure with information needed
   204  * by SDL_ConvertAudio() to convert a buffer of audio data from one format
   205  * to the other.
   206  * This function returns 0, or -1 if there was an error.
   207  */
   208 extern DECLSPEC int SDLCALL SDL_BuildAudioCVT(SDL_AudioCVT *cvt,
   209 		Uint16 src_format, Uint8 src_channels, int src_rate,
   210 		Uint16 dst_format, Uint8 dst_channels, int dst_rate);
   211 
   212 /* Once you have initialized the 'cvt' structure using SDL_BuildAudioCVT(),
   213  * created an audio buffer cvt->buf, and filled it with cvt->len bytes of
   214  * audio data in the source format, this function will convert it in-place
   215  * to the desired format.
   216  * The data conversion may expand the size of the audio data, so the buffer
   217  * cvt->buf should be allocated after the cvt structure is initialized by
   218  * SDL_BuildAudioCVT(), and should be cvt->len*cvt->len_mult bytes long.
   219  */
   220 extern DECLSPEC int SDLCALL SDL_ConvertAudio(SDL_AudioCVT *cvt);
   221 
   222 /*
   223  * This takes two audio buffers of the playing audio format and mixes
   224  * them, performing addition, volume adjustment, and overflow clipping.
   225  * The volume ranges from 0 - 128, and should be set to SDL_MIX_MAXVOLUME
   226  * for full audio volume.  Note this does not change hardware volume.
   227  * This is provided for convenience -- you can mix your own audio data.
   228  */
   229 #define SDL_MIX_MAXVOLUME 128
   230 extern DECLSPEC void SDLCALL SDL_MixAudio(Uint8 *dst, const Uint8 *src, Uint32 len, int volume);
   231 
   232 /*
   233  * The lock manipulated by these functions protects the callback function.
   234  * During a LockAudio/UnlockAudio pair, you can be guaranteed that the
   235  * callback function is not running.  Do not call these from the callback
   236  * function or you will cause deadlock.
   237  */
   238 extern DECLSPEC void SDLCALL SDL_LockAudio(void);
   239 extern DECLSPEC void SDLCALL SDL_UnlockAudio(void);
   240 
   241 /*
   242  * This function shuts down audio processing and closes the audio device.
   243  */
   244 extern DECLSPEC void SDLCALL SDL_CloseAudio(void);
   245 
   246 
   247 /* Ends C function definitions when using C++ */
   248 #ifdef __cplusplus
   249 }
   250 #endif
   251 #include "close_code.h"
   252 
   253 #endif /* _SDL_audio_h */