include/SDL_audio.h
author Sam Lantinga <slouken@libsdl.org>
Sun, 23 Sep 2001 17:39:30 +0000
changeset 188 901e45fd0432
parent 1 cf2af46e9e2a
child 251 b8688cfdc232
permissions -rw-r--r--
*** empty log message ***
     1 /*
     2     SDL - Simple DirectMedia Layer
     3     Copyright (C) 1997, 1998, 1999, 2000, 2001  Sam Lantinga
     4 
     5     This library is free software; you can redistribute it and/or
     6     modify it under the terms of the GNU Library General Public
     7     License as published by the Free Software Foundation; either
     8     version 2 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     Library General Public License for more details.
    14 
    15     You should have received a copy of the GNU Library General Public
    16     License along with this library; if not, write to the Free
    17     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
    18 
    19     Sam Lantinga
    20     slouken@devolution.com
    21 */
    22 
    23 #ifdef SAVE_RCSID
    24 static char rcsid =
    25  "@(#) $Id$";
    26 #endif
    27 
    28 /* Access to the raw audio mixing buffer for the SDL library */
    29 
    30 #ifndef _SDL_audio_h
    31 #define _SDL_audio_h
    32 
    33 #include <stdio.h>
    34 
    35 #include "SDL_main.h"
    36 #include "SDL_types.h"
    37 #include "SDL_error.h"
    38 #include "SDL_rwops.h"
    39 #include "SDL_byteorder.h"
    40 
    41 #include "begin_code.h"
    42 /* Set up for C function definitions, even when using C++ */
    43 #ifdef __cplusplus
    44 extern "C" {
    45 #endif
    46 
    47 /* The calculated values in this structure are calculated by SDL_OpenAudio() */
    48 typedef struct {
    49 	int freq;		/* DSP frequency -- samples per second */
    50 	Uint16 format;		/* Audio data format */
    51 	Uint8  channels;	/* Number of channels: 1 mono, 2 stereo */
    52 	Uint8  silence;		/* Audio buffer silence value (calculated) */
    53 	Uint16 samples;		/* Audio buffer size in samples (power of 2) */
    54 	Uint16 padding;		/* Necessary for some compile environments */
    55 	Uint32 size;		/* Audio buffer size in bytes (calculated) */
    56 	/* This function is called when the audio device needs more data.
    57 	   'stream' is a pointer to the audio data buffer
    58 	   'len' is the length of that buffer in bytes.
    59 	   Once the callback returns, the buffer will no longer be valid.
    60 	   Stereo samples are stored in a LRLRLR ordering.
    61 	*/
    62 	void (*callback)(void *userdata, Uint8 *stream, int len);
    63 	void  *userdata;
    64 } SDL_AudioSpec;
    65 
    66 /* Audio format flags (defaults to LSB byte order) */
    67 #define AUDIO_U8	0x0008	/* Unsigned 8-bit samples */
    68 #define AUDIO_S8	0x8008	/* Signed 8-bit samples */
    69 #define AUDIO_U16LSB	0x0010	/* Unsigned 16-bit samples */
    70 #define AUDIO_S16LSB	0x8010	/* Signed 16-bit samples */
    71 #define AUDIO_U16MSB	0x1010	/* As above, but big-endian byte order */
    72 #define AUDIO_S16MSB	0x9010	/* As above, but big-endian byte order */
    73 #define AUDIO_U16	AUDIO_U16LSB
    74 #define AUDIO_S16	AUDIO_S16LSB
    75 
    76 /* Native audio byte ordering */
    77 #if SDL_BYTEORDER == SDL_LIL_ENDIAN
    78 #define AUDIO_U16SYS	AUDIO_U16LSB
    79 #define AUDIO_S16SYS	AUDIO_S16LSB
    80 #else
    81 #define AUDIO_U16SYS	AUDIO_U16MSB
    82 #define AUDIO_S16SYS	AUDIO_S16MSB
    83 #endif
    84 
    85 
    86 /* A structure to hold a set of audio conversion filters and buffers */
    87 typedef struct SDL_AudioCVT {
    88 	int needed;			/* Set to 1 if conversion possible */
    89 	Uint16 src_format;		/* Source audio format */
    90 	Uint16 dst_format;		/* Target audio format */
    91 	double rate_incr;		/* Rate conversion increment */
    92 	Uint8 *buf;			/* Buffer to hold entire audio data */
    93 	int    len;			/* Length of original audio buffer */
    94 	int    len_cvt;			/* Length of converted audio buffer */
    95 	int    len_mult;		/* buffer must be len*len_mult big */
    96 	double len_ratio; 	/* Given len, final size is len*len_ratio */
    97 	void (*filters[10])(struct SDL_AudioCVT *cvt, Uint16 format);
    98 	int filter_index;		/* Current audio conversion function */
    99 } SDL_AudioCVT;
   100 
   101 
   102 /* Function prototypes */
   103 
   104 /* These functions are used internally, and should not be used unless you
   105  * have a specific need to specify the audio driver you want to use.
   106  * You should normally use SDL_Init() or SDL_InitSubSystem().
   107  */
   108 extern DECLSPEC int SDL_AudioInit(const char *driver_name);
   109 extern DECLSPEC void SDL_AudioQuit(void);
   110 
   111 /* This function fills the given character buffer with the name of the
   112  * current audio driver, and returns a pointer to it if the audio driver has
   113  * been initialized.  It returns NULL if no driver has been initialized.
   114  */
   115 extern DECLSPEC char *SDL_AudioDriverName(char *namebuf, int maxlen);
   116 
   117 /*
   118  * This function opens the audio device with the desired parameters, and
   119  * returns 0 if successful, placing the actual hardware parameters in the
   120  * structure pointed to by 'obtained'.  If 'obtained' is NULL, the audio
   121  * data passed to the callback function will be guaranteed to be in the
   122  * requested format, and will be automatically converted to the hardware
   123  * audio format if necessary.  This function returns -1 if it failed 
   124  * to open the audio device, or couldn't set up the audio thread.
   125  *
   126  * When filling in the desired audio spec structure,
   127  *  'desired->freq' should be the desired audio frequency in samples-per-second.
   128  *  'desired->format' should be the desired audio format.
   129  *  'desired->samples' is the desired size of the audio buffer, in samples.
   130  *     This number should be a power of two, and may be adjusted by the audio
   131  *     driver to a value more suitable for the hardware.  Good values seem to
   132  *     range between 512 and 8096 inclusive, depending on the application and
   133  *     CPU speed.  Smaller values yield faster response time, but can lead
   134  *     to underflow if the application is doing heavy processing and cannot
   135  *     fill the audio buffer in time.  A stereo sample consists of both right
   136  *     and left channels in LR ordering.
   137  *     Note that the number of samples is directly related to time by the
   138  *     following formula:  ms = (samples*1000)/freq
   139  *  'desired->size' is the size in bytes of the audio buffer, and is
   140  *     calculated by SDL_OpenAudio().
   141  *  'desired->silence' is the value used to set the buffer to silence,
   142  *     and is calculated by SDL_OpenAudio().
   143  *  'desired->callback' should be set to a function that will be called
   144  *     when the audio device is ready for more data.  It is passed a pointer
   145  *     to the audio buffer, and the length in bytes of the audio buffer.
   146  *     This function usually runs in a separate thread, and so you should
   147  *     protect data structures that it accesses by calling SDL_LockAudio()
   148  *     and SDL_UnlockAudio() in your code.
   149  *  'desired->userdata' is passed as the first parameter to your callback
   150  *     function.
   151  *
   152  * The audio device starts out playing silence when it's opened, and should
   153  * be enabled for playing by calling SDL_PauseAudio(0) when you are ready
   154  * for your audio callback function to be called.  Since the audio driver
   155  * may modify the requested size of the audio buffer, you should allocate
   156  * any local mixing buffers after you open the audio device.
   157  */
   158 extern DECLSPEC int SDL_OpenAudio(SDL_AudioSpec *desired, SDL_AudioSpec *obtained);
   159 
   160 /*
   161  * Get the current audio state:
   162  */
   163 typedef enum {
   164 	SDL_AUDIO_STOPPED = 0,
   165 	SDL_AUDIO_PLAYING,
   166 	SDL_AUDIO_PAUSED
   167 } SDL_audiostatus;
   168 extern DECLSPEC SDL_audiostatus SDL_GetAudioStatus(void);
   169 
   170 /*
   171  * This function pauses and unpauses the audio callback processing.
   172  * It should be called with a parameter of 0 after opening the audio
   173  * device to start playing sound.  This is so you can safely initialize
   174  * data for your callback function after opening the audio device.
   175  * Silence will be written to the audio device during the pause.
   176  */
   177 extern DECLSPEC void SDL_PauseAudio(int pause_on);
   178 
   179 /*
   180  * This function loads a WAVE from the data source, automatically freeing
   181  * that source if 'freesrc' is non-zero.  For example, to load a WAVE file,
   182  * you could do:
   183  *	SDL_LoadWAV_RW(SDL_RWFromFile("sample.wav", "rb"), 1, ...);
   184  *
   185  * If this function succeeds, it returns the given SDL_AudioSpec,
   186  * filled with the audio data format of the wave data, and sets
   187  * 'audio_buf' to a malloc()'d buffer containing the audio data,
   188  * and sets 'audio_len' to the length of that audio buffer, in bytes.
   189  * You need to free the audio buffer with SDL_FreeWAV() when you are 
   190  * done with it.
   191  *
   192  * This function returns NULL and sets the SDL error message if the 
   193  * wave file cannot be opened, uses an unknown data format, or is 
   194  * corrupt.  Currently raw and MS-ADPCM WAVE files are supported.
   195  */
   196 extern DECLSPEC SDL_AudioSpec *SDL_LoadWAV_RW(SDL_RWops *src, int freesrc,
   197 		 SDL_AudioSpec *spec, Uint8 **audio_buf, Uint32 *audio_len);
   198 
   199 /* Compatibility convenience function -- loads a WAV from a file */
   200 #define SDL_LoadWAV(file, spec, audio_buf, audio_len) \
   201 	SDL_LoadWAV_RW(SDL_RWFromFile(file, "rb"),1, spec,audio_buf,audio_len)
   202 
   203 /*
   204  * This function frees data previously allocated with SDL_LoadWAV_RW()
   205  */
   206 extern DECLSPEC void SDL_FreeWAV(Uint8 *audio_buf);
   207 
   208 /*
   209  * This function takes a source format and rate and a destination format
   210  * and rate, and initializes the 'cvt' structure with information needed
   211  * by SDL_ConvertAudio() to convert a buffer of audio data from one format
   212  * to the other.
   213  * This function returns 0, or -1 if there was an error.
   214  */
   215 extern DECLSPEC int SDL_BuildAudioCVT(SDL_AudioCVT *cvt,
   216 		Uint16 src_format, Uint8 src_channels, int src_rate,
   217 		Uint16 dst_format, Uint8 dst_channels, int dst_rate);
   218 
   219 /* Once you have initialized the 'cvt' structure using SDL_BuildAudioCVT(),
   220  * created an audio buffer cvt->buf, and filled it with cvt->len bytes of
   221  * audio data in the source format, this function will convert it in-place
   222  * to the desired format.
   223  * The data conversion may expand the size of the audio data, so the buffer
   224  * cvt->buf should be allocated after the cvt structure is initialized by
   225  * SDL_BuildAudioCVT(), and should be cvt->len*cvt->len_mult bytes long.
   226  */
   227 extern DECLSPEC int SDL_ConvertAudio(SDL_AudioCVT *cvt);
   228 
   229 /*
   230  * This takes two audio buffers of the playing audio format and mixes
   231  * them, performing addition, volume adjustment, and overflow clipping.
   232  * The volume ranges from 0 - 128, and should be set to SDL_MIX_MAXVOLUME
   233  * for full audio volume.  Note this does not change hardware volume.
   234  * This is provided for convenience -- you can mix your own audio data.
   235  */
   236 #define SDL_MIX_MAXVOLUME 128
   237 extern DECLSPEC void SDL_MixAudio(Uint8 *dst, const Uint8 *src, Uint32 len, int volume);
   238 
   239 /*
   240  * The lock manipulated by these functions protects the callback function.
   241  * During a LockAudio/UnlockAudio pair, you can be guaranteed that the
   242  * callback function is not running.  Do not call these from the callback
   243  * function or you will cause deadlock.
   244  */
   245 extern DECLSPEC void SDL_LockAudio(void);
   246 extern DECLSPEC void SDL_UnlockAudio(void);
   247 
   248 /*
   249  * This function shuts down audio processing and closes the audio device.
   250  */
   251 extern DECLSPEC void SDL_CloseAudio(void);
   252 
   253 
   254 /* Ends C function definitions when using C++ */
   255 #ifdef __cplusplus
   256 }
   257 #endif
   258 #include "close_code.h"
   259 
   260 #endif /* _SDL_audio_h */