FUNCTIONS

1. SDL_LoadWAV

   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 */
  23 #ifdef SAVE_RCSID
  24 static char rcsid =
  25  "@(#) $Id: SDL_audio.h,v 1.4.2.10 2001/02/17 01:45:30 hercules Exp $";
  26 #endif
  28 /* Access to the raw audio mixing buffer for the SDL library */
  30 #ifndef _SDL_audio_h
  31 #define _SDL_audio_h
  33 #include <stdio.h>
  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"
  41 #include "begin_code.h"
  42 /* Set up for C function definitions, even when using C++ */
  43 #ifdef __cplusplus
  44 extern "C" {
  45 #endif
  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 */
  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;
  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
  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
  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;
 102 /* Function prototypes */
 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);
 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);
 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);
 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);
 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);
 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);
 199 /* Compatibility convenience function -- loads a WAV from a file */
 200 #define SDL_LoadWAV(file, spec, audio_buf, audio_len) \
     /* [<][>][^][v][top][bottom][index][help] */
SDL_LoadWAV_RW(SDL_RWFromFile(file, "rb"),1, spec,audio_buf,audio_len)
 203 /*
 204  * This function frees data previously allocated with SDL_LoadWAV_RW()
 205  */
 206 extern DECLSPEC void SDL_FreeWAV(Uint8 *audio_buf);
 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);
 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);
 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, Uint8 *src, Uint32 len, int volume);
 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);
 248 /*
 249  * This function shuts down audio processing and closes the audio device.
 250  */
 251 extern DECLSPEC void SDL_CloseAudio(void);
 254 /* Ends C function definitions when using C++ */
 255 #ifdef __cplusplus
 256 }
 257 #endif
 258 #include "close_code.h"
 260 #endif /* _SDL_audio_h */