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Initial revision
author Sam Lantinga <slouken@lokigames.com>
date Thu, 26 Apr 2001 16:45:43 +0000
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children cf2af46e9e2a
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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 */
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, 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 */