include/SDL_audio.h
author Sam Lantinga <slouken@libsdl.org>
Sat, 13 Dec 2008 06:36:47 +0000
changeset 2866 e532417a6977
parent 2859 99210400e8b9
child 3021 f3dcf04412cf
permissions -rw-r--r--
Fixed SDL 1.2 compatibility problem.

The API specifies that SDL_OpenAudio() will fill out the 'desired' audio spec
with the correct samples and size set by the driver. This value is important
since it may be used by applications that size audio buffers, etc.

However, we want to allow advanced applications to call SDL_OpenAudioDevice()
which gets passed a const 'desired' parameter, and have the correct data filled
into the 'obtained' parameter, possibly allowing or not allowing format changes.

So... 'obtained' becomes the audio format the user callback is expected to use,
and we add flags to allow the application to specify which format changes are
allowed.

Note: We really need to add a way to query the 'obtained' audio spec.
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/*
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    SDL - Simple DirectMedia Layer
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    Copyright (C) 1997-2009 Sam Lantinga
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    This library is free software; you can redistribute it and/or
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    modify it under the terms of the GNU Lesser General Public
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    License as published by the Free Software Foundation; either
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    version 2.1 of the License, or (at your option) any later version.
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    This library is distributed in the hope that it will be useful,
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    but WITHOUT ANY WARRANTY; without even the implied warranty of
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    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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    Lesser General Public License for more details.
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    You should have received a copy of the GNU Lesser General Public
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    License along with this library; if not, write to the Free Software
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    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
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    Sam Lantinga
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    slouken@libsdl.org
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*/
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/**
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 * \file SDL_audio.h
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 *
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 * Access to the raw audio mixing buffer for the SDL library
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 */
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#ifndef _SDL_audio_h
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#define _SDL_audio_h
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#include "SDL_stdinc.h"
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#include "SDL_error.h"
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#include "SDL_endian.h"
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#include "SDL_mutex.h"
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#include "SDL_thread.h"
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#include "SDL_rwops.h"
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#include "begin_code.h"
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/* Set up for C function definitions, even when using C++ */
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#ifdef __cplusplus
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/* *INDENT-OFF* */
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extern "C" {
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/* *INDENT-ON* */
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#endif
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typedef Uint16 SDL_AudioFormat;
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/* The calculated values in this structure are calculated by SDL_OpenAudio() */
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typedef struct SDL_AudioSpec
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{
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    int freq;                   /* DSP frequency -- samples per second */
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    SDL_AudioFormat format;     /* Audio data format */
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    Uint8 channels;             /* Number of channels: 1 mono, 2 stereo */
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    Uint8 silence;              /* Audio buffer silence value (calculated) */
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    Uint16 samples;             /* Audio buffer size in samples (power of 2) */
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    Uint16 padding;             /* Necessary for some compile environments */
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    Uint32 size;                /* Audio buffer size in bytes (calculated) */
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    /* This function is called when the audio device needs more data.
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       'stream' is a pointer to the audio data buffer
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       'len' is the length of that buffer in bytes.
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       Once the callback returns, the buffer will no longer be valid.
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       Stereo samples are stored in a LRLRLR ordering.
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     */
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    void (SDLCALL * callback) (void *userdata, Uint8 * stream, int len);
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    void *userdata;
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} SDL_AudioSpec;
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/*
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 These are what the 16 bits in SDL_AudioFormat currently mean...
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 (Unspecified bits are always zero.)
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 ++-----------------------sample is signed if set
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 ||
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 ||       ++-----------sample is bigendian if set
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 ||       ||
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 ||       ||          ++---sample is float if set
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 ||       ||          ||
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 ||       ||          || +---sample bit size---+
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 ||       ||          || |                     |
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 15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00
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 There are macros in SDL 1.3 and later to query these bits.
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*/
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#define SDL_AUDIO_MASK_BITSIZE       (0xFF)
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#define SDL_AUDIO_MASK_DATATYPE      (1<<8)
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#define SDL_AUDIO_MASK_ENDIAN        (1<<12)
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#define SDL_AUDIO_MASK_SIGNED        (1<<15)
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#define SDL_AUDIO_BITSIZE(x)         (x & SDL_AUDIO_MASK_BITSIZE)
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#define SDL_AUDIO_ISFLOAT(x)         (x & SDL_AUDIO_MASK_DATATYPE)
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#define SDL_AUDIO_ISBIGENDIAN(x)     (x & SDL_AUDIO_MASK_ENDIAN)
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#define SDL_AUDIO_ISSIGNED(x)        (x & SDL_AUDIO_MASK_SIGNED)
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#define SDL_AUDIO_ISINT(x)           (!SDL_AUDIO_ISFLOAT(x))
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#define SDL_AUDIO_ISLITTLEENDIAN(x)  (!SDL_AUDIO_ISBIGENDIAN(x))
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#define SDL_AUDIO_ISUNSIGNED(x)      (!SDL_AUDIO_ISSIGNED(x))
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/* Audio format flags (defaults to LSB byte order) */
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#define AUDIO_U8	0x0008  /* Unsigned 8-bit samples */
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#define AUDIO_S8	0x8008  /* Signed 8-bit samples */
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#define AUDIO_U16LSB	0x0010  /* Unsigned 16-bit samples */
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#define AUDIO_S16LSB	0x8010  /* Signed 16-bit samples */
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#define AUDIO_U16MSB	0x1010  /* As above, but big-endian byte order */
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#define AUDIO_S16MSB	0x9010  /* As above, but big-endian byte order */
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#define AUDIO_U16	AUDIO_U16LSB
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#define AUDIO_S16	AUDIO_S16LSB
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/* int32 support new to SDL 1.3 */
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#define AUDIO_S32LSB	0x8020  /* 32-bit integer samples */
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#define AUDIO_S32MSB	0x9020  /* As above, but big-endian byte order */
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#define AUDIO_S32	AUDIO_S32LSB
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/* float32 support new to SDL 1.3 */
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#define AUDIO_F32LSB	0x8120  /* 32-bit floating point samples */
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#define AUDIO_F32MSB	0x9120  /* As above, but big-endian byte order */
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#define AUDIO_F32	AUDIO_F32LSB
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/* Native audio byte ordering */
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#if SDL_BYTEORDER == SDL_LIL_ENDIAN
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#define AUDIO_U16SYS	AUDIO_U16LSB
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#define AUDIO_S16SYS	AUDIO_S16LSB
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#define AUDIO_S32SYS	AUDIO_S32LSB
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#define AUDIO_F32SYS	AUDIO_F32LSB
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#else
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#define AUDIO_U16SYS	AUDIO_U16MSB
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#define AUDIO_S16SYS	AUDIO_S16MSB
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#define AUDIO_S32SYS	AUDIO_S32MSB
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#define AUDIO_F32SYS	AUDIO_F32MSB
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#endif
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/* Which audio format changes are allowed when opening a device */
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#define SDL_AUDIO_ALLOW_FREQUENCY_CHANGE    0x00000001
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#define SDL_AUDIO_ALLOW_FORMAT_CHANGE       0x00000002
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#define SDL_AUDIO_ALLOW_CHANNELS_CHANGE     0x00000004
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#define SDL_AUDIO_ALLOW_ANY_CHANGE          (SDL_AUDIO_ALLOW_FREQUENCY_CHANGE|SDL_AUDIO_ALLOW_FORMAT_CHANGE|SDL_AUDIO_ALLOW_CHANNELS_CHANGE)
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/* A structure to hold a set of audio conversion filters and buffers */
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struct SDL_AudioCVT;
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typedef void (SDLCALL * SDL_AudioFilter) (struct SDL_AudioCVT * cvt,
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                                          SDL_AudioFormat format);
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typedef struct SDL_AudioCVT
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{
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    int needed;                 /* Set to 1 if conversion possible */
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    SDL_AudioFormat src_format; /* Source audio format */
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    SDL_AudioFormat dst_format; /* Target audio format */
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    double rate_incr;           /* Rate conversion increment */
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    Uint8 *buf;                 /* Buffer to hold entire audio data */
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    Uint8 *coeff;               /* Filter coefficients: either big windowed sinc filter, or 6 IIR lowpass coefficients */
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    Uint8 *state_buf;           /* Sample history for either the FIR or IIR filter. For IIR filter, first two elements are X, second two are Y, and state_pos toggles the order */
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    int state_pos;              /* Position in the state */
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    int len_sinc;               /* Length of windowed sinc filter, in appropriate units (not necessarily bytes) */
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    int len;                    /* Length of original audio buffer */
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    int len_cvt;                /* Length of converted audio buffer */
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    int len_mult;               /* buffer must be len*len_mult big */
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    int len_div;                /* destination length = len_mult / len_div * src length */
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    double len_ratio;           /* Given len, final size is len*len_ratio ( len_ratio = len_mult / len_div ) */
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    SDL_AudioFilter filters[10];        /* Filter list */
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    int filter_index;           /* Current audio conversion function */
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} SDL_AudioCVT;
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/* Function prototypes */
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/* These functions return the list of built in audio drivers, in the
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 * order that they are normally initialized by default.
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 */
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extern DECLSPEC int SDLCALL SDL_GetNumAudioDrivers(void);
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extern DECLSPEC const char *SDLCALL SDL_GetAudioDriver(int index);
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/* These functions are used internally, and should not be used unless you
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 * have a specific need to specify the audio driver you want to use.
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 * You should normally use SDL_Init() or SDL_InitSubSystem().
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 */
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extern DECLSPEC int SDLCALL SDL_AudioInit(const char *driver_name);
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extern DECLSPEC void SDLCALL SDL_AudioQuit(void);
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/* This function returns the name of the current audio driver, or NULL
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 * if no driver has been initialized.
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 */
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extern DECLSPEC const char *SDLCALL SDL_GetCurrentAudioDriver(void);
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/*
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 * This function opens the audio device with the desired parameters, and
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 * returns 0 if successful, placing the actual hardware parameters in the
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 * structure pointed to by 'obtained'.  If 'obtained' is NULL, the audio
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 * data passed to the callback function will be guaranteed to be in the
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 * requested format, and will be automatically converted to the hardware
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 * audio format if necessary.  This function returns -1 if it failed 
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 * to open the audio device, or couldn't set up the audio thread.
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 *
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 * When filling in the desired audio spec structure,
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 *  'desired->freq' should be the desired audio frequency in samples-per-second.
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 *  'desired->format' should be the desired audio format.
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 *  'desired->samples' is the desired size of the audio buffer, in samples.
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 *     This number should be a power of two, and may be adjusted by the audio
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 *     driver to a value more suitable for the hardware.  Good values seem to
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 *     range between 512 and 8096 inclusive, depending on the application and
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 *     CPU speed.  Smaller values yield faster response time, but can lead
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 *     to underflow if the application is doing heavy processing and cannot
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 *     fill the audio buffer in time.  A stereo sample consists of both right
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 *     and left channels in LR ordering.
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 *     Note that the number of samples is directly related to time by the
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 *     following formula:  ms = (samples*1000)/freq
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 *  'desired->size' is the size in bytes of the audio buffer, and is
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 *     calculated by SDL_OpenAudio().
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 *  'desired->silence' is the value used to set the buffer to silence,
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 *     and is calculated by SDL_OpenAudio().
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 *  'desired->callback' should be set to a function that will be called
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 *     when the audio device is ready for more data.  It is passed a pointer
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 *     to the audio buffer, and the length in bytes of the audio buffer.
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 *     This function usually runs in a separate thread, and so you should
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 *     protect data structures that it accesses by calling SDL_LockAudio()
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 *     and SDL_UnlockAudio() in your code.
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 *  'desired->userdata' is passed as the first parameter to your callback
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 *     function.
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 *
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 * The audio device starts out playing silence when it's opened, and should
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 * be enabled for playing by calling SDL_PauseAudio(0) when you are ready
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 * for your audio callback function to be called.  Since the audio driver
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 * may modify the requested size of the audio buffer, you should allocate
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 * any local mixing buffers after you open the audio device.
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 */
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extern DECLSPEC int SDLCALL SDL_OpenAudio(SDL_AudioSpec * desired,
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                                          SDL_AudioSpec * obtained);
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/*
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 * SDL Audio Device IDs.
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 * A successful call to SDL_OpenAudio() is always device id 1, and legacy
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 *  SDL audio APIs assume you want this device ID. SDL_OpenAudioDevice() calls
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 *  always returns devices >= 2 on success. The legacy calls are good both
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 *  for backwards compatibility and when you don't care about multiple,
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 *  specific, or capture devices.
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 */
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typedef Uint32 SDL_AudioDeviceID;
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/*
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 * Get the number of available devices exposed by the current driver.
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 *  Only valid after a successfully initializing the audio subsystem.
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 *  Returns -1 if an explicit list of devices can't be determined; this is
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 *  not an error. For example, if SDL is set up to talk to a remote audio
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 *  server, it can't list every one available on the Internet, but it will
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 *  still allow a specific host to be specified to SDL_OpenAudioDevice().
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 * In many common cases, when this function returns a value <= 0, it can still
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 *  successfully open the default device (NULL for first argument of
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 *  SDL_OpenAudioDevice()).
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 */
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extern DECLSPEC int SDLCALL SDL_GetNumAudioDevices(int iscapture);
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/*
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 * Get the human-readable name of a specific audio device.
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 *  Must be a value between 0 and (number of audio devices-1).
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 *  Only valid after a successfully initializing the audio subsystem.
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 *  The values returned by this function reflect the latest call to
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 *  SDL_GetNumAudioDevices(); recall that function to redetect available
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 *  hardware.
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 *
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 * The string returned by this function is UTF-8 encoded, read-only, and
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 *  managed internally. You are not to free it. If you need to keep the
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 *  string for any length of time, you should make your own copy of it, as it
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 *  will be invalid next time any of several other SDL functions is called.
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 */
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extern DECLSPEC const char *SDLCALL SDL_GetAudioDeviceName(int index,
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                                                           int iscapture);
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/*
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 * Open a specific audio device. Passing in a device name of NULL requests
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 *  the most reasonable default (and is equivalent to calling SDL_OpenAudio()).
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 * The device name is a UTF-8 string reported by SDL_GetAudioDevice(), but
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 *  some drivers allow arbitrary and driver-specific strings, such as a
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 *  hostname/IP address for a remote audio server, or a filename in the
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 *  diskaudio driver.
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 * Returns 0 on error, a valid device ID that is >= 2 on success.
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 *  SDL_OpenAudio(), unlike this function, always acts on device ID 1.
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 */
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extern DECLSPEC SDL_AudioDeviceID SDLCALL SDL_OpenAudioDevice(const char
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                                                              *device,
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                                                              int iscapture,
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                                                              const
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                                                              SDL_AudioSpec *
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                                                              desired,
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                                                              SDL_AudioSpec *
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                                                              obtained,
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                                                              int
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                                                              allowed_changes);
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/*
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 * Get the current audio state:
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 */
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typedef enum
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{
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    SDL_AUDIO_STOPPED = 0,
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    SDL_AUDIO_PLAYING,
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    SDL_AUDIO_PAUSED
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} SDL_audiostatus;
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extern DECLSPEC SDL_audiostatus SDLCALL SDL_GetAudioStatus(void);
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extern DECLSPEC SDL_audiostatus SDLCALL
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SDL_GetAudioDeviceStatus(SDL_AudioDeviceID dev);
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/*
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 * This function pauses and unpauses the audio callback processing.
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 * It should be called with a parameter of 0 after opening the audio
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 * device to start playing sound.  This is so you can safely initialize
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 * data for your callback function after opening the audio device.
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 * Silence will be written to the audio device during the pause.
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 */
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extern DECLSPEC void SDLCALL SDL_PauseAudio(int pause_on);
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extern DECLSPEC void SDLCALL SDL_PauseAudioDevice(SDL_AudioDeviceID dev,
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                                                  int pause_on);
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/*
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 * This function loads a WAVE from the data source, automatically freeing
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 * that source if 'freesrc' is non-zero.  For example, to load a WAVE file,
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 * you could do:
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 *	SDL_LoadWAV_RW(SDL_RWFromFile("sample.wav", "rb"), 1, ...);
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 *
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 * If this function succeeds, it returns the given SDL_AudioSpec,
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 * filled with the audio data format of the wave data, and sets
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 * 'audio_buf' to a malloc()'d buffer containing the audio data,
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 * and sets 'audio_len' to the length of that audio buffer, in bytes.
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 * You need to free the audio buffer with SDL_FreeWAV() when you are 
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 * done with it.
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 *
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 * This function returns NULL and sets the SDL error message if the 
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 * wave file cannot be opened, uses an unknown data format, or is 
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 * corrupt.  Currently raw and MS-ADPCM WAVE files are supported.
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 */
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extern DECLSPEC SDL_AudioSpec *SDLCALL SDL_LoadWAV_RW(SDL_RWops * src,
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                                                      int freesrc,
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                                                      SDL_AudioSpec * spec,
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                                                      Uint8 ** audio_buf,
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                                                      Uint32 * audio_len);
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/* Compatibility convenience function -- loads a WAV from a file */
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#define SDL_LoadWAV(file, spec, audio_buf, audio_len) \
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	SDL_LoadWAV_RW(SDL_RWFromFile(file, "rb"),1, spec,audio_buf,audio_len)
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/*
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 * This function frees data previously allocated with SDL_LoadWAV_RW()
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 */
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extern DECLSPEC void SDLCALL SDL_FreeWAV(Uint8 * audio_buf);
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/*
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 * This function takes a source format and rate and a destination format
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 * and rate, and initializes the 'cvt' structure with information needed
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 * by SDL_ConvertAudio() to convert a buffer of audio data from one format
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 * to the other.
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 * Returns -1 if the format conversion is not supported, 0 if there's
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 *  no conversion needed, or 1 if the audio filter is set up.
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 */
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extern DECLSPEC int SDLCALL SDL_BuildAudioCVT(SDL_AudioCVT * cvt,
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                                              SDL_AudioFormat src_format,
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                                              Uint8 src_channels,
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                                              int src_rate,
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                                              SDL_AudioFormat dst_format,
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                                              Uint8 dst_channels,
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                                              int dst_rate);
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/* Once you have initialized the 'cvt' structure using SDL_BuildAudioCVT(),
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 * created an audio buffer cvt->buf, and filled it with cvt->len bytes of
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 * audio data in the source format, this function will convert it in-place
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 * to the desired format.
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 * The data conversion may expand the size of the audio data, so the buffer
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 * cvt->buf should be allocated after the cvt structure is initialized by
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 * SDL_BuildAudioCVT(), and should be cvt->len*cvt->len_mult bytes long.
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 */
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extern DECLSPEC int SDLCALL SDL_ConvertAudio(SDL_AudioCVT * cvt);
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/*
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 * This takes two audio buffers of the playing audio format and mixes
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 * them, performing addition, volume adjustment, and overflow clipping.
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 * The volume ranges from 0 - 128, and should be set to SDL_MIX_MAXVOLUME
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 * for full audio volume.  Note this does not change hardware volume.
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 * This is provided for convenience -- you can mix your own audio data.
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 */
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#define SDL_MIX_MAXVOLUME 128
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extern DECLSPEC void SDLCALL SDL_MixAudio(Uint8 * dst, const Uint8 * src,
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                                          Uint32 len, int volume);
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/*
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 * This works like SDL_MixAudio, but you specify the audio format instead of
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 *  using the format of audio device 1. Thus it can be used when no audio
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 *  device is open at all.
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 */
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extern DECLSPEC void SDLCALL SDL_MixAudioFormat(Uint8 * dst,
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                                                const Uint8 * src,
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                                                SDL_AudioFormat format,
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                                                Uint32 len, int volume);
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/*
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 * The lock manipulated by these functions protects the callback function.
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 * During a LockAudio/UnlockAudio pair, you can be guaranteed that the
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 * callback function is not running.  Do not call these from the callback
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 * function or you will cause deadlock.
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 */
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extern DECLSPEC void SDLCALL SDL_LockAudio(void);
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extern DECLSPEC void SDLCALL SDL_LockAudioDevice(SDL_AudioDeviceID dev);
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extern DECLSPEC void SDLCALL SDL_UnlockAudio(void);
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extern DECLSPEC void SDLCALL SDL_UnlockAudioDevice(SDL_AudioDeviceID dev);
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/*
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 * This function shuts down audio processing and closes the audio device.
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 */
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extern DECLSPEC void SDLCALL SDL_CloseAudio(void);
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extern DECLSPEC void SDLCALL SDL_CloseAudioDevice(SDL_AudioDeviceID dev);
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/*
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 * Returns 1 if audio device is still functioning, zero if not, -1 on error.
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 */
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extern DECLSPEC int SDLCALL SDL_AudioDeviceConnected(SDL_AudioDeviceID dev);
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/* Ends C function definitions when using C++ */
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#ifdef __cplusplus
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/* *INDENT-OFF* */
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}
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/* *INDENT-ON* */
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#endif
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#include "close_code.h"
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#endif /* _SDL_audio_h */
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/* vi: set ts=4 sw=4 expandtab: */