src/audio/SDL_sysaudio.h
author Ryan C. Gordon <icculus@icculus.org>
Tue, 22 Jul 2014 21:41:49 -0400
changeset 9012 aa058c87737b
parent 8149 681eb46b8ac4
child 9031 e963a13a720c
permissions -rw-r--r--
Added audio device buffer queueing API.
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/*
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  Simple DirectMedia Layer
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  Copyright (C) 1997-2014 Sam Lantinga <slouken@libsdl.org>
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  This software is provided 'as-is', without any express or implied
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  warranty.  In no event will the authors be held liable for any damages
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  arising from the use of this software.
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  Permission is granted to anyone to use this software for any purpose,
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  including commercial applications, and to alter it and redistribute it
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  freely, subject to the following restrictions:
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  1. The origin of this software must not be misrepresented; you must not
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     claim that you wrote the original software. If you use this software
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     in a product, an acknowledgment in the product documentation would be
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     appreciated but is not required.
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  2. Altered source versions must be plainly marked as such, and must not be
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     misrepresented as being the original software.
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  3. This notice may not be removed or altered from any source distribution.
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*/
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#include "../SDL_internal.h"
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#ifndef _SDL_sysaudio_h
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#define _SDL_sysaudio_h
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#include "SDL_mutex.h"
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#include "SDL_thread.h"
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/* The SDL audio driver */
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typedef struct SDL_AudioDevice SDL_AudioDevice;
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#define _THIS   SDL_AudioDevice *_this
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/* Used by audio targets during DetectDevices() */
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typedef void (*SDL_AddAudioDevice)(const char *name);
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/* This is the size of a packet when using SDL_QueueAudio(). We allocate
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   these as necessary and pool them, under the assumption that we'll
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   eventually end up with a handful that keep recycling, meeting whatever
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   the app needs. We keep packing data tightly as more arrives to avoid
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   wasting space, and if we get a giant block of data, we'll split them
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   into multiple packets behind the scenes. My expectation is that most
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   apps will have 2-3 of these in the pool. 8k should cover most needs, but
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   if this is crippling for some embedded system, we can #ifdef this.
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   The system preallocates enough packets for 2 callbacks' worth of data. */
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#define SDL_AUDIOBUFFERQUEUE_PACKETLEN (8 * 1024)
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/* Used by apps that queue audio instead of using the callback. */
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typedef struct SDL_AudioBufferQueue
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{
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    Uint8 data[SDL_AUDIOBUFFERQUEUE_PACKETLEN];  /* packet data. */
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    Uint32 datalen;  /* bytes currently in use in this packet. */
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    Uint32 startpos;  /* bytes currently consumed in this packet. */
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    struct SDL_AudioBufferQueue *next;  /* next item in linked list. */
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} SDL_AudioBufferQueue;
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typedef struct SDL_AudioDriverImpl
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{
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    void (*DetectDevices) (int iscapture, SDL_AddAudioDevice addfn);
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    int (*OpenDevice) (_THIS, const char *devname, int iscapture);
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    void (*ThreadInit) (_THIS); /* Called by audio thread at start */
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    void (*WaitDevice) (_THIS);
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    void (*PlayDevice) (_THIS);
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    Uint8 *(*GetDeviceBuf) (_THIS);
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    void (*WaitDone) (_THIS);
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    void (*CloseDevice) (_THIS);
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    void (*LockDevice) (_THIS);
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    void (*UnlockDevice) (_THIS);
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    void (*Deinitialize) (void);
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    /* !!! FIXME: add pause(), so we can optimize instead of mixing silence. */
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    /* Some flags to push duplicate code into the core and reduce #ifdefs. */
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    int ProvidesOwnCallbackThread;
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    int SkipMixerLock;  /* !!! FIXME: do we need this anymore? */
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    int HasCaptureSupport;
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    int OnlyHasDefaultOutputDevice;
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    int OnlyHasDefaultInputDevice;
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} SDL_AudioDriverImpl;
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typedef struct SDL_AudioDriver
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{
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    /* * * */
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    /* The name of this audio driver */
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    const char *name;
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    /* * * */
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    /* The description of this audio driver */
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    const char *desc;
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    SDL_AudioDriverImpl impl;
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    char **outputDevices;
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    int outputDeviceCount;
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    char **inputDevices;
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    int inputDeviceCount;
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} SDL_AudioDriver;
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/* Streamer */
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typedef struct
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{
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    Uint8 *buffer;
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    int max_len;                /* the maximum length in bytes */
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    int read_pos, write_pos;    /* the position of the write and read heads in bytes */
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} SDL_AudioStreamer;
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/* Define the SDL audio driver structure */
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struct SDL_AudioDevice
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{
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    /* * * */
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    /* Data common to all devices */
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    /* The current audio specification (shared with audio thread) */
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    SDL_AudioSpec spec;
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    /* An audio conversion block for audio format emulation */
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    SDL_AudioCVT convert;
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    /* The streamer, if sample rate conversion necessitates it */
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    int use_streamer;
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    SDL_AudioStreamer streamer;
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    /* Current state flags */
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    int iscapture;
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    int enabled;
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    int paused;
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    int opened;
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    /* Fake audio buffer for when the audio hardware is busy */
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    Uint8 *fake_stream;
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    /* A semaphore for locking the mixing buffers */
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    SDL_mutex *mixer_lock;
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    /* A thread to feed the audio device */
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    SDL_Thread *thread;
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    SDL_threadID threadid;
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    /* Queued buffers (if app not using callback). */
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    SDL_AudioBufferQueue *buffer_queue_head; /* device fed from here. */
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    SDL_AudioBufferQueue *buffer_queue_tail; /* queue fills to here. */
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    SDL_AudioBufferQueue *buffer_queue_pool; /* these are unused packets. */
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    Uint32 queued_bytes;  /* number of bytes of audio data in the queue. */
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    /* * * */
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    /* Data private to this driver */
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    struct SDL_PrivateAudioData *hidden;
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};
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#undef _THIS
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typedef struct AudioBootStrap
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{
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    const char *name;
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    const char *desc;
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    int (*init) (SDL_AudioDriverImpl * impl);
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    int demand_only;  /* 1==request explicitly, or it won't be available. */
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} AudioBootStrap;
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#endif /* _SDL_sysaudio_h */
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