src/audio/SDL_sysaudio.h
author Ryan C. Gordon
Wed, 18 Mar 2015 02:01:17 -0400
changeset 9394 bb28e5281770
parent 9393 ed79a66e57e5
child 9397 d72d2aa46341
permissions -rw-r--r--
Bunch of reworking to how we manage audio devices.

Device enumeration now happens at startup and then is managed exclusively
through hotplugging instead of full redetection. The device name list now has
a unique "handle" associated with each item and SDL will pass this to the
backend so they don't have to figure out how a human readable name maps to
real hardware for a second time.

Other cleanups, fixes, improvements, plus all the audio backends updated to
the new interface...largely untested at this point, though.
     1 /*
     2   Simple DirectMedia Layer
     3   Copyright (C) 1997-2014 Sam Lantinga <slouken@libsdl.org>
     4 
     5   This software is provided 'as-is', without any express or implied
     6   warranty.  In no event will the authors be held liable for any damages
     7   arising from the use of this software.
     8 
     9   Permission is granted to anyone to use this software for any purpose,
    10   including commercial applications, and to alter it and redistribute it
    11   freely, subject to the following restrictions:
    12 
    13   1. The origin of this software must not be misrepresented; you must not
    14      claim that you wrote the original software. If you use this software
    15      in a product, an acknowledgment in the product documentation would be
    16      appreciated but is not required.
    17   2. Altered source versions must be plainly marked as such, and must not be
    18      misrepresented as being the original software.
    19   3. This notice may not be removed or altered from any source distribution.
    20 */
    21 #include "../SDL_internal.h"
    22 
    23 #ifndef _SDL_sysaudio_h
    24 #define _SDL_sysaudio_h
    25 
    26 #include "SDL_mutex.h"
    27 #include "SDL_thread.h"
    28 
    29 /* The SDL audio driver */
    30 typedef struct SDL_AudioDevice SDL_AudioDevice;
    31 #define _THIS   SDL_AudioDevice *_this
    32 
    33 /* Audio targets should call this as devices are added to the system (such as
    34    a USB headset being plugged in), and should also be called for
    35    for every device found during DetectDevices(). */
    36 extern void SDL_AddAudioDevice(const int iscapture, const char *name, void *handle);
    37 
    38 /* Audio targets should call this as devices are removed, so SDL can update
    39    its list of available devices. */
    40 extern void SDL_RemoveAudioDevice(void *handle);
    41 
    42 /* Audio targets should call this if an opened audio device is lost while
    43    being used. This can happen due to i/o errors, or a device being unplugged,
    44    etc. If the device is totally gone, please also call SDL_RemoveAudioDevice()
    45    as appropriate so SDL's list of devices is accurate. */
    46 extern void SDL_OpenedAudioDeviceDisconnected(SDL_AudioDevice *device);
    47 
    48 
    49 /* This is the size of a packet when using SDL_QueueAudio(). We allocate
    50    these as necessary and pool them, under the assumption that we'll
    51    eventually end up with a handful that keep recycling, meeting whatever
    52    the app needs. We keep packing data tightly as more arrives to avoid
    53    wasting space, and if we get a giant block of data, we'll split them
    54    into multiple packets behind the scenes. My expectation is that most
    55    apps will have 2-3 of these in the pool. 8k should cover most needs, but
    56    if this is crippling for some embedded system, we can #ifdef this.
    57    The system preallocates enough packets for 2 callbacks' worth of data. */
    58 #define SDL_AUDIOBUFFERQUEUE_PACKETLEN (8 * 1024)
    59 
    60 /* Used by apps that queue audio instead of using the callback. */
    61 typedef struct SDL_AudioBufferQueue
    62 {
    63     Uint8 data[SDL_AUDIOBUFFERQUEUE_PACKETLEN];  /* packet data. */
    64     Uint32 datalen;  /* bytes currently in use in this packet. */
    65     Uint32 startpos;  /* bytes currently consumed in this packet. */
    66     struct SDL_AudioBufferQueue *next;  /* next item in linked list. */
    67 } SDL_AudioBufferQueue;
    68 
    69 typedef struct SDL_AudioDriverImpl
    70 {
    71     void (*DetectDevices) (void);
    72     int (*OpenDevice) (_THIS, void *handle, const char *devname, int iscapture);
    73     void (*ThreadInit) (_THIS); /* Called by audio thread at start */
    74     void (*WaitDevice) (_THIS);
    75     void (*PlayDevice) (_THIS);
    76     int (*GetPendingBytes) (_THIS);
    77     Uint8 *(*GetDeviceBuf) (_THIS);
    78     void (*WaitDone) (_THIS);
    79     void (*CloseDevice) (_THIS);
    80     void (*LockDevice) (_THIS);
    81     void (*UnlockDevice) (_THIS);
    82     void (*FreeDeviceHandle) (void *handle);  /**< SDL is done with handle from SDL_AddAudioDevice() */
    83     void (*Deinitialize) (void);
    84 
    85     /* !!! FIXME: add pause(), so we can optimize instead of mixing silence. */
    86 
    87     /* Some flags to push duplicate code into the core and reduce #ifdefs. */
    88     /* !!! FIXME: these should be SDL_bool */
    89     int ProvidesOwnCallbackThread;
    90     int SkipMixerLock;  /* !!! FIXME: do we need this anymore? */
    91     int HasCaptureSupport;
    92     int OnlyHasDefaultOutputDevice;
    93     int OnlyHasDefaultInputDevice;
    94     int AllowsArbitraryDeviceNames;
    95 } SDL_AudioDriverImpl;
    96 
    97 
    98 typedef struct SDL_AudioDeviceItem
    99 {
   100     void *handle;
   101     struct SDL_AudioDeviceItem *next;
   102     char name[];
   103 } SDL_AudioDeviceItem;
   104 
   105 
   106 typedef struct SDL_AudioDriver
   107 {
   108     /* * * */
   109     /* The name of this audio driver */
   110     const char *name;
   111 
   112     /* * * */
   113     /* The description of this audio driver */
   114     const char *desc;
   115 
   116     SDL_AudioDriverImpl impl;
   117 
   118     /* A mutex for device detection */
   119     SDL_mutex *detectionLock;
   120     SDL_bool captureDevicesRemoved;
   121     SDL_bool outputDevicesRemoved;
   122     int outputDeviceCount;
   123     int inputDeviceCount;
   124     SDL_AudioDeviceItem *outputDevices;
   125     SDL_AudioDeviceItem *inputDevices;
   126 } SDL_AudioDriver;
   127 
   128 
   129 /* Streamer */
   130 typedef struct
   131 {
   132     Uint8 *buffer;
   133     int max_len;                /* the maximum length in bytes */
   134     int read_pos, write_pos;    /* the position of the write and read heads in bytes */
   135 } SDL_AudioStreamer;
   136 
   137 
   138 /* Define the SDL audio driver structure */
   139 struct SDL_AudioDevice
   140 {
   141     /* * * */
   142     /* Data common to all devices */
   143     SDL_AudioDeviceID id;
   144 
   145     /* The current audio specification (shared with audio thread) */
   146     SDL_AudioSpec spec;
   147 
   148     /* An audio conversion block for audio format emulation */
   149     SDL_AudioCVT convert;
   150 
   151     /* The streamer, if sample rate conversion necessitates it */
   152     int use_streamer;
   153     SDL_AudioStreamer streamer;
   154 
   155     /* Current state flags */
   156     /* !!! FIXME: should be SDL_bool */
   157     int iscapture;
   158     int enabled;
   159     int paused;
   160     int opened;
   161 
   162     /* Fake audio buffer for when the audio hardware is busy */
   163     Uint8 *fake_stream;
   164 
   165     /* A mutex for locking the mixing buffers */
   166     SDL_mutex *mixer_lock;
   167 
   168     /* A thread to feed the audio device */
   169     SDL_Thread *thread;
   170     SDL_threadID threadid;
   171 
   172     /* Queued buffers (if app not using callback). */
   173     SDL_AudioBufferQueue *buffer_queue_head; /* device fed from here. */
   174     SDL_AudioBufferQueue *buffer_queue_tail; /* queue fills to here. */
   175     SDL_AudioBufferQueue *buffer_queue_pool; /* these are unused packets. */
   176     Uint32 queued_bytes;  /* number of bytes of audio data in the queue. */
   177 
   178     /* * * */
   179     /* Data private to this driver */
   180     struct SDL_PrivateAudioData *hidden;
   181 };
   182 #undef _THIS
   183 
   184 typedef struct AudioBootStrap
   185 {
   186     const char *name;
   187     const char *desc;
   188     int (*init) (SDL_AudioDriverImpl * impl);
   189     int demand_only;  /* 1==request explicitly, or it won't be available. */
   190 } AudioBootStrap;
   191 
   192 #endif /* _SDL_sysaudio_h */
   193 
   194 /* vi: set ts=4 sw=4 expandtab: */