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Added audio device buffer queueing API.

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icculus committed Jul 23, 2014
1 parent dfc7535 commit f30e120aa9e89e2a3f56e462f0f4d230469739c2
Showing with 469 additions and 12 deletions.
  1. +1 −0 .hgignore
  2. +103 −4 include/SDL_audio.h
  3. +201 −8 src/audio/SDL_audio.c
  4. +26 −0 src/audio/SDL_sysaudio.h
  5. +3 −0 src/dynapi/SDL_dynapi_overrides.h
  6. +3 −0 src/dynapi/SDL_dynapi_procs.h
  7. +4 −0 test/Makefile.in
  8. +1 −0 test/README
  9. +127 −0 test/loopwavequeue.c
@@ -73,6 +73,7 @@ test/Makefile
test/SDL2.dll
test/checkkeys
test/loopwave
test/loopwavequeue
test/testatomic
test/testaudioinfo
test/testautomation
@@ -155,6 +155,9 @@ typedef Uint16 SDL_AudioFormat;
*
* Once the callback returns, the buffer will no longer be valid.
* Stereo samples are stored in a LRLRLR ordering.
*
* You can choose to avoid callbacks and use SDL_QueueAudio() instead, if
* you like. Just open your audio device with a NULL callback.
*/
typedef void (SDLCALL * SDL_AudioCallback) (void *userdata, Uint8 * stream,
int len);
@@ -171,8 +174,8 @@ typedef struct SDL_AudioSpec
Uint16 samples; /**< Audio buffer size in samples (power of 2) */
Uint16 padding; /**< Necessary for some compile environments */
Uint32 size; /**< Audio buffer size in bytes (calculated) */
SDL_AudioCallback callback;
void *userdata;
SDL_AudioCallback callback; /**< Callback that feeds the audio device (NULL to use SDL_QueueAudio()). */
void *userdata; /**< Userdata passed to callback (ignored for NULL callbacks). */
} SDL_AudioSpec;


@@ -273,9 +276,11 @@ extern DECLSPEC const char *SDLCALL SDL_GetCurrentAudioDriver(void);
* to the audio buffer, and the length in bytes of the audio buffer.
* This function usually runs in a separate thread, and so you should
* protect data structures that it accesses by calling SDL_LockAudio()
* and SDL_UnlockAudio() in your code.
* and SDL_UnlockAudio() in your code. Alternately, you may pass a NULL
* pointer here, and call SDL_QueueAudio() with some frequency, to queue
* more audio samples to be played.
* - \c desired->userdata is passed as the first parameter to your callback
* function.
* function. If you passed a NULL callback, this value is ignored.
*
* The audio device starts out playing silence when it's opened, and should
* be enabled for playing by calling \c SDL_PauseAudio(0) when you are ready
@@ -474,6 +479,100 @@ extern DECLSPEC void SDLCALL SDL_MixAudioFormat(Uint8 * dst,
SDL_AudioFormat format,
Uint32 len, int volume);

/**
* Queue more audio on non-callback devices.
*
* SDL offers two ways to feed audio to the device: you can either supply a
* callback that SDL triggers with some frequency to obtain more audio
* (pull method), or you can supply no callback, and then SDL will expect
* you to supply data at regular intervals (push method) with this function.
*
* There are no limits on the amount of data you can queue, short of
* exhaustion of address space. Queued data will drain to the device as
* necessary without further intervention from you. If the device needs
* audio but there is not enough queued, it will play silence to make up
* the difference. This means you will have skips in your audio playback
* if you aren't routinely queueing sufficient data.
*
* This function copies the supplied data, so you are safe to free it when
* the function returns. This function is thread-safe, but queueing to the
* same device from two threads at once does not promise which buffer will
* be queued first.
*
* You may not queue audio on a device that is using an application-supplied
* callback; doing so returns an error. You have to use the audio callback
* or queue audio with this function, but not both.
*
* You should not call SDL_LockAudio() on the device before queueing; SDL
* handles locking internally for this function.
*
* \param dev The device ID to which we will queue audio.
* \param data The data to queue to the device for later playback.
* \param len The number of bytes (not samples!) to which (data) points.
* \return zero on success, -1 on error.
*
* \sa SDL_GetQueuedAudioSize
* \sa SDL_ClearQueuedAudio
*/
extern DECLSPEC int SDLCALL SDL_QueueAudio(SDL_AudioDeviceID dev, const void *data, Uint32 len);

/**
* Get the number of bytes of still-queued audio.
*
* This is the number of bytes that have been queued for playback with
* SDL_QueueAudio(), but have not yet been sent to the hardware.
*
* Once we've sent it to the hardware, this function can not decide the exact
* byte boundary of what has been played. It's possible that we just gave the
* hardware several kilobytes right before you called this function, but it
* hasn't played any of it yet, or maybe half of it, etc.
*
* You may not queue audio on a device that is using an application-supplied
* callback; calling this function on such a device always returns 0.
* You have to use the audio callback or queue audio with SDL_QueueAudio(),
* but not both.
*
* You should not call SDL_LockAudio() on the device before querying; SDL
* handles locking internally for this function.
*
* \param dev The device ID of which we will query queued audio size.
* \return Number of bytes (not samples!) of queued audio.
*
* \sa SDL_QueueAudio
* \sa SDL_ClearQueuedAudio
*/
extern DECLSPEC Uint32 SDLCALL SDL_GetQueuedAudioSize(SDL_AudioDeviceID dev);

/**
* Drop any queued audio data waiting to be sent to the hardware.
*
* Immediately after this call, SDL_GetQueuedAudioSize() will return 0 and
* the hardware will start playing silence if more audio isn't queued.
*
* This will not prevent playback of queued audio that's already been sent
* to the hardware, as we can not undo that, so expect there to be some
* fraction of a second of audio that might still be heard. This can be
* useful if you want to, say, drop any pending music during a level change
* in your game.
*
* You may not queue audio on a device that is using an application-supplied
* callback; calling this function on such a device is always a no-op.
* You have to use the audio callback or queue audio with SDL_QueueAudio(),
* but not both.
*
* You should not call SDL_LockAudio() on the device before clearing the
* queue; SDL handles locking internally for this function.
*
* This function always succeeds and thus returns void.
*
* \param dev The device ID of which to clear the audio queue.
*
* \sa SDL_QueueAudio
* \sa SDL_GetQueuedAudioSize
*/
extern DECLSPEC void SDLCALL SDL_ClearQueuedAudio(SDL_AudioDeviceID dev);


/**
* \name Audio lock functions
*

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