Contradiction in the core audio queue services API
Contradiction in the core audio queue services API
- Subject: Contradiction in the core audio queue services API
- From: Stephen Thomas <email@hidden>
- Date: Tue, 20 Oct 2009 10:48:55 +0530
Hi,
In the following document,
http://developer.apple.com/mac/library/documentation/MusicAudio/Reference/AudioQueueReference/Reference/reference.html
There is a contradiction(Contradiction is highlighted in red
color). In the parameter list of AudioQueueNewOutput, it is mentioned
that, callback will get called after the buffer is played.
But in the description of AudioQueueOutputCallback, it is contradicted.
Which is true in this case?
AudioQueueNewOutput
Creates a new playback audio queue object.
OSStatus AudioQueueNewOutput (
const AudioStreamBasicDescription *inFormat,
AudioQueueOutputCallback inCallbackProc,
void *inUserData,
CFRunLoopRef inCallbackRunLoop,
CFStringRef inCallbackRunLoopMode,
UInt32 inFlags,
AudioQueueRef *outAQ
);
Parameters
- inFormat
The
data format of the audio to play. For linear PCM, only interleaved
formats are supported. Compressed formats are also supported.
- inCallbackProc
A
callback function to use with the playback audio queue. The audio queue
calls this function when the audio queue has finished playing a buffer.
See AudioQueueOutputCallback.
-------------------------------------------------------------------------------------------------
AudioQueueOutputCallback
Defines a pointer to a callback function that is called when an audio queue buffer is available for reuse.
typedef void (*AudioQueueOutputCallback) (
void *inUserData,
AudioQueueRef inAQ,
AudioQueueBufferRef inBuffer
);
Discussion
You specify a callback function when creating a new playback audio queue with the AudioQueueNewOutput
function. The callback is invoked each time its playback audio queue
has acquired the data from an audio queue buffer, at which point the
buffer is available for reuse. Typically, your callback then fills the
newly-available buffer with data from a file or other buffer, and then
reenqueues the buffer for playback.
When your application receives a call to the AudioQueueOutputCallback
function, you cannot assume that the audio data from the
newly-available buffer has been played. To ensure that all queued audio
has finished playing, use the AudioQueuePropertyListenerProc property listener callback function, set to listen to the kAudioQueueProperty_IsRunning property.
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