AudioStreamBasicDescription

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本文介绍如何使用Core Audio API配置音频播放队列，包括设置采样率、位深、声道等参数，并通过回调函数填充播放缓冲区。

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AudioStreamBasicDescription format; // 声音格式设置，这些设置要和采集时的配置一致

memset(&format, 0, sizeof(format));

format.mSampleRate = 44100; // 采样率 (立体声 = 8000)

format.mFormatID = kAudioFormatLinearPCM; // PCM 格式

format.mFormatFlags = kLinearPCMFormatFlagIsSignedInteger | kLinearPCMFormatFlagIsPacked;

format.mChannelsPerFrame = 1;  // 1:单声道；2:立体声

format.mBitsPerChannel = 16; // 语音每采样点占用位数

format.mBytesPerFrame = (format.mBitsPerChannel /  * format.mChannelsPerFrame;

format.mFramesPerPacket = 1;

format.mBytesPerPacket = format.mBytesPerFrame * format.mFramesPerPacket;

AudioQueueRef queue;

AudioQueueNewOutput(&format,

                AQPlayer::AQOutputCallback,

                this,  // opaque reference to whatever you like

                CFRunLoopGetCurrent(),

                kCFRunLoopCommonModes,

                0,

                &queue);

const int bufferSize = 0xA000;  // 48K - around 1/2 sec of 44kHz 16 bit mono PCM

for (int i = 0; i < kNumberBuffers; ++i)

    AudioQueueAllocateBufferWithPacketDescriptions(queue, bufferSize, 0, &mBuffers[i]);

AudioQueueSetParameter(queue, kAudioQueueParam_Volume, 1.0);

UInt32 category = kAudioSessionCategory_MediaPlayback;

AudioSessionSetProperty(kAudioSessionProperty_AudioCategory, sizeof(category), &category);

AudioSessionSetActive(true);

// prime the queue with some data before starting

for (int i = 0; i < kNumberBuffers; ++i)

    OutputCallback(queue, mBuffers[i]);

AudioQueueStart(queue, NULL);

在CallBack中填出数据：

void OutputCallback(void* inUserData, AudioQueueRef inAQ, AudioQueueBufferRef inCompleteAQBuffer) {