c – iOS：如何在运行时使用音频单元重新采样音频(PCM数据)？

我有一个音频单元设置如下.

- (void) setUpAudioUnit {
    OSStatus status;
    AudioComponentInstance audioUnit;
    AudioComponent inputComponent;
    AudioComponentDescription audioComponentDescription;
    AudioStreamBasicDescription audioStreamBasicDescription;

    // Describe audio component
    audioComponentDescription.componentType = kAudioUnitType_Output;
    audioComponentDescription.componentSubType = kAudioUnitSubType_VoiceProcessingIO;
    audioComponentDescription.componentFlags = 0;
    audioComponentDescription.componentFlagsMask = 0;
    audioComponentDescription.componentManufacturer = kAudioUnitManufacturer_Apple;

    // Get component
    inputComponent = AudioComponentFindNext(NULL,&audioComponentDescription);

    // Get audio units
    status = AudioComponentInstanceNew(inputComponent,&audioUnit);
    checkStatus(status);

    // Enable IO for recording
    UInt32 flag = 1;
    status = AudioUnitSetProperty(audioUnit,kAudioOutputUnitProperty_EnableIO,kAudioUnitScope_Input,kInputBus,&flag,sizeof(flag));
    checkStatus(status);

    // Enable IO for playback
    status = AudioUnitSetProperty(audioUnit,kAudioUnitScope_Output,kOutputBus,sizeof(flag));
    checkStatus(status);

    // Describe format
    audioStreamBasicDescription.mSampleRate         = AUDIO_SAMPLE_RATE;
    audioStreamBasicDescription.mFormatID           = kAudioFormatLinearPCM;
    audioStreamBasicDescription.mFormatFlags        = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;
    audioStreamBasicDescription.mFramesPerPacket    = AUDIO_FRAMES_PER_PACKET;
    audioStreamBasicDescription.mChannelsPerFrame   = AUDIO_CHANNELS_PER_FRAME;
    audioStreamBasicDescription.mBitsPerChannel     = AUDIO_BITS_PER_CHANNEL;
    audioStreamBasicDescription.mBytesPerPacket     = AUDIO_BYTES_PER_PACKET;
    audioStreamBasicDescription.mBytesPerFrame      = AUDIO_BYTES_PER_FRAME;

    // Apply format
    status = AudioUnitSetProperty(audioUnit,kAudioUnitProperty_StreamFormat,&audioStreamBasicDescription,sizeof(audioStreamBasicDescription));
    checkStatus(status);


    /* Make sure we set the correct audio category before restarting */
    UInt32 audioCategory = kAudioSessionCategory_PlayAndRecord;
    status = AudioSessionSetProperty(kAudioSessionProperty_AudioCategory,sizeof(audioCategory),&audioCategory);

    checkStatus(status);


    status = AudioUnitSetProperty(audioUnit,sizeof(audioStreamBasicDescription));
    checkStatus(status);


    // Set input callback
    AURenderCallbackStruct callbackStruct;
    callbackStruct.inputProc = recordingCallback;
    callbackStruct.inputProcRefCon = (__bridge void *)(self);
    status = AudioUnitSetProperty(audioUnit,kAudioOutputUnitProperty_SetInputCallback,kAudioUnitScope_Global,&callbackStruct,sizeof(callbackStruct));
    checkStatus(status);

    // Set output callback
    callbackStruct.inputProc = playbackCallback;
    callbackStruct.inputProcRefCon = (__bridge void *)(self);
    status = AudioUnitSetProperty(audioUnit,kAudioUnitProperty_SetRenderCallback,sizeof(callbackStruct));
    checkStatus(status);

    // Disable buffer allocation for the recorder (optional - do this if we want to pass in our own)
    flag = 0;
    status = AudioUnitSetProperty(audioUnit,kAudioUnitProperty_ShouldAllocateBuffer,sizeof(flag));


}

音频设置如下.

kOutputBus 0
kInputBus 1
AUDIO_SAMPLE_RATE 44100
AUDIO_FRAMES_PER_PACKET 1
AUDIO_CHANNELS_PER_FRAME 1
AUDIO_BITS_PER_CHANNEL 16 
AUDIO_BYTES_PER_PACKET 2
AUDIO_BYTES_PER_FRAME 2

我正在接收录制回调的PCM数据

audioBufferList->mBuffers[0].mData

那么,我如何将这个PCM数据从44.1KHz重新采样到8KHz,反之亦然？
我已经google了很多,但没有找到任何代码示例或直接指令.

找到这些线程,但这些都没有提供明确的指示.

> Which built in AudioUnit can resample audio?
> Changing sample rate of an AUGraph on iOS

任何代码示例或信息都非常受欢迎.