音频队列和iOS4?

下面的代码过去曾为我工作。我现在用iOS4试试,运气不好。它在模拟器中工作,但我没有听到设备本身的任何声音。我首先试着把一些样本记录到 NSMutableData

AudioSessionInitialize(NULL, NULL, NULL, NULL);
UInt32 sessionCategory = kAudioSessionCategory_PlayAndRecord; 
AudioSessionSetProperty(kAudioSessionProperty_AudioCategory, sizeof(sessionCategory), &sessionCategory);
AudioSessionSetActive(true);

AudioQueueNewOutput(&m_format,&OutputCallback,self,CFRunLoopGetCurrent(), kCFRunLoopCommonModes,0,&m_device);   
AudioQueueBufferRef nBuffer=NULL;
AudioQueueAllocateBuffer(m_device,[data length],&nBuffer);
nBuffer->mAudioDataByteSize=[data length];
[data getBytes:(nBuffer->mAudioData) length:(nBuffer->mAudioDataByteSize)];
AudioQueueEnqueueBuffer(m_device,nBuffer,0,NULL);
AudioQueueStart(m_device,NULL);