Play audio from AVCaptureAudioDataOutputSampleBufferDelegate - iphone

Question

I'm capturing audio using AVCaptureAudioDataOutputSampleBufferDelegate
_captureSession = [[AVCaptureSession alloc] init];
[self.captureSession setSessionPreset:AVCaptureSessionPresetLow];
// Setup Audio input
AVCaptureDevice *audioDevice = [AVCaptureDevice
defaultDeviceWithMediaType:AVMediaTypeAudio];
AVCaptureDeviceInput *captureAudioInput = [AVCaptureDeviceInput deviceInputWithDevice:audioDevice error:&error];
if(error){
NSLog(#"Error Start capture Audio=%#", error);
}else{
if ([self.captureSession canAddInput:captureAudioInput]){
[self.captureSession addInput:captureAudioInput];
}
}
// Setup Audio output
AVCaptureAudioDataOutput *audioCaptureOutput = [[AVCaptureAudioDataOutput alloc] init];
if ([self.captureSession canAddOutput:audioCaptureOutput]){
[self.captureSession addOutput:audioCaptureOutput];
}
[audioCaptureOutput release];
//We create a serial queue
dispatch_queue_t audioQueue= dispatch_queue_create("audioQueue", NULL);
[audioCaptureOutput setSampleBufferDelegate:self queue:audioQueue];
dispatch_release(audioQueue);
/*We start the capture*/
[self.captureSession startRunning];
Delegate:
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {
// do something with sampleBuffer
}
The question is how can i play audio from sampleBuffer?

Answer 1

You can create NSData from the CMSampleBufferRef using the following code and then play it with AVAudioPlayer.
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {
AudioBufferList audioBufferList;
NSMutableData *data= [NSMutableData data];
CMBlockBufferRef blockBuffer;
CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer(sampleBuffer, NULL, &audioBufferList, sizeof(audioBufferList), NULL, NULL, 0, &blockBuffer);
for( int y=0; y< audioBufferList.mNumberBuffers; y++ ){
AudioBuffer audioBuffer = audioBufferList.mBuffers[y];
Float32 *frame = (Float32*)audioBuffer.mData;
[data appendBytes:frame length:audioBuffer.mDataByteSize];
}
CFRelease(blockBuffer);
AVAudioPlayer *player = [[AVAudioPlayer alloc] initWithData:data error:nil];
[player play];
}
I'm worried about how this will do performance wise though. There probably is a better way to do what you are trying to accomplish.