Question

我想在不创建文件的情况下计量音频输入电平。我已经阅读了各种帖子并找到了这些方法：

使用AVAudioRecorder并写入/ dev / null（这确实是一个好主意但在iOS 8/9上对我不起作用）
使用对我有用的AVCaptureSession，但我不知道这可能会对AppStore提交（第一个问题）产生什么影响。另一个不好的方面似乎是它会在iPad2上不断使用大约10％的CPU （第二个问题）。

这是我的代码，受到类似SO帖子的启发：

func startCapture() {
    if let device : AVCaptureDevice = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeAudio){

        do {
            self.session = AVCaptureSession()
            try device.lockForConfiguration()

            let audioInput = try AVCaptureDeviceInput(device: device)
            device.unlockForConfiguration()

            if(self.session.canAddInput(audioInput)){
                self.session.addInput(audioInput)
                print("added input")
            }


            let audioOutput = AVCaptureAudioDataOutput()

            audioOutput.setSampleBufferDelegate(self, queue: dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0))

            if(self.session.canAddOutput(audioOutput)){
                self.session.addOutput(audioOutput)
                print("added output")
            }


            //supposed to start session not on UI queue coz it takes a while
            dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)) {
                print("starting captureSession")
                self.session.startRunning()
            }

        } catch {

        }
    }
}

func captureOutput(captureOutput: AVCaptureOutput!, let didOutputSampleBuffer sampleBuffer: CMSampleBuffer!, fromConnection connection: AVCaptureConnection!) {

    var buffer: CMBlockBuffer? = nil

    // Needs to be initialized somehow, even if we take only the address
    var audioBufferList = AudioBufferList(mNumberBuffers: 1,
                                          mBuffers: AudioBuffer(mNumberChannels: 1, mDataByteSize: 0, mData: nil))

    CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer(
        sampleBuffer,
        nil,
        &audioBufferList,
        sizeof(audioBufferList.dynamicType),
        nil,
        nil,
        UInt32(kCMSampleBufferFlag_AudioBufferList_Assure16ByteAlignment),
        &buffer
    )

    let abl = UnsafeMutableAudioBufferListPointer(&audioBufferList)

    for buffer in abl {
        let samples = UnsafeMutableBufferPointer<Int16>(start: UnsafeMutablePointer(buffer.mData),
                                                        count: Int(buffer.mDataByteSize)/sizeof(Int16))

        var sum:Int64 = 0

        for sample in samples {
            let s = Int64(sample)
            sum = (sum + s*s)
        }

        dispatch_async(dispatch_get_main_queue()) {

            print( String(sqrt(Float(sum/Int64(samples.count)))))
        }
    }
}

iOS：无需创建文件的音频录制计量

0 个答案: