使用swift中的AVCaptureAudioDataOutputSampleBufferDelegate捕获音量级别

Question

我正在尝试使用AVCaptureDevice等进行音量级别编译和运行，但值似乎是随机的，我也一直遇到溢出错误。

编辑：

RMS范围也是0到20000左右是正常的吗？

        if let audioCaptureDevice : AVCaptureDevice = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeAudio){



            try audioCaptureDevice.lockForConfiguration()

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

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


            let audioOutput = AVCaptureAudioDataOutput()

            audioOutput.setSampleBufferDelegate(self, queue: GlobalUserInitiatedQueue)

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


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

...

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

    // 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))
    //this needs to be in method otherwise only runs 125 times?
    var blockBuffer: CMBlockBuffer?

    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:Int = 0
        for sample in samples {
            sum = sum + Int(sample*sample)

        }

        let rms = sqrt(Double(sum)/count)
    }

Answer 1

看来我有它的工作。在做任何操作之前，我把sample送到了Int64。

        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 +=s*s
        }


        dispatch_async(dispatch_get_main_queue()) {

            self.volLevel.text = String(sqrt(Float(sum/Int64(samples.count))))
        }

Answer 2

我玩过你的例子。这是一个完整的swift 2代码片段：

// also define a variable in class scope, otherwise captureOutput will not be called
    var session : AVCaptureSession!



    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)))))
        }
    }
}

Answer 3

使用AVCaptureAudioDataOutputSampleBufferDelegate的方法

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

从最后一个参数获取AVCaptureConnection。

然后从AVCaptureAudioChannel获得connection.audioChannels

然后你可以从它获得音量水平：

audioChannel.averagePowerLevel
audioChannel.peakHoldLevel