iOS:创建简单的音频波形动画

Question

我正在尝试录制音频AVAudioRecorder.我需要创建一个这样的简单波形:

当用户对着麦克风说话时,圆圈表示用户语音的等级.我尝试使用此代码测量语音,但代码未检测到任何缓冲区而无法正常工作:

func levelTimerCallback(timer:Timer) {

    //we have to update meters before we can get the metering values
    audioRecorder.updateMeters()

    //print to the console if we are beyond a threshold value. Here I've used -7
    if audioRecorder.averagePower(forChannel: 1) > -7 {

        print(" level I'm hearin' you in dat mic ")
        print(audioRecorder.averagePower(forChannel: 0))
    }
}    

录制音频:

func startRecording() {

        let audioSession = AVAudioSession.sharedInstance()
        do {

       // Audio Settings
            settings = [
                AVFormatIDKey: Int(kAudioFormatMPEG4AAC),
                AVSampleRateKey: 12000,
                AVNumberOfChannelsKey: 1,
                AVEncoderAudioQualityKey: AVAudioQuality.high.rawValue
            ]


            audioRecorder = try AVAudioRecorder(url: self.directoryURL(), settings: settings)
            audioRecorder.delegate = self
            audioRecorder.prepareToRecord()
            audioRecorder.isMeteringEnabled = true


        } catch {

            finishRecording(success: false)
        }

        do {

            try audioSession.setActive(true)
            audioRecorder.record()

            TIMERRRRR = Timer.scheduledTimer(timeInterval: 0.02, target: self, selector: #selector(ViewController.levelTimerCallback), userInfo: nil, repeats: true)

        } catch {

        }

    }

Answer 1

我能看到的两个问题.

首先,您正在使用功能中的错误频道号进行测试levelTimerCallback.您的测试应该是针对频道0.

另一个是它的价值-7实际上非常大.averagePower返回介于-160和0之间的浮点数.尝试针对-160进行测试以开始并增加该值以降低灵敏度.

这会将您的测试更改为:

if audioRecorder.averagePower(forChannel: 1) > -160 {
    ...
}

输入只有一个通道,计数从0开始.您可以在以后的通话中使用此功能audioRecorder.averagePower.

要获得线性比例,您需要进行插值.更改值scale以更改范围.proportion将在0和之间scale.

let lowerLimit: Float = -100.0

func levelTimerCallback(timer:Timer) {

    audioRecorder.updateMeters()

    let power = audioRecorder.averagePower(forChannel: 0)
    if power > lowerLimit {
        // proportion will have a value between 0 and scale
        let scale: Float = 10.0
        let proportion = -scale * (power - lowerLimit) / lowerLimit
    }
}

编辑:修正比例计算