快速将AVAudioEngine AVAudioPCMBuffer转换为PowerLevel

Question

I've been working on a project to create an application that displays the power level from the microphone. I'm aware of the AVAudioRecorder class what provides the average/peak power, but I want to be able only to record the power level for certain bands. I used the AudioUnitEQ class to set up the bands, and have attached it to an AVAudioEngine and started recording. Currently, I've been using the installTap method to get the AVAudioPCMBuffer, which is where I'm stuck. Is there a way to convert this to a power level? Also, could my approach to this be entirely wrong?

Answer 1

You can get avg/peek like this code.

engine.installTap(......) { buffer in 
    guard let data = buffer.floatChannelData?[0] else {
        return
    }
    var dbData = [Float](repeating: 0.0, count: data.count)
    var one: Float = 0.0
    vDSP_vdbcon(&data, 1, &one, &dbData, 1, data.count, 1)

    var avgLevel: Float = 0.0
    var peakLevel: Float = 0.0
    vDSP_rmsqv(dbData, 1, &avgLevel, vDSP_Length(buffer.frameLength))
    vDSP_maxmgv(dbData, 1, &peakLevel, vDSP_Length(buffer.frameLength))
}