ios - 当我使用 installTap(onBus 进行多声道音频？

Question

当我使用 installTap(onBus 进行多声道音频？

如果 channel 数 > 1，那么它将包含左麦克风？或者它将包含来自左麦克风和右麦克风的样本？

当我使用 iphone 模拟器时 Format = pcmFormatFloat32, channelCount = 2, sampleRate = 44100.0, not Interleaved

我使用此代码

let bus = 0
inputNode.installTap(onBus: bus, bufferSize: myTapOnBusBufferSize, format: theAudioFormat) {
            (buffer: AVAudioPCMBuffer!, time: AVAudioTime!) -> Void in
            self.onNewBuffer(buffer)
        }

func onNewBuffer(_ inputBuffer:AVAudioPCMBuffer!)
{
    var samplesAsDoubles:[Double] = []

    for i in 0 ..< Int(inputBuffer.frameLength)
    {
        let theSample = Double((inputBuffer.floatChannelData?.pointee[i])!)
        samplesAsDoubles.append( theSample )
    }
}

print("number of input busses = \(inputNode.numberOfInputs)")

它打印
输入总线数 = 1

对于我在 block 内部的缓冲区中的 samplesAsDoubles 数组中的每个样本，它将来自哪个 channel ？这个样本是什么时候记录的？

Answer 1

从 floatChannelData 的标题注释中:

The returned pointer is to format.channelCount pointers to float. Each of these pointers is to "frameLength" valid samples, which are spaced by "stride" samples.

If format.interleaved is false (as with the standard deinterleaved float format), then the pointers will be to separate chunks of memory. "stride" is 1.

FloatChannelData 为您提供了一个 2D 浮点数组。对于非交错的 2 channel 缓冲区，您可以像这样访问单个样本:

let channelCount = Int(buffer.format.channelCount)
let frameCount = Int(buffer.frameLength)

if let channels = buffer.floatChannelData {  //channels is 2D float array
    for channelIndex in 0..<channelCount {
        let channel = channels[channelIndex] //1D float array
        print(channelIndex == 0 ? "left" : "right")
        for frameIndex in 0..<frameCount {
            let sample = channel[frameIndex]
            print("    \(sample)")
        }
    }
}