尝试通过多点连接将音频从麦克风流传输到另一部电话 [英] Trying to stream audio from microphone to another phone via multipeer connectivity

问题描述

我正在尝试通过Apples Multipeer Connectivity框架将音频从麦克风流式传输到另一部iPhone.要进行音频捕获和播放，我使用的是AVAudioEngine(非常感谢节奏拳头的回答

I am trying to stream audio from the microphone to another iPhone via Apples Multipeer Connectivity framework. To do the audio capturing and playback I am using AVAudioEngine (much thanks to Rhythmic Fistman's answer here).

我通过在输入上安装一个抽头来从麦克风接收数据，由此我得到了AVAudioPCMBuffer，然后将其转换为UInt8数组，然后将其流式传输到另一部手机.

I receive data from the microphone by installing a tap on the input, from this I am getting a AVAudioPCMBuffer which I then convert to an array of UInt8 which I then stream to the other phone.

但是当我将数组转换回AVAudioPCMBuffer时，我得到了EXC_BAD_ACCESS异常，编译器指向了将字节数组再次转换为AVAudioPCMBuffer的方法.

But when I am converting the array back to an AVAudioPCMBuffer I get an EXC_BAD_ACCESS exception with the compiler pointing to the method where I am converting the byte array to AVAudioPCMBuffer again.

这是我要提取，转换和流式处理输入内容的代码:

Here is the code for where I'm taking, converting and streaming the input:

input.installTap(onBus: 0, bufferSize: 2048, format: input.inputFormat(forBus: 0), block: {
                (buffer: AVAudioPCMBuffer!, time: AVAudioTime!) -> Void in

                let audioBuffer = self.typetobinary(buffer)
                stream.write(audioBuffer, maxLength: audioBuffer.count)
            })

我的两种转换数据的功能(取自 Martin.R 的回答

My both functions for converting the data (taken from Martin.R's answer here):

func binarytotype <T> (_ value: [UInt8], _: T.Type) -> T {
    return value.withUnsafeBufferPointer {
        UnsafeRawPointer($0.baseAddress!).load(as: T.self)
    }

}

func typetobinary<T>(_ value: T) -> [UInt8] {
    var data = [UInt8](repeating: 0, count: MemoryLayout<T>.size)
    data.withUnsafeMutableBufferPointer {
        UnsafeMutableRawPointer($0.baseAddress!).storeBytes(of: value, as: T.self)
    }
    return data
}

在接收端:

func session(_ session: MCSession, didReceive stream: InputStream, withName streamName: String, fromPeer peerID: MCPeerID) {
    if streamName == "voice" {

        stream.schedule(in: RunLoop.current, forMode: .defaultRunLoopMode)
        stream.open()

        var bytes = [UInt8](repeating: 0, count: 8)
        stream.read(&bytes, maxLength: bytes.count)

        let audioBuffer = self.binarytotype(bytes, AVAudioPCMBuffer.self) //Here is where the app crashes

        do {
            try engine.start()

            audioPlayer.scheduleBuffer(audioBuffer, completionHandler: nil)
            audioPlayer.play()
       }catch let error {
            print(error.localizedDescription)

        }
    }
}

问题是，我可以来回转换字节数组并从中播放声音，然后再将其流化(在同一部电话中)，但不能在接收端创建AVAudioPCMBuffer.有谁知道为什么转换在接收端不起作用?这是正确的方法吗?

The thing is that I can convert the byte array back and forth and play sound from it before I stream it (in the same phone) but not create the AVAudioPCMBuffer on the receiving end. Does anyone know why the conversion doesn't work on the receiving end? Is this the right way to go?

任何帮助，想法/建议都将不胜感激.

Any help, thoughts/input about this would be much appreciated.

推荐答案

您的AVAudioPCMBuffer序列化/反序列化错误.

Your AVAudioPCMBuffer serialisation/deserialisation is wrong.

Swift3的投放方式发生了很大变化&似乎比Swift2需要更多的复制.

Swift3's casting has changed a lot & seems to require more copying than Swift2.

这是在[UInt8]和AVAudioPCMBuffer s之间进行转换的方式:

Here's how you can convert between [UInt8] and AVAudioPCMBuffers:

N.B :此代码假定单浮点数据为44.1kHz.
您可能要更改它.

N.B: this code assumes mono float data at 44.1kHz.
You might want to change that.

func copyAudioBufferBytes(_ audioBuffer: AVAudioPCMBuffer) -> [UInt8] {
    let srcLeft = audioBuffer.floatChannelData![0]
    let bytesPerFrame = audioBuffer.format.streamDescription.pointee.mBytesPerFrame
    let numBytes = Int(bytesPerFrame * audioBuffer.frameLength)

    // initialize bytes to 0 (how to avoid?)
    var audioByteArray = [UInt8](repeating: 0, count: numBytes)

    // copy data from buffer
    srcLeft.withMemoryRebound(to: UInt8.self, capacity: numBytes) { srcByteData in
        audioByteArray.withUnsafeMutableBufferPointer {
            $0.baseAddress!.initialize(from: srcByteData, count: numBytes)
        }
    }

    return audioByteArray
}

func bytesToAudioBuffer(_ buf: [UInt8]) -> AVAudioPCMBuffer {
    // format assumption! make this part of your protocol?
    let fmt = AVAudioFormat(commonFormat: .pcmFormatFloat32, sampleRate: 44100, channels: 1, interleaved: true)
    let frameLength = UInt32(buf.count) / fmt.streamDescription.pointee.mBytesPerFrame

    let audioBuffer = AVAudioPCMBuffer(pcmFormat: fmt, frameCapacity: frameLength)
    audioBuffer.frameLength = frameLength

    let dstLeft = audioBuffer.floatChannelData![0]
    // for stereo
    // let dstRight = audioBuffer.floatChannelData![1]

    buf.withUnsafeBufferPointer {
        let src = UnsafeRawPointer($0.baseAddress!).bindMemory(to: Float.self, capacity: Int(frameLength))
        dstLeft.initialize(from: src, count: Int(frameLength))
    }

    return audioBuffer
}

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