尝试通过多点连接将音频从 microphone 流式传输到另一个 phone

Question

我正在尝试通过 Apple Multipeer Connectivity 框架将音频从微型 phone 流式传输到另一个 iPhone。为了进行音频捕获和播放，我正在使用 AVAudioEngine（非常感谢 Rhythmic Fistman's answer ）。

我通过在输入端安装一个水龙头从 microphone 接收数据，由此我得到一个 AVAudioPCMBuffer，然后将其转换为一个 UInt8 数组，然后将其流式传输到另一个 phone.

但是当我将数组转换回 AVAudioPCMBuffer 时，我得到一个 EXC_BAD_ACCESS 异常，编译器指向我再次将字节数组转换为 AVAudioPCMBuffer 的方法。

这里是我要获取、转换和流式传输输入的代码：

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)
            })

我转换数据的两个函数（取自Martin.R's answer ）：

func binarytotype <T> (_ value: [UInt8], _: T.Type) -> T {
    return value.withUnsafeBufferPointer {
        UnsafeRawPointer([=12=].baseAddress!).load(as: T.self)
    }

}

func typetobinary<T>(_ value: T) -> [UInt8] {
    var data = [UInt8](repeating: 0, count: MemoryLayout<T>.size)
    data.withUnsafeMutableBufferPointer {
        UnsafeMutableRawPointer([=12=].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在流式传输之前从中播放声音（在相同的 phone 中）但不在接收端创建 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？

如有任何帮助，thoughts/input 将不胜感激。

Answer 1

你的AVAudioPCMBufferserialisation/deserialisation错了。

Swift3 的转换发生了很大变化，而且似乎比 Swift2 需要更多的复制。

以下是 [UInt8] 和 AVAudioPCMBuffer 之间的转换方法：

N.B：此代码假定单声道浮点数据为 44.1kHz。
你可能想改变它。

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 {
            [=10=].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([=10=].baseAddress!).bindMemory(to: Float.self, capacity: Int(frameLength))
        dstLeft.initialize(from: src, count: Int(frameLength))
    }

    return audioBuffer
}

尝试通过多点连接将音频从 microphone 流式传输到另一个 phone

Trying to stream audio from microphone to another phone via multipeer connectivity

swift

avfoundation

audio-streaming

swift3

avaudioengine