Convert Avaudiopcmbuffer to Nsdata and Back

Convert AVAudioPCMBuffer to NSData and back

Buffer length is frameCapacity * bytesPerFrame. Here are functions that can do conversion between NSData and AVAudioPCMBuffer.

extension AVAudioPCMBuffer {
    func data() -> Data {
        let channelCount = 1  // given PCMBuffer channel count is 1
        let channels = UnsafeBufferPointer(start: self.floatChannelData, count: channelCount)
        let ch0Data = NSData(bytes: channels[0], length:Int(self.frameCapacity * self.format.streamDescription.pointee.mBytesPerFrame))
        return ch0Data as Data
    }
}

func toPCMBuffer(data: NSData) -> AVAudioPCMBuffer? {
    let audioFormat = AVAudioFormat(commonFormat: .pcmFormatFloat32, sampleRate: 8000, channels: 1, interleaved: false)!  // given NSData audio format
    guard let PCMBuffer = AVAudioPCMBuffer(pcmFormat: audioFormat, frameCapacity: UInt32(data.length) / audioFormat.streamDescription.pointee.mBytesPerFrame) else {
        return nil
    }
    PCMBuffer.frameLength = PCMBuffer.frameCapacity
    let channels = UnsafeBufferPointer(start: PCMBuffer.floatChannelData, count: Int(PCMBuffer.format.channelCount))
    data.getBytes(UnsafeMutableRawPointer(channels[0]) , length: data.length)
    return PCMBuffer
}

Converting AVAudioPCMBuffer to NSData

I don't see any method named inTotalBitsPerChannel in either of the code samples you linked to; instead, they both seem to use mBytesPerFrame. You will also need .pointee to dereference the pointer. Finally, in modern Swift, you should generally prefer to use Data over NSData. So, basically, I think your extension should work if you rewrite the last line to:

let ch0Data = Data(bytes: channels[0], count: Int(frameCapacity * format.streamDescription.pointee.mBytesPerFrame))

Converting NSData to AVAudioPCMBuffer

You're using the wrong AVAudioBuffer subclass. AVAudioPCMBuffer is for uncompressed "Pulse-code modulation" audio. You want AVAudioCompressedBuffer instead.

How to play audio from AVAudioPCMBuffer converted from NSData

ended up using an objective-c function:data is getting converted fine

-(AudioBufferList *) getBufferListFromData: (NSData *) data
{
    if (data.length > 0)
    {
        NSUInteger len = [data length];
        //NSData *d2 = [data subdataWithRange:NSMakeRange(4, 1028)];
        //I guess you can use Byte*, void* or Float32*. I am not sure if that makes any difference.
        Byte* byteData = (Byte*) malloc (len);
        memcpy (byteData, [data bytes], len);
        if (byteData)
        {
            AudioBufferList * theDataBuffer =(AudioBufferList*)malloc(sizeof(AudioBufferList) * 1);
            theDataBuffer->mNumberBuffers = 1;
            theDataBuffer->mBuffers[0].mDataByteSize =(UInt32) len;
            theDataBuffer->mBuffers[0].mNumberChannels = 1;
            theDataBuffer->mBuffers[0].mData = byteData;
            // Read the data into an AudioBufferList
            return theDataBuffer;
        }
    }
    return nil;
}

How to convert audio so that it can be streamed across devices

Here you go:

func audioBufferToNSData(PCMBuffer: AVAudioPCMBuffer) -> NSData {
    let channelCount = 1  // given PCMBuffer channel count is 1
    let channels = UnsafeBufferPointer(start: PCMBuffer.floatChannelData, count: channelCount)
    let data = NSData(bytes: channels[0], length:Int(PCMBuffer.frameCapacity * PCMBuffer.format.streamDescription.pointee.mBytesPerFrame))
    return data
}

func dataToAudioBuffer(data: NSData) -> AVAudioPCMBuffer {
    let audioFormat = AVAudioFormat(commonFormat: .pcmFormatFloat32, sampleRate: 44100, channels: 1, interleaved: false)
    let audioBuffer = AVAudioPCMBuffer(pcmFormat: audioFormat, frameCapacity: UInt32(data.length) / audioFormat.streamDescription.pointee.mBytesPerFrame)
    audioBuffer.frameLength = audioBuffer.frameCapacity
    let channels = UnsafeBufferPointer(start: audioBuffer.floatChannelData, count: Int(audioBuffer.format.channelCount))
    data.getBytes(UnsafeMutableRawPointer(channels[0]) , length: data.length)
    return audioBuffer
}

How to send NSData over an OutputStream

Pretty sure you want to replace this:

let length = self.inputStream!.read(&buffer, maxLength: buffer.count)
let data = NSData.init(bytes: buffer, length: buffer.count)

With

let length = self.inputStream!.read(&buffer, maxLength: buffer.count)
let data = NSData.init(bytes: buffer, length: length)

Also, I am not 100% sure that the random blocks of data will always be ok to use to make the audio buffers. You might need to collect up the data first into a bigger block of NSData.

Right now, since you always pass in blocks of 8192 (even if you read less), the buffer creation probably always succeeds. It might not now.

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