ZBSimpleRecorder.swift

import UIKit
import AVFoundation


class ZBSimpleRecorder: NSObject {

    var audioEngine: AVAudioEngine?
    var file: ExtAudioFileRef?

    func start(fileURL:URL) {
        self.stop()

        func M4aFormat() -> AudioStreamBasicDescription {
            return AudioStreamBasicDescription(mSampleRate: 44100,
                                               mFormatID: kAudioFormatMPEG4AAC,
                                               mFormatFlags: AudioFormatFlags(MPEG4ObjectID.aac_Main.rawValue),
                                               mBytesPerPacket: 0,
                                               mFramesPerPacket: 1024,
                                               mBytesPerFrame: 0,
                                               mChannelsPerFrame: 2,
                                               mBitsPerChannel: 0,
                                               mReserved: 0)
        }

        audioEngine = AVAudioEngine()
        guard let audioEngine = audioEngine else {
            return
        }

        let audioSession = AVAudioSession.sharedInstance()
        try? audioSession.setCategory(AVAudioSessionCategoryRecord)
        try? audioSession.setMode(AVAudioSessionModeVoiceChat)
        try? audioSession.setActive(true, with: .notifyOthersOnDeactivation)

        guard let inputNode = audioEngine.inputNode else { fatalError("Audio engine has no input node") }
        let recordingFormat = inputNode.outputFormat(forBus: 0)

        var outputFormat = M4aFormat()
        var status = noErr
        status = ExtAudioFileCreateWithURL(fileURL as CFURL, kAudioFileM4AType, &outputFormat, nil, AudioFileFlags.eraseFile.rawValue, &file)
        assert(status == noErr)
        var codecManufacturer = kAppleSoftwareAudioCodecManufacturer
        status =  ExtAudioFileSetProperty(file!, kExtAudioFileProperty_CodecManufacturer, UInt32(MemoryLayout<UInt32>.size), &codecManufacturer)
        assert(status == noErr)
        status =  ExtAudioFileSetProperty(file!, kExtAudioFileProperty_ClientDataFormat, UInt32(MemoryLayout<AudioStreamBasicDescription>.size), recordingFormat.streamDescription)
        assert(status == noErr)

        inputNode.installTap(onBus: 0, bufferSize: 1024, format: recordingFormat) { (buffer: AVAudioPCMBuffer, when: AVAudioTime) in
            let numberOfFrames = buffer.frameLength
            let audioBufferList = buffer.audioBufferList
            let status = ExtAudioFileWrite(self.file!, numberOfFrames, audioBufferList)
            assert(status == noErr)
        }

        audioEngine.prepare()
        try? audioEngine.start()
    }

    func stop() {

        guard let audioEngine = audioEngine else {
            return
        }

        let audioSession = AVAudioSession.sharedInstance()
        try? audioSession.setActive(false, with: .notifyOthersOnDeactivation)

        if let file = file {
            ExtAudioFileDispose(file)
            self.file = nil
        }

        audioEngine.stop()

    }

}