CODEWITHSUNDEEP
swiftxcodeavaudioengineavkit
Michael Jajou
Michael Jajou

Reputation: 392

Writing Buffer from AVAudioNodeTap to AVAudioFile (Save audio recording from AVAudioEngine)

I am using AVAudioEngine to monitor microphone input. After the AudioEngine stops I would like to save the audio received into an AVAudioFile for future use.

This is my current implementation, and the file does contain data. It is a wav file, but it is not a playable audio file. I am thinking there may be something wrong in my formatting, here is my approach.

    private enum Setting {
        static let formatID = Int(kAudioFormatLinearPCM)
        static let sampleRate = 16000
        static let numberOfChannels = 1
        static let encoderQuality = AVAudioQuality.min.rawValue
    }

    private let settings: [String: Any] =
        [AVFormatIDKey: Setting.formatID,
         AVSampleRateKey: Setting.sampleRate,
         AVLinearPCMIsFloatKey: true,
         AVNumberOfChannelsKey: Setting.numberOfChannels,
         AVEncoderAudioQualityKey: Setting.encoderQuality]


    func record() {
        let mixer = AVAudioMixerNode()
        audioEngine.attach(mixer)
        let format = AVAudioFormat(settings: settings)
        audioEngine.connect(audioEngine.inputNode, to: mixer, format: audioEngine.inputNode.inputFormat(forBus: 0))
        audioEngine.connect(mixer, to: audioEngine.outputNode, format: format)
        
    guard let destinationURL = FileManager.default.whs_generateWAVFile() else { return }
        do {
            file = try AVAudioFile(forWriting: destinationURL, settings: mixer.outputFormat(forBus: 0).settings, commonFormat: .pcmFormatFloat32, interleaved: true)
            mixer.installTap(onBus: 0, bufferSize: 1024, format: mixer.outputFormat(forBus: 0)) { (buffer, time) in
                do { try self.file?.write(from: buffer); print("Wrote \(buffer)") } catch { print("Error: \(error)") }
            }
            audioEngine.prepare()
            do { try audioEngine.start() } catch { print("Big error:  \(RecordingError.audioEngineStart.description)"); return }
        } catch {
            print("Big Error:  \(RecordingError.audioEngineStart.description), \(error)")
        }
    }

Upvotes: 2

Views: 1504

Answers (1)

martinjbaker
martinjbaker

Reputation: 1484

It's because you haven't closed the AVAudioFile you're recording to. Set file to nil when stopping the engine and the wav file will be playable.

Upvotes: 2

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