Audio Recording With Timeout Swift

Question

I'm using AVAudioEngine to record audio in my iOS app. I want to stop the recording automatically if there is no audio input for a specified duration (e.g., 5 seconds). How can I achieve this?

Here is the code I have so far for starting the recording:

 func startRecording() throws {
 guard let engine = self.audioEngine, let mic = mic else { return }
 let micFormat = mic.inputFormat(forBus: 0)
 self.state = .recording
 let startTime = DispatchTime.now()
 mic.installTap(onBus: 0, bufferSize: 4096, format: micFormat) { (buffer, when) in
 // Data(buffer: buffer, time: when)
 let sampleData = UnsafeBufferPointer(start: buffer.floatChannelData![0], count: Int(buffer.frameLength))
 // print(buffer)
 let currentTime = DispatchTime.now()
 let elapsedTime = currentTime.uptimeNanoseconds - startTime.uptimeNanoseconds
 let timeout = 5
 let isFinal = elapsedTime > timeout * 1_000_000_000
 self.baseData = buffer.data().base64EncodedString()
 if isFinal {
 self.stopRecording()
 }
 }
 if engine.isRunning { return }
 try engine.start()
 }

i believe there should be something that i need to do in that install tap closure but not sure how.

Answer 1

To stop the recording automatically after a specified period of silence (e.g., 5 seconds) using AVAudioEngine, you need to monitor the audio buffer’s amplitude level and detect if the audio input level stays below a certain threshold (silence threshold) for the specified duration.

func startRecording() throws {
 guard let engine = self.audioEngine, let mic = mic else { return }
 let micFormat = mic.inputFormat(forBus: 0)
 let silenceThreshold: Float = 0.01 // Adjust based on what you consider silence
 let silenceTimeout: TimeInterval = 5 // 5 seconds of silence to stop recording
 var silenceStartTime: TimeInterval? // Tracks when silence started
 self.state = .recording
 mic.installTap(onBus: 0, bufferSize: 4096, format: micFormat) { [weak self] (buffer, _) in
 guard let self = self else { return }
 // Analyze the audio buffer
 let channelData = buffer.floatChannelData?[0]
 let frameLength = Int(buffer.frameLength)
 // Compute the RMS (Root Mean Square) to detect audio level
 let rms = channelData?.prefix(frameLength).reduce(0, { 0ドル + 1ドル * 1ドル }).squareRoot() ?? 0
 // Check if the audio level is below the silence threshold
 if rms < silenceThreshold {
 // Start counting silence duration
 if silenceStartTime == nil {
 silenceStartTime = Date().timeIntervalSince1970
 } else if let startTime = silenceStartTime,
 Date().timeIntervalSince1970 - startTime > silenceTimeout {
 // Stop recording if silence duration exceeds timeout
 DispatchQueue.main.async {
 self.stopRecording()
 }
 }
 } else {
 // Reset silence start time if audio is detected
 silenceStartTime = nil
 }
 }
 if !engine.isRunning {
 try engine.start()
 }
}
func stopRecording() {
 guard let engine = self.audioEngine else { return }
 if engine.isRunning {
 engine.stop()
 mic?.removeTap(onBus: 0)
 }
 self.state = .stopped
 print("Recording stopped due to silence.")
}