Using AVAudioEngine to schedule sounds for low-latency metronome

Question

I am creating a metronome as part of a larger app and I have a few very short wav files to use as the individual sounds. I would like to use AVAudioEngine because NSTimer has si

Answer 1

I was able to make a buffer containing sound from file and silence of required length. Hope this will help:

// audioFile here – an instance of AVAudioFile initialized with wav-file
func tickBuffer(forBpm bpm: Int) -> AVAudioPCMBuffer {
    audioFile.framePosition = 0 // position in file from where to read, required if you're read several times from one AVAudioFile
    let periodLength = AVAudioFrameCount(audioFile.processingFormat.sampleRate * 60 / Double(bpm)) // tick's length for given bpm (sound length + silence length)
    let buffer = AVAudioPCMBuffer(PCMFormat: audioFile.processingFormat, frameCapacity: periodLength)
    try! audioFile.readIntoBuffer(buffer) // sorry for forcing try
    buffer.frameLength = periodLength // key to success. This will append silcence to sound
    return buffer
}

// player – instance of AVAudioPlayerNode within your AVAudioEngine
func startLoop() {
    player.stop()
    let buffer = tickBuffer(forBpm: bpm)
    player.scheduleBuffer(buffer, atTime: nil, options: .Loops, completionHandler: nil)
    player.play()
}