AppleSequencer export m4a format file error When use Audiokit? - audiokit

Question

I am a newbie to swift developer, I am now trying to make some music apps. I have been using audiokit frameworks to solve some audio problems. Audiokit is very helpful to me. I use AppleSequencer to initialize the audio and complete the correct playback.
But now I have some problems. Specifically, when I export the file using engine.renderToFile, I get a noise file.
The following is the main code part, I also uploaded the relevant code to the github address:https://github.com/devlong/sequenceExport.git
import AudioKit
import AVFoundation
class SequenceExport: NSObject {
static let shared = SequenceExport.init()
private override init(){}
var mixer = Mixer();
var sequencer : AppleSequencer?
var engine = AudioEngine()
var currentMidiSample:MIDISampler?
var track : MusicTrackManager?
func setCurrentSequencer() {
let instrumentName = "edm-kit"
currentMidiSample = MIDISampler.init(name: instrumentName)
engine.output = currentMidiSample;
do {
try engine.start()
} catch {
Log("AudioKit did not start \(error)")
}
let directory = "Sounds/\(instrumentName)"
let resetPath = Bundle.main.path(forResource:instrumentName, ofType: "aupreset", inDirectory: directory)
do{
try currentMidiSample!.loadPath(resetPath!)
}catch let error {
print("************load resetPath error!!!!!!:\(error)")
}
sequencer = AppleSequencer(filename: "tracks")
track = sequencer!.newTrack()
for index in 0...4 {
track!.add(
noteNumber:MIDINoteNumber(5+index),
velocity: 100, //调节单个音符声音
position: Duration.init(beats: Double(index)),
duration: Duration.init(seconds: 0.5))
}
sequencer!.setGlobalMIDIOutput(currentMidiSample!.midiIn)
sequencer!.setTempo(120)
sequencer!.setLength(Duration.init(beats: 4))
sequencer!.enableLooping()
sequencer!.play()
}
func exportM4a() {
guard let outputURL = try? FileManager.default.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: false).appendingPathComponent("audio_file_new.m4a") else { return }
print("outputURL !!!!!!:\(outputURL)")
guard let format = AVAudioFormat(commonFormat: .pcmFormatFloat32, sampleRate: 44100, channels: 0, interleaved: true) else {
fatalError("Failed to create format")
}
let file = try! AVAudioFile(forWriting: outputURL, settings: format.settings)
do{
try engine.renderToFile(file, maximumFrameCount: 1_096, duration: 5) {
self.sequencer!.play()
} progress: { progress in
// print("progress !!!!!!:\(progress)")
}
}catch let error {
print("export !!!!!!:\(error)")
}
}
}
I tried to find many ways. Audiokit has a way to export mid format, but this is not my requirement. I need to find out how to export m4a, mp3 and other format files from AppleSequencer. Can anyone help me?
If anyone has a way, I hope to help me make changes in the github code, which will help more people who encounter such problems.
I have uploaded the code to the address:https://github.com/devlong/sequenceExport.git

Answer 1

I think that AppleSequencer just won't run in outside of a real time context, so nothing happens when you try to use renderToFile. You could use a NodeRecorder to recorder the track as its being played, but that would be in real time, not super fast.