Offline audio render with AudioKit for iOS < 11

Question

I have 4 AKPlayer nodes and each one is connected to some effects and finally they are mixed together. I want to render offline the output for iOS > 9.0 but I can't figure out how.

edit : I have implemented the render and separated it for iOS >11 While iOS>11 renderToFile seems to do well, but for iOS <11 the rendered file has some lags and jumps forward at some seconds, resulting silent in the end.

here is my render function :

do{
    if #available(iOS 11, *) {
        let outputFile = try AKAudioFile(forWriting: url, settings: [:])
        _ = AudioKit.engine.isRunning
        try AudioKit.renderToFile(outputFile, duration: karaPlayer.duration, prerender: {
            self.seekTo(time: 0)
        })
    }else {
        let offlineNode = AKOfflineRenderNode(self.mixer)
        AudioKit.output = offlineNode
        offlineNode.internalRenderEnabled = false
        try AudioKit.start()    
        self.seekTo(time: 0)
        try offlineNode.renderToURL(url, duration: self.karaPlayer.duration)
        self.karaPlayer.stop()
        self.voicePlayer.stop()
        offlineNode.internalRenderEnabled = true    
    }
} catch {
    print(error)
    print("Couldn't render output file")
}

mixer's inputs are 2 AKPlayer Nodes that read from a ".caf" file.

What have you tried? It's best to provide a [minimal, complete, and verifiable example](https://stackoverflow.com/help/mcve). — Jerod Johnson, May 08 '18 at 16:38
@JerodJohnson I have tried AKOfflineRenderNode but it is not supporting iOS < 11.0 — Whotan, May 08 '18 at 16:43

score 4 · Answer 1 · answered May 09 '18 at 05:55

If you want to use iOS11+ you can use AudioKit's render to file:

/// Render output to an AVAudioFile for a duration.
///     - Parameters
///         - audioFile: An file initialized for writing
///         - seconds: Duration to render
///         - prerender: A closure called before rendering starts, use this to start players, set initial parameters, etc...
///
@available(iOS 11.0, macOS 10.13, tvOS 11.0, *)
public func renderToFile(_ audioFile: AVAudioFile, seconds: Double, prerender: (() -> Void)? = nil) throws {

If you need support for iOS9+ use AKOfflineRenderNode's render to URL function:

@available(iOS, obsoleted: 11) @available(tvOS, obsoleted: 11) @available(macOS, obsoleted: 10.13) open class AKOfflineRenderNode: AKNode, AKComponent, AKInput {

public typealias AKAudioUnitType = AKOfflineRenderAudioUnit
public static let ComponentDescription = AudioComponentDescription(effect: "mnrn")
private var internalAU: AKAudioUnitType?

open var internalRenderEnabled: Bool {
    get { return internalAU!.internalRenderEnabled }
    set { internalAU!.internalRenderEnabled = newValue }
}

open func renderToURL(_ url: URL, seconds: Double, settings: [String: Any]? = nil) throws {
    return try internalAU!.render(toFile: url, seconds: seconds, settings: settings)
}

I have edited my question, would be great if you take a look at @Aurelius — Whotan, Jun 10 '18 at 14:30

Offline audio render with AudioKit for iOS < 11

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