AVAudioEngine警告:"不推荐使用Carbon Component Manager来托管音频单元"

Question

我正在为Mac编写我的第一个音频应用程序,它加载外部音频单元并使用它通过AVAudioEngine实例播放声音,我一直看到这个警告:

警告:140:此应用程序或其使用的库正在使用已弃用的Carbon Component Manager来托管Audio Units.将来的版本中将删除对此的支持.此外,这使主机与版本3音频单元不兼容.请转到AudioComponent.h中的API.

我已经从使用AVAudioUnitComponents转换到AudioComponents(现在通过这个api访问),我希望能解决这个问题,但是当我调用start()我的引擎时,我仍然会看到这个警告.

任何想法在这里出了什么问题？据我所知,我不再使用已弃用的API.AVAudioEngine是否有可能在引擎盖下使用已弃用的API？

这是我正在使用的代码的片段.我正在调用selectInstrument我使用AudioComponents API检索的描述.

public func selectInstrument(withDescription description: AudioComponentDescription, callback: @escaping SelectInstrumentCallback) {
    AVAudioUnit.instantiate(with: description, options: []) { avAudioUnit, error in
        guard let unit = avAudioUnit else {
            callback(nil)
            return
        }

        self.disconnectCurrent()
        self.connect(unit: unit)

        unit.auAudioUnit.requestViewController { viewController in
            callback(viewController)
        }
    }
}

private func disconnectCurrent() {
    guard let current = currentInstrument else { return }
    self.engine.disconnectNodeInput(engine.mainMixerNode)
    self.engine.detach(current)
    self.currentInstrument = nil
    self.engine.stop()
}

private func connect(unit: AVAudioUnit) {
    let hardwareFormat = self.engine.outputNode.outputFormat(forBus: 0)
    self.engine.connect(self.engine.mainMixerNode, to: self.engine.outputNode, format: hardwareFormat)
    self.engine.attach(unit)
    do {
        try ExceptionCatcher.catchException {
            let stereoFormat = AVAudioFormat(standardFormatWithSampleRate: hardwareFormat.sampleRate, channels: 2)
            self.engine.connect(unit, to: self.engine.mainMixerNode, format: stereoFormat)
        }
    } catch {
        let monoFormat = AVAudioFormat(standardFormatWithSampleRate: hardwareFormat.sampleRate, channels: 1)
        self.engine.connect(unit, to: self.engine.mainMixerNode, format: monoFormat)
    }

    unit.auAudioUnit.contextName = "Running in AU host demo app"
    self.currentInstrument = unit

    do {
        // Carbon Component Manager warning issued here:
        try self.engine.start()
    } catch {
        print("Failed to start engine")
    }
}

谢谢你的帮助!