I have an AVMutableAudioMix and use MTAudioProcessingTap to process the audio data.But After I pass the buffer to AVAudioEngine and to render it with renderOffline,the audio has no any effects...How can I do it? Any idea?
Here is the code for MTAudioProcessingTapProcessCallback
var callback = MTAudioProcessingTapCallbacks(version: kMTAudioProcessingTapCallbacksVersion_0, clientInfo:UnsafeMutableRawPointer(Unmanaged.passUnretained(self.engine).toOpaque()), init: tapInit, finalize: tapFinalize, prepare: tapPrepare, unprepare: tapUnprepare) { tap, numberFrames, flags, bufferListInOut, numberFramesOut, flagsOut in
guard MTAudioProcessingTapGetSourceAudio(tap, numberFrames, bufferListInOut, flagsOut, nil, numberFramesOut) == noErr else {
preconditionFailure()
}
let storage = MTAudioProcessingTapGetStorage(tap)
let engine = Unmanaged<Engine>.fromOpaque(storage).takeUnretainedValue()
// render the audio with effect
engine.render(bufferPtr: bufferListInOut,numberOfFrames: numberFrames)
}
And here is the Engine code
class Engine {
let engine = AVAudioEngine()
let player = AVAudioPlayerNode()
let pitchEffect = AVAudioUnitTimePitch()
let reverbEffect = AVAudioUnitReverb()
let rateEffect = AVAudioUnitVarispeed()
let volumeEffect = AVAudioUnitEQ()
let format = AVAudioFormat(commonFormat: .pcmFormatFloat32, sampleRate: 44100, channels: 2, interleaved: false)!
init() {
engine.attach(player)
engine.attach(pitchEffect)
engine.attach(reverbEffect)
engine.attach(rateEffect)
engine.attach(volumeEffect)
engine.connect(player, to: pitchEffect, format: format)
engine.connect(pitchEffect, to: reverbEffect, format: format)
engine.connect(reverbEffect, to: rateEffect, format: format)
engine.connect(rateEffect, to: volumeEffect, format: format)
engine.connect(volumeEffect, to: engine.mainMixerNode, format: format)
try! engine.enableManualRenderingMode(.offline, format: format, maximumFrameCount: 4096)
reverbEffect.loadFactoryPreset(AVAudioUnitReverbPreset.largeRoom2)
reverbEffect.wetDryMix = 100
pitchEffect.pitch = 2100
try! engine.start()
player.play()
}
func render(bufferPtr:UnsafeMutablePointer<AudioBufferList>,numberOfFrames:CMItemCount) {
let buffer = AVAudioPCMBuffer(pcmFormat: format, frameCapacity: 4096)!
buffer.frameLength = AVAudioFrameCount(numberOfFrames)
buffer.mutableAudioBufferList.pointee = bufferPtr.pointee
self.player.scheduleBuffer(buffer) {
try! self.engine.renderOffline(AVAudioFrameCount(numberOfFrames), to: buffer)
}
}
}
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