AVAudioEngine change playback rate in real time (AVAudioUnitVarispeed is non real time)

I am using the AVAudioEngine to play back samples in an iOS game. I would like to change the play back rate of a sample in real time. When using AVAudioUnitVarispeed for chaging the play back rate it creates stutters in the game as it isn't processed in real time (as stated here:AVAudioUnitTimeEffect)

The other option I found to change the rate is by using an AVAudioEnvironmentNode and change the rate of the AVAudioPlayerNode. That works without creating stutters but limits the valid values for the rate from 0.5 to 2.0 (I need higher rates then 2.0). See here: AVAudio3DMixing.

Are there any other ways to play back a sample with a rate control in real time?

AVAudioEngine change playback rate in real time (AVAudioUnitVarispeed is non real time)
 
 
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