slowing down speeding up a realtime stream?
I could not sleep. So I developed the impossible. Slowing down and speeding up a realtime audio stream…
What is so special with that???
Well, If you have a file in memory, you easily can slow down and speed up that by just playing it slower or faster, like with a sampler. But this won‘t work with a realtime audio stream (i.e. as an AudioUnit effect processor). Because you merely get a super small block of audio data for the DSP per cycle and the progress is unknown, you cannot look into future. And you also can't force the host producing discontinuity in fundamental time and sample rate - with other words, an audio unit cannot tell the host to change the tempo or its sample rate or pitch, it‘s technically and conceptionally not even possible… do you actually see the problem here?
But I did it . Anyhow .
The trick is just a latency that is short enough and at same time large enough to emulate speed down and speed up effects (like scratching a Vinyl) on a realtime stream. Theoretically I even could keep the pitch constant with some other trick too ...
I do not even know, whether this would be of any interest or is possible to put into a finished product. ^^
PLEASE note that we offer 2 different and widely underrated realtime pitch shifters as AUv3 units, available for years now. A time domain pitch shifter and a frequency domain pitch shifter, which both are fundamentally different in tech and sound.