Currently the audio task shares the same memory space for input and output. That means that if Julia is busy (for instance the JIT is compiling something) and so the callback isn't running, the input just gets fed back to the output, so you hear an echo and feedback.
So far this is confirmed on OSX, not sure if it happens on Linux as well. It probably depends on what the underlying audio system does when the audio deadline is missed.
Currently the audio task shares the same memory space for input and output. That means that if Julia is busy (for instance the JIT is compiling something) and so the callback isn't running, the input just gets fed back to the output, so you hear an echo and feedback.
So far this is confirmed on OSX, not sure if it happens on Linux as well. It probably depends on what the underlying audio system does when the audio deadline is missed.