I was going to add this to an existing topic, but the system discouraged me from doing so.

I am looking for some words of advice and/or consolation.

I have been trying to create a convolution reverb plugin. I was not aware of and did not use the JUCE convolution class. Instead I used the JUCE FFT engine to roll my own version of fast convolution with overlap add. The good news is that I got it to work (sort of) but I would never foist it on an unsuspecting user. If the IR exceeds a second or maybe two, it cannot meet the hard real time limit. I see the basic problem as this: the FFT size is N + B - 1 rounded up to the next power of 2, where N is the number of IR samples and B is the sample buffer size. Since N >> B, the computation time is dominated by the IR size and is nearly independent of the buffer size. However, it is the buffer size that determines the time limit. I tried combining blocks of samples into superblocks for processing and feeding a queue, but that increases latency and doesn’t really solve the real time problem. I also considered using a separate thread, but that would probably lead to unpredictable and probably bad behavior.

I originally thought that convolution was an impractical approach, but a kindly journal reviewer pointed me to references on “fast convolution”. Well, it may be practical, but with FFT orders of 19 or 20, it seems to be a bit of a stretch.