I am doing realtime audio. Let's say I have a signal $x(n)$ which is passed in blocks of 512 (siobuffer) to the program filter/FFT method. Within this block I want to convolve the signal with the filter $u(n)$ (impulse response) of length 8192K. So I zero pad the asio block from 513 to 8192K, do FFT of both arrays and multiply the results. After IFFT, I get the convolved signal $y(n)$ of length 8192K which I want to pass to the output asio buffer (lets say of length 512, too).
Now comes my problem: how much overlap-add to use? From my understanding, I must overlapp add the whole 8192K to the last byte, no? This means I divide $y(n)$ of 8192 by 512 into 16 blocks and subsequently overlapp-add all those 512 blocks to the next processed input blocks. When I read about overlap add in general, there are always examples where people have outputs $y(n)$ just a little longer than the input, so they normally overlap add approximately 1.5 of a imputblock.
Is there a mistake in my thoughts? Do I just need to overlapp add parts of $y(n)$, or must I overlap add all my 16 blocks each time?