I would like to process 12 to 20 seconds of incoming audio at a sample rate of 44100. I must process this audio in real time in an STM embedded kit (perhaps also an Android Smartphone). I'm trying to detect and count the number of occurrences of a signal of roughly 6500 samples inside the incoming audio. The maximum FFT available is of 1024 samples.
I was thinking about applying overlap-add but the number of coefficients would be 6500 and that's larger than maximum FFT size of 1024. I tried to simulate this in Matlab using fftfilt but the function help says:
If you supply a value for n, fftfilt chooses an FFT length, nfft, of 2^nextpow2(n)and a data block length of nfft - length(b) + 1. If n is less than length(b), fftfilt sets n to length(b).
This makes me think that I'm forced to use an FFT of at least 6500 samples (which I can't) and then process 1 incoming audio sample at a time (super inefficient).
What can I do?