On Sun, Apr 26, 2015 at 01:00:40PM -0400, Tim E. Real wrote: > Fons do you have any insight into wavelets and how they might > be better for lower latency pitch detection than FFT?
I don't think they will allow you to have better latency if all other aspects of performance are kept equal. Don't expect magic from wavelets - they can't provide information that isn't there. What they allow you to do is modify the tradeoff between resolution in time and frequency. But the product of the two is limited by the 'uncertaintly principle' in all cases: better resolution in time means less resolution in frequency and vice versa. There is no way to break this limit *unless* you make assumptions about the signal to be detected and accept failure if these are not valid. Human hearing seems to do this. In the case of a guitar signal there are some valid assumptions, e.g. the maximum number of notes and the typical exponential decay of their envelope. For the last ten years or so, a new technique called 'compressive sensing' has been a hot topic in DSP. It is being used to do all sorts of things that at first sight seem impossible, such as recovering a signal from random samples well below the Nyquist rate. It again depends on making certain assumptions about the analysed signal, in this case that there exists a 'sparse' representation of it. The whole theory behind CS is a bit counter-intuitive but mathematically perfectly sound. I'm pretty sure it will lead to some new ways to do pitch detection. Ciao, -- FA A world of exhaustive, reliable metadata would be an utopia. It's also a pipe-dream, founded on self-delusion, nerd hubris and hysterically inflated market opportunities. (Cory Doctorow) _______________________________________________ Linux-audio-dev mailing list [email protected] http://lists.linuxaudio.org/listinfo/linux-audio-dev
