Hi, in the rfft (as opposite to the fft) the missing dataset is supposed to be 0, that means if you think of a stereo channel as input, the second channel does not contain data/is muted. the missing data it is not related to time or index. the information in both domains (time and frequency) is always exact the same. marius.
Frank Barknecht wrote: > Hallo, > hard off hat gesagt: // hard off wrote: > >>>> cos^2+sin^2=1 >> ah! >> >> so, actually the FFT doesn't HAVE to use imaginary numbers....but they >> are just used because "the complex-number system is >> two-dimensional and that signals to be analysed are presumed to be >> two-dimensional. They are decomposable into a sum of circular >> trajectories" >> >> every day a bit more of this falls into place. > > An interesting thing to note is that the rfft outputs two signals, > where seemingly only one signal comes in. How can that be? Actually > what comes into the rfft object are two values as well: One is the > usual signal amplitude visible as a patch cord, and the other is: > time! > > Time is not visible in Pd, it's just there and normally always walks > on. But inside of a FFT-subpatch, time is frozen for the duration of a > block (or rather: the "current time" is assumed to be infinite or > eternal) to allow calculating a different representation: the > frequency domain representation. If you think about this freezing of > time for too long this is actually quite mind-blowing as well. > > Ciao _______________________________________________ [email protected] mailing list UNSUBSCRIBE and account-management -> http://lists.puredata.info/listinfo/pd-list
