robert bristow-johnson wrote: > anyway, while i have done this sliding Hann window before, i haven't > done it for a sliding DFT. but i would be excited to see a good > implementation of constant Q filterbank that is very close to > perfect reconstruction if the modification in the frequency domain > is null. one could make a Hann windowed DTFT evaluated at a finite > number of arbitrary frequencies. i just wonder if a sliding Hann > window would be best. but, using a truncated cosine as the impulse > response of the TIIR, whatever shape of the window would have to be > a sum of truncated cosines (plus the constant term). but you could > make a nice frequency analyzer of log-spaced, constant-Q, > filterbanks with a bank of truncated IIRs and pre-multiplying the > input to each filter by e^(-j omega n). making them add up to a > wire is a harder problem.
Isn't this pretty much what my Gaborator library (gaborator.com) does? It performs constant Q analysis using Gaussian windows, and resynthesis that reconstructs the original signal to within about -115 dB using single precision floats. It's not exactly "sliding" since the output samples of the filters are not at the original sample rate but decimated by powers of two depending on the bandwidth of each filter, but that could be seen as a feature since it means any frequency-domain modifications can run more efficiently as they have fewer samples to process. For example, if you are modifying a frequency band with a center frequency of 50 Hz and a bandwidth of 10 Hz, there is little point in running that modification at a full 44.1 or 48 kHz sample rate. -- Andreas Gustafsson, g...@waxingwave.com _______________________________________________ dupswapdrop: music-dsp mailing list music-dsp@music.columbia.edu https://lists.columbia.edu/mailman/listinfo/music-dsp
