I think the PFB FIR is not a reversible process. It sums samples and decimates, so that you have fundamentally lost the information that would be required to recover the input time series. However, as Gerry points out, it is possible to invert just the FFT component, leaving what is essentially a windowed time series that not unrelated to the original time series.
Aaron On Mon, Dec 8, 2014 at 10:15 AM, Jonathan Weintroub < [email protected]> wrote: > Hi Gerry, > > I am glad someone is interested in this. To be clear we have a need for > an inverse PFB, but have not developed one ourselves—no where near to ready > to publish. ;) Our take was the “step by step” was needed, inverse FFT > followed by FIR, and that probably it would not be entirely trivial. While > inverse FFT itself is rather simple. > > I put the question to the list serve in the hope someone has already > worked on this. I hereby bump this up, perhaps this is a better time to do > so, compared to Friday afternoon. > > Jona > > > > On Dec 5, 2014, at 7:12 PM, Gerry Harp <[email protected]> wrote: > > > > Hi Jonathan > > > > This is interesting. Is an inverse PFB is just a PFB using an inverse > FFT? That should be very close by possibly not bit-perfect inversion. > > > > Or are you considering a step-by-step inverse of the PFB algorithm? I'm > interested because there are traps. Small numerical errors are magnified > when you compute the inverse FIR filter on the data after inverse FFT. At > least I think so. > > > > I'd be interested in your implementation of the inverse PFB. You should > publish it. > > > > Thanks > > > > Gerry > > > > The reason I'm asking is that if you lose any > > > > On 05-Dec-14 01:36 PM, Jonathan Weintroub wrote: > >> Hello CASPERites, > >> > >> Has anyone implemented an _inverse_ PFB? That is a block taking > channelized PFB data and reproducing the original time series. > >> > >> If so, is the code/mdl/yellow block available? > >> > >> Thanks, > >> > >> Jonathan > >> > >> > >> > > > > > -- Aaron Parsons 510-406-4322 (cell) Campbell Hall 523, UCB
