hi Aaron,
I think this depends on what you use for the filter coefficients. In
theory there are pairs of "analysis" and "synthesis" filters that let
you exactly reconstruct the original input signal. In practice I think
errors caused by quantization, overflow, etc are probably the main
source of trouble. I haven't attempted this myself, but from what I've
heard this seems to be a tricky thing to get right.. probably depends on
what exactly is going to be done with the reconstructed timeseries, what
level of artifacts are acceptable, etc.
Cheers,
Paul
On 2014-12-08 11:24, Aaron Parsons wrote:
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
>>
>>
>>
>
