Hi Dirk, this is more of a general DSP question than a GNU Radio question:
How do these filters relate to each other? My gut feeling is that this gets a lot easier as soon as you tell us why you're doing this, i.e. for what purpose :) Best regards, Marcus On 11.03.2017 19:28, Dirk Gorissen wrote: > Hello all, > > Given a stream of samples I would like to apply n slightly different > filters to it with n being able to be chosen at runtime. Then combine > the results back to a single stream. > > As a test I built a flowgraph with the following chains in parallel for n = 6 > > | -> decimating fir filter 1 -> complex to mag -> | > stream -> | -> decimating fir filter 2 -> complex to mag -> | -> Max -> > ... > | .... > | > | -> decimating fir filter n -> complex to mag -> | > > So the same stream is sent to each chain (decimation is 1) and the > output of each chain is pushed through a big Max block with 6 inputs. > > This works but not particularly elegant and a bit annoying to change > if I suddenly decide I want to change n. In particular it also does > not seem computationally efficient. > > What I would like is to replace the above by a single block that > > - replicates the input n times > - applies each filter on each replica > - combines the output again to a single stream > - have a tunable n parameter > - is fast > > I did this with an Embedded python block doing essentially this: > > for i in range(n): > out[i] = scipy.signal.lfilter(taps[i], 1, input) > > This is using exactly the same taps as in the chain case. This works > but the output is different and worse than what I get with the > separate chains. As a test, instead of lfilter I tried: > > gnuradio.filter.fir_filter_ccc(1,taps[i]).work(input[0],output) > > Thinking perhaps that is a closer replica. But couldnt get it to work.. > > I suspect there should be an easy / natural way of doing this in > gnuradio. Looked at the filter bank / channelliser blocks but failed > to get anywhere. > > So what is the best way forward to do this? > > Many thanks > Dirk > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
