On Tue, Jun 24, 2014 at 2:15 PM, Andy Walls <[email protected]> wrote:
> Hi, > > I have a Polyphase Arbitrary Resampler block in a flow graph and I want > to set the "Sample Delay" parameter so GnuRadio delays tags properly. > > With the following parameters: > > Input Sample Rate: Fs > Resampling Rate: r = output_rate / Fs > Number of Filters: N > Taps: taps=firdes.low_pass_2(N, N*Fs, ..., ..., ...,) > > The best I can figure is to set: > > Sample Delay: int(round((math.ceil(len(taps)/N) - 1.0)/2.0)) > > because GnuRadio applies this "Sample Delay" as offset to the tags > before scaling the tag offsets by the resampling rate r. > > Can anyone confirm this is correct, or is there something I'm missing? > > Thank you. > > Regards, > Andy > Andy, Take a look at pfb_arb_resampler.cc. In the constructor, it calculates the sample delay. It's close to what you're thinking, but scaled for the polyphase filterbank partitioning. Tom
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