Hi Marcus, I tested again my problem with connecting a data file (file source) to the fir filter and read the output with the one resulted from Matlab. The error which appears due to the data precision is in acceptable order.
However, when I directly connect my tx to the fir filter, it did something strange after sometime which causes a great error with respect to the Matlab one. *I think the problem is with my tx! I really confused!! I just wanna know how could I identify the problem and how could I fix it? * My scheme: *[image: Inline image 1]* Best, Mostafa On Wed, Oct 15, 2014 at 9:03 PM, Marcus Müller <marcus.muel...@ettus.com> wrote: > Hello Mostafa, > > filtering is a inherently lossy operation: it's an operation that involves > multiplication and addition of floating point numbers. > Matlab internally uses double (float64) values, whereas GNU Radio, > usually, uses single precision (float32) numbers for performance reasons. > Now, without knowing what kind of signal you are filtering with what kind > of taps you are using with what kind of GNU Radio filters and what Matlab > functions, there's nothing to guess on how these differences occur. > What I *can* say though is that I've never seen an item drop in GNU > Radio's runtime, and we have strong tests against that. Now, it's entirely > possible that any of our filter implementations might have bugs, but I kind > of doubt that. It's most probably simply numeric accuracy that kills your > samples. > > Greetings, > Marcus > > > > On 15.10.2014 18:07, Mostafa Alizadeh wrote: > > Hi all, > > It seems this is a ridiculous question, however, I didn't find any solution > for my problem. > > I have already a bunch of custom blocks connected to each other which play > role as a transmitter (tx). I want to connect tx to a fir filter by using > fir_filter_ccc block. I set the filter taps with specific ones. I also have > this filter in Matlab. The output of the filter is connected to a sink file. > > When I see the output (tx) and filtering it by Matlab and comparing it with > the output of the gnuradio filter, I see both of the following: > > 1) Both matlab and gnuradio filtered output, have little difference in a > range of 0.01. (I'm using gr_complex data). > > 2) After a while, Matlab output and GNURadio's output will differ as high > as 1000 in magnitude!! > > I guess, there is item drops in this filtering. I know, the probability of > this event is so weak, anyway, item drop even can happen in GNURadio? > > Where is my problem? > > Best, > Mostafa > > > > > _______________________________________________ > Discuss-gnuradio mailing > listDiscuss-gnuradio@gnu.orghttps://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > -- *********************************************************** Department of Electrical Engineering Aboureyhan Building MMWCL LAB Amirkabir University Of Technology Tehran IRAN Tel: +98 (919) 158-7730 LAB: http://ele.aut.ac.ir/~mmwcl/?page_id=411 Homepage: http://ele.aut.ac.ir/~alizadeh/ ***********************************************************
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