Complex FIR and Stereo support for rtl_fm

Miroslav Slugeň thunder.m at email.cz
Mon Sep 16 09:38:18 UTC 2013


Hi, i used git from 14.9.2013, if you get errors from actual git it 
could be because some functions might go into upstream, i also add as 
attachment just rtl_fm.c so just replace it your version with this 
version and it should work.

I have RDS decoder also, but it is very ugly and not all issues are solved.

Miroslav Slugeň
+420 724 825 885

Michał Morański napsal(a):
> W dniu 2013-09-13 15:22, Miroslav Slugeň pisze:
>> Hi again,
>>
>> I am working on my own SDR project for Stereo FM radio support, but i
>> would like to also improve quality for rtl_fm application, i made
>> unoficial patch to add:
>>
>> Complex FIR - to filter strong signals close to wanted signal
>> Real FIR - to filter pilot from FM
>> Stereo FIR
>> Stereo Deemphasis
>> AGC support - it can give better resolution of IQ data
>>
>> Some other improvments in FM radio code.
>>
>> All FIR filters has 3 possible variants, simple, LUT, SSE2 instricts,
>> of course SSE is the fastest one and it should works on Intel Atoms,
>> but not on ARM.
>>
>> Feel free to use any part of code in any of you programs, I know that
>> this code is little to much to add it into rtl_fm, but maybe it could
>> somebody help to recieve HW stereo FM radio.
>>
>> Speed of SSE code is much better than anything you can get around
>> here, on Core i7 it consume only 5% of one CPU, so i could demodulate
>> at least 80 channels at the same time in stereo quality of course.
>>
>> I tried this code only on AMD64 and GCC Linux, so i am not sure if it
>> can be compiled under windows.
>>
> Hi! Very nice to hear, that someone working on Stereo FM reception. I'm
> building a small remote devices with rtl-dongles as fm stereo receivers.
> Now i'm using gnu-radio to decode fm-stereo, but as you all know,
> gnu-radio is a large and heavy project and it's wasting its
> capatibilities in that role.
> It would be very nice if native rtl-sdr software can decode fm-stereo.
>
> Which version of rtl-sdr was used as base version? I'm getting errors
> after applying the patch to last version:
>
> patching file rtl_fm.c
> Hunk #2 succeeded at 47 (offset 5 lines).
> Hunk #3 succeeded at 87 (offset 9 lines).
> Hunk #4 succeeded at 144 (offset 9 lines).
> Hunk #5 succeeded at 169 (offset 9 lines).
> Hunk #6 succeeded at 190 (offset 9 lines).
> Hunk #7 FAILED at 239.
> Hunk #8 FAILED at 258.
> Hunk #9 succeeded at 314 (offset 13 lines).
> Hunk #10 succeeded at 420 (offset 13 lines).
> Hunk #11 succeeded at 994 (offset 13 lines).
> Hunk #12 FAILED at 1106.
> Hunk #13 succeeded at 1148 (offset 15 lines).
> Hunk #14 succeeded at 1259 (offset 35 lines).
> Hunk #15 succeeded at 1268 (offset 35 lines).
> Hunk #16 succeeded at 1290 (offset 35 lines).
> Hunk #17 succeeded at 1301 with fuzz 2 (offset 36 lines).
> Hunk #18 succeeded at 1351 (offset 38 lines).
> Hunk #19 succeeded at 1378 (offset 38 lines).
> Hunk #20 succeeded at 1389 (offset 38 lines).
> Hunk #21 succeeded at 1508 (offset 50 lines).
> Hunk #22 succeeded at 1527 (offset 50 lines).
> 3 out of 22 hunks FAILED -- saving rejects to file rtl_fm.c.rej
>
> P.S. Are you planning to add support for RDS in the future?
>
> Regards, Michał.
>
>
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