I have a fundamental misunderstanding of the filter system in gnuradio. I
would appreciate some help. I wrote a simple C++ testbench to help me
figure out what's going on, but it continues to not behave as I expect. I
am using fir_filter_fff with 29 taps that I set. I send an impulse into the
filter and want to see the filter taps at the output in response. The first
sample that comes out is correct, but every sample after the first is
either the smallest or largest number representable by float. The code that
does this is below.
float impulse[29] =
{1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}; // 29 samples
long
float filter_taps[29] = {0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1} //
input to filter
shape_filter = new gr::filter::kernel::fir_filter_fff(1, filter_taps);
for(int i = 0; i < 29; i++) {
filter_out[i] = shape_filter->filter(&impulse[i]);
}
Printing filter_out to the screen produces:
0.1 0 8.12753e-44 1.61149e-43 -4.16205e-20 -8.32411e-20
-1.24862e-19 -1.66482e-19 1.13358e+21
When I expect to see
0.1 0.2 0.3 0.4 etc.., the taps of the filter that I set above
You can see only the first output matches the expected.
*What am I doing wrong here?*
Thanks,
Rich
On Wed, Aug 19, 2015 at 12:02 PM, Richard Bell <[email protected]>
wrote:
> That fixed the problem. Thank you.
>
> Rich
>
> On Wed, Aug 19, 2015 at 11:56 AM, Tom Rondeau <[email protected]> wrote:
>
>> On Wed, Aug 19, 2015 at 2:17 PM, Richard Bell <[email protected]>
>> wrote:
>>
>>> I'm having some trouble getting my code to compile. I get the following
>>> error:
>>>
>>> error: ‘kernel’ does not name a type
>>> kernel::fir_filter_ccf *d_shape_filter;
>>>
>>> To my *_impl.h file I added the following:
>>> #include <gnuradio/filter/fir_filter.h>
>>>
>>> private:
>>> kernel::fir_filter_ccf *d_shape_filter;
>>>
>>> To my CMakeLists.txt file I added FILTER to the dependency list:
>>> set(GR_REQUIRED_COMPONENTS RUNTIME FILTER)
>>>
>>> I'm not sure where to go from here. What else needs to happen to call
>>> kernel::fir_filter_ccf?
>>>
>>> Thanks,
>>> Rich
>>>
>>
>>
>> Probably a namespace issue. You've included the fir_filter.h, I'm
>> assuming. Now, instead of referencing it as "kernel::fir_filter_ccf" use
>> the full namespace "gr::filter::kernel::fir_filter_ccf".
>>
>> Tom
>>
>>
>>
>>> On Wed, Aug 19, 2015 at 9:39 AM, Richard Bell <[email protected]>
>>> wrote:
>>>
>>>> Thank you Jeff. Those are perfect.
>>>>
>>>> Rich
>>>>
>>>> On Tue, Aug 18, 2015 at 3:34 PM, Jeff Long <[email protected]> wrote:
>>>>
>>>>> Rich,
>>>>>
>>>>> hilbert_fc.cc and filter_delay_fc both use kernel::fir_filter in a
>>>>> relatively easy to understand way.
>>>>>
>>>>> Jeff
>>>>>
>>>>>
>>>>> On 08/18/2015 04:26 PM, Richard Bell wrote:
>>>>>
>>>>>> Hi all,
>>>>>>
>>>>>> Would someone please recommend a good starting point in C++ source
>>>>>> code
>>>>>> that demonstrates how one uses the kernel::fir_filter. I started
>>>>>> following the pfb_clock_sync method of implementing it, but then
>>>>>> realized this had been customized a bit for the polyphase approach.
>>>>>>
>>>>>> I'm not doing anything fancy, I'm building a modulator and need to
>>>>>> pass
>>>>>> symbols through a shaping filter. The shaping filter is what I need
>>>>>> the
>>>>>> FIR filter for.
>>>>>>
>>>>>> Appreciated,
>>>>>> Rich
>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> Discuss-gnuradio mailing list
>>>>>> [email protected]
>>>>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>>>>>>
>>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Discuss-gnuradio mailing list
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>>>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>>>>>
>>>>
>>>>
>>>
>>> _______________________________________________
>>> Discuss-gnuradio mailing list
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>>>
>>>
>>
>
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