Re: [Discuss-gnuradio] Efficient notch filters

[Martin Dvh]

John Clark wrote:
> Martin Dvh schrieb:
>> ALso note that the current standard multitap IIR implementation
>> probably has a bug, (See my mail with a fix for that in the
>> mailinglist archive)
>>   
> 
> What would be the effect of this bug? I think this is used in a FFT
> application I have. So, if it is a 'serious' problem, I'd
> like to fix it... if it is a 'less that serious' problem, I can wait
> until it filters out to the main set of code...
It is hard to describe the seriousness of this bug.
See problem desciption and patch:
http://lists.gnu.org/archive/html/discuss-gnuradio/2007-07/msg00164.html
and
http://www.olifantasia.com/pub/projects/gnuradio/mdvh/mypatches/gri_iir/

I think the order in which the shifted samples are processed is wrong.
This means that the filter response would be different from that expected.
Since this code is not (much) used in the gnuradio examples it is hard to come 
up with examples.
After my patch the code does work for me.

But at the moment I only use my own specialized optimized implementation of a 
resonating IIR which is totaly unrelated to this implementation.
(Note this optimized version is not yet in svn (will be some day) and can only 
do a resonating fir not any other)

Greetings,
Martin
> 
> John Clark.
> 
>