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Re: [Discuss-gnuradio] Xlate FIR filter broken in gr 3.7


From: Andrew Davis
Subject: Re: [Discuss-gnuradio] Xlate FIR filter broken in gr 3.7
Date: Thu, 8 Aug 2013 16:01:47 -0500

Also, this change breaks a very important and very used part of hundreds of projects over the last ten years to make a variable name make slightly more since, when you could just change the variable name to 'frequency_shift' and leave the functionality the way it was.

Andrew


On Thu, Aug 8, 2013 at 3:56 PM, Andrew Davis <address@hidden> wrote:
Center frequency of the received signal or center where I want to move it to? It's not intuitive ether way, the parameter name should be changed to what it actually is: 'frequency_shift' and it should behave exactly like multiplication does, you multiply a positive frequency you get a positive shift, negative frequency, down shift by that much, simple.

Andrew


On Thu, Aug 8, 2013 at 3:45 PM, Tom Rondeau <address@hidden> wrote:
On Thu, Aug 8, 2013 at 4:37 PM, Stephen Harrison
<address@hidden> wrote:
> I agree.. the new way is more intuitive but then again it broke a bunch of
> my GRC patches.. :)
>
>
> On Thu, Aug 8, 2013 at 1:36 PM, Sylvain Munaut <address@hidden> wrote:
>>
>> Hi,
>>
>> > The "old style" version of the block in gnuradio-core in 3.6.5.1 works
>> > correctly.  The "new style" version of the block in gr-filter in 3.6.5.1
>> > has the sign change.  When all the old-style blocks were removed for
>> > 3.7, this of course left only the changed one.
>>
>> Personally I always thought that the previous block (in 3.6) was
>> "weird" because the parameter was named "Center freq" but you in fact
>> had to give it the frequency shift you wanted. The new one behaves
>> more like I expect.
>>
>> Cheers,
>>
>>     Sylvain

Yes, this change was made on purpose for exactly that reason. As
Johnathan noted, the new block after the 3.7 API change had this new
way of handling the parameter, but the old block didn't change (for
API compatibility reasons). I think the new way is more intuitive as
well since I, too, always messed it up myself. As Sylvain said, we
called it 'center frequency' but it was being treated as the value
used to actually shift the signal, not the center frequency of the
channel.

The real mistake here was not announcing this as a change in our 3.6 -
3.7 conversion document.

--
Tom
Visit us at GRCon13 Oct. 1 - 4
http://www.trondeau.com/grcon13

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