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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 19:47:17 -0500

> "center_frequency" /always/ refers to the frequency of the incoming signal.

So what if i'm transmitting, or just "shifting" a signal "frequency" for another reason?

I understand that "center freq" maybe should mean what you think it does, but wouldn't it make more sense to change the internal parameter name to one that makes more intuitive sense instead of changing the whole block functionality and breaking backwards compatibility just to match the internal variable's name?

Google "freq xlating fir filter" you can see just how many papers, projects, videos, tutorials, etc.. will need to be fixed less they cause more confusion and no one can figure out which way it works.

If your decision is firm, we need to at least fix the internal Gnuradio demo apps that may need fixed or their tuning sliders reversed.

Sorry if this post sounded like a rant ( API breaks bug me :) )

Thank you for you consideration,

On Thu, Aug 8, 2013 at 5:46 PM, Tom Rondeau <address@hidden> wrote:
On Thu, Aug 8, 2013 at 5:51 PM, Marcus D. Leech <address@hidden> wrote:
> On 08/08/2013 05:01 PM, Andrew Davis wrote:
> 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

Referring to an earlier comment, "center_frequency" /always/ refers to
the frequency of the incoming signal. It would/could/should never be
confused as the center frequency of the signal used to down convert
the incoming signal. This was a bug in the original code and I took
the opportunity to fix it in the 3.7 block.

> I have to agree.  It's one thing to muck with the API semantics of a block
> that is "new" and hardly anyone has used.  It's quite another to
>   make a change like this on a block that has been in use for many years,
> with folks having figured out the semantics, despite the odd naming.
> --
> Marcus Leech
> Principal Investigator
> Shirleys Bay Radio Astronomy Consortium
> http://www.sbrac.org

With everything else that we've changed in 3.7, changing a + to a -
seems like a pretty simple thing. The fix will stay.

I have updated the wiki page that discusses the changes needed to go
from 3.6 to 3.7 to include this omission

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