Re: [Discuss-gnuradio] Peak detector block does not really work. It need to be fixed

[Eric Blossom]

On Tue, Aug 24, 2010 at 01:49:09PM -0700, Phong Do wrote:
> 
> Hello Tom,
> 
> Can you explain me why should gr_peak_detector need negative inputs ?

If you use grep, you can find places in the code where it is used, and
then answer your own question.

> What about the variable "look ahead" ? I wrote in the last message that
> "look ahead" has no function in gr_peak_detector.

My guess is that look_ahead was a feature that turned out not to be
needed to solve the problem at hand, but was accidentally left in the
constructor. 

> Do you know how can I add this feature in peak detector ?

Yes.  Write the code that implements it.

Eric


> On Thu, Aug 12, 2010 at 8:26 AM, Phong Do <address@hidden> wrote:
> >
> > Hello,
> >
> > I'm working now with peak_detector block and find out that some functions
> > don't really work.
> > I've used the following 2 blocks:
> >
> > - Peak Detector (gr_peak_detector): the parameter "look ahead" seems have
> > no
> > function. I gave "look ahead" many values but the peak value did not
> > change.
> > I've seen in the gr_peak_detector_xx.cc that the variable d_look_ahead is
> > called but it is not used in the main program. So I think the developer
> > has
> > forgotten this function.
> >
> > - Peak Detector 2 (gr_peak_detector2): in this block "look ahead" is used,
> > but sometimes the peak detector freezes (output signal stops running in
> > scope sink).
> > I've changed the cpp code a little bit and it does not freeze anymore. But
> > I'm not sure if the detector will work correctly after that.
> > Here is what I've changed:
> > original code: return tmp - 1;
> > changed code: return tmp;
> >
> > Can anyone of the development team have a look at the 2 cpp ?
> >
> > best regards
> > Phong Do
> 
> Keep in mind that the gr_peak_detector actually expects negative
> inputs. So if your signal goes from 0 to 100, adjust it so that it
> goes from -100 to 0.
> 
> Of course, I say "keep in mind" even though we probably haven't
> provided any documentation in the code to that affect...
> 
> Tom