Re: [Patch-gnuradio] FM Preemphasis Filter

[Eric Blossom]

On Wed, Dec 12, 2007 at 08:47:44AM -0500, Robert Roberts wrote:
> Hello,
> 
> A couple years ago I was working with GNURadio and noticed that the 
> filtering weights for the Preemphasis Filter used in FM transmission 
> had not been implemented. I submitted some code at that time.  I was 
> browsing the source and found that it's still listed as a "FIXME"
> 
> http://gnuradio.org/trac/browser/gnuradio/trunk/gnuradio-
> core/src/python/gnuradio/blksimpl/fm_emph.py
> 
> 
> The preemphasis filter should be the inverse of the deemphasis filter, 
> so copying the deemphasis code and swapping the Ataps for the Btaps 
> should implement it.  I did this previously and it worked well.
> 
> If there's anyone who's actively working on the code that could update 
> this, I'd appreciate it.
> 
> 
> Sincerely,
> ~Chris Roberts~
> 

Hi Chris,  can you please send it again.

IIRC, the pre-emph filter that's specified in the specs I looked at
were not exactly the inverse of the de-emph.

Eric