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RE: [Discuss-gnuradio] filters

From: Ettus, Matt
Subject: RE: [Discuss-gnuradio] filters
Date: Tue, 29 Jan 2002 10:57:56 -0800

> On the general channel selection filter (son of VrComplexFIRfilter), 
> I plan to have the callback build the prototype low pass, 
> then tranform
> it depending on the channel center frequency.  This will allow us to
> "tune" on the fly.

Sounds good.  What method of filter design?
> > Have you gotten that SPUC code integrated?
> Nope.  If you need it now, I'll get to it.

I just need generic FIR filters.  I guess I could whip up something to get
me by for the short term.

Question:  I'm all in favor of using STL types like vector, but I always
worry about whether they do bounds checking.  That could get expensive.

> I'm working on the RS stuff, and got a nice answer back from Phil Karn
> on how to handle the (207,187) codec.  With the given API, I need to
> prefix the message with 48 zeros.  This converts the (207+48,187+48)
> into (255,235) which his code directly handles.  With an API change,
> we could save a few cycles, since the 48 zeros could be skipped.

It would be interesting to see how fast you can get this to run.  The code
is efficient, but 20mbits/sec is a lot.  I got nervous yesterday when I saw
that Phil said he could only Viterbi decode ~9 Mbits/sec on a 1 GHz PIII
using SSE optimized code.  Then I realized he was using a code with a much
longer constraint length than HDTV.


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