Re: [Discuss-gnuradio] Comb Filter

[cswiger]

On Tue, 4 Jan 2005, Prateek Dayal wrote:

> Can you please suggest  a site, where I can find the specifications
> for the comb filter etc for NTSC decoding. From the books that I have,
> it is not very clear ...
>

Just for giggles today I did a little research into comb filters
and found this page, altho it's audio application:

http://ccrma.stanford.edu/~jos/pasp/Feedforward_Comb_Filter_Amplitude.html

and other pages on the same site. A basic comb filter is pretty easy to
create:

comb = gr.fir_filter_fff (1, [1, 0, 0, 0, 0, 1])

will give you 5 notches between 0 and sample rate, etc. However I didn't
see anything specific to ntsc seperation (that I could understand ;).
I used that with some noise and the fft display and it indeed makes a comb
filter.

Like Eric said using something like the above might not be fast
enough for real-time video.

--Chuck