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Re: [Discuss-gnuradio] working example gnuradio TV receiver for NTSC and

From: Eric Blossom
Subject: Re: [Discuss-gnuradio] working example gnuradio TV receiver for NTSC and PAL (black and white)
Date: Fri, 7 Jan 2005 14:49:02 -0800
User-agent: Mutt/1.5.6i

On Fri, Jan 07, 2005 at 07:21:02PM +0100, Martin Dvh wrote:
> I also found this old code, which was at some day part of gnuradio.
> http://savannah.gnu.org/cgi-bin/viewcvs/gnuradio/gnuradio/src/pspectra/lib/vrp/needs-work/VrTV.h?rev=1.3&content-type=text/vnd.viewcvs-markup
> It is a software NTSC decoder which does seem to try to get the
> vertical sync right.  I studied some time on it to try to grasp what
> they are doing with the sync, but is very hard to read code.
> I think that they count the number of samples taken and as soon as a
> vertical sync pulse is due they start looking for it.  They even
> increase the number of filter taps at this precise moment to have
> temporary better signal quality.

The code is pretty crufty, but I suspect that it actually worked at
one time.  There are probably some ideas that can be hoisted from it.

One of the beauties of software signal processing is that it's
possible to run in different states.  For example, a computationally
expensive search phase to establish sync, and then a cheaper local
search to ensure that sync is still locked.

Thanks for all your effort on this.  
It'll be great to have an NTSC and PAL receiver!


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