Decoding NTSC tv

I’m looking to decode NTSC with my gnuradio. I found
thishttp://www.danielgarcia.info/thesis/ online where someone usedan
older USRP and gnuradio version to decode NTSC and PAL.I was able to
mangle his script a bit to run with newer gnuradioand UHD. (I
hard-coded in some of the parameters for quick testing, it needs some
polish once completed).However I still just get a black screen, so we’re
notall the way there yet.
Anyone around familiar with this code? The original code seemedto have
a sample rate of around 1Ms/sec (ie. adc rate 64M decimated64 times, if
I read the code correctly). Is this enough for a tv signal?It looks
like an NTSC channel is around 6M wide (with color andsound), right?
I’m going to try to get a stronger signal to test with and play withit
some more, but if anyone is interested in helping, I’d welcomethe
assistance.

On Fri, Jun 10, 2011 at 3:12 PM, open bts [email protected] wrote:

to have a sample rate of around 1Ms/sec (ie. adc rate 64M decimated
64 times, if I read the code correctly). Is this enough for a tv signal?
It looks like an NTSC channel is around 6M wide (with color and
sound), right?

I’ve not played with this code, no, but 1 MHz bandwidth doesn’t sound
like
it’ll work. You can see the spectrum mask here:
http://en.wikipedia.org/wiki/NTSC

1 MHz doesn’t get you a whole lot of information in NTSC. You really
need
the entire 6 MHz.

I’m going to try to get a stronger signal to test with and play with
it some more, but if anyone is interested in helping, I’d welcome
the assistance.

Where are you getting NTSC transmissions now, anyway? Only low power TV
is
left in the US to transmit on NTSC, and I think most of them have moved
away
from it, too. I’m sure there’s still signals out there, I’m just
wondering
where and what services would still be using it. I also don’t know the
state
of NTSC outside of the US, but it was fairly limited to being with.

Tom

you could use a VCR right? channel 3? or cable TV provideri made a bunch
of capture files with my USRP as they shut down the analog signals.
shortly after my raid5 array crashed and i never made backups
i did try another one, its uploaded
herehttp://kd8eyf.org/capture_files/i never tested it so i have no idea
what it looks like but my fft showed a nice NTSC signal

Fri, 6/10/11, Tom R. [email protected] wrote:
From: Tom R. [email protected]
Subject: Re: [Discuss-gnuradio] decoding NTSC tv
To: “open bts” [email protected]
Cc: [email protected]
Date: Friday, June 10, 2011, 6:52 PM

On Fri, Jun 10, 2011 at 3:12 PM, open bts [email protected] wrote:

I’m looking to decode NTSC with my gnuradio. I found
thishttp://www.danielgarcia.info/thesis/online where someone usedan
older USRP and gnuradio version to decode NTSC and PAL.

I was able to mangle his script a bit to run with newer gnuradioand UHD.
(I hard-coded in some of the parameters for quicktesting, it needs some
polish once completed).However I still just get a black screen, so we’re
not

all the way there yet.
Anyone around familiar with this code? The original code seemedto have a
sample rate of around 1Ms/sec (ie. adc rate 64M decimated64 times, if I
read the code correctly). Is this enough for a tv signal?

It looks like an NTSC channel is around 6M wide (with color andsound),
right?
I’ve not played with this code, no, but 1 MHz bandwidth doesn’t sound
like it’ll work. You can see the spectrum mask
here:http://en.wikipedia.org/wiki/NTSC

1 MHz doesn’t get you a whole lot of information in NTSC. You really
need the entire 6 MHz.

I’m going to try to get a stronger signal to test with and play withit
some more, but if anyone is interested in helping, I’d welcomethe
assistance.

Where are you getting NTSC transmissions now, anyway? Only low power TV
is left in the US to transmit on NTSC, and I think most of them have
moved away from it, too. I’m sure there’s still signals out there, I’m
just wondering where and what services would still be using it. I also
don’t know the state of NTSC outside of the US, but it was fairly
limited to being with.

Tom

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