Re: [Discuss-gnuradio] decoding NTSC tv

[dave k]

you could use a VCR right? channel 3? or cable TV provider

i 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 here

http://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 Rondeau <address@hidden> wrote:

From: Tom Rondeau <address@hidden>
Subject: Re: [Discuss-gnuradio] decoding NTSC tv
To: "open bts" <address@hidden>
Cc: address@hidden
Date: Friday, June 10, 2011, 6:52 PM

On Fri, Jun 10, 2011 at 3:12 PM, open bts <address@hidden> wrote:

I'm looking to decode NTSC with my gnuradio.  I found this

http://www.danielgarcia.info/thesis/ online where someone used

an older USRP and gnuradio version to decode NTSC and PAL.

I was able to mangle his script a bit to run with newer gnuradio

and 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 not

all the way there yet.

Anyone around familiar with this code?  The original code seemed

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

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