RE: [Discuss-gnuradio] No horizontal sync with ntsc tv reception

[Walker, Robert CIV NAVSURFWARCENDIV Crane, Code 80EW]

I believe Daniel Garcia implemented this a while ago.

Check http://www.danielgarcia.info/thesis/ for info.

I tested it and it seemed to work, but only when my TVRX was connected to cable TV.  When hooked to an antenna, apparently the signal was not strong enough for the sync to function.

Rob

>On Mon, Oct 01, 2007 at 01:55:30PM -0500, Nirali Patel wrote:
> Hi,
>
>
> I am working on ntsc tv reception as a precursor to hdtv reception. I am
> using usrp_rx_cfile.py to capture samples to a file from the TV_RX board and
> then playing back using usrp_tv_rcv_nogui.py. The picture displayed does not
> seem to have horizontal sync (picture keeps moving from left to right). I
> have tried setting different decimation factors, the best I can use without
> overruns is a factor of 8 and the picture still rolls in horizontal
> direction. My understanding was that the decimation factor would only affect
> the horizontal resolution not the ability to sync, but I could be wrong. The
> commands that I use for capture and playback are:
>
> ./usrp_rx_cfile.py -R B -d 16 -f 531.25M -s tv1.out
>
> ./usrp_tv_rcv_nogui.py -f 531.23M -n -i tv1.out sdl
>
> 
>
> where 531.25 Mhz is the picture carrier of the ntsc channel with lower band
> edge at 530Mhz.
>
> I have also tried using -f 533M to set the tuning frequency to centre of the
> band but no significant change in picture sync.
>
> If anyone has experienced similar problem I would appreciate the guidance.
> Does the antenna setting have any influence on h-sync? My office is in the
> interior of the building so would it help to move towards the exterior?
>
> Thanks in advance for any help.
>
> Nirali Patel
>
>
>If you look at the code, there's a comment at the top that says that
>synchroniziation isn't implemented:
>
>
>  """
>  Reads from a file and generates PAL TV pictures in black and white
>  which can be displayed using ImageMagick or realtime using gr-video-sdl
>  (To capture the input file Use usrp_rx_file.py, or use usrp_rx_cfile.py
>--output-shorts if you have a recent enough usrp_rx_cfile.py)
>  Can also use usrp directly as capture source, but then you need a higher
>decimation factor (64)
>  and thus get a lower horizontal resulution.
>  There is no synchronisation yet. The sync blocks are in development but not
>yet in cvs.
>
>  """
>
>
>Eric