No horizontal sync with ntsc tv reception

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 P.

On Mon, Oct 01, 2007 at 01:55:30PM -0500, Nirali P. wrote:

the horizontal resolution not the ability to sync, but I could be wrong. The

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

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