Hi,
Finally, I got my first HDTV screenshot tonight. It’s
from KTVU’s “The Loop”.
Here’s how I did it:
 Download ATSC stream off USRP with the following
parameters:
TVRX’s rf freq = 725e6
USRP’s center freq = 43.75e6
Decim = 8
TVRX’s Gain = 88;
USRP’s format = 0x300
Mux = 0xf0f0f0f0
See ktvucomplex.png for the FFT pic
 Upsample 8Ms/s complex data to 40Ms/s complex data:
for every sample in the 8Ms/s data, add 4 zeros, then
followed by a lowpass filter.

Downsample 40Ms complex data to 20Ms/s complex
data:
remove every other sample from the 40Ms/s sample data 
Frequency Translate the center frequency from 0Hz
to 5.75MHz 
Keep the Inphase part of the 20Ms/s complex data
to get 20Ms/s real data:
See ktvureal.png for the FFT pic
 Feed the 20Ms/s real data into Gnuradio 0.9’s
atsc_rx.
Voila! The finally screenshot is here: ktvuThe
Loop.jpg
Cheers!
Mao