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[Discuss-gnuradio] Replicated Eric Blossom's decoding of HDTV signals t

From: John Gilmore
Subject: [Discuss-gnuradio] Replicated Eric Blossom's decoding of HDTV signals tonight
Date: Wed, 14 May 2003 03:40:02 -0700

On Tuesday, May 13, 2003, I succeeded in using GNU Radio to record
portions of HDTV programs off the public airwaves from KQED-DT
(channel 30) in San Francisco, and displayed them on my computer.  Two
still images from the recorded programs are visible at the bottom of


Along the way, I improved the instructions in the Wiki, and some
small bugs in the code were fixed.

This replication of Eric's successful experiment was done with the
code checked out of the public CVS archives, following the published
instructions, and using purchased hardware substantially similar to
Eric's dual Athlon system (upon which the first software-only decoding
of HDTV signals was done).  The only significant help I got from Eric,
besides occasional encouragement and advice, was when he provided me
with a modified tuner board that includes a tiny "daughter board" for
setting the gain controls of the tuner.  (This replaces the use of
three separate "bench" power supplies for the tuner board, instead
using a small wall-wart power brick.)  The schematic for the tuner
board is available on the Wiki.

Verifying that third parties can replicate a scientific experiment
is an essential part of the scientific method, and guards against
errors of fact as well as mistakes made in documenting what was done.
There's no error.  GNU Radio is able to record and decode off-the-air
HDTV programs, and the free Xine player is able to display them.

        John Gilmore

PS: Many people contributed to building this capability, besides Eric
and I.  The credit should be shared broadly throughout the GNU Radio
contributor community -- you know who you are -- and shared with the
LiViD, Xine, Python, and SWIG developer communities, who did many of
the big "hard parts".  Much more work remains to be done to make this
a practical and useful technique for end-users, and I'm sure that the
community will continue improving GNU Radio and Xine.  GNU Radio's new
Python scripting support should make it much easier for relative
novices to contribute big improvements to its user interfaces and
software integration.

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