[sclug] Digital TV card and channel recognition

Dickon Hood dickon-ml at fluff.org
Fri Dec 11 19:59:07 UTC 2009

On Fri, Dec 11, 2009 at 19:03:27 +0000, Alex Butcher wrote:

: I /think/ once you've found one multiplex (e.g. via a manual seed, or brute
: force scanning), there's information to tell the STB what channels the rest
: are on.

There is.  It's called the Bouquet Association Table ('BAT' for short; see
ETSI EN-300-486 (if you have access to it) for details.  If you're
terminally bored, that is), and that's what scan parses to locate other

My best guess as to why commercial receivers don't do this is because it's
entirely possible to have two different DVB-* systems which don't
interact; ie, it's possible to have one or both sets which don't include
each other's multiplex / transponder information in the BAT.  You'll get
something similar with DVB-T here, if you've got two regions available;
one of my neighbours[0] has both Crystal Palace and Hannington available
to her, and a scan using her aerial won't pick up both of them.  A
brute-force does, and lets her see both BBC London and BBC South, each
from a different transmitter.

: Failing that, <http://www.ukfree.tv/transmitters.php> might help. I
: suspect Hannington will be best for most people in SCLUG.

Or the Oxford transmitter, if you're up that end of town.  Possibly.  And
apparently Henley has one, too.

You'd never guess I've spent the last three years or so doing this stuff,
would you...

[0] Fiona, for those few who may care :-)

Dickon Hood

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