Hdtv tx

Gang - I’ve been playing with the atsc transmitter and have a few notes
to report.

First, a good definition of “real time transmitter” would include a
firewire video camera, the processing to make an mpeg transport stream
(whatever that is, I’m not a video guy), then the atsc_tx out to the
usrp and a flea power transmitter, which can be picked up by a nearby
common consumer hdtv.

Otherwise, since you have to do some processing (and that could be
slow, I dunno) to make an mpeg transport stream out of a dvd or whatever
anyway, you might as well do the atsc encoding offline as well, ending
up with a 200GB file of rf with 2 hours you just dump out to the
usrp with no processing at all.

Anyway, I’ve send a short mpeg clip around the loop consisting of a
partial 2.x module (atsc.pad, randomizer, rs-encoder, interleaver and
trellis encoder) and the rest in 0.9 (field_sync_mux, symbol mapper,
weaver mod head, filter, rate converter (munged to use 19.2 instead
of 20MSps) and weaver mod tail) ending up with a 19.2MSps file of
‘real’ short data. From that it should be easy to convert to complex,
mix down from 5.75MHz to 0, and decimate by 3 to get something
suitable for the usrp and over the air.

The 19.2MSps short rf data was then decoded by a part 0.9 and part 2.x
receiver to get the original video back.

The 2.x field_sync_mux didn’t work.


Ok, a rough atsc transmitter benchmark: as it is now with almost
all the signal processing still taking place in the 0.9 code, that
is, one processor running 100% and the 2.0 script in the single
digit percent utilization - a 9 second mpeg stream takes 104
seconds to encode. Using 2GHz Opterons.