| email@example.com writes:
|> When the US decided on the digital TV standard did they pick one that
|> is universal across the globe or did we just create another PAL vs
|> NTSC debacle?
| US decided to use their own digital TV standard ATSC.
| European countries designed their own DVB standard set
| for digital TV.
| They are basically at least as different as the old
| PAL vs NTSC issue. There are many techniques on those
| pretty similar (for example MPEG2 video compression)
| and many things different (used modulation, supported
| image resolutions etc..).
It part, the difference in the way TV is broadcast over the air influenced
the choice of OTA broadcast modulation. Europe typically has lots of low
power transmitters scattered in a lot of small area locations. The US has
fewer big transmitters that cover wide areas.
The 8VSB modulation has a lower ratio of peak power to average power. That
makes it more suitable for higher power transmitters where the cost of the
"head room" for waveform peaks can be great. The COFDM modulation has a
higher ratio of peak power to average power, making it more suitable for the
lower power transmitters. 8VSB generally performs better better in weak
signal situations against "white" noise. COFDM generally performs better
in situations involving multiple reflections of the same signal. Both
systems have been improved greatly to the point where, had the tests been
done with such improvement, the results may have been different. But what
is done is done. BTW, cable TV in the US uses QAM which in many ways will
perform like 8VSB.
It would be nice if MPEG4 could be retrofitted to ATSC. I've heard that is
under consideration. It will require upgrades to home TV decoders to be
able to receive it. My guess is, if the FCC approves the use of MPEG4, it
will be optional to use. Stations would have the choice to trade getting
more programs per MHz and not being receivable by some number of households
that receive TV over the air ... vs ... fewer programs per MHz and being
recievable by all the digital TV tuners.
I would have preferred to see ATSC adopt the European frame rates int the
standard, in addition to all that are there now. That way when playing a
program originating in Europe, it could be broadcast at the native frame
rate. Being able to handle 25 and 50 fps would be trivial.
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
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