We have been able to broadcast multiple HD and SD signals in a 6 MHz channel
for more than a decade. But let’s not fool ourselves about the quality of the
delivered signals; pre-filtering can significantly reduce encoding stress, but
it ALSO reduces delivered resolution. And it is uncommon for broadcasters to
deliver multiple programs with high motion content (e.g. sports) in these
multiplexes.
What Bert is missing in this discussion is that the vast majority of consumers
do not watch these broadcast signals; they are watching signals delivered to
cable systems, DBS systems, and now VMVPD systems. And THESE signals are almost
ALWAYS of better quality than the highly compressed signals that are being
squeezed into broadcast multiplexes, as they are encoded for delivery via
dedicated digital links and even the public internet.
On Mar 22, 2020, at 10:09 PM, Manfredi (US), Albert E
<albert.e.manfredi@xxxxxxxxxx> wrote:
Heh heh. Many of the old issues, still being discussed. For what it's worth,
and for those who might not know, there has been a heck of a crunching down
of spectrum, for US OTA broadcast stations. It is now common to see two major
stations in a market, sharing a single 6 MHz channel. (The stations continue
to use their old channel number for ID, but it's what they call a virtual
channel. So users are universally unaware. You can tell best by doing a
manual channel scan, or look up the frequencies at the FCC site.)
More to the point, it is common to see these two stations both broadcasting
HD, in this shared 6 MHz channel. And both also broadcasting a complement of
480i SD programs, all in that same, shared, 6 MHz channel.
Well, guess what. The HD streams can be either 720/60p or 1080/60i, and still
fit into that single 6 MHz channel, shared with several SD streams. And the
HD looks like good HD, to boot.
All of this, using 8T-VSB cum MPEG-2 (H.262) compression. These religious
battles can rage on, year after decade. Even in the face of evidence that the
religion is, as always religions are, egregiously overstated.
Stay safe. Wash hands. Keep a distance.
Bert
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