Webcasting as a replacement for traditional broadcasting (was Re: Wackie 'ol Friday)

Sun Jun 9 16:47:34 UTC 2013

The view from my side, as both a broadcaster and a consumer of both
broadcast and 'webcast' content:

>From what I've been led to understand in my time in broadcast*, the
decision wasn't made because of power costs but because they (the Grand
Alliance and the FCC) believed that 8VSB would work better over the US both
due to terrain and propagation differences and due to our markets of
television transmitters and need to place co-channel (same frequency)
transmitters relatively nearby with minimal interference.  Some argue that
(C)OFDM would have been a better choice even taking those things into
account.  Which should have been chosen based on what criteria is a long
discussion in and of itself but we've got 8VSB (at least for now).

As for the mobile thing, I don't know if anyone had thought that far
ahead.  It seems silly now since I had a 2" rear-projection portable NTSC
TV that was made in the mid-to-late 1980s (Sony Watchman) and now they are
trying to 'solve' the mobile delivery 'problem'.  ATSC M/H adds a lot of
error correction as well as 'training data' to make the M/H stream 'easy'
to detect and decode, even with Doppler and multipath effects (see ATSC
A/153 part 2 for detail) - this reduces the data rate available for the
'main' (A/53) data significantly and does not create nearly as much
available for the M/H (A/153) data.  This sounds even sillier when you
realize that ATSC standard A/49, first published in 1993, was a "Ghost
Canceling Reference Signal for NTSC" (ghosting on NTSC is a symptom of
multipath).

As for 'webcasting' replacing RF broadcasting, I think we're a ways out if
it will even ever happen in the general case yet alone every case.  RF
broadcast is very efficient, as previously mentioned.  As a broadcaster, I
push 19.393 Mbps of content 'into the air' for everyone around to receive
at once.  As a consumer, I have four tuners attached to what amounts to a
few pieces of wire and I can receive roughly 80 Mbit of non-blocking data
'through the air'.  My ISP provides me a downlink speed of roughly 10
Mbps.  If I were in a larger market, I'd be able to receive even more data
(non-blocking with more tuners or blocking from my POV if I didn't have
enough tuners for every channel); even if the ISP provided downlink speeds
scaled up similarly, there would be much more data available 'through the
air'.  The people who live near me have the opportunity to receive that
same 80 Mbit of data without any transit costs.
Can CDNs replace some of what is now broadcast? Likely.  By reducing data
rates (with better compression technologies as well as simply compressing
more) and providing content that viewers want, they could (Netflix and
others are already doing this with some content).  There is, of course, a
lingering societal question about "shared viewing experiences" for shows
having set delivery schedules by broadcast.  Live content and local
content, however, will still be (in my opinion) best served by RF broadcast
for some time to come due to both the inherent efficiencies in the system
and the ease of localization for end-users.

* The ATSC Digital Television Standard (A/53) was developed, documented,
and formalized from the late 1980s through the mid 1990s (A/53 Part 1,
Annex A describes the history).  I wasn't working in television until 2000
or so and I wasn't doing television broadcast-related work until 2008.

- Eric

Eric Adler
Broadcast Engineer