Quoting towards the bottom:
"Focusing on a broadcast standard that has a path for improvement and growth as
part of a digital infrastructure that will include cellular smart devices and
broadband connectivity as well as over the air reception, the decision was to
move away from transport streams and instead embrace internet protocol (IP) for
carrying the data. I remember being very happy when we reached this decision.
Virtually every other part of the ecosystem that we are trying to move into is
IP-based."
I keep reading this sort of thing, and I am surprised that it's still being
repeated.
In a frequency-divided broadcast medium, the only things that matter are to
identify the frequency channel in use, the packet type in that channel, and to
permit synchronous playback at the receiver. Anything IP has to offer that
beyond this is pretty much irrelevant. And at the same time, IP doesn't
consider "frequency channel."
1. Frequency channel: Out of scope for IP.
2. Identify packet type: No question IP can do this. But so can MPEG-2 TS. In
fact, MPEG-2 TS can also identify an MPEG-2 TS frame that is carrying IP or
MAC-addressed packet content.
3. Synchronous playback: You use a timestamp in each packet, to permit the
receiver to dole packets out at the right speed. This can be done with RTP,
layered on top of IP, sure enough. But it can also be done with MPEG-2 TS. So
for instance, ATSC 2.0 does claim to use IP, but its packets are timed using
MPEG-2 TS. IP is just additional overhead.
4. Destination addresses for routing of packets: Not useful in broadcast. The
receiver can identify packets anyway, and it's not like they need to be routed
through a routed network.
It might be instructive that matter of fact, the normal way of carrying IP over
satellite channels is to use MPEG-TS at the link layer.
So why this pretense? IP is meant to permit packets to be routed through
two-way routed networks. Synchronous delivery is a kludge added on top of IP,
such as RTP, Flash, QuickTime, Real. Why pretend that one-way OTA (or cabled)
broadcast needs to change to IP?
Bert
-----------------------------------------------------
http://www.tvtechnology.com/opinions/0004/atsc-30s-global-future-is-a-blank-slate/276736
ATSC 3.0’s Global Future is a Blank Slate
Panel of industry leaders discuss the next stages of development for ATSC 3.0
August 5, 2015
By Bill Hayes
GHENT, BELGIUM - I spent the third week of June in Ghent, Belgium, attending
and speaking at the IEEE BTS International Symposium on Broadband Multimedia
Systems and Broadcasting, or BMSB as we refer to it. The vast majority of the
material presented is research based papers from university engineering
students from around the world. Much of the focus of their work are ways to
enhance and improve broadcasting technologies. It’s actually kind of refreshing
because it often seems that broadcasting technology is thought of as outdated
or outmoded and on its last legs. At the BMSB it was apparent that there are a
wealth of creative young minds working on ideas and proposals that demonstrate
that broadcast technology has a bright future if it is given the chance to
evolve and adapt.
One of the most interesting technologies being presented was layered division
multiplexing, or LDM. LDM technology is one of the proposals that has been
submitted to the physical layer group within the ATSC TG3 for consideration in
the ATSC 3.0 standard. LDM and ATSC 3.0 have attracted participation and
research from around the world and there are no shortage of ideas, models and
tests associated with the technology that demonstrate its effectiveness at
providing terrestrial broadcast stations with an effective way to reach mobile
devices, indoor receivers and traditional stationary viewers with a
multiplicity of services up to and including UHD-1.
With my participation on the ATSC 3.0 standard, I have been hearing and reading
about LDM since the first presentation I saw at a BTS Annual Broadcast
Symposium a few years ago. Since then there have been numerous papers and
presentations done, much of it available online. It is well worth the time to
do a little research and read up on this technology because it will likely be a
very important part of the future of broadcast television.
On November 11, 2011, I was in Shanghai for a summit on the future of broadcast
television and the creation of the Future of Broadcast Television (FoBTV)
group. The summit and the group that formed out of it united and agreed to work
on a global broadcast television standard. Since the formation of FoBTV, the
BMSB has consistently closed with a panel of leaders and luminaries from FoBTV
and the industry to discuss the future and how things are progressing. I
moderate the session. I like to ask tough questions about our progress and lack
of progress, our technical challenges as well as our political challenges.
Each year I see more and more that the technical challenges, while not
inconsequential, pale in comparison to the political challenges. Each country
involved seeks to manage its broadcasting resources to best meet the perceived
needs of its population and the mission and political objectives of its
government. This year was no exception. ATSC 3.0 has progressed and is on track
to become a candidate standard in the near future. Since many of the
participants working on ATSC 3.0 are also members of working groups and
committees within FoBTV, they are moving in parallel.
However, the item that interested me the most this year was a technical
decision with some peculiar ramifications. If you look under the hood of ATSC
3.0 you will find that some of the components are closely related to the DVB-T
suite of technologies. As a matter of fact, some people within the technology
committees thought that ATSC 3.0 was going to be DVB-T2 with an ATSC sticker
over it. But when the decision was made to not constrain ATSC 3.0 to backward
compatibility, the groups working on the standard were given a blank slate.
Focusing on a broadcast standard that has a path for improvement and growth as
part of a digital infrastructure that will include cellular smart devices and
broadband connectivity as well as over the air reception, the decision was to
move away from transport streams and instead embrace internet protocol (IP) for
carrying the data.
I remember being very happy when we reached this decision. Virtually every
other part of the ecosystem that we are trying to move into is IP-based. Yet in
my discussions with the panel it became obvious that in the DVB environment
transport streams are the method of choice and there doesn’t seem to be any
motivation to change. I guess I naively assumed that there would be a DVB-T3
that would move to IP-based delivery. I was a little disheartened to be told
that there really isn’t much discussion going on in that area and that when IP
was evaluated some time back, it didn’t provide enough benefit to be worth the
change.
When the decision was made within ATSC to not be constrained to backward
compatibility, one of the primary drivers was that the compromises that would
have to be made to the capabilities of the new standard would be so great it
wouldn’t be worth doing. Another primary driver was that if we stayed with what
we have, the future outlook was bleak. So sitting still isn’t an option, nor is
making an incremental change; so while the way forward is not as clear as we’d
like, digging in and staying put isn’t a viable option either.
I am still hopeful that the group that is working on the next generation of
broadcast technologies is creating a standard that has global potential, if not
in this iteration then perhaps in the next. Anyone who thinks the transition of
television broadcasting to digital stops when the analog service shuts down
doesn’t understand the nature of digital technology.
----------------------------------------------------------------------
You can UNSUBSCRIBE from the OpenDTV list in two ways:
- Using the UNSUBSCRIBE command in your user configuration settings at
FreeLists.org
- By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word
unsubscribe in the subject line.