From the article:
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.
On Aug 5, 2015, at 9:55 PM, Manfredi, Albert E <albert.e.manfredi@xxxxxxxxxx>
wrote:
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.
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