[opendtv] Re: Spectrum is too valuable

  • From: Craig Birkmaier <brewmastercraig@xxxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Thu, 12 Nov 2015 14:04:32 -0500

On Nov 11, 2015, at 8:26 PM, Manfredi, Albert E <albert.e.manfredi@xxxxxxxxxx>
wrote:

No, Craig. I explained how a relatively small amount of broadband spectrum,
per household, could carry multiple HD streams, and your response was that HD
requires 19 Mb/s. You can't weasel out of that one.

Last Friday when I wrote about the number of homes that can be served using
DOCSIS 3.1, I provided the following info about bandwidth requirements for HD:

How much does a home need? 25 Mbps can support about 2 HD streams with
MPEG-2, perhaps 3 streams with h.264. This may be sufficient for a home with
two residents, but may not be sufficient for a home with four or more
residents.

You are correct that I have said some content requires the full 18-19 Mbps of
bandwidth we are discussing here - especially 1080i for high action sports.
That's a fact, as I still see compression artifacts in the CBS NFL games in
this market. To be fair, that station borrows bits for a SD sub channel.

What you do not take into consideration is that digital compression codecs are
low pass filters - and that does not include any low pass filtering prior to
encoding that reduces resolution. The codecs replace high frequency detail with
correlated noise.
Compress a little and all we see is less detail;
Compress a bit more and we start to see mosquito noise;
Compress too much and we see blocking artifacts.

Thus it is absolutely possible to resample a high quality HD image to
progressive scan SD resolution and deliver more detail in the same bandwidth
than the original HD image that is bit starved in that bandwidth.

I stand by my analysis. You cannot recover enough 6 MHz channels to deliver the
same level of quality subscribers now get from the linear MPEG-2 streams, to
deliver the same level of quality via UDP streams, even using h.264, to 500
homes served by a single POD operating at 1 GHz.



http://www.lighterra.com/papers/videoencodingh264/

720p 1280x720 4.0 2.56 2496 64
720p HQ 1280x720 5.0 3.20 3072 128

At what frame rate, and for what level of action.

As I pointed out, these numbers are on the low side, and do not take into
account the content being encoded. The vast majority of OTT services like
Netflix, are encoding low action 24p content.

So, this is **precisely** what I already informed you about, Craig. With
Internet streaming, you need only 5 Mb/s to a home, for very decent TV
service, unless multiple people want to stream HD simultaneously.

We disagree. I agree you can deliver very decent TV service in 5 Mbps. That's
why I argued for progressively scanned SDTV two decades ago. But only the least
demanding HD content can be delivered in 5Mbps, even with h.264.

So while you are time traveling into the past to promote very decent TV via the
Internet, Netflix is launching a UHDTV service that requires almost 18 Mbps for
one 24P stream.

The infrastructure can be made to handle TV, Craig, and the needed edge
servers are added/improved as demand dictates.

The infrastructure IS handling OTT TV delivery, even real HD, at the level of
demand needed today. You cannot have it both ways. If you need edge servers to
"handle it" as demand dictates, then the broadband infrastructure can be added
as demand dictates.

And this is also important. If you read the DOCSIS 3.1 standard, you will
note that the **only** way DOCSIS 3.1 can manage ~10 Gb/s per PON is by doing
assuming these two points:

1. That there are no MPEG-2 TS broadcast streams on that PON. All dedicated
to broadband service, like I said.

That is clearly not true. You can dedicate a portion of the 1 GHz available in
the most up to date 1 GHz HFC systems; you do not need the entire GHz. Cox is
deploying DOCSIS 3.1 in many systems next year - these are 1 GHz systems that
will continue to offer linear MPEG-2 TS streams.

2. That the usable spectrum is just about doubled, from ~900 MHz to ~1800 MHz.

Can you point me to a 1.8 GHz HFC system Bert?

Ron may be better equipped to talk about this, but I have heard of no plans for
cable systems to upgrade to 1.8 or 2 GHz systems. Ron noted that DOCSIS 3.1
channels can be set up at many sizes, and that 200 MHz channels may be the
norm. For most cable systems that still offer analog TV, it should be possible
to add two 200 MHz DOCSIS channels if you turn off the analog service. I expect
that will happen long before the cabled systems recover channels now dedicated
to MPEG-2 TS streams.

OFDM is used at much higher frequencies for cellular and other applications, so
I see no reason why DOCSIS 3.1 would not work on a 2 GHz system. But cable
systems are already experiencing emissions problems at 1 GHz, and you must look
at the length and condition of the coax runs from the PONs, and other real
world issues that degrade from the theoretical to the real world.

The numbers I quoted were for ideal 0db conditions.

So, Craig, how many households, at 5 Mb/s, could be fed from a single PON? Or
even at 15 Mb/s? How does that compare with your average of 500 households
per PON today?

I already gave you the numbers at least twice. Under ideal conditions a 500
home PON that uses ONLY DOCSIS 3.1 in a 1 GHz HFC system could provide just
over 11 Mbps to each home.

Regards
Craig


----------------------------------------------------------------------
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.

Other related posts:

  1. Home
  2. opendtv
  3. Archive
  4. 11-2015