[opendtv] Re: Global standard

  • From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
  • To: "opendtv@xxxxxxxxxxxxx" <opendtv@xxxxxxxxxxxxx>
  • Date: Mon, 30 Apr 2012 15:36:20 -0500

Mike Tsinberg wrote:

> So what would be ideal package of most widely used Internet
> transport and compression protocol if it's adopted to broadcast?
> Let's assume each channel is 20 Mb/s, the modulation, RF power
> and tower spacing stay the same. Can wefit two or more 1080i
> signals into that channel?

Why insist on Internet protocol at all, would be my first question, if the 
stream is to be broadcast over the air, satellite, or cable? Why not let the 
broadcast streams use MPEG-2 TS, and allow broadcasters to ALSO provide 
Internet streams, as they already do, for distribution over the Internet?

For Internet distribution, what's wrong with H.264, or in the future H.265, 
over either some TCP scheme like RTMP, or RTP/RTCP, depending on what the ISP 
net needs or prefers? Since the host devices support both schemes, and since 
the use case is different, you don't need to force only one solution.

For instance, you can't do IP Multicast over TCP. And IP Multicast is not 
supported and to end, over the Internet, except in exceptional cases. So it's 
up to ISPs to decide what gets sent how. ISP nets can take the content and can 
create an in-ISP-only IP multicast, for example. A good way to go.

But again, as far as the OTA broadcast and the cable/DBS broadcast streams, 
there's not much reason to be using IP overhead. Especially when you have to 
deal with questions like, what IP Multicast destination address would you use?

For IPv4, that's a non-trivial question. For IPv6, it's easier to answer, if 
you assume all the receivers out there are IPv6 capable.

Adding in the IP overhead introduces a whole new set of compatibility issues 
that are not necessary, when it comes to actual broadcast distribution of the 
content. For OTA broadcast, I don't see why, as of today, you'd look any 
further than DVB-T2 with the newest H.265 compression scheme. That keeps the 
broadcasters involved legitimately, provides for good spectral efficiency, and 
the peak power requirements are more reasonable than those of DVB-T1, promising 
easier spectrum packing. (Although the latter probably not as good as ATSC.)

Bert

 
 
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