[opendtv] Re: Punching Above Its Weight, Upstart Netflix Pokes at HBO - NYTimes.com

  • From: Craig Birkmaier <craig@xxxxxxxxxxxxx>
  • To: "opendtv@xxxxxxxxxxxxx" <opendtv@xxxxxxxxxxxxx>
  • Date: Tue, 25 Feb 2014 07:31:35 -0500

> On Feb 24, 2014, at 5:44 PM, "Manfredi, Albert E" 
> <albert.e.manfredi@xxxxxxxxxx> 
> 
> Which can also describe exactly as one would do IP-based VOD.

Not exactly. Let's reset this discussion, as I used a term that caused some un 
intended confusion for Bert.

There are two sides to the modern cable plant - three if you want to include 
those systems that also offer an analog tier. I used the term QAM side to 
describe the portion of the system that delivers live digital video streams; 
Bert notes that the IP side also uses QAM modulation to carry IP packets to 
cable modems. So for clarity I will use the terms live side and IP side. The 
analog tier is also a live side service, with identical channels to the live 
digital channels, although there are many more digital channels than analog.

One of the earliest services installed at the head end was commercial 
insertion. This started before the systems moved to digital. When they upgraded 
to digital it became necessary to insert ads in both the analog channels and 
their digital equivalents. The commercial insertion servers had two options to 
create clean MPEG-2 TS streams. Create a continuous analog stream and encode 
it; splice ads into the MPEG-2 TS streams. Both methods are in widespread use. 

VOD services came later. Again, they are head-end based, playing out MPEG-2 TS 
streams to the digital STBs that only understand MPEG-2. Most of these streams 
are movies that do not contain ads, although some systems ad pre-roll and 
pistol roll ads and promos. These servers may need to play out the same asset 
to multiple homes at different starting times; the server pulls streams from a 
single file making multiple streams that get modulated onto live channels. 

While the basic techniques are not that different from a server designed to 
create IP streams for delivery over the Internet, there are important 
differences. Modern IP servers have enhanced capabilities like rate control to 
deal with the bandwidth available to each unicast client, and they can insert 
commercial on the fly. The MPEG-2 TS servers used for the live side of a cable 
plant just playout pre produced streams; they do not have rate control or the 
ability to insert ads into streams.

Regards
Craig 
 
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