More HD is coming. What, when and where is up to each region. Many area's need to work on "reclaiming" some spectrum which can be used for more HD launches. Reclaiming bandwidth can come from migrating an analog channel to digital, or re-optimizing a multiplex so that 3 HD channels can fit in the same space a regular analog channel would fit. Migrating HD from the normal 2:1 to a 3:1 mux would be unnoticed for most people since the channel mapping stayed the same, it was just the source that changed. Each analog channel slot can contain up to 12 (soon to be 15 with new grooming) SD digital channels. Many Comcast systems have over 2/3rds of their bandwidth dedicated to Analog channels. It is vital that these channels are migrated to digital for better resource allocation over the RF network.
With any channel launch or frequency change, there is a LONG drawn out process that must be followed. The FCC requires notice to be given for any channel changes or removals/repositions. Corporate must approve any channel change requests and then there is the marketing side with contracts, timing and advertising. For any MAJOR changes Comcast is required to give 30 days notice, and just getting that out can sometimes be troublesome. One way around a 30 day notice in a channel add would be a soft launch. A soft launch is when channels will appear 'out of the blue'. Usually a week or two later there will be an ad in your local paper saying that the channels will be available 30 days from now, but you can enjoy a 'free preview' today.
It's also because of this required notice, along with the mis-match of channel maps, channel locations, etc, between all the various systems throughout their history of acquisitions that you end up having the channels all over the place. Comcast tries to stick things where they can find room. A region may have 30+ channel lineups to handle each with it's own bandwidth limitations. Imagine playing a really hard game of Soduku. If you simply make a change to a multiplex in one area, it's likely to affect 30 other area's because they are pulling the video from the same multicast IP address. Everyone must be coordinated and on the same page. Adding/changing channels can be a very messy and tedious project.
Definitions:
Multiplex - communicates two or more signals over a common channel
Mux - Shorthand for Multiplex. 2:1 Mux means 2 signals are broadcast over a common channel. 3:1 means 3 signals are broadcast over a common channel, etc.
RF - Radio Frequency
SD - Standard Definition (up 480i resolution)
HD - High Definition (1280x720p or 1920x1080i resolution)
Multicast - addressing is a network technology for the delivery of information to a group of destinations simultaneously using the most efficient strategy to deliver the messages over each link of the network only once, creating copies only when the links to the multiple destinations split.
Bandwidth - The width, usually measured in hertz, of a frequency band; Of a signal, the width of the smallest frequency band within which the signal can fit; A measure of data flow rate in digital networks typically in bits per second; The capacity, energy or time required
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by cypherstream 
last modified: 2009-05-22 15:29:36 |
