We’ll take a break from the lingo of IPTV this week in favor of a more fundamental question: How much bandwidth does it take to send linear and on-demand video over IP?

The short answer: Less. Less than it takes to deliver “traditional” digital TV streams, anyway. Why? Three reasons.

Reason #1: If you’re prepping for video over IP (meaning video over the path now used by cable modems), you might as well do advanced compression. The two move in lockstep.

Advanced compression – variously called MPEG-4, AVC and H.264 – makes it possible to squish two to three times more HD streams into the same channel size (6 MHz, or, the equivalent of around 40 Mbps.)

To put that in perspective, today’s compression – MPEG-2 – slims standard definition (SD) TV streams to 3.75 Mbps, and HD streams to around 15 Mbps.

By contrast, MPEG-4 skinnies SD streams down to 1 Mbps or less, and HD streams as low as 4 Mbps. (This is highly dependent on screen size.)

In bandwidth costs, that’s a big savings right there.

Reason #2: IP video – at least the on-demand stuff – will be switched. Switching is a bandwidth efficiency method all by itself.

Reason #3: The built-in statistical gains that come with moving video packets through wider packaging. What wider packaging? The bonded, or “wideband” channels, that come with the DOCSIS 3.0 cable modem specification.

Statmux refresher: If compression squeezes video streams to their smallest state, statistical multiplexing hyper-organizes those compressed bits, for the ride to homes.

Right now, in “traditional” digital video, statmuxing organizes multiple video streams more efficiently, inside one 6 MHz channel. In a four-channel wideband bond, though, the statmux gets to work across 24 MHz. The extra elbow room, space-wise, translates into more little gaps that can be filled with video packets.

The supplier community, and especially those who sell the gear that will enable video over IP – meaning Cable Modem Termination Systems (CMTS) and in-home gear – says that moving video over IP can save as much as 40% in bandwidth, compared to traditional means. (They have a dog in this hunt, of course.)

This conversation typically veers into talk of variable bit rate encoding vs. adaptive streaming. More on that another time.

Here’s another example of video lingo from different sectors bumping into one another: The way video is streamed on the Web, versus the way it works on cable. (Or broadcast, or satellite, or telco, for that matter.)

It’s hard to keep it all straight. Hence this week’s translation.

Original Internet video streaming dates back to the dial-up days. Streaming meant video bits flowing over the Internet, which could be viewed on the computer screen as they arrived — if, of course, there’d been no dropped packets along the way.

Next came the “progressive download.” The biggie. Adobe Flash, Microsoft Silverlight, and YouTube use it, among many others. The “progressive” part means you watch the video that progressively spills into your PC’s hard drive, as a file, after a comfortable chunk of it had loaded into your browser’s cache.

The new big thing in Web video is “adaptive streaming,” sometimes also called “fragmented MPEG-4.” It mixes traditional streaming with file-based delivery. The “adaptive” part means multiple video files of the same content are each encoded into two- to four-second chunks. That way, the client can switch between files on the fly, at varying bit rates, depending on available bandwidth.

Example: You’re watching an HD video stream on your computer. At the moment, and probably unbeknownst to you, it’s coming in at a throughput rate of around 7 Megabits per second (Mbps). Suddenly, the Internet sneezes — congestion. In the background, your player knows to hop to a 5 Mbps stream, or a 3 Mbps stream.

On the linear cable side, digital video is encoded in one of two ways: Constant bit rate (CBR), or variable bit rate (VBR). Both deal with how the bits are stuffed into a pipe of fixed size (6 MHz, or 38.8 Mbps). Variable bit rate is harder to do, but more efficient; it finds ways to fill the pipe completely, smooshing bits into all blank space. “Zero nil bits,” as they say. Almost all linear video uses VBR encoding these days, thanks to statistical multiplexing.

VOD, on the other hand, still uses CBR, as does switched digital video – meaning that a fixed amount of the available bandwidth is ascribed to each stream (3.75 Mbps per stream for standard definition video; 15 Mbps for HD).

In that sense, Internet adaptive streaming of fragments is like VBR for on-demand. Near-VBR, for lack of a better term, because fixed file sizes (2 Mbps, 4 Mbps, 6 Mbps) are still on the scene.  You click to play a stream; it’s sent in a way that optimizes quality, depending on available bandwidth.

That’s the basics of Internet vs. cable encoding, for video streaming. Next week: Your own personal Faraday cage? Really?

Recently, a reader posted a question to this column’s Jan. 18 translation on 3D-TV and bandwidth.

“If HDTV is 6x the bandwidth for satellite transport via MPEG-2,” wrote the optimistically-named ‘3D 2010,’ “what is the rule-of-thumb bandwidth necessary for HD 3D?”

First, a distinction: That “6x” number signifies the uncompressed bit rate for HDTV. This matters especially to that link between the set-top and the TV, known as HDMI, which also talks in uncompressed digital.

Another baseline: Let’s say 3D-TV is a feature layer on top of a 720P or 1080i HDTV (because it is), and that it expects incoming pictures to be delivered at 60 frames per second.

To send a true, full-resolution, stereoscopic image to that 1080i or 720p HD display would indeed use twice as many bits, over the uncompressed (HDMI) interface. Why: Because the TV expects 60 frames per second, yet you’re sending two images – one for each eye.

So, to keep it at the same resolution and frame rate, uncompressed, it’d take two times as many bits to do 3D-TV. If there’s a rule of thumb, 3D-2010, that’s pretty close.

However. That third dimension in 3D is depth. For your brain to perceive depth, extra processing is required – which makes resolution anomalies in the original two dimensions less perceptible.

In other words, your brain is so busy extrapolating depth, it likely doesn’t notice the lower resolution on the streams representing each eye.

That’s why you hear people on the bandwidth side of the chain use terminology like “frame compatibility,” and you hear makers of 3D-TVs (and some content owners) use terms like “full resolution 3D.”

Frame compatibility crams the left and right eye images into one frame, each at a lower resolution. It fits into the same space as 2D, needs no special transport handling, and theoretically can’t be resolved as lower resolution to the human eye — because the addition of depth perception blunts a hyper-critical focus on each frame’s resolution.

Here’s how 3D-TV will likely emerge as a cable service, at least in the beginning:  On-demand, through the VOD or switched digital video (SDV) passageways, to a set-top outfitted with any updated requirements for 3D-TV.

Like so: You want 3D, Customer Bob? Here’s a new box. Here’s the menu of 3D titles. Knock yourself out.

Longer term, watch for two developments: Another extension of video compression, called Multi-View Coding (MVC), to further squish HD and 3D signals down into a more transport-friendly size, and faster versions of what HDMI does to move uncompressed 3D signals between set-tops and 3D-TVs, at 60 frames per second.

Speaking of 3D-TV, the darling of this year’s Consumer Electronics Show: It all seems very … 2004. That was the year anyone trekking around the Las Vegas Convention Center saw something new and shiny and everywhere. It was called HDTV.

At the time, and from the perspective of anyone in the bandwidth business, big questions loomed around the bandwidth-gobbling implications of high definition television.

Refresher: HDTV images contain 6x the picture information of standard definition digital TV. Even with compression (MPEG-2), 6x the picture info meant that only two, maybe three HDTV video streams could shimmy into the same channel width (6 MHz) that carried 10 to 12 standard-def streams.

It was (and is) a big deal. Cable responded, with analog spectrum reclamation, switched digital video, and 1 GHz upgrades. (Whew.)

Now here comes 3D-TV – which is essentially two HDTV streams, one for each eye. Double the bandwidth. Right?

Kind of. This week’s translation isolates just the transport part of 3DTV – because heaven knows there’s lots of moving parts in this next chapter

The buzz at CES, from a transport perspective, emerged in lingo like “frame compatibility” vs. “full-resolution.”

Here’s what that means: In order to get 3D signals over the plant, in a bandwidth-friendly way, it’s necessary to wriggle both “frames” – the images for each eye – into one frame. People tend to call this “over/under,” or “side-by-side.”

In all cases, it describes how the frames are jammed onto the conveyor belt, so to speak – one frame over another, or one frame next to the other.

To the network, “frame compatibility” makes a 3D signal look like 2D. The 3DTV knows what to do with each kind of incoming 3D frame, to pop it back out on the screen in 3D.

Either way, it’s another simulcast, on top of SD and HD.

The drawback, from a purist perspective, is that the encoding into side-by-side or over/under necessarily means that each frame offers less than “full resolution” to each eye.

Blu-Ray, an optical media, does offer full-rez to each eye, which is why you’ll see a big push, later this year, for 3D Blu-Ray players and titles. (Think Avatar in your living room.)

The good news is that the frame compatibility exists, and that 3D-TV manufacturers already support decoding of all types, which means there won’t be a “format war” – at least not on this part of the 3D food chain.

Nothing like a few years of bankruptcy drought to color the imaginations of the resource-challenged! In this season’s techie-wish roundup, Charter Engineering takes the candycane.

Let’s start with Doug Ike, VP of advanced video and applications for the MSO, who wants “a fully-featured, tru2way-based guide — that fits in a DCT-2000.” (Good luck with that.)

Also on Ike’s wish list: A magic bandwidth wand. “Wave it over any congested plant and presto! Gobs more bandwidth.” (“Of course,” he adds dryly, “our product team has the magic bandwidth gobbling wand.”)

Marwan Fawaz, Charter’s CTO, seeks not just EBIF-based applications, but 3D EBIF apps. (Ditto for longtime 3DTV observer, EBIF evangelist and Starz  senior director of advanced services Rebecca Rusk Lim, who hankers for a 3DTV with rhinestone-encrusted shutter glasses.)

Bob Blackburn, senior director of digital engineering for Charter, seeks an iphone app that “uses the internal GPS, cross-referenced to an extensive cartographic database, resulting in precise directions to the nearest Guinness dispensary.”  Brilliant!

Tom Gorman, VP of field operations for Charter, seeks a pair of “RF goggles,” to see how much signal is on the plant at any given location.

Also on Gorman’s wish list: A “customer attitude leakage detector.” As a tech rolls up to a home, the gizmo glows in accordance with the customer’s demeanor, ranging from “happy go lucky” to “potential hostage taker.”

Marv Nelson, VP of professional development for SCTE, wants a “small, USB-type dongle that identifies me as a cable customer and allows full access to all of my accounts and services when I’m outside my service area.”

Tops on the list for gadget connoisseur Mike Hayashi, EVP of advanced engineering and technology for Time Warner Cable, is a wireless Skype camera. Intent: An alternative to walking around, talking into his Macbook — in a multi-level house. With a medium-sized dog underfoot.

Also: “Anything that’s better than an iPhone (I tried Android, etc….they all kind of suck.”) And: Standardized power adaptors for all chargers (“and I’m not talking about a giant octopus.”) Lastly: A two-car lift for his garage.

Arthur Orduna, CTO of Canoe Ventures, stepped up to wanting a way to break free of compulsive Blackberry dipping. “I want a couple of free sessions to a self-help group to break this insidious habit,” he said, dipping into his Blackberry.

For Bob Zitter, CTO of HBO: “I wish I had an eReader that would be permissible to use when the airplane is waiting on the runway or flying under 10,000 feet.”

Ray Starbird, CEO of Northpoint Media and former Cox director of strategy, just wants Google Voice on his iPhone, for heaven’s sake. “The two together could be as delicious as chocolate and peanut butter … and if AT&T is concerned now, wait ‘til Google assimilates Gizmo5 and adds real phone lines and number portability into Google Voice.”

For interactive TV maven Tracy Swedlow: A digital assistant that cleans her house. (Yes, please!)

May all your wishes find you. Merry, merry!