In cable, making room for more new stuff is two-pronged.

First is the chronic question of bandwidth: How many slots on the digital shelf can go to more HD and VOD? How many for any new 3D and Internet-protocol TV offerings?

The second prong is the matter of sheer physical space. If you’re the keeper of headends and hubs - heating, cooling, power, rack arrangements, wiring - it’s not a good day when the headend starts looking like the five-pound bag, with another 10 pounds of new stuff on the way.

At issue, in large part, are those impressively nerdy mainstays of digital cable: the QAMs. Quadrature amplitude modulators are necessary to imprint digital signals onto the physical plant, for transmission to subscribing homes.

Pretty much everything needs a QAM in cable, including the new stuff. But up until now, most service categories attracted their own vendors, each with their own QAMs. There are QAM suppliers for video and QAM suppliers for voice and data.

Right now, the densest packing of video QAMs is eight per port. For broadband data, four. Switched digital video? Up to 16. IPTV will need a few to start, then more as the service develops.

Right now, they all exist in isolation. Different racks, different batches of gear.

That’s why the industry’s headend caretakers - led by Comcast - posed this question: Why not make the QAM spigots denser, and more capable of sending information across service categories?

If you’ve gotten this far, you’re probably hip to a relatively new, Comcast-specific term: “CMAP,” which stands for Converged Multiservice Access Platform. It grew out of another Comcast acronym: “NGAA,” which stands for “Next Generation Access Architecture.”

If you dabble in the cable-modem termination system landscape, this is probably sounding a lot like the “modular CMTS” conversations that dominated the broadband cable scene a few years ago.

This is different, in that it’s a blueprint for gear.

Here’s what CMAP isn’t: It’s not a new version of DOCSIS, nor is it an active CableLabs project. That’s because it’s a product definition, not an interface specification. In other words, it doesn’t mess with how data talks when it moves from one port to another. Instead, it suggests a way to mix and match QAMs for video, voice and data services, in a denser way. 160 of them, per port, with room to grow.

This is at the write-the-specs stage now. They turn into CMAPs as soon as next year, with launches expected the year after. More on this as it develops.