That project, internally dubbed "Mux 3.0," aims to apply to ITV data the same type of multiplexing techniques used for video services that allow MSOs to cram multiple standard- and high-definition channels into one 6MHz channel slot. In some cases, 10 or more SD networks may be sharing the same slice of spectrum. (See Comcast Unit Sizes Up 4:1 HD Compression .)
ITV data traditionally comes through at a fixed bit rate -- sometimes called constant bit rate (CBR) -- while digital video channels use variable bit rate (VBR), which allows the amount of bandwidth used for each channel to flex up and down and fit inside one 38.8Mbit/s channel slot. One key idea behind Mux 3.0 is to apply VBR-style optimization to ITV data and make those apps more efficient from a bandwidth perspective.
For example, an Enhanced TV Binary Interchange Format (EBIF)-based app from Canoe Ventures LLC (the cross-MSO advanced advertising venture) occupies about 100Mbit/s of bandwidth. It's early days for Canoe, but when it starts to reach scale and hundreds of apps on hundreds of networks start coming down the pipe, cable could have a bandwidth crunch on its hands. (See Canoe Boots Up Interactive Ad Campaign .)
"It's in the early days; we're fine right now," Canoe chief technology officer Arthur Orduna said in October at an event at the The Cable Center , in reference to Canoe's ITV deployment and its relationship to the new CableLabs project. "It's an issue that's been recognized," he added, noting that the new bandwidth optimization capabilities for ITV should be ready by the time that market begins to truly scale.
There's no immediate need for Mux 3.0, but the probable bandwidth issues surrounding the potential of cable ITV, with EBIF as the catalyst, were the genesis of the project.
CableLabs isn't saying much about Mux 3.0, but a source familiar with the project says it's "fast-tracked" and looking to define a "control plane interface" between the multiplexers and the various entities involved with cable ITV, including Canoe and its MSO partners.
CableLabs is said to be looking at three different ways to handle the bandwidth crunch, with some more complex than others:
- The simplest method is to just drop any apps if there isn't room for them. For example, if there's 500kbit/s of bandwidth available, and 700Kbit/s worth of apps coming through, the system could just chop off the excess. CableLabs is working on filtering and business rules for how such decisions would be made.
- Since it's possible that dropping those apps won't always be an option (revenue driving interactive ads, for example), CableLabs is also looking at how to borrow some bandwidth from the video to make room for the ITV apps, which sums up the VBR equivalent described earlier.
- The most complicated option is to slow down the ITV carousel, which is used to distribute the applications down the plant. But this isn't an option in all cases, either, because some apps are synched up, or "bound," to a live program or advertisement and need to arrive at a specific time. However, this slow-down approach may come in handy for "unbound" ITV apps, such as games, that aren't associated with a live TV program.
The working group at CableLabs tasked with this project, sources say, is currently gathering use cases from MSOs, and the plan is to create a technical document on how to handle all the options and roll them up into a set of "operational guidelines" for ITV app developers and video encoding vendors.
That work isn't limited to EBIF apps, so it's likely to also include more advanced (and potentially, more bandwidth-intensive) tru2way apps.
Although there's no urgent need for Mux 3.0, the project is one of several that have come into play as cable puts the pieces in place for massive EBIF deployments. Earlier on, the industry scrambled to execute an extensive "pipe cleaning" exercise to ensure that EBIF apps weren't dropped or corrupted in some way as they snaked through processors, multiplexers, and other elements of the cable network. (See Cable Breaks Out the ITV Drano .)
— Jeff Baumgartner, Site Editor, Light Reading Cable