As cable seeks to take greater advantage of broadband video, it faces a sizeable challenge. Not only does cable have to keep pace with the soaring consumption of video on tablets, smartphones, smart TVs, laptops and game players, but it eventually needs to migrate its linear television channels to Internet protocol (IP) delivery processes and formats.

Cable's digital video services were built upon quadrature amplitude modulation (QAM) technology that is enormously successful in delivering hundreds of linear channels, HDTV and video-on-demand (VoD) to set-top boxes (STBs). Cable's increasing broadband capabilities give providers the opportunity to deliver all video content, including VoD, linear and over-the-top (OTT), using IP, with the promise of greater efficiency and lower cost.

But, according to a new Heavy Reading report, "Multicast ABR to Keep Cable IP Video Streams Flowing," the industry must make the IP transition gingerly without leaving QAM in the dust. IP video poses its own challenges, and cable operators must ensure TV viewers aren't left staring at spinning wheels, waiting for videos to appear or squinting at fuzzy pictures. Cable faces another longstanding challenge because traditional television is delivered in a multicast (one to many) manner while IP content is delivered in unicast (one to one).

"What we have right now largely in the cable space is a mess," says Jim Barkley, principal engineer in technology and product at Comcast, who is driving the company's architecture for VoD, cloud DVR and content delivery network (CDN).

During an INTX 2016 panel session, Barkley summed up the situation: "We started with linear QAM and we've added on to that and in that time we really haven't stepped back and looked at what the whole of the system looks like. We've been adding services and the existing services have been making money so there really wasn't much of an opportunity or desire to sit back and figure out how to take this mess that we have and turn it into something reasonable."

The Heavy Reading report focuses on cable's effort to use adaptive bit rate (ABR) and marry it with multicast delivery of linear channels. The overall aim of multicast ABR (M-ABR) is to maintain quality of service (QoS) across IP-based video services, avoid latency as viewers change channels and optimize performance throughout video delivery.

To support IP migration, Comcast's Barkley and others advocate a "converged content delivery platform" for IP and QAM video. Following in the wake of the converged cable access platform (CCAP), this newer initiative is aimed at promoting common encoding, packaging and CDN delivery, layered with common advertising and data collection systems.

The report also explores multicast ABR for cable, including its benefits, implementation, supporting technologies and key challenges. It features a "Supplier Comparison" chart of technology companies that support M-ABR and provide products and solutions for IP video delivery by US cable service providers and content providers.

The industry's debate over the right balance of M-ABR, unicast and QAM will continue for some time, Heavy Reading says. Cable providers may arrive at different answers depending on their architectures and IP product roadmaps.

QAM is not going away soon but the clock is ticking, according to Heavy Reading. Consumers, especially younger demographics, increasingly watch TV programming on IP devices. 4K Ultra HDTV is coming into view, adding to the bandwidth requirements and delivery challenges.

— Craig Leddy, Contributing Analyst, Heavy Reading