Cloud-Based DVR: Under the Hood

Delivery Architecture Vastly Different Than VOD 10/16/2015 1:30 PM Eastern

New Orleans -- Turns out that delivering cloud-based DVR services is a whole lot different than delivering video on demand (VOD), even though the “ordering” process looks essentially the same: Open the app, pick the show of interest, push “play.”


That’s because VOD uses caches to store common content, while cloud-DVR (cDVR) requires an individual copy every time someone pushes “play” -- “which renders CDN caching useless -- this is individual to you, so there’s no caching,” said Neill Kipp, distinguished engineer within the Comcast VIPER (Video IP Engineering & Research) division at Thursday’s “Moving Set-Top Functions to the Cloud Session” here at the SCTE Cable-Tec Expo (and during which Kipp burst into song on several occasions, in order to manage a sudden case of speaker jitters -- it totally worked.).


Comcast began outfitting its systems with cloud-DVR components in 2014 -- mostly load-balanced “Super8” packagers, DASH-based origin servers, and lots and lots of storage. In one region, serving about 180,000 subscribers, the cDVR array stores close to 16 Petabytes of data.


“It’s a huge deployment, a real big thing -- all those discs, we had to buy, rack, and stack; every six weeks, we’d turn up another system,” Kipp said.


From a usage perspective, the cloud DVR service sees the most action “when nothing’s on,” Kipp said. “What we see is that when popular shows are on, people watch live TV -- but when nothing’s on, that’s when we see spikes.”


Asked why the cDVR service settled on MPEG-DASH (Moving Pictures Experts Group/Dynamic Adaptive Streaming over HTTP) rather than HLS (HTTP Live Streaming), Kipp and co-presenter Raj Nair, chief technology officer of Ericsson’s Mediaroom line, noted that DASH does a better job of handling multiple audio feeds and multiple codecs


 “HLS throws up its hands and says ‘I wasn’t designed to do that, I was designed to work on an iPad,’” Kipp said, adding: “DASH is a little more powerful.”


When asked if the elimination of local DVR storage signals the end of the set-top box, Kipp gave a provisional yes: “Is  this the beginning of the end of the traditional set-top box? Yes -- don’t make me ship you one, don’t make me roll a truck.”


But whether set-top box, gateway or dongle, “you still need a client,” noted panel moderator Marwan Fawaz, partner with Sarepta Advisors. “The question is whether we’ll still have any local storage in the home.”


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