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Comcast Content Delivery Summit Keynote: Live Linear Explained

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“I’m not going to be talking about a CDN,” said Jason Burgess, a Comcast software and systems architect, during his Content Delivery Summit 2014 keynote address. “Today, I’d like to talk to you about Xfinity TV Go.

Xfinity TV Go has “over 30,000 hours of on-demand programming and 50 channels of live television,” Burgess said. “We call our IP video development platform VIPER."

As the lead on Comcast’s VIPER IP video engineering team, Burgess is responsible for the architecture and development of solutions for adaptive bitrate delivery of video-on-demand and linear content for Xfinity TV Go and other next-generation IP video products at Comcast.

“For on-demand, or VOD, we transcode high-quality course content into multi-bitrate MPEG-4 and then prepackage content into a Common Intermediate Format based on DASH,” Burgess said. These additional extensions to DASH make it easier for Comcast to handle the content distribution internally.

“Whenever someone requests the content, we have CDN edges scattered across 25 sites across the United States,” Burgess said. “The CIF storage is a multi-petabyte system that we replicate across both sites.”

Burgess then explained the live linear approach of VIPER.

“Everything is completely identical to the VOD system,” Burgess said, noting that RAM is used for live linear rather than the multi-petabyte storage for on-demand content.

“One of the best features we have is Download & Go,” said Burgess, discussing the fact that Comcast subscribers can download a large part of the on-demand library thanks to a single digital rights management (DRM) solution. The DRM solution ties into approximately 25 key license servers geographically dispersed around the United States.

“In addition, we don’t apply the DRM until the request time,” said Burgess, noting that this provides for quick response in the case of a breach.

“We collect events from every IP player, including the Xfinity TV Go app,” Burgess said. “This lets us diagnose issues in real-time, a key feature for operations team so that they can determine whether certain areas of the country are experiencing low playback quality." Comcast then uses the data to provide self-healing capabilities for the system.

Burgess described the analytics architectures starting with the applications, then moving to data collection, data processing, and data persistence via MemSQL accessible via a real-time applications programming interface (API).

“This data is then available to our operations team, as well as any application views,” said Burgess.

Burgess also talked about advertising, noting that Xfinity TV Go used industry-standard ad standards.

“We use industry standards but have also worked with standards bodies to create new standards where needed,” Burgess said. “We have ways to create segment boundaries anywhere in the stream based on metadata we receive. We also are able to support local and national dynamic ad insertion (DAI) on line streams.”

Xfinity uses Freewheel and other ad-decision systems, and the analytics platform allows for “complete and accurate accounting for linear ad viewing.”

“We now have the ability to individual target users for ads,” Burgess said, noting that several customers are excited about this ability.

“The CDN can no longer help you, because the CDN can’t cache hundreds of thousands of unique copies of the manifest,” said Burgess.

Burgess described a solution that Comcast created to work within the CDN’s limitations, based on a master manifest. Comcast is also looking to address manifest manipulation on the client side, but that has challenges, not the least of which is working with Apple.

Comcast is beginning to gain insight into what decisions an end-user makes when faced with a blackout. Burgess also noted that emergency alerts are possible on Xfinity TV Go for the first time, even though they have not yet been used.

“VIPER has been designed from the ground up to enable rapid development and deployment of IP video applications,” Burgess said. “This allows for other options for deployment, since we can support other formats and DRM providers in our just-in-time packager.”

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