BBC Talks Resilient Cloud-Based Broadcast System
“On average we receive 7 million requests every day for the BBC iPlayer, our catch-up video service,” said Stephen Godwin, senior technical architect at the BBC, today at Streaming Media West. “That accounts for about 2 percent of the total BBC consumption.”
Godwin spoke in a session titled "How the BBC Built a Resilient Broadcast Grade System in the Cloud," where Godwin noted that the BBC iPlayer is the largest VOD service in the U.K. He noted that last year the BBC iPlayer served 36.5 billion minutes of content.
“Most video content the BBC makes available online is only available in the UK,” said Godwin. “But it is very popular.”
Depending on exact rights, content is available for streaming for between 7-45 days, on almost 1000 devices. The device types include PCs, iOS, Android, WindowsPhone, smart TVs, set-top boxes—with both streaming and download available on both Android and iOS devices.
“We also allow content downloading for viewing up to 30 days for iOS and Android, so you can watch it anywhere,” said Godwin.
With the popularity of iPlayer, the BBC found itself facing a challenge of creating a new and better ingest and transcoding workflow system. The new system is called Video Factory.
“Video Factory is designed to be scalable from the ground up, and to use the cloud,” said Godwin.
“We wanted something that would scale,” said Godwin. “The system we were replacing was 4-5 years old, and a hardware solution, and we didn’t plan for it to support smartphones. On the old system, we started running into limits, including storage limits.”
”When we designed the new system, we wanted a system that would scale in capability and price,” said Godwin. “The old system has some single-points-of-failure. We wanted to move to a model where we had the resiliency of the broadcast chain.”
Godwin then walked through Video Factory’s four major live-stream components: Mezzanine, Time-Addressable Media Store, Playout Data, and Transcoding.
In the Mezzanine Capture module, a broadcast-grade encoder uses 3Gbps HD via SDI to ingest up to 24 channels. Content is then passed through an RTP chunker to creates 80 MB files. Content is stored at 10 Mbps for SD and 30 Mbps for HD.
For Time-Addressable Media Store, a chunk-concatenating submodule gathers all the segments together to create a file that covers an broadcast entire time period.
“It’s the world’s best PVR,” said Godwin, noting that requests can be made in hour or half-hour long timeframes.
In the Transcoding module, a file-based ingest is available, as is a live ingest logic. Both are passed through the transcode abstraction layer to be sent to cloud-based encoders.
“At the moment we’re primarily using Elemental Cloud,” said Godwin, noting that other “on the ground” transcode solutions can be used.
“Why do we just use transcoding in the cloud?” asked Godwin, somewhat rhetorically, before giving an example that BBC One Regional News at the prime-time news hour splits into 19 separate local broadcasts.
“This news hour is a perfect pattern for elastic architecture,” he said.
He then explained how the BBC can spin up transcoding instances just before the news hour ends. The elastic approach, according to Godwin, means that they’ve been able to lower the time from live-to-on-demand availability to about 20 minutes. This is in stark contrast to the 8-10 hour timeframe it has taken in the past with local transcoders on the old system.
Video Factory is based on twenty components in total and entirely message-driven using Amazon’s Simple Queuing Service (SQS).
“Message-oriented architectures have been around more than ten years,” said Godwin, “and it is very well understood.”
In terms of deployment, Godwin said that software development for Video Factory began in earnest about a year ago, with the old system being turned off in September. He noted that they used 18 developers over the year’s time, and it has been running now completely finished for over two months.
“We deployed the transcode abstraction layer first,” he added. “Glastonbury was the first big test, with 170 odd hours of video made available. We then built the mezzanine system and deployed that, and that was our safety net to capture anything that was broadcast.”
Godwin then said rollout continued via various modules, with small amounts of code going live at once to reduce the risk and provide an easy way to roll back.
“What do we get?” said Godwin, referring to Video Factory benefits. “More video content is available online, we get faster delivery of live programmes, and we can now do iPlayer Premieres—episodes available online seven days before broadcast.”
An example of this premiere approach was recently used for BBC Three.
“What if you watch content before it appears on TV?” an announcer asks on video that Godwin played. “We want to make it the best TV service in the world.”
Godwin set a baseline for comparison between live television broadcast audiences and online viewing of iPlayer premieres. For BBC Three, Godwin said a programme with 1.5 million viewers is considered a fairly good audience viewing level.
“For the initial online episode of a recent show, before it was broadcast, we got 1.5 million video requests,” said Godwin. “In some of the later episodes in one series, we sometimes got 2 million video requests for the online content before it broadcast.”
An additional benefit is the ability to use iPlayer for exclusive content.
“We also sometimes have more content than we can broadcast,” said Godwin, using Glastonbury as an example. “So we now offer iPlayer Exclusive, offering some Glastonbury content only online.”
Finally, Godwin discussed possible additional enhancements to Video Factory.
“Our current simulcast system is really old and can’t handle HD,” said Godwin. “We also want to integrate Video Factory with our simulcast chain” which would allow the BBC to stream live broadcasts at the same time to devices and television.
Scroll down to watch Godwin's full presentation:
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