Hulu’s Move to DASH
The U.S. OTT service's Baptiste Coudurier talks about the hard work—and black magic—behind the smooth migration to MPEG-DASH, which now accounts for 75% of its traffic
This article appears in the Autumn 2015 issue of the European edition of Streaming Media magazine, and in the July/August 2015 issue of the U.S. magazine.
Since adding Chromecast to its list of supported devices in 2013, U.S.-based Hulu has been working to extend support for MPEG-DASH inside its various players without disrupting existing format support. The secret of this painless migration is the engineering of DASH-compliant video segments that are also backwards compatible with Smooth Streaming players. As of now, more than 75% of Hulu’s traffic is served through the new segments format, and the migration continues without increasing the deployed files inventory.
This is an unusual move in the industry, the kind of technology strategy that provides an ideal lesson for other publishers looking to make the move to DASH. In this exclusive interview, Baptiste Coudurier, Hulu’s principal software development lead and architect of this format migration, shares his insights on Hulu’s incremental approach for leveraging DASH and how it has benefited the OTT service and its customers. And while Hulu isn't available outside of the U.S., the lessons to be learned from its move to DASH are applicable to any OTT service in the world.
Hulu and Hulu Plus
Hulu has one of the biggest audiences for OTT video after giants such as Netflix and YouTube. Hulu started in 2007 and established a successful business publishing movies and programs from American broadcasters such as NBC, ABC, and Fox on the web the day after they air. The service launched its subscription tier, Hulu Plus, in 2010. Hulu Plus offers a lighter ad load than the free version, is available on living room and mobile devices, and has more content.
Hulu has also developed an authentication integration program with cable operators in which Adobe Pass bridges the customer’s cable ID with his or her Hulu ID. This unlocks more content on Hulu, as well as early availability windows for specific content. This creates additional complexity in access management, but some rules never vary: Geolocation is ensured for the U.S. territory and military bases only, and 100% of the content is secured through DRM.
Hulu’s competitors are services such as Netflix, Amazon Prime Video, and more recently HBO Now. Hulu’s key advantage is that it has recent episodes of current TV. Hulu is successful because of its reach—it currently has 9 million subscribers and is available on multiple devices. Combine the reach and the publication speed with the volume of programs and you’ll get a sense of why it’s crucial for Hulu to simplify and optimize content preparation workflows to an extreme degree.
When Multiscreen Meant Chaos
Before working for Hulu, Baptiste Coudurier was already one of the major contributors to the FFmpeg codebase, a sharp expert in broadcast codecs and workflows. When he was a student at EPITA (a well-known French engineering university), he started walking through the MP4 maze and acquired the knowledge that proved useful to work for SmartJog and finally Hulu. When you encounter him today, you can still feel the same curiosity level that his biography suggests, and it’s no surprise that his real job is to push the limits of technology. The impetus behind his current quest can be found in the early days of the multiscreen Hulu.
“When I started working at Hulu, in 2009, we had only a web player, not even playing H.264—it was still delivering VP6/MP3 FLVs over RTMP,” Coudurier says. “My job was to extend the content preparation workflow and allow Hulu to deploy on a booming range of devices. It was a crazy race to ensure video quality, scale the workflow, and launch on new devices.”
With the launch of Hulu on the iPad in March 2010, the developments around HLS accelerated, and soon Hulu was on PlayStation 3, Roku, and Xbox 360. “It was already a fragmented landscape,” Coudurier says. “We had to do RTMPE on the desktop and HLS/AES on the devices, launching on all the devices in a very short timeline. In June 2010, all of it was in beta, and we were just in time for Hulu Plus beta, which went public 5 months later.”
At this time, the industry started to emphasize the need for strong protection of high-value content, mandating the use of DRM on all platforms wherever it was possible. So Coudurier and his team had to implement DRM or media encryption in record time on all the platforms, an effort that he summarizes by saying: “We decided to do everything, as it was impossible to find a common platform for all of our devices.
“For the desktop, the refactoring of the player in Silverlight to support Smooth Streaming and PlayReady DRM was too much effort,” he says. “Our fastest path was to stay in Flash and use Access DRM. On Android we didn’t have much choice so we implemented the Widevine Classic format. On Windows Phone, we had to use Smooth Streaming and PlayReady, which we extended soon after to Wii U and other devices.” With HLS still in AES, the output format scope had widened to four different packaging of H.264/AAC files, all incompatible with each other. That meant four times the storage space and CDN footprint, and still a lot of workflow challenges and troubleshooting for Hulu’s video experts to handle.
Smooth Leads to DASH
“When we started with Smooth, it was the simplest choice to cover a wide range of new devices, as PlayReady was widespread,” Coudurier says. “Sometimes we weren’t able to deliver the best possible experience, like on the Wii platform where the Smooth profile was limited, but over time we reached a very satisfying experience level with Smooth Streaming, on platforms like PlayStation 4 or Xbox One.”
By this time, the Hulu team had acquired a good experience with the Smooth Streaming format, tackling the difficulties of ad insertion in this environment and mastering the Protected Interoperable File Format (PIFF) (go2sm.com/piff) that powers Smooth Streaming. (For a list and definition of all the acronyms in this article, see the glossary at the end of this article.)
“In 2013, we saw the Chromecast as a perfect opportunity to dive into the DASH world,” Coudurier says. “We had already seen that DASH was quite close to Smooth Streaming, and we were searching for a way to combine both DASH and Smooth manifests with ISO Base Media File Format (ISO-BMFF) (go2sm.com/bmff) video segments. That’s when we deprecated our old Smooth packaging lib with a new DASH packaging lib, on which we added a Smooth compatibility layer.”
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