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The State of Server-Side Ad Insertion 2018
For years, SSAI has promised targeted advertising in a seamless stream that defeats the ad blockers. Has the promise finally been realized?
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SSAI is one of the crucial innovations that has allowed over-the-top (OTT) video to become a viable industry, because it opens up paths to monetization and helps to both absorb infrastructure costs and create profit centers where cost centers have existed. But while technologists are bullish on SSAI, some vendors and content publishers are a bit more cautious. This article takes a look at the state of SSAI, both its successes and the challenges it still faces, including scaling to large audiences and privacy concerns.

According to a recent Interactive Advertising Bureau study called “Live Video Streaming: A Global Perspective,” 70 percent of consumers watch digital video once a day, 67 percent have live streamed content, and more than half (52 percent) prefer free, ad-supported content. Stream stitching and SSAI allow ads to be inserted directly into the programming stream, making for a more seamless viewing experience.

“If you can stitch ads in on the server-side and make sure the VAST [Video Ad Serving Template] impression pings associated with the individual ads are properly tracked, then all of a sudden you can send out one integrated stream,” says Chris Xiques, senior director of video infrastructure at CBS Interactive. “There’s no buffer wheels where you’re waiting for the ads to load in the middle of the stream. It looks more like television.”

And if SSAI makes viewers happy, it’s making content publishers and distributors even happier. “The move to SSAI has opened up significant live and linear OTT inventory,” says Allen Klosowski, senior vice-president of the advanced solutions group at ad serving platform SpotX. SSAI has simplified video on demand (VOD) as well, because the same technology can be deployed across all media assets. “This has quickly driven scale in multi-platform distribution and monetization for our clients,” he says.

What Is SSAI?

“SSAI seamlessly inserts ads into streaming video content, allowing monetization on any device that can play video,” says Andrew Broadstone, director of product management at Brightcove. SSAI works with both Live or VOD and is really the only way to have live advertising (more on that later).

Previously, ad stitching came about because of device fragmentation in which some viewing devices lacked client-side capabilities. The crux of the problem is that most current ad technologies, including programmatic trading, viewability, measurement, and interactivity, were first created for the client-side ad serving and weren’t supported by SSAI. This is no longer true.

SSAI creates an individualized media stream for each unique viewer, in which different viewers get different ads. The ad break communicates with an ad decision server, which decides what to serve each particular viewer, based on information such as viewing history, demographics, and geographical location. All of this takes places on the server side.

“The thing to know about server-side ad stitching is that the video chunks for the ads and content are not literally being stitched together. All you’re really doing is knitting text files together,” says Xiques. “You’re basically taking manifests that point to ad segments and the manifest that points to content segments and creating a new manifest that points to them both.”

A simple graphic breakdown showing how TV ads in the original broadcast stream (top) are replaced by different ads in the individually targeted stream (bottom). Image courtesy Switch Media.

Defeating the Ad Blockers

“SSAI is the only way to show ads on many of the growing diversity of connected TV devices, where it is difficult or impossible to build custom clients for every device,” says Broadstone. “These platforms represent a significant area of growth among our media customers. Traditional web publishers also are using SSAI more to avoid ad blockers and to improve the user experience.”

“Ad blockers work by detecting ad calls that are made in the client. However, with server-side stitching, the ad call and ad stitching are performed before the stream reaches the client, meaning the ad blocker doesn’t detect an ad call and therefore is unable to block the response,” says David Springall, founder and CTO of Yospace, which provides server-side dynamic ad insertion for live and VOD streaming.

Preventing ad blocking is one benefit of SSAI, since the stream can’t be detected as coming from a known ad-serving URL. Another benefit is being able to replace and personalize ads already embedded in a stream.

Balancing Personalization and Privacy

Magnus Svensson, media solution consultant at Eyevinn Technology, helped Bonnier Broadcasting, MTG, Discovery Networks Nordics, and Telia Co. develop a technical specification for SSAI. The broadcasters were not able to monetize online streams when distributed by an operator, since it was sending out content with the original broadcast ads with no ability to measure ad views. To start selling online advertising, they needed to make changes in the distribution workflows. “The trend in the Nordic region and in Europe now is definitely moving away from client going to server side,” Svensson says.

The project eventually was extended to include all the major broadcasters in Sweden together with the operator and distributors agreeing to start doing server-side ad insertion. “We developed a technical specification highlighting how this should be done between a broadcaster and an operator starting with Sweden, but since most Swedish broadcasters are across the Nordics, it’s all now starting to spread there.”

Svensson says he spent an equal amount of time addressing data privacy as he did the technical requirements to implement SSAI. Telia is now able to offer ad personalization and frequency capping while anonymizing data to follow new General Data Protection Regulation (GDPR) guidelines. Telia is targeting based on approximate geographic area (since the exact area is considered personally identifiable information), content, screen size, and device type. The specification document can be found online.

“There’s no real logical reason to stick to doing any client-side [ad insertion],” says Svensson. “The only thing remaining is to agree on some kind of ad tracking server side as well, because today the only way of doing proper tracking is done doing client-side insertion.” The same tracking can now be done on the server side, but the measurement organizations are less comfortable with this. He adds, “The measurement institutes and ad agencies don’t really trust server side, because it’s opened up a little bit more for fraud that you can actually manipulate the data.”

The fear of leaving ad dollars on the table was enough motivation to get the Scandinavian groups to work together. So what are the technical issues that anyone implementing SSAI needs to look at?

Handling Ad Breaks

The first step is identifying how the video player knows what’s an ad and what is content. Broadcast content generally has a SCTE (Society of Cable Telecommunications Engineers) marker embedded as part of the stream, which includes information about when an ad break starts and how long it is. Traditional broadcast has two types of SCTE markers—104 for baseband (HD-SDI) and 35 for IP video. These markers are “read” and translated to OSMF cuepoint messages that are passed between server and player for content/ad stitching via discontinuity signals. But not all content has SCTE markers.

In order to support SSAI, the client needs to be able to handle HLS DISCONTINUITY tags or MPEG-DASH manifests containing multiple periods. In SSAI, you don’t start and stop a stream as you do in client-side ad insertion (CSAI). Instead, the segments are delivered in a continuous stream server-side, with ad segments stitched into the manifest. DISCONTINUITY tags (or, for MPEG-DASH, multiple periods) are used to inform the player that the upcoming segments have different characteristics. The presentation time stamp (PTS) reset is one clear example; changes in frame rate end encoding are other differences that might occur between the original video and the ad segments.

“Because of how the SSAI component can in a scalable way create the virtual streams it is also required that the video player is capable of playing HLS with DISCONTINUITY tags and MPEG DASH containing multiple periods,” Jonas Birmé, solution architect at Eyevinn Technology, wrote in an August 2017 blog post. "These are the mechanisms in the streaming formats that makes it possible to replace video chunks in the original media stream with the ad video chunks.”

The packager chunks the video stream into encrypted video file segments according to the different DRM systems and also creates the streaming format manifests. “To signal where an ad break start and ends in the case of HLS it can use the tags EXT-X-CUE-OUT and EXT-X-CUE-IN, and for MPEG DASH it creates a new period,” Birmé notes. “The SSAI component then fetches the HLS-and MPEG DASH-streams from the origin and parses the streaming format manifests to be able to create a personalized and unique virtual stream for the viewer. The virtual streams also contain the necessary information that the DRM decryption module needs to be able to acquire a license from the DRM system.

“[T]o be able to have server-side ad insertion and DRM protection you need a DRM provider that can handle more than one DRM system and an SSAI component that can handle both HLS and MPEG DASH,” Birmé concludes. “If you don’t have the DRM requirement it is sufficient with an SSAI component that handles only HLS as most devices can handle HLS as long it is unencrypted.”

A schematic showing the SSAI specification adopted by Bonnier Broadcasting, MTG, Discovery Networks Nordics, and Telia company. “The trend in the Nordic region and in Europe now is definitely moving away from client [and] going to server side,” says Magnus Svensson of Eyevinn Technology, which helped develop the specification. Click for a larger version. Image courtesy Eyevinn.

Another Use Case

Every video publisher and distributor will have unique requirements when it comes to SSAI, and not all applications support SCTE markers.

“I work at a media company and we have rules about users not being able to skip ads, not playing an ad more than once, and requirements to do third-party tracking of ad playback. That means that there are components in our player that need to know exactly when an ad is on the screen so that seeking can be disabled in the UI and video click-through can be passed to advertiser’s web sites,” says Xiques. “There’s no standard way of interpreting SCTE-35 markers on the 15 different application platforms that I support.

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