Understand CDN Qualification Programs

Big content distribution networks qualify codecs for station streams
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Big content distribution networks qualify codecs for station streams

The past 12 months have seen a dramatic upturn in new products related to streaming media, along with an explosive growth in streaming to mobile devices. This rapid growth has caught many broadcasters by surprise.

Most streaming media operations began as add-ons to terrestrial broadcasting stations, using cast-off audio processors and a hodge-podge of PCs, sound cards and related gear. Sound quality and expectations were both fairly low.

All of that has changed. Better encoders and audio processing algorithms are enabling top-quality sound for streaming audio, and with backups, there is an expectation of zero downtime.

If the broadcaster is planning streamcasting to a large audience, the signal usually is delivered to a content distribution network such as Akamai, Arkena, Limelight or Level3, who handle the mass dissemination of the streaming signal. Each CDN has its own set of requirements for the media streams they receive, and broadcasters who want to deliver a quality stream to both fixed and mobile online listeners need to understand codec specifications and CDN qualification programs.

I spoke with both CDNs and encoder manufacturers to get an overall perspective on station/CDN working relationships, and what qualification really means.

Because of the large scale on which they operate, content delivery networks are able to offer services to broadcasters that smaller, non-CDN operations often cannot. For example, your content and listenership can go viral at any moment or have regular surges for special events. CDNs offer elastic bandwidth to manage these irregular traffic flows.

With cloud storage, CDNs can upload and distribute content locally from anywhere in the world, ensuring high availability and increasing the speed of delivery. Cloud storage also enables broadcasters to monetize and repurpose content in ways that fit into existing workflows.

Unlike traditional broadcasting, which indirectly measures listener demographics, streaming media offers exact numbers of who is listening, for how long and where. A big part of the decision a station makes in its CDN choice may hinge on the quality and availability of the analytics that the CDN offers. Knowing that it’s important to clients, some CDNs offer analysis services that help customers make the most of the analytics package.

Codec certification by CDNs is a new topic to many broadcasters. There are various flavors of CDNs and various services are offered. When shopping for encoders, certification from a CDN can be reassuring, as it is an official proof of compatibility. Customers may be willing to pay more for a certified product, and while it is early in the game, there may be a significant difference in price between certified and non-certified encoders, as manufacturers pass the costs of certification on to customers. In any event, it is a topic that management and engineering needs to understand before it is time to sign contracts.

Stations shopping around for a CDN to distribute their stream will discover there are differences in technical requirements and level of customer service. The majority of CDNs support Real Time Messaging Protocol (RTMP) ingest. However, there are some that also require an HTTP Live Streaming (HLS) feed. CDN requirements for adaptive bitrate (ABR) streaming can differ, with some requiring that the supplier send either one high-quality stream, or several streams of varying quality.

Some CDNs charge for transcoding, and this cost often drives many content suppliers to output several high-quality streams from their encoder. The advantage of this approach is that the station can manage stream quality all the way to the end user, rather than rely on the CDN’s transcoding capabilities.

In order to set its own benchmark and ensure the stability of the encoder, some CDNs will test the compatibility of the connection between the station’s encoder and the CDN’s access point. At Akamai, headquartered in Cambridge, Mass., there is a test lab dedicated to qualifying encoders. As explained by Victor Wong, senior software development engineer in test-MCDN servers, and Jason Toohey, engineering manager-MCDN services, there have been two driving forces for the certification process for encoders.

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The Akamai Network Operations Control Center.
Courtesy Akamai

“Customers call us with complaints and issues about encoders not working properly,” said Toohey, “And we’re their first contact. The problem usually boils down to issues such as how closely the encoder adheres to streaming standards, or other software issues, such as how well their retry algorithm works after an interruption. We often end up in a reactive mode, trying to put out fires, which isn’t good.”

Wong said the lab is also used as a resource. “The other way that we get involved is when manufacturers come to us with either hardware or software encoders and ask for them to be qualified.” He said the qualification process at Akamai is fairly formalized. On its website are guidelines and a checklist. Once manufacturers have gone through these preliminary steps, the next step is submission of the encoder to Akamai for formal evaluation.

“For hardware, they send us the device and we evaluate it in the lab. For software encoders, we have them publish a stream to Akami, and we evaluate that,” said Toohey.

While Akamai takes a business-like approach to encoder qualification, Limelight Networks, based in Tempe, Ariz., tends to take a more customer-centered, “high-touch” approach.

Limelight’s Adam Diep, director product management-video, said, “While encoder certification can be helpful in choosing new equipment, qualification criteria can be inconsistent from one program to the next, since there are no industry standards. We reduce concerns through a high-touch engagement with customers to make sure that they have a reliable integration of all the components in the streaming workflow.”

He added that an end-to-end solution may be created and configured by Limelight; the encoder is just one part of that process. It was an interesting contrast of approaches between Akamai and Limelight to deliver a quality stream; Akamai supports its program where the CDN certifies the encoder, whereas Limelight works with customers on the stream from end to end.

For the developers of streaming encoders, qualification by a CDN provides a level of reassurance to the customer, and is also official proof of compatibility. Laurent Gros, product manager, video at Digigram, said the process can be long and involved.

“A lot of it depends on the CDN. In some cases, they do not offer certification, so it falls on the manufacturer to perform such testing. Of the CDNs that do provide certification testing, some request remote access to the encoder for evaluation, and others ask the manufacturer to provide the encoder unit for several months. In the latter case, the manufacturer must pay a monthly fee to maintain the certification agreement.”

With several major CDNs and a number of smaller ones in existence, and more CDNs on the way, how many certifications are practical and realistic for manufacturers? “

Certifications are necessary only for the major CDNs such as Akamai, Level3 and Arkena,” said Gros. “For the other CDNs, standard functionality is sufficient.”

For equipment manufacturers, CDN certification can be a costly process, although none of those I contacted were willing to give specific dollar amounts. Certification involves significant integration and testing time on the part of the developer to guarantee correct interfaces for the stream and for user authentication, and there also may be additional costs paid to the CDN for their qualification program.

Adoption of streaming media by listeners has reached the tipping point. A recent survey conducted jointly by Edison Research and Triton Digital shows the number of Americans listening monthly to online media is now 53 percent, or 143 million. This represents a huge opportunity for broadcasters to consolidate their brands online and maximize advertising revenue.

To do that, however, they need to streamline their streaming operations. Online activities need to be afforded the same professionalism and expertise that was lavished on terrestrial broadcasting in the past. Establishing a partnership with a Content Distribution Network can help to ensure a consistent, quality online signal. Good analytics can give precise information on how many people are listening, where and for how long. And using an encoder that has been certified by your CDN will guarantee that your stream won’t be plagued by those weird little glitches and intermittent outages that occur when a codec is almost compatible with the network, but not 100 percent.

Tom Vernon is a longtime contributor to Radio World.


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