Dolby flies flag of ABR-friendly audio

Audio sometimes gets lost in the noise of video technology. But what more quickly degrades a viewer’s quality of experience (QoE) than a voice not synchronized with picture or loudness levels that fluctuate wildly between channels? The bottom line upfront: Pay TV operators neglect audio at the peril of losing both eyes and ears of their customers.

That’s the kind of pitch that the audio experts at Dolby Laboratories are used to making to the companies that license their technology on behalf of the end users. At this year’s IBC, with operators having gained another year of experience with multi-screen and adaptive bit-rate (ABR)-based video, Dolby took the occasion to rally the industry around Dolby Digital Plus (DD+), an enhanced audio compression scheme positioned as a more efficient way to handle advanced audio than High-Efficiency Advanced Audio Encoding (HE-AAC).

“People have figured out the video,” said Craig Knudsen, Director of Strategic Partners in Professional Solutions at Dolby. “The premium audio is a relatively new piece, and how that interworks with various ABR formats is something that we’re really pushing hard now on to get the encoder vendors to up to their game in terms of audio delivery.”

Knudsen noted that some of the drivers of advanced video now include over-the-top (OTT) providers. “HBO Go, Netflix, Vudu, Hulu have all adopted DD-plus and are delivering in adaptive formats with our codec,” he said. Manufacturers of multi-screen devices also have become promoters, with Amazon including DD+-enabled features (including “virtual surround sound”) in the description of its 7-inch Kindle Fire HD, released September 6. According to Dolby, more than 940 million DD+ devices have shipped.

One of Dolby’s messages at both IBC and NAB was how the DD+ interworks with adaptive bit rate video. One demo showed how a video stream is able to retain the full capabilities of 5.1 (five speakers, one sub-woofer) even as a network conditions degrades from 5.0 Mbps to 192 Kbps. Only at 128 Kbps does DD+ shift to 2.0 (two speakers). At the very bottom, the audio collapses in to a mono sound field. “In terms of transition, it can do that in a seamless manner, no clicks, pops or anything,” Knudsen said.

The key to this kind of performance across any of the various ABR and digital rights management (DRM) schemes with a single stream is integrating DD+ within network encoders. In practical terms, that means an encoder vendor obtains a license agreement and software developer kit (SDK) from Dolby. The company then implements DD+ through its own graphical user interface (GUI) and then submits the implementation to Dolby for approval.

The HE-AAC alternative, according to Dolby, is not only multiple streams, according to bit rates and devices, but also unpredictability. In the case of ad insertion, that means variation among encoders resulting in a lack of seamless transitions and resets, prolonged mutes and other impairments that irritate viewers, embarrass content owners and lead advertisers to withhold payments.

One company that agreed with the need for an efficient solution and went through this process of integrating with Dolby is RGB Networks. The driver from RGB’s perspective was ABR streaming to the set-top box, which has audio requirements higher than second-screen devices.

“If you want to hear 5.1 audio and truly experience the noises and explosions that are happening and you want to distribute to different devices, including the set-top box, the only way (was) to create multiple versions for that stream,” Ramin Farassat, RGB Vice President of Product Marketing and Business Development, says.

Farassat said this recent enhancement of Dolby’s technology allows for stereo to run at a low bit rate, and then as network conditions improve, it jumps to 5.1. “If I were doing it with today’s technology, there’s a break,” he said. “With Dolby, it’s a seamless switch.”