- News & Analysis
- Video & Audio
- White Papers
- Industry Reports
As more Pay TV content is delivered as streaming video to the television, so the requirements for improved audio become more obvious. If operators want consumers to move seamlessly between their broadcast and IP services within their UI environment, like when they are watching VOD on hybrid STBs, they need to avoid a sudden loss of quality from, for example, 5.1 Surround Sound to simple stereo.
Raising the streaming Quality of Experience (QoE) to match that of broadcast delivery encompasses many challenges. We need subtitling and audio description to become the norm, and trick-play functions to match a local PVR for content delivered from the cloud. There are high hopes that improved compression and CDN technologies will deliver broadcast-standard picture quality and reliability at some point.
With so many things to think about, the spotlight has only recently turned to audio, but this is now an important theme for multiscreen headend providers. Envivio announced recently that the newest versions of its Envivio Muse encoding/transcoding solutions will support Dolby Digital Plus in all formats for live and on-demand applications, “providing pristine surround sound at lower bitrates on any screen.”
RGB Networks, another company providing converged headends for multiscreen and STB delivery, has been putting an even bigger emphasis on audio this year. According to Nabil Kanaan, Senior Director of Product Marketing at the company, the biggest trend in transcoding today is the use of ABR (Adaptive Bitrate Streaming) in the living room for devices that feed into televisions, which could be the primary set-top box and maybe a connected TV device.
This is driving the interest in 5.1 Surround Sound and RGB Networks now supports Dolby Digital Plus (DD+), the enhanced audio compression scheme, for HLS (HTTP Live Streaming ABR) and HDS (HTTP Dynamic Streaming ABR). “This is where our customer activity has started but it will be needed across the board for anyone doing adaptive streaming into the living room,” he adds.
At IBC last year Dolby made a big pitch to content owners and platform operators about the need for Surround Sound in the ABR environment. The company demonstrated how DD+ works with adaptive video. One demo showed how a video stream retained the full capabilities of 5.1 audio (five speakers, one sub-woofer) even as network conditions degraded from 5Mbps to 192 Kbps.
HBO GO, Netflix, Vudu and Hulu have all adopted DD+ and are delivering in adaptive formats with the codec. Channel owners and Pay TV operators are a natural target for this technology and are bound to offer a competitive response.
To turn AC-3 compressed video (classic 5.1 Surround Sound) into Enhanced AC-3 (Dolby Digital Plus), an RGB Networks transcoder fully decodes and then re-encodes the audio, takes care of the metadata and synchronizes the new audio stream with all the various bitrate video streams that are exiting the transcoder to make up the multiscreen ABR profiles.
Historically, one audio profile was used regardless of the video bitrates or packaging, but now you can start to mix and match, which means that if, for example, there are eight video bitrate profiles, the lower four can be assigned AC-3 (classic 5.1) and the top four can be given Enhanced AC-3 (DD+). Then you can drop out of 5.1 altogether if the bit rates go down to, say 500Kbps (stereo) or 192Kbps (mono).
This could be a typical ABR range configured at the headend but it is unlikely that all eight profiles would be available to any one device. Instead, the top four might be for connected TV devices and some tablets, and the bottom four for some tablets and smartphones, as an example.
Kanaan says improved ABR audio is part of what his company calls Multiscreen 2.0. He argues that you cannot deliver 5.1 Surround Sound over the broadcast network and then drop down to stereo over IP if the content is being consumed via the same device, like an STB. “We want to hide the fact that the video you are watching is streamed adaptively,” he says.