DVB-I Promises Sub-Second Latency for Broadcast and IP
TV standards body DVB is working to enable an open standards-based approach to OTT and broadband television.
DVB-I will deliver services over the internet to devices with broadband access and also over managed networks, with operator support. All connected devices are in its scope, not just TVs and STBs.
"The aim of DVB-I is to do for IP services what DVB have done for broadcast," explains DVB chair Peter MacAvock. "Services will be signalled and distributed in a standardised manner, so a specific app is not required. For users it will mean a more consistent experience, though they don’t have to know or care whether a service arrives via broadcast or IP. Broadcasters can deploy a service once to a wide range of devices, and manufacturers can make a single consistent user experience for DVB-I and broadcast services."
DVB-I deployments can be standalone, or broadcast and IP delivery can be combined to create a single hybrid offering. The latter would incorporate services delivered via both methods, making optimal use of the different characteristics of each channel.
"The first premise is to replicate the broadcast experience on broadband-delivered content, but once we go down that road we open up a whole other set of possibilities in terms of being able to mix different types content, offer enhanced services, and offer different versions of a service, targeting different groups of users in a way that is not feasible with broadcast."
Some examples include the provision of accessibility options such video with signing, or versions of content with special technical characteristics such as UHD.
For much of the functionality required by DVB-I, decent technical standards are already available. Content delivery will use the DVB-DASH specification which is already deployed by many broadcasters, often in conjunction with HbbTV.
This will be augmented by a low-latency mode, for which the technical specification has been approved, to ensure that the overall delay for live OTT channels is the equivalent to broadcast.
"LL-DASH takes the MPEG DASH specification and profiles it for delivering low latency services," MacAvock says. "It implies that the amount of time for a service to make it through the network is not a minute or 30 seconds but [on] the order of seconds—and potentially fractions of a second.
"Of course, this requires this system to be implemented correctly. We know live distribution of content over broadband networks are only going to get more important, and we don’t want situations in live sports, for example, where people learn about an event on Twitter a good while before it is streamed."
The forthcoming DVB specification on Multicast Adaptive Bit Rate (mABR) will offer further opportunities for broadcasters and network operators to work together to optimise delivery to large numbers of receivers simultaneously.
"The main aim of the DVB-I ecosystem is designed to virtualise the concept of a media service," MacAvock says. "DVB as service definition is network-agnostic. A DVB broadcast stream received in the home is delivered over the network over cable, satellite, or terrestrial. DVB-I is designed to do exactly the same, so packaging of a stream would be consistent regardless of whether you have a broadcast network, a broadband network or, in future, a 5G network."
The DVB is in discussions internally and with stakeholders about 5G network integration.
Another goal is to remove the need for vertical integration by which broadcasters or their partners have to customise delivery for each device. The resulting economies of scale would be useful to free to air broadcasters, operators and pay TV providers, MacAvock said.
DVB-I will also offer the ability to deploy to receivers a single integrated service list including services available over both broadcast and IP.
"In terms of making DVB-I functionally equivalent to DVB (for digital TV), the major missing piece from a standards perspective is a service layer," says Peter Lanigan chair of the DVB Commercial Module working group. "This is used to signal the services and content that are available, meaning the information used by a TV set (or smartphone, tablet, etc.) to populate the channel list and the EPG.
"This will probably involve the most significant technical choices for the DVB in writing the DVB-I specifications. Several existing technologies are candidates to be adopted and, if necessary, extended to fulfil the requirements. One challenge that the DVB will have to solve is how a receiver starts the process of service discovery and locates the service list."
DVB members include the BBC, Dolby Labs, Sky, DirecTV, Arqiva, Canal+, Samsung, and Ericsson. The industry will get its first close-up look of DVB-I at IBC with release of the first specifications scheduled later this year.
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