Scalable distribution system for IP broadcasting

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ABSTRACT

The commoditisation of media consumption devices in recent years presents an opportunity to experiment with new content experiences that decompose traditional media content into discrete objects that can be recombined by receivers in many different ways.

IP-based networks, both wired and wireless are expected to deliver these objects to consumers, but the need to scale them up to very large audience sizes, especially for simultaneous linear consumption, requires the development of advanced distribution technologies that are fit for this purpose.

INTRODUCTION

Time-shifted media consumption – especially the viewing of content on demand – continues to erode the viewing share of traditional linear television.

However, the split in the UK is still around 15% (time-shifted) to 85% (linear) and while the trend towards ondemand consumption will probably continue for drama and entertainment, we believe that mass linear viewing will remain a mainstay for news, sport and other live coverage.

At the same time, valuable terrestrial spectrum is being reallocated from broadcasting to cellular radio telecommunications, meeting a perceived consumer demand for mobile data. Some of this capacity will be used for on-demand media consumption on the move.

The scope for traditional broadcasters to introduce better-quality television services on today’s digital terrestrial television platform is thus constrained. As broadcasters turn their attention increasingly to wired and cellular networks for the delivery of their linear services, the ubiquity of Internet Protocol technology presents an opportunity to converge distribution mechanisms around common networking standards.

As part of its public service remit to address all licence fee payers, the BBC has for a long time provided over-the-top Internet simulcasts of its linear television and radio channels, latterly as part of its successful iPlayer service. These are gradually migrating from proprietary technologies to standards-based formats like MPEG-DASH to ensure the widest possible reach, including commodity web browser clients and mobile devices as well as connected television sets and set-top boxes.

Streams are encoded at several different bit rates and clients adapt dynamically between these as network conditions vary. From an initial starting position where the BBC operated its own Internet streaming infrastructure, third-party Content Delivery Network (CDN) partners nowadays help us to meet an ever-increasing audience demand for IP-delivered media services. But the current unicast mode of delivery, where each viewer receives a unique stream from a CDN edge cache, is inefficient, costly and doesn’t scale to audience sizes comparable with linear broadcast that we anticipate in the medium to long term.