The EBU has published guidelines to help broadcasters set meaningful SLAs (Service-level Agreements) for content distribution, including both streaming and media file transfer over IP infrastructures. At present this covers only managed infrastructures since the EBU has decided that it is not yet practical to specify SLAs for uncontrolled networks comprising multiple domains owned by different service providers. The main focus seems to be at present on use of third-party data networks for media transport to exploit their reduced provisioning cost and turnaround time compared with traditional distribution.
But greater benefits may follow from the flexibility that IT-based distribution infrastructures will bring, for example in making it easier to create multiple-language versions of content for different international markets. This has been highlighted by some early applications of cloud-based media distribution, one example being the Association of Tennis Professionals (ATP) using a cloud video production platform from London-based Aframe to ingest footage of tennis events and incorporate localized audio tracks and graphics. Before this, the ATP relied on overnight shipment of tapes and hard drives to share tennis footage globally outside of the big events such as grand slams.
But the EBU believes it is important to establish a solid foundation for media distribution over data networks within which SLAs can be clearly defined. It has specified four categories of service. One is Permanent Service, normally involving long-term contracts similar to other telecom services, such as a permanent link between two studios. The second category is permanent service with occasional use, involving a booking system with guaranteed response time. This would typically be used for less popular sports events as well as occasional coverage, where the broadcaster needs guaranteed access at certain times but not enough to justify a permanent contract.
The third category is shared infrastructure with occasional use, allocating resources on a first-come-first-served basis with no guarantee of availability. However, it could involve a booking system allowing broadcasters guaranteed access at some point in the future, but not always at a time of their choosing. Clearly this could involve coverage of events at venues that themselves require booking. The final category is temporary service for special once-off events that may last anytime from a few days to a few months, typically major concerts or sporting events such as the Olympic Games, where numerous broadcasters require content contribution from the scene.
Although aimed at broadcasters, the EBU’s guidelines also contain an important message for service providers, which is that media distribution has different requirements for SLAs from standard data such as emails. SLA requirements for broadcast audio/video are more stringent and require closer engagement between both parties. This applies to professional audio as much as video, as this has all the service requirements of Voice over IP but with additional quality factors such as need for higher sustained bandwidth, along with lower and more constant latency. For the video tolerance of jitter and out-of-sequence IP packets is much lower than for other applications, because of the need to keep down buffering time, in turn to minimize end-to-end transmission delay.
The document focuses on high-level issues that need to be considered in negotiating SLAs for media transport, and will be followed by a more detailed in-depth paper covering specific use cases and the technical parameters involved.
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