From W3C Wiki

The session explored cross-device synchronization scenarios, including shared video viewing, lip-sync use cases, distributed music playback, video walls, cross-device animations, etc. These scenarios require mechanisms to (1) synchronize the local clock with an external one, (2) distribute a timeline, and (3) harness the media playback or animation. A pure JavaScript-based approach only works to some extent; proper cross-device sync needs native browser support. The Timing Object spec defines an API to expose cross-device sync mechanisms to Web applications. Discussion revealed that harnessing the media playback is not trivial as media rendering is often handled by the hardware itself, and that loose synchronization where e.g. a device temporarily runs out-of-sync could improve UI responsiveness in some cases. Work on the spec will continue in the Multi-Device Timing Community Group. Interested parties are invited to join the group!