Synchronizing multiple WebRTC streams

w3c / media-production-workshop

W3C Workshop on Web and Media production

https://www.w3.org/2021/03/media-production-workshop/

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Synchronizing multiple WebRTC streams #51

Open tidoust opened 3 years ago

tidoust commented 3 years ago

How to keep multiple live feeds, e.g. from multiple cameras, in sync. Any way to embed timestamps in the streams?

Raised in:

WebRTC in live media production

murillo128 commented 3 years ago

The timestamp is already specified, however it is not widely implemented: https://w3c.github.io/webrtc-extensions/#rtcrtpcontributingsource-dictionary

Missing piece is how to synchronize tracks, maybe via: https://henbos.github.io/webrtc-timing/

chrisn commented 3 years ago

There's a BBC R&D blog post that talks about synchronisation of WebRTC streams, which proposes using NMOS timing RTP header extensions to enable a synchronised playback mode.

alvestrand commented 3 years ago

For background info: Is there info on how the broadcasters do this today - eg do they keep camera clocks in sync, or do they adapt the media in some fashion?

alvestrand commented 3 years ago

Some discussion of synchronization here: https://w3c.github.io/mediacapture-main/getusermedia.html#introduction

rektide commented 2 years ago

Two mentions I can throw into the pot:

The MediaSession Coordinator work. Mentioned in https://github.com/w3c/mediasession/issues/266 and available at https://github.com/WebKit/explainers/tree/main/MediaSessionCoordinator
The Timing Object work mentioned above in their synchronization section.

I have some comments there, but supporting more varied use cases like webrtc make me appreciate variety of situations that a good synchronized playback system needs be able to support.