Re: [media-and-entertainment] Use of WebRTC for media content distribution

Hi Chris and all.

Thank you for sharing this blog post. It nicely documents some of the
issues with sync and also hints to future possibilities arising given that
this issue were to be resolved.

A few general comments on the sync challenges discussed with respect to
WebRTC.

- timestamps in the data is a requirement for sync, and it would be great
if upcoming standardization work would target making this available.
- synchronization also requires some kind of mechanism for adjusting the
playback/media clock.
- one important question is who gets to adjust/control the media clock? In
RTP type solutions the media clock is essentially controlled by the sender,
and signalling for clock and control is done over the media stream. While
you can get good sync this way, sync would still be limited to media
carried by those streams.
- In the multi-device timing CG we have advocated the other solution, where
the media clock, control and synchronization is solved by a separate
mechanism. In our proposal one would simply supply a timing object to the
HTML5MediaElement (or WebRTC MediaStream), and then it would just
synchronize itself. This makes for a flexible solution where it is easy to
sync webrtc with *whatever else* you want to synchronize it with, also
across devices. It also means that one can avoid added complexity for media
streaming protocols and standards.
 - the blog also reported problems with maintaining sync (once
established): This is a shared problem with HTML5 Media Elements. As some
of you already know, we have demonstrated that this can be solved for HTML5
elements with a javascript wrapper ( though there are some issues making it
harder that it needs to be). Unfortunately, with WebRTC this is not
possible as the media clock is not exposed.

Best, Ingar Arntzen






2018-05-30 12:45 GMT+02:00 Chris Needham via GitHub <sysbot+gh@w3.org>:

> On a related note, we have been investigating WebRTC in a media production
> environment, and encountered issues with synchronisation between different
> WebRTC media streams. Here's a [blog post](https://www.bbc.co.uk/rd
> /blog/2017-07-synchronising-media-browser) that describes the use case in
> more detail.
>
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