Re: [AVT] Syncronization of co-located clients?
Stephen Casner <casner@acm.org> Sun, 03 July 2005 23:22 UTC
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Date: Sun, 03 Jul 2005 16:21:58 -0700
From: Stephen Casner <casner@acm.org>
To: Greg Herlein <gherlein@herlein.com>
Subject: Re: [AVT] Syncronization of co-located clients?
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On Sun, 3 Jul 2005, Greg Herlein wrote: > I found this as well - might provide a mechanism for sync based > on SMPTE time code: > > http://www.ietf.org/internet-drafts/draft-singer-smpte-rtp-01.txt > > Assuming all clients controlled the playout buffer using the > SMPTE time code, this could likely do it. My particular > application is on a local LAN (a controlled VLAN actually) so I > am not expecting the network to present significant problems. I don't think the SMPTE timecodes help unless they are representing an absolute time in the future, where the sender has made a prediction about the amount of time needed for propagation to all receivers and buffering time within each receiver. That might work in a controlled LAN environment, but it is not a general solution. The BBN Synchronization Protocol that I mentioned is based on using synchronized clocks at the receivers (e.g., using NTP). Each receiver relates its earliest possible playout time for a media timestamp to real time, and communicates that back to the controller. The controller finds the latest of these times and informs all the receives so they can choose the same playout time. There's more to it than that, of course. Sync "epochs" were used to deal with media clock drifts, etc. [I state the above without having read the paper in a long time. I seem to remember a centralized controller, but it could be done in a distributed manner as well.] -- Steve _______________________________________________ Audio/Video Transport Working Group avt@ietf.org https://www1.ietf.org/mailman/listinfo/avt
- [AVT] Syncronization of co-located clients? Greg Herlein
- [AVT] Re: Syncronization of co-located clients? lazzaro
- Re: [AVT] Syncronization of co-located clients? Stephen Casner
- Re: [AVT] Syncronization of co-located clients? Greg Herlein
- Re: [AVT] Syncronization of co-located clients? Chuck Harrison
- Re: [AVT] Syncronization of co-located clients? skillzero
- Re: [AVT] Syncronization of co-located clients? Stephen Casner
- Re: [AVT] Syncronization of co-located clients? lazzaro