RE: webtv-ISSUE-21: Time synchronisation

JC,



As an example, AwoX achieves below +/-10ms using PTP (aka IEEE 1588-2002) within its commercial synchronized solutions above UPnP AV.



Regards,

Olivier



From: Russell Berkoff [mailto:r.berkoff@sisa.samsung.com]
Sent: mardi 7 juin 2011 03:10
To: Jean-Claude Dufourd; public-web-and-tv@w3.org
Subject: RE: webtv-ISSUE-21: Time synchronisation



Hello,



I'm told that IEEE-802.1AS is quite good at getting devices to synchronize to a common timebase (down to the 10's of nS).



UPnP actions to do scheduled playback such as  SyncPlay() (based on the availability of well synchronized device timebases) were added in AV-4. This approach is different than the previous approach of having a UPnP Control Point just send a Play command to the renderer at the "right" moment.



Sorry I couldn't provide the pointers to the specs earlier.



Regards,

Russell Berkoff



From: public-web-and-tv-request@w3.org [mailto:public-web-and-tv-request@w3.org] On Behalf Of Jean-Claude Dufourd
Sent: Monday, June 06, 2011 10:32 AM
To: public-web-and-tv@w3.org
Subject: Re: webtv-ISSUE-21: Time synchronisation



I would think the actual relevant section in the second document to be 2.5.9 Clocksync (within the theory of operations you point to in another email).
All examples point to a synchronisation in seconds. I can believe that this technology allows a synchronization with a precision of seconds.
We believe there is no way to achieve lip-sync (-20ms to +40ms) with such a mechanism based on UPnP 1.0, regardless of the media transport technology used.
Best regards
JC

On 6/6/11 10:47 , Russell Berkoff wrote:

Hello,



The submitted test case is redundant with facilities available in UPnP.



UPnP AV-4 provides Linked Content Metadata (Object Linking) as well as Precision Time Synchronization facilities. As previously mentioned in this forum, the current UPnP specifications are now available at no charge.



Please refer to:



http://www.upnp.org/specs/av/UPnP-av-ContentDirectory-v4-Service.pdf



Appendix G: Content Authoring with Object Linking



and



http://www.upnp.org/specs/av/UPnP-av-AVTransport-v3-Service.pdf



2.4.25 SyncPlay()



Regards,

Russell Berkoff





--
JC Dufourd
Directeur d'Etudes/Professor
Groupe Multimedia/Multimedia Group
Traitement du Signal et Images/Signal and Image Processing
Telecom ParisTech, 37-39 rue Dareau, 75014 Paris, France
Tel: +33145817733 - Mob: +33677843843 - Fax: +33145817144



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