RE: webtv-ISSUE-21: Time synchronisation

Hello,
 
Just to clarify....
 
I did not submt the indicated use-case (ISSUE-21). I only commened that precision timed-playback was an (optional) feature supported by UPnP AV-4 that would address the stated requirement.
 
Regards,
Russell Berkoff
Samsung
 

________________________________

From: public-web-and-tv-request@w3.org on behalf of Jean-Claude Dufourd
Sent: Tue 6/7/2011 1:18 AM
To: public-web-and-tv@w3.org
Subject: Re: webtv-ISSUE-21: Time synchronisation


Thanks to Russell and Olivier for pointing out the precise technology that allows this type of synchronisation.

However, is this feature present in all discovery and service protocols that HNTF has to consider ? I do not think so.
So it may be a valid request to have this feature in HNTF, to provide it when the underlying technologies don't.

An argument such as "this feature is already in this standard so do not touch it" is difficult to accept, specially if the standard in question does not follow the W3C patent policy. 

Best regards
JC


On 7/6/11 08:05 , Olivier Carmona wrote: 

	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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-- 
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