RE: webtv-ISSUE-21: Time synchronisation

Hello,

Yes...Object Linking & Clock Synchronization are new features in the latest release UPnP release (AV-4). The specs are now available.

DLNA usually takes what it chooses from various UPnP releases rather than implementing all functionality specified in a particular UPnP release.

UPnP (AV-4) Object Linking is more targeted at associating content rather than playing content at a particular time. An example would be still photos associated with a movie scene. The playback of the associated stream is controlled by the user rather than specified in the presentation stream, i.e. if the user chooses to view the associated content they can do so, the associated content is not pushed to the end-user or companion device.

UPnP (AV-4) does allow for precision timed playback of content. An example would be multi-room audio where echo effects need to be avoided or simply having independent network connected speakers attached to an AV receiver. In these cases UPnP allows a Control Point to determine if all the devices are using a common time-base and can command devices to start rendering at a deterministic time to avoid synchronization issues. 

The actual time synchronization protocols are specified via IEEE-802.1AS and IEEE-1722 although other time synchronization protocols are allowed such as SNTP for less demanding applications. These protocols operate independent of the UPnP layer.

Regards,
Russell Berkoff
Samsung

-----Original Message-----
From: Matt Hammond [mailto:matt.hammond@rd.bbc.co.uk] 
Sent: Monday, June 06, 2011 2:49 AM
To: public-web-and-tv@w3.org; Russell Berkoff
Subject: Re: webtv-ISSUE-21: Time synchronisation

Hi,


Many thanks for the pointers into the UPnP specs. This is new functionality in the latest release?

Does this function enable a companion device to time its own presentation of content (eg. a web application showing a slideshow) to that of the UPnP device if the UPnP device is tuned to a broadcast service (for example)?  
In this scenario it would not be appropriate or necessarily feasible to achieve synchronisation by commanding the device to commence playback at a particular master clock time.

The clock synchronisation protocol is not itself a part of UPnP? In which case, perhaps an application would also need access to this service on the home network too?


regards


Matt

On Mon, 06 Jun 2011 09:47:51 +0100, Russell Berkoff <r.berkoff@sisa.samsung.com> 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
>


-- 
| Matt Hammond
| Research Engineer, BBC R&D, Centre House, London 
| http://www.bbc.co.uk/rd/

Received on Tuesday, 7 June 2011 00:56:36 UTC