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Re: Shared Motion - multi-device synchronization and media control for the Web.

From: Sangwhan Moon <smoon@opera.com>
Date: Wed, 17 Dec 2014 17:31:52 +0900
Message-ID: <CAFWyatquZdE6H50yVoMu=i4G_VYQsR6dh3J01e-+V5yhi_ysog@mail.gmail.com>
To: Ingar Mæhlum Arntzen <ingar.arntzen@gmail.com>
Cc: "public-web-and-tv@w3.org IG" <public-web-and-tv@w3.org>, Njål Borch <njaal.borch@gmail.com>, Dominique Hazael-Massieux <dom@w3.org>, François Daoust <fd@w3.org>
On Fri, Dec 12, 2014 at 9:50 PM, Ingar Mæhlum Arntzen <
ingar.arntzen@gmail.com> wrote:
>
>
> Dear IG Members
>
>
> We would like to present ourselves to this forum, as we share your
> interest in improving the Web as a platform for broadcast and multi-device
> media, and because we have some contributions which you might find relevant.
>
> My collegue (Njål Borch) and myself (Ingar Arntzen) are researchers
> working for NORUT (Northern Research Institute), Tromsø, Norway. Over the
> last couple of years we have focused on timing, synchronization and media
> control in multi-device media. Currently NORUT is in charge of the
> workpackage that deals with this topic in MediaScape, a FP7 EU project
> aiming to provide a fundament for multi-device Web applications. The
> consortium includes BBC R&D, Vicomtech, IRT, NEC, NORUT, BR and W3C.
>
> To the point: We have invented and developed the concept of  "Shared
> Motion", a generic mechanism for synchronization and media control in
> time-sensitive, multi-device Web applications. This mechanism has already
> been included as fundamental component in the multi-device architecture
> explored within the MediaScape project.
>
> To give you a rough idea what this is about:
> - Shared Motion synchronizes *globally*, thus multi-device
> synchronization is not limited to Intranet or specific network carrier.
> - Shared Motion synchronizes across Internet with errors < 10ms, and works
> fine even under poor network conditions (e.g. edge - albeit a modest
> reduction in precision may be expected)
>

This is a "out of plain curiosity" question, but it wasn't clear from the
paper how the < 10ms synchronization
deals across devices using different codecs - would it be possible to share
how that bit works?

While I am not a expert in this area, from my experience if a synchronized
seek request happens between
two devices that are decoding using different codecs there is a high chance
of the different streams having
different i-frames, which will require the decoder to advance to a i-frame,
which could end up making the two
devices go out of sync.

Stream 1: IBBPBBPBBPBBPBBPIBBPBBPBBPBBPBBPI
Stream 2: IBBPBBPIBBPBBPBPBBPIBPBBPBBPBBBPI
              ^
         Seek request
                 ^
       Stream 2 Decode Starts
                          ^
                Stream 1 Decode Starts



-- 
Sangwhan Moon [Opera Software ASA]
Software Engineer | Tokyo, Japan
Received on Wednesday, 17 December 2014 08:32:19 UTC

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