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

On Wed, Dec 17, 2014 at 5:31 PM, Sangwhan Moon <smoon@opera.com> wrote:
>
>
>
> 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
>
>

That should have looked like this: (Silly rich text mail clients.)

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