- From: Ingar Mæhlum Arntzen <ingar.arntzen@gmail.com>
- Date: Fri, 4 Dec 2015 08:47:54 +0100
- To: "Igarashi, Tatsuya" <Tatsuya.Igarashi@jp.sony.com>, public-webtiming@w3.org
- Cc: "fd@w3.org" <fd@w3.org>, public-web-and-tv IG <public-web-and-tv@w3.org>, Ingar Mæhlum Arntzen <ingar.arntzen@norut.no>, Njaal Borch <njaal.borch@norut.no>
- Message-ID: <CAOFBLLrgWpoACS3HuY4HCjFgqxocbexGkq77ATJp3e3rrwT5eA@mail.gmail.com>
Dear Tatsuya "As I understood, If a web page contains one video element and synchronize it with another device. There is not much difference between the example x and example 6. But if a web page contains multiple video elements, the TimeObject helps the application to synchronize these with another device." Not exactly. I meant if your media experience is only one video in one web page (not synchronized with anything) - then default playback mode is ok (timed playback mode also ok). As soon as you want to time-align video playback with something else (video from another angle, race statistics and infographics, video ads, etc), in the same web page, or in other webpages on other devices - support for timed playback will make that a lot easier and better. Time-aligning other stuff to the playback of video is already possible (track element, popcornjs etc) - however the current timing model (currentTime + timeupdate event) of the media element is not a good starting point with respect to precision - particularly in the distributed scenario. These solutions also typically depend on a single media element being the master. This is a huge limitation. In contrast, support for timed playback mode opens up for precise synchronization in massively distributed applications - think thousands of smart phones doing synchronized playback in a stadium - or millions in a broadcasting audience. Also. as indicated by, Paul Gausman, the timing object spec is not only about video playback. The home page of the timingsrc project gives a very high level summary of the advantages of the timing object spec. http://webtiming.github.io/timingsrc/index.html Best, Ingar 2015-12-04 5:50 GMT+01:00 Igarashi, Tatsuya <Tatsuya.Igarashi@jp.sony.com>: > Thank you, Ingar, > > > > I just want to understand the advantage of timing object spec. > > > > As I understood, If a web page contains one video element and synchronize > it with another device. There is not much difference between the example x > and example 6. But if a web page contains multiple video elements, the > TimeObject helps the application to synchronize these with another device. > > > > >If all you want to do is to play a video in a single video element - then > this distinction is of marginal interest. > > >However, if you want to time-align video playback with something else - > in the same web >page or on another device, this distinction becomes > important. > > >You may read more about this distinction in the timing object spec under > "timed playback mode" [1] > > > > -***---***---***---***---***---***---***---***---***--***---***---***- > > Tatsuya Igarashi (Tatsuya.Igarashi@jp.sony.com) > > Innovative Technology Development Div, System R&D Group > > Sony Corporation > > > > > > > > > > > > *From:* Ingar Mæhlum Arntzen [mailto:ingar.arntzen@gmail.com] > *Sent:* Tuesday, December 01, 2015 8:52 PM > *To:* Igarashi, Tatsuya > *Cc:* fd@w3.org; public-web-and-tv IG; Ingar Mæhlum Arntzen; Njaal Borch > *Subject:* Re: Review of the Timing Object specification > > > > Dear Tatsuya Igarashi > > > > Thank you ! > > > > These two examples represent different approaches to similar goals. > > > > In example X you ask the video to play - an it plays in its own timframe > (progression defined ultimately by the media stack). > > In example 6 you specify a timing object as timeframe (progression > ultimately defined by performance.now() or a timing provider) and asks the > video to align itself. > > > > If all you want to do is to play a video in a single video element - then > this distinction is of marginal interest. > > However, if you want to time-align video playback with something else - in > the same web page or on another device, this distinction becomes important. > > You may read more about this distinction in the timing object spec under > "timed playback mode" [1] > > > > We have demonstrated that it is somewhat possible in JavaScript to force a > video element to be time-aligned with a timing object. This works best when > variable playbackrate is supported by the video element. The solution is > based on continuously monitoring the diff between timing object and > currentTime of video element, and performing appropriate adjustments. You > can check out the code here [2] > > > > We also have published a report [3] on how well media elements currently > responds to such "abuse". However, in order to improve further, browser > support is required. > > > > You may also verify example 6 in your own browser by opening this demo [4] > of two videos synchronized by the timing object. JS libraries are available > in the timingsrc repository [5] > > > > [1] > http://webtiming.github.io/timingobject/#media-elements-and-the-timing-object > > > [2] > https://github.com/webtiming/timingsrc/blob/master/source/mediasync/mediasync.js > > [3] > https://lists.w3.org/Archives/Public/public-webtiming/2015Oct/0003.html > > [4] > https://github.com/webtiming/timingsrc/blob/master/examples/mediasync.html > > [5] https://github.com/webtiming/timingsrc > > > > > > Hope this is clarifying :) > > > > Best regards, > > > > Ingar Arntzen > > > > > > > > > > > > > > > > 2015-12-01 11:26 GMT+01:00 Igarashi, Tatsuya <Tatsuya.Igarashi@jp.sony.com > >: > > Hi, > > > > Media Timeline Synchronize is one of the most interesting topics in Media > industry. > > > > I wonder that the following two examples are the same semantically. Most > media player of browsers do not support any of playback speed rates. Also, > execution of javascript code is not in real-time. How does the Time Object > proposal improve accuracy of timeline synchronization of HTML5 media? > > > > Example 6: Use timing object to control a video > > var video; // Pointer to a video element in the DOM > > var to = new TimingObject(); > > video.timingsrc = to; // Video now directed by timing object > > > > // Start timing object (video seeks and starts by implication) > > to.update({ position: 5.0, velocity: 1.0 }); > > > > Example X : synchronize media timeline of a video > > var video; // Pointer to a video element in the DOM > > > > // Sync media timeline (video seeks and starts with the rate) > > video.currentTime=5.0;video.playbackRate=1.0;video.play(); > > > > -***---***---***---***---***---***---***---***---***--***---***---***- > > Tatsuya Igarashi (Tatsuya.Igarashi@jp.sony.com) > > Innovative Technology Development Div, System R&D Group > > Sony Corporation > > > > > > -----Original Message----- > From: Francois Daoust [mailto:fd@w3.org] > Sent: Tuesday, December 01, 2015 1:22 AM > To: 'public-web-and-tv IG' > Cc: 'Ingar Mæhlum Arntzen'; 'Njaal Borch' > Subject: Review of the Timing Object specification > > > > Hi Web and TV IG participants, > > > > Back at TPAC in Sapporo, I presented the Timing Object specification, > developed by the Multi-Device Timing Community Group to enable single- and > cross-device synchronization scenarios. I took an action to send the draft > spec to the Web and TV IG for review. > > > > The Multi-Device Timing Community Group would welcome your feedback on the > spec by 8 January 2016 (so that it can decide on next steps early next > year). The latest draft is available for review at: > > > > http://webtiming.github.io/timingobject/ > > > > The Multi-Device Timing Community Group does not anticipate any major > change to the specification by January. Main open issues are referenced > from within the spec itself to ease review from an external perspective. > The group uses GitHub to track issues otherwise: > > > > https://github.com/webtiming/timingobject/issues > > > > At this stage, the CG is particularly interested in: > > > > 1. discovering Web and TV use cases and requirements that the spec may not > properly address 2. discussing the proposed mechanism to associate a timing > object to an external timing resource through code provided by a > third-party timing resource provider; 3. evaluating the main technical > hurdles from an implementation perspective. > > > > The CG also invites all interested parties to join the Multi-Device Timing > CG and let themselves known. > > > > Thanks, > > Francois. > > > > PS: Some of you wondered at TPAC whether there existed an open-source > prototype implementation of the spec in JavaScript. Ingar and Njaal have > been working on it, see announcement today at: > > > https://www.w3.org/community/webtiming/2015/11/30/first-implementation-of-timing-object-draft-spec/ > > > > > > > >
Received on Friday, 4 December 2015 07:48:31 UTC