[whatwg] Comments about the track element

Cyril Concolato cyril.concolato at telecom-paristech.fr
Tue Jul 24 06:18:44 PDT 2012

Dear WhatWG,

During the ongoing SVG F2F meeting, the SVG WG discussed the use case of 
displaying SVG graphics on top of a video, in a synchronous manner.

The SVG WG believes that for such use case, it is necessary to indicate 
to the browser that the SVG and video content should stay synchronized 
(no matter what happens to the video playback), and to let the browser 
handle the synchronization internally. The SVG WG resolved to include 
such indication as part of the Web Animation specification, for instance 
using the HTML mediagroup attribute or the MediaController API.

However, the SVG WG thinks it would also be interesting to leverage the 
native UI controls of the video element to select (or deactivate) the 
display of the SVG content on top of the video, in a similar manner to a 
subtitle track. Obviously, the HTML 5 track element would be a suitable 
option for that. However, currently it only allows text tracks. So, the 
SVG WG would like HTML to allow the track element's URL to identify an 
SVG resource, and in that case the track kind would be 'graphics'. There 
would be a need to define how the graphics are displayed on top of the 
video, for instance reusing the viewport/viewbox negotiation phase. 
There would also be a need to make a more generic Track API or to 
replace the TextTrack API by the SVG API when the track is of kind 

The SVG WG would like to have your feedback on this matter.

Cyril Concolato, on behalf of the SVG WG (as part of SVG ACTION-3320)

Cyril Concolato
Maître de Conférences/Associate Professor
Groupe Multimedia/Multimedia Group
Telecom ParisTech
46 rue Barrault
75 013 Paris, France

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