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Accessibility/Video Text Format: Difference between revisions
further additions to intro
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The new elements are not an extension to HTML5 and are not planned to be. There are hooks into HTML through the [http://www.whatwg.org/specs/web-apps/current-work/multipage/video.html#timed-tracks TimedTracks] API in HTML5 by which the WMML elements are exposed to the Web page that bears the media resource and the link to the WMML document. Some of these HTML5 APIs are only objects in HTML5, but are actual elements in WMML. | The new elements are not an extension to HTML5 and are not planned to be. There are hooks into HTML through the [http://www.whatwg.org/specs/web-apps/current-work/multipage/video.html#timed-tracks TimedTracks] API in HTML5 by which the WMML elements are exposed to the Web page that bears the media resource and the link to the WMML document. Some of these HTML5 APIs are only objects in HTML5, but are actual elements in WMML. | ||
The aim behind this way of defining WMML is to create a format that existing HTML5 parser implementations can parse with only a small number of extensions, rather than having to invent a completely new parsing model. Also, the reuse of CSS will allow reuse of existing implementations for styling and positioning. This should vastly help Web browsers to implement support for WMML, even and particularly including the richer features. | The aim behind this way of defining WMML is to create a format that existing HTML5 parser implementations can parse with only a small number of extensions, rather than having to invent a completely new parsing model. The extensions are designed to map into existing HTML5 APIs so should not create an unacceptable overhead. Also, the reuse of CSS will allow reuse of existing implementations for styling and positioning. This should vastly help Web browsers to implement support for WMML, even and particularly including the richer features. | ||
Note: A WMML document is a non-HTML document that contains HTML elements but is not an XML-with-namespaces document. This is on purpose so as to allow reuse of HTML parsers. | |||
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The main difference between SRT and WMML is that WMML is HTML-like and thus requires more markup. But that is offset by the ability to easily extend WMML with existing HTML and CSS features. | The main difference between SRT and WMML is that WMML is HTML-like and thus requires more markup. But that is offset by the ability to easily extend WMML with existing HTML and CSS features. | ||
WebSRT tries to extend SRT with features that have been deemed [http://wiki.whatwg.org/wiki/Timed_tracks required for a collection of use cases around captions, subtitles, and karaoke]. While this results in a fairly dense document definition, it also has the drawback that it is not easily extensible to slightly new applications, such as overlays on videos with ads, or captions with images, icons, or hyperlinks in them. Further, WebSRT is not a XML-based markup and thus requires implementation of a new parsing unit into Web browsers. Such new parsing code should be kept to a minimum, while continuing to provide flexibility of what can be displayed in time-synchronisation with videos. | WebSRT tries to extend SRT with features that have been deemed [http://wiki.whatwg.org/wiki/Timed_tracks required for a collection of use cases around captions, subtitles, and karaoke]. While this results in a fairly dense document definition, it also has the drawback that it is not easily extensible to slightly new applications, such as overlays on videos with ads, or captions with images, icons, or hyperlinks in them. Further, WebSRT is not a XML/HTML-based markup and thus requires implementation of a new parsing unit into Web browsers. Such new parsing code should be kept to a minimum, while continuing to provide flexibility of what can be displayed in time-synchronisation with videos. | ||
TTML has tried to be such a format. It is XML-based and has CSS-like formatting instructions. However, it has diverged too much from HTML/CSS that it is not easily possible to reuse existing HTML & CSS parsing code to interprete a TTML document. At the time of its definition, it seemed like a sensible thing to do in order to stay in sync with XHTML, with XML namespaces and with XSL-FO, but in the modern HTML5 space, these have proven to be a hinderance to implementation in modern Web browsers. | TTML has tried to be such a format. It is XML-based and has CSS-like formatting instructions. However, it has diverged too much from HTML/CSS that it is not easily possible to reuse existing HTML & CSS parsing code to interprete a TTML document. At the time of its definition, it seemed like a sensible thing to do in order to stay in sync with XHTML, with XML namespaces and with XSL-FO, but in the modern HTML5 space, these have proven to be a hinderance to implementation in modern Web browsers. | ||