= File Extension =
Files in this format are to be of text/
x-tdht mime type . Files in this format should have a file extension of .tdht .
= The TDHT format changes from HTML =
,070" end="00:00:02 ,270">
,280" end="00:00:04 ,270">
<p>We had an agreement to keep things casual.</p>
,280" end="00:00:06 ,660">
<p>Susan made her feelings clear.</p>
,800" end="00:00:10 ,100">
<p>So if I was with another woman, that wouldn't bother you? No, it wouldn't.</p>
Right now, TDHT is based on [http://www.w3.org/TR/html401/ HTML4.01], but it should also be possible to work on [http://www.whatwg.org/specs/web-apps/current-work/ HTML5], which is still in flux.
The following changes to
HTML4.01 are made for TDHT:
In TDHT1.0 we restrict
it to just contain a sequence of div tags:
The div tags in turn can contain anything that HTML div tags can contain, thus enabling a very flexible, but time-aligned text model.
== 2. The div element ==
HTML4.01, the [http://www.w3.org/TR/html401/struct/global.html#h-7.5.4 div element] is defined as follows:
The Time entity
is defined in HTML5: http://www.whatwg.org/specs/web-apps/current-work/#valid-time-string .
= Rendering in a Web Browser =
A TDHT file is meant to be associated with a audio or video file and rendered in a Web browser in sync with the audio or video file.
The TDHT file's div elements are not rendered into an existing HTML page, but rather a TDHT file creates its own [http://www.whatwg.org/specs/web-apps/current-work/#the-iframe-element iframe-like] new nested browsing context.
This is because a TDHT file can come from a different URI than the Web page and thus for security reasons and for general base URI computations a nested browsing context is the better approach with the DOM nodes of the hosting page and the DOM nodes of the TDHT document in different owner documents. That way, the hosting document has the security origin of its own URL and the TDHT document has the security origin of its URL .
The rendering and CSS view port are either by default the rectangle occupied by the given <video> or <audio > tag, or an area provided for by the hosting HTML page. The zoom factor of the iframe must be set to such a value that the width of the view port established by the iframe is equally wide in CSS px as the video frame is wide in codec pixels. (Example: If the video encodes a frame that is 240 pixels wide but is displayed at 480 CSS px wide, the zoom factor of the iframe should be 200% so that the box that on the outsize measures 480 px seems like a box of 240 px from within the iframe. )
When the browser happens upon a TDHT file , it must create a document by calling createDocument() on DOMImplementation and then calling open() on the created document. The browser must insert a <html> element in the HTML namespace as the root element of the document and insert <head> and <body > elements in the HTML namespace into the root element.
A TDHT file can either be received by a HTML parser in one go (as a TDHT file ) or a div -less TDHT file can be received together with its <head > tag and create a HTML shell into which the <div > elements can be added as they come (e. g. from a video file that is decoded and played back in parallel) by using a HTML fragment parser.
The <head> tag must decode into a DOMString (using REPLACEMENT CHARACTER on errors) and set the TDHT DOM property of the <head> element to the DOMString.
As the browser plays the video, it must render the TDHT <div> tags in sync. As the start time of a <div> tag is reached, the <div> tag appears, and it is removed as the <div> tag's end time is reached. If no start time is given, the start is assumed to be 0, and if no end time is given, end is assumed to be infinity.
As the browser has parsed the TDHT file or its consitutent <div> tags, it is expected to keep the structure in memory. When seeking happens on the video, it can then decide upon which <div> tags are supposed to be active at the seek time and display these.
= Encapsulation into Ogg =
The codec-specific header data for the OggText ident header is the <head>..</head> part of the TDHT file. The complete <head> tag including all its subtags is encoded into the ident header unchanged.
tags are the data packets of the TDHT text codec and are thus encapsulated into the data packets as text codec data. A complete <div> including all its subtags is encoded into one data packet each.