- From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
- Date: Wed, 2 Mar 2011 08:00:30 +1100
- To: David Singer <singer@apple.com>
- Cc: Bob Lund <B.Lund@cablelabs.com>, Sean Hayes <Sean.Hayes@microsoft.com>, "public-html@w3.org" <public-html@w3.org>
On Tue, Mar 1, 2011 at 5:46 AM, David Singer <singer@apple.com> wrote: > > On Feb 27, 2011, at 16:39 , Silvia Pfeiffer wrote: > >> For both of the below to work, the browser has to implement an >> extraction of the cues from the binary media resource into a TextTrack >> with TextTrackCues, which then exposes it to the browser and to >> JavaScript. Since by default only TextTracks of @kind=subtitles or >> @kind=captions are rendered and these can only contain raw text, it >> probably makes sense to declare both the content advisory descriptor >> and the image-based caption as @kind=metadata. >> > > Yes, I would have the media type of these be 'text', the coding format be something suitable, and the 'kind' (purpose, function, really) be something that indicated it's metadata of some sort. > > I think a general API > > Tell: > * what the times at which the content of this track changes (in the case that the UA has a time-map, e.g. a complete caption or media file) > * when the content of this track changes (i.e. a frame-by-frame callback) > * what the content of this track is at this (possibly current) time > > covers the uses, doesn't it? Yes, and I believe that is already in the spec through the TimedTrack API. > * what the times at which the content of this track changes (in the case that the UA has a time-map, e.g. a complete caption or media file) A TextTrackCue provides the start and end time of its cue: http://www.whatwg.org/specs/web-apps/current-work/multipage/video.html#texttrackcue . It also raises events onenter and onexit. > * when the content of this track changes (i.e. a frame-by-frame callback) The TextTrack raises a oncuechange event: http://www.whatwg.org/specs/web-apps/current-work/multipage/video.html#texttrack . > * what the content of this track is at this (possibly current) time The TextTrack has a list of the currently active cues in the "activeCues" field: http://www.whatwg.org/specs/web-apps/current-work/multipage/video.html#texttrack . My point simply was that we are already able to support this through the current spec - it's just a matter of the browsers exposing the in-band tracks. And since these track types cannot be rendered as subtitles or captions, they would necessarily be @kind=metadata. > Bob's message talks of the information being repeated -- carouseled -- but that is just refreshing what the terminal already knew. I don't think that those should constitute a change of content. I agree - and I thought that's what I said in the next paragraph: >> In the case of the content advisory descriptor, I would expect the >> browser to indeed only expose the change of the descriptor in a new >> cue. Anything else is just repeated information. Cheers, Silvia.
Received on Tuesday, 1 March 2011 21:01:24 UTC