[whatwg] How to handle multitrack media resources in HTML
jeroen at longtailvideo.com
Mon Apr 18 01:30:40 PDT 2011
Hey Ian, all,
Sorry for the slow response ..
>>>> There's a big difference between text tracks, audio tracks, and video
>>>> tracks. While it makes sense, for instance, to have text tracks
>>>> enabled but not showing, it makes no sense to do that with audio
>>> Audio and video tracks require more data, hence it's less preferred to
>>> allow them being enabled but not showing. If data wasn't an issue, it
>>> would be great if this were possible; it'd allow instant switching
>>> between multiple audio dubs, or camera angles.
>> I think we mean different things by "active" here.
>> The "hidden" state for a text track is one where the UA isn't rendering
>> the track but the UA is still firing all the events and so forth. I don't
>> understand what the parallel would be for a video or audio track.
>> Text tracks are discontinuous units of potentially overlapping textual
>> data with position information and other metadata that can be styled with
>> CSS and can be mutated from script.
>> Audio and video tracks are continuous streams of immutable media data.
> Video and audio tracks do not necessarily produce continuous output - it is perfectly legal to have "gaps" in either, eg. segments that do not render. Both audio and video tracks can have metadata that affect their rendering: an audio track has a volume metadata that attenuates its contribution to the overall mix-down, and a video track has matrix that controls its rendering. The only thing preventing us from styling a video track with CSS is the lack of definition.
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