Re: Resolving TextTrackCue issues

On Sun, Sep 8, 2013 at 3:43 AM, Glenn Adams <glenn@skynav.com> wrote:
>
> On Fri, Sep 6, 2013 at 11:24 PM, Silvia Pfeiffer <silviapfeiffer1@gmail.com>
> wrote:
>>
>> On Fri, Sep 6, 2013 at 2:43 AM, Glenn Adams <glenn@skynav.com> wrote:
>> >
>> >
>> > On Thu, Sep 5, 2013 at 8:19 AM, Silvia Pfeiffer
>> > <silviapfeiffer1@gmail.com>
>> > wrote:
>> >>
>> >> > Could we compared example codes?
>> >>
>> >> I can give you an example: if you have TTML in-band in MP4, it's
>> >> caption content, a browser has no parser and renderer for it, but can
>> >> in theory extract the cues from the MP4 encapsulation -
>> >>
>> >> - the WHATWG spec would either not expose them to JS at all, or expect
>> >> them to be exposed as VTTCue objects with @kind=metadata
>> >
>> >
>> > This would not work, since VTTCue interprets cues of kind metadata as
>> > WebVTT
>> > metadata text [1], which is most definitely incompatible with TTML that
>> > has
>> > been serialized into intermediate synchronic document instances, each of
>> > which is effectively an XML document.
>> >
>> > [1]
>> >
>> > https://dvcs.w3.org/hg/ttml/raw-file/tip/ttml2/spec/ttml2.html#extension-designations
>>
>> So this is what we have to resolve. Why do you think VTTCue of
>> @kind=metadata can't contain TTML intermediate synchronic document
>> instances (i.e. a XML document) ?
>
>
> 1. Because WebVTT metadata text is incompatible with representing a
> serialized TTML document entity unless one applies a transfer encoding
> first, such as BASE64.

I don't follow. Can you give an example of a serialized TTML document
entity ? I thought it was XML and not binary?


> 2. Because TTML is not related to VTT, and pretending that TTML is WebVTT
> metadata text just  confuses authors and implementers.

Agreed - some renaming would be necessary. VTTCue could be called TextCue.

> 3. Because TTML content will not be @kind=metadata, but rather captions,
> subtitles, descriptions, etc. In other words, a renderable @kind.

If it's not parsed & rendered by the browser, according to the logic
expressed in this thread, it is exposed as @kind=metadata with the
semantic use expressed in @inBandMetadataTrackDispatchType .


Silvia.

Received on Saturday, 7 September 2013 23:28:46 UTC