Remove ttp:mediaDuration.

[nigelmegitt]

Alongside the removal of mediaDuration in #323 we need to remove mediaDuration as discussed at TPAC 2017. The indefinite end time can be resolved using clipBegin (or its renamed equivalent) instead as per #483.

[skynavga]

If we do not add clip{Begin,End} then we still need a way to to resolve overall indefinite duration on document time line, which argues for retaining ttp:mediaDuration. Note that TTT [1] uses a command line option, --external-duration, to provide this information at present (in the absence of a ttp:mediaDuration parameter or equivalent).

[palemieux]

The desired duration can remain indefinite by the processing model, leaving the task of determining the effective duration to the document processing context.

imscJS, for instance, outputs an ISD with an end time of infinity in the case of indefinite duration.

[css-meeting-bot]

The Working Group just discussed Remove ttp:mediaDuration. ttml2#549, and agreed to the following resolutions:

• RESOLUTION: Remove ttp:mediaDuration

The full IRC log of that discussion

<nigel> Topic: Remove ttp:mediaDuration. ttml2#549
<nigel> github: https://github.com/w3c/ttml2/issues/549
<nigel> Glenn: If the processor does not know what duration to use then indefinite durations could
<nigel> .. not be resolved to a finite interval. I see the comment that ISD can now have an indefinite
<nigel> .. end time. I'm willing to go with removal at this point.
<nigel> RESOLUTION: Remove ttp:mediaDuration

[skynavga]

Since we have a WG resolution to proceed on this, and since nobody is proposing to keep ttp:mediaDuration, I have merged the approved PR early to facilitate closing #76. If someone wishes to object to the WG resolution #549 (comment), feel free to reopen #549 with specific comments.

[skynavga]

Closing this issue with no further action since ttp:mediaDuration has already been removed (w3c/ttml2@a40894c).