Replacing TTML parsing with imscJS library

[TobbeEdgeware]

This is an effort to get IMSC-1 compliant by replacing our own TTML parser with imscJS.

Both text and image profiles of IMSC-1 are supported.

The SMPTE-TT image mode is also supported for legacy image subtitle sources.

The same library is also used for parsing subtitles for Smooth Streaming.

[palemieux]

@TobbeEdgeware Is there a schedule for the merge, so that an updated release of imscJS can be coordinated?

[TobbeEdgeware]

@palemieux This is ready for inclusion and is decided to be in Release 2.6.0 of dash.js.

I hope @AkamaiDASH or @bbcrddave can merge the PR today or beginning of next week.

Upgrading from imscJS-1.0.0.beta.3 to to 1.0.0 can be done at any time before the 2.6.0 release.

[TobbeEdgeware]

@nicosang For some reason, clahub tool does not acknowledge that you (or Orange) has signed the contribution license agreement. Can you please press the clahub "Details" link above and fill in the form (again)?

[bbert]

Hi,
We (Orange) signed a long time the contribution license agreement.
When we try to valid the agreement on clahub, we get an error ("We're sorry, but something went wrong")

[TobbeEdgeware]

@bbert I tried with my private github account and also got a

message. However, I then refreshed the page and a got a form to fill in. Can you try that?

If it doesn't work, I'll ask @wilaw to try to fix this on the clahub side.

[bbert]

In order to be able to validate the CLA, CLAHub requires our Github organization (Orange-OpenSource) to allow accessing account's private data.
Our lawyers have some concerns about this situation and do not want to give the permission until the situation has been clarified. This may take some time...

[TobbeEdgeware]

Since Orange has signed the CLA, and there seems to take some time to fix clahub, I merge this now.