IMSC1? & TTML

Overview of IMSC1? and imscJS: https://drive.google.com/open?id=0B_OQLEGiaO-RamRTam5Edkc1cXc

- more information desired about IMSC1?

	- what IMSC1? is?
	- how can I write parser and converter and renderer and a packager?
	- how do I convert to/from other formats, like CEA 608 and WebVTT
	- image vs text since IMSC1? supports both
	- can IMSC1? be used for live captioning during video conference (very low latency captioning)?
	- who uses IMSC1??

- how can I write a packager?

	- ISO 23000-19 specifies packaging into ISO BMFF (https://www.iso.org/standard/71975.html)

- who uses IMSC1??

	- SMPTE (IMF) (https://doi.org/10.5594/SMPTE.ST2067-2.2016)
	- MPEG (CMAF) [iOS 11 support (http://subtitling.irt.de/cmaf/)]
	- DVB (https://www.dvb.org/resources/public/standards/a174_dvb_ttml_subtitling_systems.pdf)
	- CTA (WAVE) (https://cta.tech/Research-Standards/Standards-Listing/WAVE-Project/WAVE-Project.aspx)
	- ATSC (https://www.atsc.org/wp-content/uploads/2016/12/A343-2016-Captions-and-Subtitles.pdf)

- how do I convert to/from other formats, like CEA 608 and WebVTT

	- from CEA 608: https://www.smpte.org/sites/default/files/rp2052-10-2012.pdf
	- (draft) WebVTT: https://w3c.github.io/ttml-webvtt-mapping/

- image vs text

	- text-based subtitles/captions should be present (image is not a substitute, but a supplement)
	- Text essence
		- resolution-independent
		- allows styling to be modified at rendering
		- translation
		- accessibility devices
	- Image essence
		- complete visual control
		- not limited to text and available fonts, e.g. missing characters in some languages
		- not limited by TTML layout and typographical capabilities


 - imscJS reduce divergence and lower barriers to adoption
	 - BSD-licensed open source library that implements IMSC1? rendering in its entirety
	 - support for roll-up is highly desirable
	- what about non-CSS based renderers