[Bug 704881] Partial ATSC_user_data and CEA-708 Closed Captions Support

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=704881
  GStreamer | gst-plugins-bad | git

--- Comment #37 from cjunwang <cjun.wang at samsung.com> 2014-08-06 07:47:22 UTC ---
There are still 2 issues.

1. whether combine ccdec and cea708dec plugin together. 
If combined, new plugin need implement both 708 and 608 decoding. It seems more
complicated. but one of its merit is, it's easier to use. In most of
circumstances user just want watch only one of 608/708 services:
NTSC_CC_FIELD_1, NTSC_CC_FIELD_2, or one of 708 service.
http://en.wikipedia.org/wiki/CEA-708

If seperated, every 608/708 decoder can focus on itself. 



2. whether cea708dec or cea608dec need output image directly, or there should
be a new plugin for closed caption overlay?
Now cea708dec output is pango-markup text, which can be rendered with
textoverlay, or textrender. 

If do not write new plugin, closed caption has some features, which need modify
textoverlay/textrender. 
1)decoded cc buffer's duration is not fixed. That means when text buffer
display, it's not determined yet when text will be destroyed. 
Does GstBuffer need add support?
https://bugzilla.gnome.org/show_bug.cgi?id=734219
2)cc window's position is not fixed
3)it's possible to have multiple closed caption windows displayed at same time,
although it's seldom used. 
4)...
If write new plugin, new plugin will deal with these things.

Any suggestion or comments are welcomed...

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