Closed Caption support
Submitted by Edward Hervey @bilboed
Link to original bug (#678146)
Description
Right now we don't suport any kind of Closed Caption (not to be confused with subtitles).
https://en.wikipedia.org/wiki/Closed_captioning
There are a few problems that need to be solved:
- CC format support
There are a few standards out there for CC, the main ones are:
- CEA 608 and 708
- teletext
teletext is supported by teletextdec (needs to be checked). An alternative would be the vbidec element (which wasn't ported to 0.10).
the zvbi library seems to have support for CEA 608 and maybe 708, this would need to be investigated. Proper caps need to be determined also.
CEA 608/708 require a new element
- Extracting CC stream
For teletext it is always contained as a separate stream in the container format (mostly mpeg-ts).
This is where it gets really painful.
For CEA 608/708 it is almost always contained in either the mpeg video stream (as user data) or in the h264 RBSP stream (as SEI data).
So the question is:
- where to parse it. The logical place would be in the mpegvideo/h264 parsers.
- How to expose it. Do we create a new pad ? Do we emit them as messages ?
There is also CEA 608/708 in quicktime/iso file formats, see bug 606643