This pertains to #2648 (although this is a new feature, not a replacement) and #1404. A CEA-708 decoder that follows the CEA-708-E standard, decodes closed caption data from User Data Registered by Rec. ITU-T T.35 SEI messages, and returns them as cues in Shaka's internal cue format. Furthermore, this pull request fixes and cements some of the logic surrounding CEA-608 and CEA-708 tag parsing on the Dash Manifest Parser.
Format:
Similar to the CEA-608 decoder, cues are emitted in Shaka's internal format (lib/text/cue.js). This decoder makes use of nested cues. The top level cue is always a blank cue with no text, and each nested cue inside it contains text, as well as a specific style, or linebreak cues to facilitate line breaks. This also allows for inline style (color, italics, underline) changes.
Details:
- ASCII (G0), Latin-1 (G1), and CEA-708 specific charsets (G2 and G3) all supported.
- Underlines, colors, and Italics supported, set as a property on each nested cue.
- Positioning of text is supported. (Exception: In CEA-708 the default positioning is left, in this decoder it is centered.)
- Positioning of windows not supported, but relevant fields that could be used to support this are extracted and left as a TODO.
This replaces mux.js for CEA608 decoding. Applications will no longer need to include mux.js for CEA support, and mux.js will only be necessary for TS transmuxing.
Closes#2648
Joey Parrish
michellezhuo
Muhammad Haris