+/*
+ * A subtitle track.
+ *
+ * Required fields when a demuxer creates a subtitle track are:
+ * > id
+ * - ID of this track
+ * - must be unique for all tracks within a single job,
+ * since it is used to look up the appropriate in-FIFO with GetFifoForId()
+ * > format
+ * - format of the packets the subtitle decoder work-object sends to sub->fifo_raw
+ * - for passthru subtitles, is also the format of the final packets sent to sub->fifo_out
+ * - PICTURESUB for banded 8-bit YAUV pixels; see decvobsub.c documentation for more info
+ * - TEXTSUB for UTF-8 text marked up with <b>, <i>, or <u>
+ * - read by the muxers, and by the subtitle burn-in logic in the hb_sync_video work-object
+ * > source
+ * - used to create the appropriate subtitle decoder work-object in do_job()
+ * > config.dest
+ * - whether to render the subtitle on the video track (RENDERSUB) or
+ * to pass it through its own subtitle track in the output container (PASSTHRUSUB)
+ * - for legacy compatibility, all newly created VOBSUB tracks should default to RENDERSUB
+ * - since only VOBSUBs are renderable (as of 2010-04-25), all other newly created
+ * subtitle track types should default to PASSTHRUSUB
+ * > lang
+ * - user-readable description of the subtitle track
+ * - may correspond to the language of the track (see the 'iso639_2' field)
+ * - may correspond to the type of track (see the 'type' field; ex: "Closed Captions")
+ * > iso639_2
+ * - language code for the subtitle, or "und" if unknown
+ */