APPENDIX 8 – Closed Captions in X-Pert Modules

The text below concerns the management of 608 and 708 CC files, as well as the operation of the DMT 608/708 Decoder.

First, when you work with Closed Captions, you need to keep in mind the following issues:

Most existing files, as well as all files that are captured with X-Pert Ingest have only 608 CC, meaning that they need to be transcoded to 708 CC in some way.

Files that only have 708 CC will not produce 608. Transcoding from 708 CC to 608 CC is usually impossible. Thus, one can rarely find files that only have 708 CC but such files will not contain 608 CC. Files need to have BOTH 608 and 708 CC, meaning that probably ALL of the incoming content is going to have 608 CC. So, having a 608 to 708 CC transcoder and ingesting 608 CC only will be transparent to the files and it will make no difference if the file is kept in its original 708 CC format, or if it is transcoded.

In case the original 708 CC is lost and only the transcoded 608 CC version is kept, the lost data will probably contain only bells and whistles, which could exist in 708 (in the form of fancier fonts), but the content of the CC file in terms of text, position of lines, colors, and so on, will be the same.

 

Afterwards, the following technical aspects need to be taken under consideration:

 

Full CC Ingestion (608 and 708) from the original source – via SD-SDI or HD-SDI streaming

Support of DVD, ATSC and SCTE-20/21 CCs in MPEG files (PS, SPTS, MPTS).
Note: Only ATSC supports 708 CC

Support of DVD, ATSC, SCTE-20/21 in H.264 files (via MainConcept©)
Note: MainConcept© has a lot of bugs and many of the files may present errors in the abovementioned formats

Support of DVD, ATSC, SCTE-20/21 in live streams (MPEG by DMT, H.264 by MainConcept© – same as above)

Support of 708 CC in live digital inputs (SD-SDI, HD-SDI) - SMPTE-334-2

All of the above will lead to a pass-through of the available CCs. Sources that only contain 608 CC, will also be transcoded to 708 CC.