CEA-608, SD only: it is read directly from Line 21 of the picture data (= first visible line. Note the white "blocks" in the picture – these are encoded closed captions). It is being extracted from the picture and written as a closed captioning track into the QuickTime movie.
CEA-708, HD only: it is read from VANC Line 9, which is not a visible line. It is directly copied as a SMPTE334M packet into the closed captioning track of the QuickTime movie.
No special setup is required. If you see the CC logo in the just:in User Interface Closed Captions are being recognized and recorded into the QuickTime movie, SCC sidecar file (appropriate Destination Preset necessary) or into the MXF container (XDCAM HD422 only) automatically.
As for now the following configurations are supported: