Adtec digital mediaHUB-HD 422 (version 1.01.10_M_2) Manual - Manual (Page 85)

EIA-608/708 Captions
The new line of Adtec encoders (mediaHub HD Pro, mediaHub HD 422, and edje 5100) supports EIA-608 Captions in
standard definition mode and EIA-708 Captions in high definition mode. The 708 captions must be carried as SMPTE-334M
payloads with a DID of 0x61 and an SDID of 0x01.
The 608 to 708 conversion is especially useful in ATSC Terrestrial Applications.
In standard definition mode, the encoder automatically looks for 608 captions on line 21 when captions (CLC) are set to ATSC.
When encoding 708 captions, the user may enter the Vertical Ancilleray line that the data resides on. We have found that it is
common for most networks to put their data on VANC Line 9, the Adtec configured default.
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