- Language Codes: Are specified in CD-Text and unspecified in ITTS, i.e. 0x00 is default language on ITTS and Unknown/non-listed language in CD-Text. In other words, CD-Text does know what English is, for ITTS it is just the nth language.
- Packet size: CD-Text packages “consist of a 4-byte header, 12 bytes of payload, and 2 bytes of CRC”, “ITTS packets have a length of 48 bytes: an 8 byte header
and a 40 byte TEXT or DATA string.”
- Fields: ITTS has no predefined fields like Album, Artist and so on but arbitrary text, CD-Text does not have any arbitrary text
- Location: CD-Text is defacto only stored in the Lead-In, ITTS is stored parallel to the content
- Synchronisation: Due to the location, CD-Text natuarally has no synchronisation, except showing the fields of the current track, ITTS has synchronisation.
- Copy Protection: CD-Text has a flag for copy protecting the text, ITTS does not have anything similar
- Storage in some kind of subchannels
- ISO 8859-1 as basis for the text-encoding
To conclude, in my opinion two non-related standards except a similar era and use-cases. By far the most common citation of ITTS/IEC 61866 is totally off.
3rd gen DCC text could be similar and/or related to CD-Text, though.
ITTS could be stored in the R through W-subcode on CDs which is otherwise only used by CD+G, CD+MIDI and as mentioned by CD Text during the Lead-In. Some early CD-players have a dedicated Subcode output jack, devices for this are about as rare as the ITTS box. I pick one player with this jack up and after I’m finished with my ITTS emulator I will create ITTS-CDs.