SMPTE ST 291-1:2011

This standard specifies the basic formatting structure of the ancillary data space in digital video data streams in the form of 10 bit words. Application of this standard includes, but is not limited to, 525-line and 625-line standard definition digital television interfaces (component and composite), high definition digital television interfaces (750 and 1125 lines), and D-Cinema interfaces that provide 8-bit or 10-bit ancillary data spaces.
Space available for ancillary data packets is defined in documents specifying connecting interfaces.
Ancillary data packet payload definitions for a specific application are specified by a SMPTE Standard, Recommended Practice, or Registered Disclosure Document, or by a document generated by another organization, a company, or an individual (an Entity). When a payload format is registered with SMPTE, an application document describing the payload format is required, and the registered ancillary data packet is identified by a registered data identification word.
This standard specifies the basic formatting structure of the ancillary data space in digital video data streams in the form of 10 bit words. Application of this standard includes, but is not limited to, 525-line and 625-line standard definition digital television interfaces (component and composite), high definition digital television interfaces (750 and 1125 lines), and D-Cinema interfaces that provide 8-bit or 10-bit ancillary data spaces.
Space available for ancillary data packets is defined in documents specifying connecting interfaces.
Ancillary data packet payload definitions for a specific application are specified by a SMPTE Standard, Recommended Practice, or Registered Disclosure Document, or by a document generated by another organization, a company, or an individual (an Entity). When a payload format is registered with SMPTE, an application document describing the payload format is required, and the registered ancillary data packet is identified by a registered data identification word.