SMPTE ST 12M-1 PDF

This Standard specifies a time and control code for use in television and accompanying audio systems operating at nominal rates¹ of 60, 59.94, 50, 30, 29.97, 25, 24, and 23.98 frames per second. This standard defines a time address, binary groups, and flag bit structure. The standard also defines a binary group flag assignment, a linear time code transport, and a vertical interval time code transport.

This standard defines primary data transport structures for Linear Time Code (LTC) and Vertical Interval Time Code (VITC). This standard defines the LTC modulation and timing for all video formats. This standard also defines the VITC modulation and location for 525/59.94 and 625/50 analog composite and component systems only.

Note: The digital representation of analog VITC (D-VITC) is specified in SMPTE 266M and is defined for 525/59.94 and 625/50 digital component systems only. High Definition formats, such as those documented in SMPTE 274M and SMPTE 296M, should use Ancillary Time Code (ATC) as specified in SMPTE 12M-2 (formerly SMPTE RP 188) for transport of time code in the digital video data stream. For future implementations of time code for digital Standard Definition formats, the use of ATC rather than D-VITC is encouraged.

¹The reader is cautioned that non-integer values are abbreviated. These abbreviations may be seen throughout this document. See § 5.1.2 for additional information.