SMPTE time code (the old style stuff), is an 80-bit code, that can be read bidirectionally. At play speed it’s a harsh waveform around 2kHz. Often clipped to get better edges in the reader.
I didn’t check the links above, but it does contain asymmetric preamble/sync blocks which allow you to determine the direction to read the bits (msb-lsb or vice-versa).
It doesn’t need an external reference, all you do is sample the ‘audio’ until you find one of the preambles - then start building up your time value.
There are several info bits that define info about the code block, and of course almost half the data bits are not for the ‘time’, but may be used to hold USER BITS... often reel numbers, date, or even time copied from a source medium.