Transmission standards without an embedded clock, like NRZ (»SDIF-2«), may face a serious problem: word-clock (i.e. the frame) and audio data (i.e. the contents) may deviate from each other, owing to different propagation delay times when travelling along different paths.

The SDIF-2 standard is extremely touchy in this respect, as not only the frame, but also the bit clock is derived from a word clock that may be separately guided. With a mismatch as low as ±1.6%, the bit assignment is lost. Result: the best-case is a signal louder or lower by 6dB, in the worst- case, however, the signal may crackle and clatter heavily, when the transitions between two bit-valencies are scanned, instead of the steady states midway between adjacent transitions.

Compared to SDIF-2, self-clocking transmission codes like the biphase-mark (»AES/EBU«) are well-behaved. Problems occur only with deviations greater than ±25%, and even then only when, real bad luck, a sample transition gets damaged. A minute step in time later, the next word will be captured instead, which will change nothing but add 20µs of transport delay.