More details on the sync word

For the most stringent case, out of sync audio shouldn't be delayed by more than 15 mS (more or less a 60 fps frame, source) so a good design goal would be an order less, say 1000 µS. Audio samples (@44kHz) are spaced 23 µS apart. So we need to locate start of the sync word (simply a short sinus signal) with a certainty better than 43 samples... Easy: the fit below is correct within ½ sound sample (orange dots represent samples from an audio track with exaggerated noise).

The yet to be coded postprod program 1PPS2LTC will try to determine the best estimate for the time "0", corresponding to the µcontroller reception of the 1PPS GPS signal. By trial an error, I'll determine the sync word length necessary to locate correctly its start within 43 samples, so there's plenty of room.