Thu Sep 13, 2012 4:32 am
To answer my own question, in case anybody else needs this info. The flag is the MSB of Binary Group 1 in the timecode ancillary packet, on line 10. All the other bits in all the other binary groups can be zero, and DBB1 (see smpte RP188) is all zeros. 1 to trigger recorder, 0 to stop it. Unfortunately, it has to be in record mode, because in playback mode the flag is ignored.