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Brainstorm improving synchronization with FAX modes
FAX modes have no sync pulses (1200 Hz tone) but many FAX transmissions have long enough white (2300 Hz tone) to black (1500 Hz tone) and black to white transitions, that could be used to synchronize. The idea is as follows: if another transition happens near the predicted next transition (60 seconds per minute / 120 lines per minute = 0.5 seconds per line), we should use those to synchronize horizontally. Of course these transitions can happen many times per line, so we need to track multiple transitions. We should also track both transitions, not just white to black (or black to white) for more diversity. This will at least help to prevent skew, which is unavoidable because of SFO (sample frequency offset) and Doppler effect.
