Video over sound — our own dumb protocol, h-sync & v-sync included.
FRAME : 16 x 12 grayscale (192 px)
RATE : 25 fps — a full frame every 40 ms on the wire
V-SYNC : 500 Hz burst — marks start of frame
H-SYNC : 800 Hz burst — marks start of each of 12 rows
PIXEL BAND : 1200 Hz (black) → 2600 Hz (white), linear on brightness
SYMBOL : 40ms / 205 slots per frame; FFT peak → freq → value
DECODE : lock on V-SYNC → clock the frame → fast best-effort sampler
NOTE : at 25 fps the slots are blisteringly short, so decode is
best-effort — the TRANSMITTER is the star of this show.
NOTE : this is NOT SSTV nor any standard mode. It's our own
beautifully unreliable invention. If neighbors complain,
that's a feature.