I just wire a straight 7486 here to combine the H, V sync to get composite
Assuming you just need a single XOR gate (which is normal for this), then
you could use the 4 NAND gates in a 74x00 to make one. The schematic is
well-knon, but in case you've not coem across it :
---------+-----------|\
| | >o---+
| +---|/ |
+-|\ | +--|\
| >o--+ | >o----
+-|/ | +--|/
| +---|\ |
| | >o----+
--------+-----------|/
If you need an XNOR gate, I think you can use a similar circuit with 4
NOR gates (e.g. all the gates in a 74x02)
Also, inverting an odd number of the 2 inputs and output (that is, a
single input, the output, or all 3) will change an XOR to an XNOR or vice
versa, while invertian and even number (both inputs, or one input and the
output) ahs no effect. .
-tony