PAL video OSD circuit PIC12F683 PIC C language prepared by the software operating frequency is 25MHz circuit using many materials (solid and supply filter capacitor oscillator) circuit diagram source C, have the hex code
PIC PAL video OSD
The PIC is overclocked with a 25 Mhz crystal but it should accept it with no problem. If you want not to overclock it, then use a 20 Mhz crystal and see C source code to know what adjustment to do. The result will be thiner pixel width.