Do I have match impedance while routing PAL video tracks?
A golden rule for deciding on whether matching impedances are required is that if the highest signal frequency (including relevant harmonics) has a wavelength of X then, the longest un-terminated signal track is X/10.

15 MHz has a wavelength of 20 metres so, you should consider using matching impedances and correct balanced routing (where applicable) if the connection length is longer than 2 metres. 

However, taking into account that the velocity of propagation along PCB tracks is about two-thirds of the speed of light means that the original 20 metre wavelength for 15 MHz (the maximum frequency) is reduced to 13.3 metres. Hence the golden rule suggests un-terminated tracks no longer than 1.33 metres.