My father-in-law has recorded my son's sports day & other things onto dvd from his dvd machine not computer & we have tried playing it back on our desktop & laptop dvd players without sucess

The dvd says

Panasonic dvd RAM RAM47
DVD-RAM 120 min/4.7GB
rewritable
2~3xspeed

Any ideas, we can play normal dvd's & picture cd's

Thanks Amanda