A NSW man who was jailed for allegedly raping and molesting his stepdaughter has had his conviction quashed after the discovery of a wedding video taken years later showing the woman patting his chest and grabbing him playfully.

The man, who cannot be named, was sentenced to a maximum of four and a half years' jail in February last year over a series of alleged assaults on his stepdaughter in the mid-1970s.

This followed his stepdaughter going to police in September 2008 and claiming that, when she was a child, the man would come into her bedroom two to three times a week and touch her genitals.

On one occasion, the woman claimed, her stepfather had raped her in the main bedroom of the family's suburban home.

These alleged incidents had been interspersed with occasional physical assaults, including strikes to the head that left the young girl with partial hearing loss and too scared to report the abuse, it was claimed.