Polyvinyl acetal films with less blocking tendency and which allow for escape of gas during laminating to form laminated composities are prepared by a process for embossing a film comprising plasticized polyvinyl acetal with a roughness Rz on at least one surfaces of 20 to 100 μm by the steps of a. extruding of plasticised polyvinyl acetal to a film with a stochastic roughness of the surfaces of Rz =1 to 70 μm, b. embossing at least one surface of the film obtained in step a) with channels having a depth of 5-50 μm, a width of 10-200 μm and a pitch of 50-2500 μm, wherein c. the surface roughness of the elevations between the channels is at most 20% lower as obtained in step a).