then how it works in lumia 920 with 8mp camera
Pureview phase 1 is Nokia 808 = 41 MPx, oversampled.
Pureview phase 2 is Nokia 920 = 8 MPx, OIS (=hardware)
So : N8 is too poor in terms of MPx for phase 1 type of PV, and has no optical stabilisation for PV phase 2.