Methods and apparatus, including computer program products, implementing and using techniques for encoding a video sequence comprising a plurality of image frames, by an encoder are described. An image frame is received from a video stream. An input is received, which indicates one or more regions in the received image frame for which a privacy mask should be applied. The one or more regions are represented by one or more coding units. The image frame is encoded into an output frame, wherein image data in the one or more regions is replaced by intra-predicted coding units with transformed coefficients set to zero, the intra-predicted coding units are obtained from a prediction stage in the encoder.