A method and apparatus for fast channel change when changing the channel from a channel being viewed full screen as a main picture to a channel being viewed in a secondary channel program display window (e.g., a picture-in-picture (PIP) window). In one implementation, during the channel change, a secondary video stream for a secondary channel program is up-sampled and displayed full screen while receiving the corresponding regular video stream for the video program, of which program contents are identical to those of the secondary video stream. The program contents of the up-sampled secondary video stream is then be replaced seamlessly with those of the corresponding regular video stream at the time when an instantaneous decode refresh (IDR) frame of the corresponding regular video stream is received. In another implementation, the last GOP packets of the corresponding regular video stream, corresponding to a secondary video stream being viewed in the secondary channel program display window, are buffered without being decoded. Upon a request for the channel change, the buffered GOP packets are decoded and displayed immediately while the decoder starts receiving the following frames in the corresponding regular video stream.