An audio/video (AV) apparatus such as a digital television set and a digital set-top-box device, which can perform additional operations such as an electronic album, MP3 and FIMS, and an additional operation performing apparatus appropriate for the digital AV apparatus. The digital AV apparatus can include an AV decoder to output video and audio data, a scaler to adjust resolutions of video data output from the AV decoder and additional information video data provided from an external video source and to output the adjusted resolution, an audio processor to process audio data output from the AV decoder and additional information audio data provided from an external audio source, and a controller to receive a command provided from an external commander and to control a selection operation of the scaler and the audio processor based on the command.