A complete video clip or sequence is processed by a video encoder to create a compressed bitstream. In order to handle the large amount of image data in a sequence of video frames, the encoder splits it up into manageable structures. This chapter looks at how a video encoder does this and how it bridges the gap between a source video, which contains multiple frames each made up of thousands or millions of pixels, and encoded data units. It also looks at the processing and storage capabilities of a practical codec that handles a relatively small region or block of data at a time. A coded picture is a compressed representation of a single video frame, or a coded field or pair of fields for interlaced video. The chapter considers the detailed operation of video codec structures in the context of the HEVC/H.265 standard.