A video encoder generates a Network Abstraction Layer (NAL) unit that contains a plurality of encoded picture partitions of the video data. The video encoder generates a bitstream that includes a variable-length value that represents an entropy-encoded first syntax element, a variable-length value that represents an entropy-encoded second syntax element, and fixed-length values that represent offset syntax elements. Lengths of each of the offset syntax elements are determinable based on the first syntax element. A video decoder uses the first syntax element, the second syntax element, and the offset syntax elements when decoding the encoded picture partitions.