This document describes the structure of data encoded with Codex High Density Image Encoding (HDE), along with algorithms for decoding the stored data. - It is the intent of this RDD to describe the structure and encoding of all fields in the HDE bitstream, such that users of the RDD can develop applications to decode HDE bitstreams and correctly identify their structure. It is specifically not the intent of this document to support development of applications encoding or creating HDE bitstreams, or the implementation of file formats based on HDE bitstreams.