Shortly after the initial higher density proposals were put forth for the 120 mm optical disk ROM, analysis and comment on proposed capacity, modulation code, error correction coding, performance, disk handling, volume and file structure, and application requirements were given by an ad hoc computer industry technical working group. As the initial proposals evolved into the DVD Specification, the motion picture industry raised the issue of copy protection for movies. To assist in finding acceptable solutions, the technical working group was expanded by consensus to a larger ad hoc group, the Copy Protection Technical Working Group (CPTWG), with participation from the motion picture (MPAA), consumer electronics (CEMA), and computer (IT) industries. Subgroups were formed to study promising areas, e.g. the Data Hiding Sub Group (DHSG) for watermarking of the video, and the Data Transmission Discussion Group for encryption of 1394 transmissions. Proceeding on a voluntary and open basis, the DHSG developed a request for proposals and undertook analysis of the multiple proposals received from many companies including Digimarc, Hewlett-Packard, Hitachi, IBM, MacroVision, NEC, Philips, Pioneer, Sony, and others.