Comparison of high definition optical disc formats Blu-ray disc players since the end of the format war. Blu-ray Disc has a higher maximum disc capacity than HD DVD (50 GB vs. 30 GB for a double layered disc). In September 2007 the DVD Forum approved a preliminary specification for the triple-layer 51GB HD DVD (ROM only) disc though Toshiba never stated whether it was compatible with existing HD DVD players. In September 2006 TDK announced a prototype Blu-ray Disc with a capacity of 200GB. TDK was also the first to develop a Blu-ray prototype with a capacity of 100GB in May 2005. In October 2007 Hitachi developed
Archival Disc intended as a consumer storage medium as of 2014, but is intended by the two companies as a solution for professional-level data archival. In order to reach a larger capacity whilst ensuring higher playback signal quality, the standard will employ crosstalk cancellation and partial response maximum likelihood (PRML) signal processing. Both companies will market the optical format under their respective brands. Sony will be using Archival Disc in within the Optical Disc Archive professional archival product range. Sony's aim is to create at least a 6TB storage medium. An emerging use case for Archival Disc has been projected for cold