HD DVD BD9 formats. HD Rec is an extension of the HD DVD format for recording HD content on regular red laser DVD-Rs/DVD-RWs using H.264/MPEG-4 AVC compression. It was approved by the DVD Forum on September 12, 2007 It is comparable to Blu-ray Disc's AVCREC. The China Blue High-definition Disc (CBHD), a high-definition optical disc format, was based upon the HD DVD format. Like the HD DVD, CBHD discs have a capacity of 15 GB single-layer and 30 GB dual-layer and can use existing DVD production lines. Unlike the HD DVD format, industry support for this format has grown steadily. HD DVD
Optical disc recording modes the data, and closed by a lead-out area. The data is addressable in sectors of 2048 bytes each, with the first sector address being zero. There are no run-out blocks as in DVD-R disc-at-once. Session-At-Once (SAO) recording allows multiple sessions to be recorded and finalized on a single disc. The resulting disc can be read by computer drives, but sessions after the first are generally not readable by CD Audio equipment. Audio Master Quality Recording was introduced by Yamaha in 2002. This recording mode significantly reduces jitter levels causing noise and clicks (-30% according to Yamaha) and improves audio and