Comparison of high definition optical disc formats comparison of the formats. Blu-ray Disc and HD DVD both support the same three video compression standards: MPEG-2, VC-1 and AVC, each of which exhibits different bitrate/noise-ratio curves, visual impairments/artifacts, and encoder maturity. Initial Blu-ray Disc titles often used MPEG-2 video, which requires the highest average bitrate and thus the most space, to match the picture quality of the other two video codecs. As of July 2008 over 70% of Blu-ray Disc titles have been authored with the newer compression standards: AVC and VC-1. HD DVD titles have used VC-1 and AVC almost exclusively since the format's introduction. Warner Bros.,
Optical disc drive on personal computers was originally a batch-oriented task in that it required specialised authoring software to create an "image" of the data to record, and to record it to disc in the one session. This was acceptable for archival purposes, but limited the general convenience of CD-R and CD-RW discs as a removable storage medium. Packet writing is a scheme in which the recorder writes incrementally to disc in short bursts, or packets. Sequential packet writing fills the disc with packets from bottom up. To make it readable in CD-ROM and DVD-ROM drives, the disc can be "closed" at any