Optical disc the DataPlay format, can have capacity comparable to that of the larger, standard compact 12 cm disc. Third-generation optical discs are in development, meant for distributing high-definition video and support greater data storage capacities, accomplished with short-wavelength visible-light lasers and greater numerical apertures. Blu-ray Disc and HD DVD uses blue-violet lasers and focusing optics of greater aperture, for use with discs with smaller pits and lands, thereby greater data storage capacity per layer. In practice, the effective multimedia presentation capacity is improved with enhanced video data compression codecs such as H.264/MPEG-4 AVC and VC-1. The following formats go beyond the
Picture disc unhappy with their quality and soon began making an improved type. A rigid blank shellac core disc was sandwiched between two illustrated sheets and each side was then topped with a substantial layer of high-quality clear plastic into which the recording was pressed. Like nearly all records being made for the general public, they were recorded at 78 rpm, but one issue was recorded at 33⅓ rpm, a speed already in use for special purposes which Victor was then unsuccessfully attempting to introduce into home use. It was the first 33⅓ rpm picture disc and the only one made until