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1概述目前市场上的DVD视频光盘主要支持两种制式: PAL(720X576＠25Hz)和NTSC(720X480＠29．94Hz)。它们采用MPEG2标准压缩,称为标准清晰度DVD或SD- DVD。随着DVD在市场上的巨大成功,在DVD光盘上存储高清晰度视频(HD-Video)日益成为DVD开发者们关注的焦点。由于HD-Video具有更高的分辨率如 1280x720甚至1920x1080,所以在通常情况下,如果采用相同的压缩技术,码流必须以更高的码率进行压缩以实现高质量的视频效果。这意味着在保证播放时间不变 (单层DVD光盘的播放时间为135分钟)的情况下,光盘的存储容量必须增加,这就要求有新的光盘制作技术和驱动技术。例如,蓝光光盘是一种存储容量更大的光盘,采用比目前DVD所用的可见红激光更短波长的蓝色的激光束来刻录数据,数据密度可比DVD增加4-10倍。但蓝光光盘无法在目前的DVD播放器上播放,不具备向后兼容性。
1 Overview DVD video discs currently on the market mainly support two formats: PAL (720X576 @ 25Hz) and NTSC (720X480@29.94Hz). They use MPEG2 standard compression, known as standard definition DVD or SD-DVD. With the DVD’s huge success in the marketplace, storing HD video on DVD discs has become a focus of attention for DVD developers. Since HD-Video has higher resolutions such as 1280x720 or even 1920x1080, in general, if the same compression technique is used, the bit stream must be compressed at a higher bit rate for high-quality video. This means that the storage capacity of the optical disc must be increased while guaranteeing the same playback time (single-layer DVD disc playback time is 135 minutes), which requires new disc production and drive technologies. For example, a Blu-ray Disc is a larger storage disc that burns data with a shorter wavelength blue laser beam than the visible red laser used on today’s DVDs, increasing the data density by 4-10 times as much as the DVD. However, Blu-ray discs can not be played on current DVD players and do not have backward compatibility.