从数字电影标准角度来看电影数字化技术的发展

Motion Picture Digital Technology Development From the Digital Cinema Standards Perspective

数字电影系统是用SMPTE标准来定义的,由国际标准化组织通过使用特殊的"快速工作程序",将这些标准再转化成ISO国际标准。标准化数字电影的目标之一是确保获得高质量的图像和声音,这个目标体现在图像压缩、空间分辨率和色彩保真度标准的技术细节上。DCP是一个整体,它包含所有图像、声音和字幕轨文件、及合成播放列表、打包列表、资产映射和一个可选的容积指数。数字电影的技术标准已认定:2K/4K必须采用JPEG 2000格式进行图像编码,声音用非压缩存储,DCP采用MXF和XML文件格式,MXF轨文件的加密使用128比特密钥的AES系统,这个系统是一个对称的加密系统,单一密钥用来加密和解密文件,并要求内容密钥置于密钥传送消息(KDM)中以安全方式传送至授权影院并放映。本文较详细的叙述了数字电影的基本技术、标准和DCP制作等。

Digital cinema system is defined by a set of SMPTE standards which have been transformed by the International Standardization Organization into ISO international standards. One of the goals of D-Cinema standardization is to ensure a high level of image and sound quality. This goal is reflected in the technical details of the standards such as image compression, spatial resolution and color fidelity. The Digital Cinema Package （DCP） is an entirety including all image, sound and subtitle track files, Composition Playlists, a Packing List, an Asset Map and an optional VolumeIndex. The technical standard of D-Cinema specifies that JPEG 2000 format must be used for 2K/4K image encoding; sound is stored uncompressed; MXF and XML formats are used for DCP; MXF track file encryption makes use of the AES system with 128-bit keys. AES is a symmetric encryption system, in which a single key is used both to encrypt and to decrypt a file. The content key must be included inside Key Delivery Message （KDM） to be transferred safely to the authorized cinemas. The paper discusses the details of D-Cinema basic technologies, standards and DCP manufactures, etc.