1)什么是MP4?我听说过它是一种"容器格式",那是指什么?

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"容器格式"容许你将不同的多媒体流(例如常用的视频和音频)组合到一个单一的文件。常见的多媒体容器有：著名的AVI (.avi), MPEG (.mpg, .mpeg), Matroska (.mkv, .mka), OGM (.ogm), Quicktime (.mov) or Realmedia (.rm, .rmvb)。Mp4是在MPEG-4标准（ISO 14496-14）中为正式的容器格式定义的一个文件扩展。MP4是流媒体，支持所有的多媒体内容（multiple audio-, video-, subtitlestreams, pictures, variable-framerates, -bitrates, -samplerates...) ，以及二维或者三维动画、用户互动、和DVD差不多的、乃至常用的AVI之类的高级内容(官方称为officially called "Rich Media" or "BIFS")2）MP4采用什么扩展文件名？- .mp4: 仅仅是官方定义的音频、视频或者高级内容、或者它们组合的文件扩展名, (and combinations)

其它相关的扩展名:

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- .m4v: .mp4 files with the WRONG extension introduced by apple for video audio files, m4v can safely be renamed to .mp4- .m4a: .mp4 files with the WRONG extension introduced by apple for audio-only files, m4a can safely be renamed to .mp4- .m4p: DRM protected files sold in iTunes, using the DRM sheme developed by apple- .m4e: renamed .sdp files used by Envivio for streaming- .m4v, .mp4v, .cmp, .divx, .xvid, .264: normally raw mpeg-4 video streams (not inside MP4)- .3gp, .3g2: used by mobile phones, can also include content not defined for .mp4 (H.263, AMR)

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