<P> Digital Copy files based on existing files include only one audio track and no subtitles, although the DVD itself may have multiple audio tracks and multiple subtitles . Also, the quality is limited by the bitrate used to encode the file which is typically relatively low and not adjusted to the device to be transferred to . </P> <P> Digital Copy files based on transcoding solutions can use the correct audio track and subtitle based on the user's location or choice and individually create the digital copy based on the target device properties (video and audio bitrate, display resolution, aspect ratio). </P> <P> Most often, Digital Copy solutions offer Windows Media or Apple iTunes files with their respective DRM services, Windows Media DRM and FairPlay . Other solutions also provide support for Sony PlayStation Portable and phones using 3GP video files and Open Mobile Alliance DRM . Some publishers limit their digital copies to Microsoft operating systems and devices . Linux - based desktop operating systems are unable to play this content . Apple computers and devices are not supported by their digital solution . </P> <P> To limit the number of free copies, the disc typically comes with a single - use code to authenticate a computer over the Internet . Alternatively, content owners can offer the Digital Copy feature as a paid service . Often the authentication code has an expiration date, rendering the copy invalid if it is used after that time . </P>

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