VOB (Video Object) is a digital video container format usually found in DVD video media. VOB contains DVD video, audio, menu, and text data such as subtitles all multiplexed together. It typically includes MPEG-1 Part 2 or MPEG-2 Part 2 video codec encoded with AAC audio. Although this format is free, some copies might be encrypted.
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AC3 is an audio format designed by Dolby Digital to offer surround sound listening. This format is available on most Blu-ray and DVD media files and is played using a Dolby Digital DVD Player. Interestingly, AC3 can be output in up to six speakers of a home stereo system. On a computer, AC3 can be opened on VLC Media Player, Apple QuickTime Player, and Windows Media Player.
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