A VOB file is normally known as a DVD Video Object file, and is one of the most common formats for storing video and audio streams on DVD discs. The VOB format also may denote a Vue d'Esprit object, which is a 3D model created for use within the application. A VOB file contains video streaming in MPEG-2 format and audio streaming in one of several formats.
VOB files are a container, which consist of 3 things. They consist of video, audio and subtitle streams. The video stream is in MPEG-2 format, the audio however can be in various forms such AC3 - which is the most common, MPEG-2 multichannel, MPEG-1 Layer 2 dual channel or PCM format. The reason AC3 is the most common is that it offers a good compromise between quality and bitrate.
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MP4 files (MPEG-4 Part 14) are multimedia files. MP4 is a container format that can store video, audio and subtitle data (as well as more depending on content). Since stores like iTunes uses this container format, and it is used with iPod and PlayStation Portable (PSP), MP4 files have become more common.
MPEG-4 Part 14 or MP4, formally ISO/IEC 14496-14:2003, is a multimedia container format standard specified as a part of MPEG-4. It is most commonly used to store digital video and digital audio streams, especially those defined by MPEG, but can also be used to store other data such as subtitles and still images. Like most modern container formats, MPEG-4 Part 14 allows streaming over the Internet. A separate hint track is used to include streaming information in the file. The only official filename extension for MPEG-4 Part 14 files is .mp4.
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