M4A is a filename extension for AAC container format and is developed by Apple Inc. M4A music is bought on the iTunes Store and does not come with DRM protection. In terms of quality, M4A is better than MP3 because it is lossless but still compressed. This means that it occupies less storage space and doesn’t lose quality over time.
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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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