M4V is a digital video container format developed by Apple Inc. It is pretty similar to the popular MP4 in terms of structure, but M4V files can sometimes be DRM protected. Today, M4V is the primary video format for iTunes Store videos and can multiplex together multiple audio and video data.
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DV (Digital Video) is a file created using a digital format and saved as raw data. A DV file contains 80-byte DIFs (Digital Interface Blocks), with each block having video, audio, and metadata. DVD files use lossy compression for videos, while sounds stay uncompressed. And although it was originally meant for tape recording, DV can also save data on hard disc drives and optical discs.
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