File Formats: The Package

Posted on August 22, 2009
Filed Under Video files | Leave a Comment

Hello friends! Today I’ll post for File Formats.

Basically, AVI and QuickTime are file formats, a collection of file headers and control information wrapped around some video (and audio) data to define the contents of a video file. In order to play a video file, you first need to know what it contains. The file can have one stream of video, or an audio stream (mono or stereo), or both, or even more than one of each. Each stream can then be stored in different ways: with different video resolutions and compression formats, and different audio formats and quality.

The AVI and QuickTime file formats define the contents of a video file — the number of streams, their type, and format. Along with the stream descriptions, the file formats also contain timing information for synchronizing the streams, particularly so the video and audio can be played in sync. The file formats also provide different mechanisms for interleaving the video and audio data within the file so that they can be processed efficiently and played, in sync, in real time.

Playing AVI and QuickTime files requires system software on the Windows and Mac platforms that can read and play video files in their supported formats. In order for your system to play a file, it’s not enough for the file format to describe how to separate out the data for each video and audio stream; it also needs to provide information about the format of the data in the stream. Video data can be stored at different resolutions, with different amounts of color information, and with different compression algorithms. The compression algorithms squish down and mix up the video so that it can be incomprehensible without the corresponding decompression algorithm. AVI and QuickTime provide extensible architectures for adding new compression algorithms to your system. These are called “codecs,” for compressor-decompressor.

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