Video files are a recognized and accepted part of using a computer or using the internet (or any other digital device that can play them); they are yet another way we can communicate, share and create using technology. A single video file is in actuality a collection of images, audio and other data and each video file has its own set of attributes including the pixel dimensions, frame rate, audio channels, and more. On top of all these variables already mentioned, there are various ways to encode and save video data, which means there are many different file formats when it comes to video. So the next logical question is – what’s a file format?

A simple explanation then would be: the structure in which any information (not just video) is stored, or encoded, in a computer file.

When talking explicitly about video file formats, there is an enormous amount of data needed to depict or reproduce a video signal correctly. The information required for this is generally compressed for ease of storage and transportation (uploading or downloading) into a container file. This is where the differences become evident since there are, depending on preference or requirement, many different types of video file containers for many different uses. The file extension for a video file refers to the container the video is in. Before looking at file formats in a bit more detail, first, a quick word about codecs – a codec (derived from encoder/decoder) is software used to compress and uncompress a video file. Codecs will always be required when using video; some video formats have codecs that are always employed while others can be used with a variety of different codecs. Now, onto the file formats.

AVI – audio video interleave (.avi is the file extension)

AVI’s are perhaps the most common type of video file format and they are also one of the oldest as they were originally developed by Microsoft when Windows 3.1 was released (note – that’s pretty damn old in computer years). At this point, avi files are becoming slightly less prevalent due to the continued evolution of digital video and the requirements of users; however, they are still the standard for the majority of users. There are simply so many legacy avi files around on the web that it will take years before they are considered obsolete.

ASF – advanced Systems Format (.asf is the file extension)

ASF is another Microsoft created container that was made for use with video files that have been compressed using the Microsoft WMV (windows media video) codec. Where it gets slightly confusing is that the files are usually designed as .wmv and not .asf. One thing that sets this apart from other file formats is that .asf files can include a type of copy protection know as digital rights management, or DRM.

QT – QuickTime (.mov or .qt is the file extension)

This type of file format was developed by Apple. The format was designed with the intention of supporting a multitude of codecs, thereby increasing its usefulness by way of added flexibility. As it is a solely proprietary creation of Apple’s, Apple can decide what it will support. Like the .asf file, the actual file extension used is often .mov and not .qt.

MPG – mpeg (.mpg is the file extension)

This type of file format is a variation on the Moving Picture Experts Group audio and video compression format. The Moving Picture Experts Group is responsible for several variations of this format (MPEG-1, MPEG-2, and MPEG-4). Mpeg files are almost as common as .avi files.

MP4 – mpeg4 (.mp4 is the file extension)

MP4 is an abbreviation for MPEG-4 Part 14; this file type is also a creation of the Moving Picture Experts Group. MP4 is a file format which allows for a combo of audio, video, subtitles and still images in a single file.

FLV – Flash Video (.flv or .swf are the file extensions)

The FLV format was created by the Macromedia Company, which in turn was acquired by software maker Adobe. Flash files today primarily utilize the H.264 encoder/decoder and are widely used for any instances of streaming video on the internet. The only major drawback with FLV files are their incompatibility with portable Apple devices (the uproar amongst users over this matter is well known; Flash files will work just fine with Apple computers though).

There are many different file formats (literally, there are hundreds) when it comes to digital video files. The ones described above are some of the more popular and widespread file types, but there are many more which don’t appear very often to the average user due to low popularity, whether or not they are proprietary and gradual phasing out or outright obsolescence (An example of ‘dead’ file format would be .rm files, or Real Media files). As video file resolution rates, compression software and technology used for viewing continues to improve and evolve, it is likely that many more file formats will be created as both need and demand dictates.

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