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Exporting your media

File formats and compression

There are many different formats available for digital video and audio.

The format that follows international standards is called MPEG for video, and mp3 for audio. The advantage of using MPEG is that it can be played by pretty much any video player. There are now 3 versions of MPEG: MPEG1, MPEG2 (which is the standard used for DVD movies) and the new MPEG 4. Most common video editing software will allow you to publish your material as MPEG 1 and 2, but you may need to buy additional software to create MPEG4 movies. Note that MPEG2 gives good results when saved at high quality but is less good at creating small, very compressed files.

There are also a number of proprietary formats available, the best known of which are Windows Media, Quicktime, Real Media and Flash Video.

All of these give good results and offer high quality with small files. One of the problems with these formats is that, unlike MPEG, they do not play in each other's software, so for example you cannot play a Real Media file in Windows Media Player. All of these have their advantages and disadvantages; for example Windows Media is free, easy to work with and the player is installed on all Windows computers. However Windows Media is not very suitable for Mac users. Flash video is high quality and most computers of all kinds have Flash Player installed.

When exporting your edited video you will also need to choose the resolution (number of pixels) and compression rate. The more you compress your file the smaller it will be but also the lower quality.



How is compression measured?

In many systems, the amount of compression is measured in terms of the target bitrate. This means the number of bits of binary information contained in the file per second of its playing time (written as bps - bits per second). The lower the target bitrate, the more compression required to achieve it, and the lower quality of the video/audio.