S3 Media Types

Information systems like web pages and databases can contain a wide range of data types: text, graphic, audio, video files.

Compression

Graphic, audio and video files can be very large and

will use a large amount of backing storage when saved onto hard disks or flash drives.
take a long time to download or upload on a network.

Compression is used to reduce the file size when it is saved or sent along a network including email attachments. However the file must be decompressed before it can be opened and used.

The disadvantage of compression is that when a file is compressed some of its data is lost. When the file is decompressed the quality of the final graphic, audio or video file will be poorer than the original.

Standard File Formats

Saving a file in its native file format means that it can only be opened if the software that created it is on the computer.

i.e. a Microsoft Word file can only be opened by a computer which has Microsoft Word.

Saving a file in a standard file format means it can be opened on any type of computer system.

Video files

The standard file formats for video files are:

mp4 (moving picture experts group), which is used to deliver high quality video and audio over the Internet.
avi (audio video interleave), which stores the video and audio in a single file. It is not compressed and of poorer quality than mp4.

Text files

The standard file formats for text files are

txt, but this means you will lose any formatting data (such as bold, italic and different fonts).
rtf (rich text format), which allows formatting to be kept.
PDF (portable document format) files keep the formatting but the text cannot be changed.

Graphic files

The standard file formats for graphic files are

jpeg (joint photographic experts group), which contains all possible colours.
gif (graphics interchange format), only has 256 colours and so is used to create charts and navigation buttons.

Both of these use compression.

Audio files

The standard file formats for audio files are

wav (waveform audio file format), used in CDs. The file sizes can be very large.
mp3, which uses compression to filter out the sound that humans cannot hear and so the quality of the sound is not affected.

The Copyright Design & Patents Act

This act covers the illegal copying of published material such as images, text, video and music.

It is illegal to do the following

make pirated (unauthorised) copies of software
run pirated software
transmit software over network connections and copy it
run multiple copies of software if only one copy was paid for
lend or sell software to other people without a license
plagiarise other people’s work e.g. text, graphics, text, videos, animations and other material taken from websites without the permission of the copyright holder.

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