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Crossing the boundary: analogue universe, digital worlds
Crossing the boundary: analogue universe, digital worlds

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4.10 Standards again

Whatever compression strategy we adopt – and most real-life approaches use a combination – we again need to have agreement. If I compress a photograph using a certain technique and send it to a friend, her computer will have to be able to decompress it again to display it. So we must have a standard agreement between the parties about how the image has been compressed.

There are many standards for image and film compression. It would be out of place to discuss in detail how they work here – the compression theme is taken up in a later course. All I'll do is note that, among the standards for image compression, two stand out – the JPEG (Joint Photographic Experts Group) and the GIF (Graphics Interchange Format) standards. Both standards reduce the number of bits used to store each pixel. GIF, for example, condenses each pixel from 24 bits to 8, by reducing the set of colours used to a smaller set, called a palette. Image data can sometimes be compressed to one twenty-fifth of the original size.

For video, the dominant standard is MPEG (Moving Picture Experts Group), which is now used in most digital camcorders.