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Chapter 12
The name MP3 began as an extension to a computer filename, devised to distinguish sound files created using MPEG-1 layer III encoding and decoding software. The PC type of computer makes use of these extension letters, up to three of them, placed following a dot and used to distinguish file types. For example, thoughts.txt would be a file called thoughts, consisting purely of text, and thoughts.doc would be a document called thoughts which could contain illustrations and formatted text, even sounds. A file called thoughts.jpg would be a compressed image file and thoughts.bmp would be an uncompressed image file. There are many such extensions, each used to identify a specific type of file. n
Note The same mp3 extension is used for sound files that have used MPEG-2 layer III with a reduced sampling rate, but there is no connection between MP3 and MPEG-3. MP3 files use a compression ratio of around 12:1, so that MP3 files stored on a recordable CD (an MP3-CD) will provide about nine hours of sound. Older CD players will not work with such a disc, but the more modern units will (they are distinguished by the MP3 logo on the casing). n
The main use of MP3, however, has been the portable MP3 player, which allows MP3 files to be recorded from downloads over the Internet. This started off as very much of an audio system for the computer buff, but like all matters pertaining to computing, this use has spread. MP3 is unlikely to appeal to those who seek perfection in orchestral music (let’s face it, what system does?), but for many other applications it offers a sound quality that is at least as good as anything that can be transmitted by AM radio or obtained from a cassette. The advantages are many. You can load the memory up with music that you like, deleting anything you do not want to hear again. You can play tracks in any order, select tracks at random, and store other music on your PC until you want it on your MP3 player. Summary MP3 uses a lossy compression, typically around 12:1, on sound files to allow for transmitting such files over the Internet, storing them in solid-state memory, magnetic drives or CD format, and replaying in small units that contain no moving parts. This type of system is the successor to the compact cassette.