At this point in the book, we keep it simple. However later sections will provide much more detail. .
MP3 is a digital (computer readable) file that represents sound (be it music, voice or other sources). MP3 involves compression to reduce the quantity of data needed to represent sound with the objective of little loss of quality. It achieves compression by filtering out redundant and irrelevant parts of the audio signal that human hearing does not perceive.
Today we have more than one type of compression format. MP3 is just one of several standard digital music formats. MP3 tends to be used as a generic term for all types of digital music formats but it actually represents the most popular and specific format from a choice of several. Formats are described in detail later but they include AAC, OGG Vorbis, WMA and others.
Most PC software takes care of all the technical details of compression and decompression by using a CODEC (coder / decoder), or if you prefer compression / decompression, to convert data from the Audio CD to a compressed format that is then decompressed for audio playback. Although it possible to take more control over some of the coding if you decide to get technical [x-ref] usually it is not necessary.
You could of course rip music from your standard audio CDs in an uncompressed digital representation. These would be stored on the PC with a .WAV extension (short for Wave). Wave files are good for manipulating the sound but are bad for storage and bandwidth as these weigh in at nearly 10 megabytes (mb) per minute (with a bit rate of 1411.2 kilobits per second (kbps) of stereo music) of music. So not only do they require lots of computer disk space but even worse .WAV files will take around 10 tens longer to download on the internet than ‘near CD quality’ MP3 files.
WAV files are uncompressed Pulse Code Modulation (PCM) files sampled at 44,100 Hz using 16 bits for each stereo channel, thus 44,100 x 16 x 2 = 1,411,200 bps.
Figure 1 : An graphical view of a sound file for a single channel of just over 10 milliseconds.
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