MP3

MP3 is a popular digital audio encoding and lossy compression format invented and standardised in 1991 by a team of engineers working in the framework of the ISO/IEC MPEG audio committee under the chairmanship of Professor Hans Musmann (University of Hannover - Germany). It was designed to greatly reduce the amount of data required to represent audio, yet still sound like a faithful reproduction of the original uncompressed audio to most listeners. In popular usage, MP3 also refers to files of sound or music recordings stored in the MP3 format on computers.

Volume normalization

As compact discs and other various sources are recorded and mastered at different volumes, it is useful to store volume information about a file in the tag so that at playback time, the volume can be dynamically adjusted.

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A few standards for encoding the gain of an MP3 file have been proposed.

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The idea is to normalize the volume (not the volume peaks) of audio files, so that the volume does not change between consecutive tracks.

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The most popular and widely-used solution for storing replay gain is known simply as "Replay Gain".

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Typically, the average volume and clipping information about an audio track is stored in the metadata tag.

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