Ymp3an independent reference on digital audio

An independent reference on digital audio. Not affiliated with the former MP3 catalogue on this domain; we do not distribute music or files. Listen to and buy music only from legal sources.

Glossary

Glossary

Conversations about digital audio are full of words that sound technical and are often used loosely. This glossary collects the key terms: formats and codecs, sound quality, and rights and sources of music. The definitions are given in general terms: look for technical details in the standards and format documentation, and for legal concepts in the text of the law.

Once you understand what bitrate and sample rate mean, it is easier to resist promises of "studio quality" in any file.

— Editor's note

How this section works: we explain common terms in plain language. Where a term is defined in a standard or a law, rely on the official wording.

Formats and codecs

Codec
An algorithm or program that encodes audio into a particular format and decodes it for playback.
MP3
MPEG-1 Audio Layer III — a lossy audio compression format. Developed with the leading involvement of Fraunhofer IIS and standardised as ISO/IEC 11172-3 in 1993. Fraunhofer's licensing programme for MP3 patents ended in 2017.
AAC
Advanced Audio Coding — a lossy compression format standardised in 1997 as MPEG-2 Part 7 and later included in MPEG-4.
Opus
An open lossy audio compression format designed for both speech and music; widely used in voice calls and streaming.
FLAC
Free Lossless Audio Codec — a lossless compression format and a Xiph.Org project. The first version was released in 2001.
ALAC
A lossless compression format: like FLAC, it allows the original signal to be fully restored.
WAV
An audio container that usually holds uncompressed data. Convenient for editing, but takes up a lot of space.

Sound quality

Bitrate
The amount of data per second of audio, usually in kilobits per second (kbit/s). In lossy formats it determines how much information is discarded. The maximum MP3 bitrate is 320 kbit/s.
Sample rate
How many times per second the audio signal is measured during digitisation. For Audio CD it is 44.1 kHz.
Bit depth
How many bits are used to record each measurement of the signal. It determines how precisely loudness is captured. For Audio CD it is 16 bits.
Lossy compression
Compression in which some information is discarded irreversibly to make the file smaller. MP3, AAC and Opus work this way. Re-encoding with lossy compression degrades quality.
Lossless compression
Compression after which the original signal is restored in full, bit for bit. FLAC and ALAC work this way.
Dynamic range
The difference between the quietest and loudest sounds in a recording. Excessive loudness compression during mixing reduces dynamic range.

Rights and sources

Copyright
An author's rights in a work, including the right to decide how it is used. In Russia it is governed by Part Four of the Civil Code of the Russian Federation; rules differ by country.
Licence
A rights holder's permission to use a work on certain terms: where, how and to what extent.
Creative Commons
A non-profit organisation founded in 2001 and a set of public licences (the first in 2002) with which authors grant permission in advance for certain uses of their work.
Public domain
Works that can be used freely, without permission or payment. A specific recording of such a work may still carry its own related rights.
Streaming
Playing music as a stream over the internet without the user permanently storing the file. It is legal when the service distributes music under agreements with rights holders.
  • Comparisons

    MP3, AAC, Opus, FLAC, ALAC and WAV compared, plus legal ways to listen to music: pros and cons.

  • Security

    The risks of pirate sites, fake installers and "free" downloaders, phishing, and copyright in general terms.

  • FAQ

    Answers about this reference, formats and files, the law and security.

Sources

  • ISO/IEC 11172-3
  • Fraunhofer IIS — the story of MP3
  • Xiph.Org — FLAC
  • Creative Commons
  • Civil Code of the Russian Federation, Part Four

Information on formats and standards is based on official sources as of the preparation date. Software, services and laws change, so check the current documentation, the services' help pages and the laws in force.