MP3 glossary
- Wave (.wav)
Wave is the standard form for uncompressed
audio on a PC. Since a wave file is uncompressed data - as close a copy to the original
analog data as possible - it is therefore much larger than the same file would be in a
compressed format such as mp3 or RealAudio. Audio CDs store their audio in, essentially,
the wave format. Your audio will need to be in this format in order to be edited using a
wave editor, or burned to an audio CD that will play in your home stereo.
- ID3 Tag name
The ID3 tag is attached to an MP3 audio file
to carry information relevant to that MP3. The development of ID3 began in 1996 when it
was released that by adding a small chunk of extra data at the start or end of the audio
data the MP3 file could hold information about the audio and not just the audio data
itself.
File management software and many
audio/media players rely on ID3 tag data when working with MP3 files to allow better
presentation, sorting and classification of files. Software is available that can edit the
information contained in an MP3's ID3 tag, commonly referred to as 'tag editors'. The
entire size of the ID3 tag is 128 bytes with a certain amount of bytes allocated to store
the song title, artist, album, year, genre and comments.
- M3U
M3U (.m3u) is the file extension for a
playlist of MP3 audio files used by many media players, including Winamp. Like the RAM
(.ram) file extension. M3U files only contain the information leading to the actual
location (local directory or remote/hyperlink) of the audio file; a .mp3 file.
A M3U file is simply a text file and can be
opened in NotePad or a similar text editor allowing you to see the local or remote
location of the actual audio file. Example:
- MP3 Encode
Encoders are central to MP3. After all,
without an encoder you wouldn't have an MP3. The software in this category allows you to
convert files at varying levels of audible quality. MP3 encoders in this section range
from simple 'drag and drop' programs to versatile programs offering a variety of options.
- MP3 Decode
MP3 decoding software is commonly used to
convert MP3 to WAV format. Often the MP3s are converted into other formats so musicians
can sample songs, while some listeners prefer to convert their MP3s to WAV and then CDA to
burn them onto a CD. A number of decoders support batch processing of files.
- Playlist
Many digital audio and multimedia players
for your computer support playlists. A playlist offers you better organization and
management of the various music files on your computer by controlling what files are
played and in what order, much like a music playlist used by radio stations. Playlists are
commonly used by amateur and professional computer DJs at parties and dances to allow a
continuous play of music, queuing programmed and requested songs. Within a playlist file
(which can be viewed as a text document) is the local (hard-drive) and/or remote
(Internet) location of each file within that playlist. As the audio player moves through
each file on the playlist, it sources that file from the specified location, either on
your hard-drive or the Internet (a URL).
- Sample rate
The sample rate of an audio recording
partially determines the overall sound quality. In the recording process, audio samples
are saved to memory or disk; the rate each sample of audio input is recorded per second is
the sample rate. The sample rate is measured in Hertz (Hz - cycles per second) and
Kilohertz (kHz - thousand cycles per second).
CD quality audio has a sample rate of
44100Hz, 16-bit (resolution) and stereo (channels). The most common sample rates are 11,
22 and 44kHz, with most recording software supporting sample rates from 6kHz up to 192kHz.
Like early footage filmed at a low frame rate looks flickered and robotic, the quality of
an audio recording decreases as the sample rate is lowered. For audio recordings destined
to be encoded to MP3, 22kHz is considered acceptable.
- Bit rate
Bit rate is the amount of information (bits)
transferred in a second ('bps' is the abbreviation of bits-per-second). In terms of MP3
audio files, the bit rate unit is more commonly referred to as 'kbps', which is
thousand-bits-per-second. The higher the bit rate or 'kbps' of an MP3 file, the higher the
sound quality. Most MP3 encoders support a range of bit rates from 24kbps
up to 320kbps (or 320,000 bits per second).
The most widely used 'standard' bit rate for MP3s is 128kbps, but below that is not
especially enjoyable to listen to. At around 160kbps there is a noticeable improvement in
the audible quality of an MP3 encoded audio file.
- Mono: One channel.
- Joint Stereo: Toggles between stereo and mono depending on
differences and similarities in the left and right channels.
- Dual channels: 2 mono channels. (Encoded independently.)
- Stereo: Normal stereo ( 2 channels)
- CBR/VBR
Constant Bit Rate (CBR) encoding means that
you encode a file at a fixed rate, such as 128 Kpbs. For many people this is a common
method of encoding MP3s. You can usually tell CBR files because they have consistent file
sizes and sound quality.
Variable Bit Rate (VBR) encoding is a method
that ensures high audio quality bit-allocation decisions during encoding. The encoder
allocates an appropriate amount of data per second, depending on the complexity of the
audio file.
If there are very complex parts in a song it
will use a quite high bit rate and a lower bit rate for something such as silence. The
average bit rate may not be as high as the bit rate of an MP3 of the same quality with
constant bit rate.
You should use VBR encoding when consistent
audio quality is the top priority.
Variable Bit Rate (VBR) files will encode
MP3 files that have a range of bit rates. Why create more data is necessary? The problem
with VBR is that some players or MP3 devices may not play them back as well as Constant
Bit Rate MP3 files.
Min Bit Rate: the minimum
bit rate to use.
Max Bit Rate: The maximum bit rate to use.
Quality Level: Indicates how well the encoder analyzes the audio. The
more it analyzes the audio, the better chance it has of getting lower bit rate frames. 0 =
highest quality and 9 = lowest quality.
- FreeDB
Freedb is a database to look up CD
information using the internet. This is done by a client (a freedb aware application)
which calculates a (nearly) unique disc ID for a CD in your CD-Rom and then queries the
database. As a result, the client displays the artist, CD-title, track list and some
additional infmations
You can also search for CD-info in the
freedb via the web-based search.
- CD Ripper
Ripping is also referred to as Digital Audio
Extraction (DAE). Depending on your operating system (platform) CD ripping software will
record the CD audio (.CDA) tracks to WAV format (eg. Windows) or AIFF (eg. Macintosh). It
is usually as simple as inserting a CD into the CD-ROM drive of your computer and
selecting the tracks to be recorded to hard drive. Ripping can also refer to the recording
of vinyl records to digital audio. Several ripping programs now incorporate the option to
encode recordings to MP3 and other compressed audio formats.
- MP3 lossy
MP3 is a lossy format. Based on the
compression settings chosen by the user, some of the audio data is thrown away or 'lost'
to decrease the actual compressed file size. This is why the more an MP3 is compressed
(low bit rate and sample rate, mono), the poorer the sound quality. As there are some
elements in any sound recording that are inaudible to the human ear, MP3s still manage to
sound good even with the loss of data.
- MPEG Version
MPEG stands for "Moving Pictures
Experts Group" and is based on a perceptual coding scheme. There are several versions
of the MPEG standard.
(MPEG defines the syntax of low bit-rate
video and audio bit streams, and the operation of conformant decoders. MP3 is actually an
abbreviation for MPEG 1 Layer 3.)
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