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Mp3, WAV and AMR Audio File Formats

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by

Darwin Paul Tüazon

on 6 October 2013

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Transcript of Mp3, WAV and AMR Audio File Formats

All About Audio Files
What is a WAV File?
Stands for Waveform Audio Format. This is a high-quality audio file type generally used for applications that require high quality, such as CDs. WAV files are uncompressed, and therefore take up some disk space, unlike MP3s or AACs, which are compressed.
What is an AMR File?
AMR
stands for
Adaptive Multi Rate
. AMR is a common audio format for various mobile devices such as cell phones and even VoIP kind of applications. In
1998
it became the
standard speech codec
. File extension is .amr.
Mp3 format
THE NAME
MPEG

is the acronym for
Moving Picture Experts Group
. This group has developed compression systems used for video data. For example, DVD movies, HDTV broadcasts and DSS satellite systems use MPEG compression to fit video and movie data into smaller spaces. The MPEG compression system includes a subsystem to compress sound, called
MPEG audio Layer-3
. We know it by its abbreviation,
MP3
.
What are Audio File Formats and Codecs?
by: Darwin Paul B. Tuazon


Audio codecs
are the libraries that are executed in multimedia players. The audio codec is actually a computer program that
compresses
or
decompresses
digital audio data according to the audio file format specifications.
An
audio file format
and
audio co
dec
(
compressor
/
decompressor
) are two very different things.
Audio Formats
Audio Formats can be broken down into three main categories:
Uncompressed formats
,
lossless compression formats
, and
lossy compression
.
Uncompressed audio formats
(often referred to as PCM formats) are just as the name suggests — formats that use no compression. This means all the data is available, at the risk of large file sizes. A WAV audio file is an example of an uncompressed audio file.
Lossless compression
applies compression to an uncompressed audio file, but it doesn't lose information or degrade the quality of the digital audio file. The WMA audio file format uses lossless compression.
Lossy compression
will result in some loss of data as the compression algorithm eliminates redundant or unnecessary information — basically it tosses what it sees as irrelevant information. Lossy compression has become popular online because of its small file size, it is easier to transmit over the Internet. MP3 and Real Audio files uses a lossy compression.
Audio Codecs
The Goal of Using Mp3 Format
The MP3 format is a compression system for music. The goal of using MP3 is to compress a CD-quality song by a factor of 10 to 14 without noticeably affecting the CD-quality sound. With MP3, a 32-megabyte song on a CD compresses down to about 3 MB. This lets you download a song much more quickly, and store hundreds of songs on your computer's hard disk.
Because WAV files are uncompressed, they contain more data and produce better, more subtle, and more detailed sounds.

A
WAV file
generally needs
10MB
for
every 1 minute
of audio, whereas an
MP3
needs about
1MB
for
every 1 minute.
The Wave file format is Windows' native file format for storing digital audio data. It has become one of the most widely supported digital audio file formats on the PC due to the popularity of Windows and the huge number of programs written for the platform.
Microsoft
and
IBM
introduced the format in
1991
for use in the
Microsoft Windows 3.1 operating system (OS)
. Long before digital audio became a staple, computer users were exposed to the WAV file as an embedded sound file that played a
chime-like sound at boot up of the Windows operating system.


This file format is based on the
Resource Interchange File Format (RIFF),
which stores audio files in indexed “
chunks
” and “
sub-chunks
.”
The WAV file had two very big things going for it when introduced.

First
, it could digitize sounds 100% faithful to the original source because it is a lossless format. “
Lossless
” means that the file format does not compromise audio quality even when it holds compressed data.
Second
, the format is very easy to edit and manipulate with software.
While this format was ideal for sound effects
, it had a
drawback
when it came to
music files
. One four-minute song could easily consume over
35 megabytes (MB) of space when saved as a WAV
. Though the cost of hard drives dropped over the years, the format was still too large for portable players with limited flash memory, which would become ubiquitous by the new millennium. Additionally, these files were not the most practical format to transfer online, especially over slow dial-up connections.
Today, the WAV file format is still widely used to archive music files in a lossless format where space is not an issue. Some CD and DVD players can also read these files when they are saved directly to a disc. More often, software that burns the files to CD will convert them in the process to the Compact Disk Audio (.cda) format, making the audio CD compatible with all players.
Compared to
WAV
,
AMR files
are much
smaller in size but are of good quality
. AMR is well supported by most of modern mobile telephone handsets.
AMR Narrowband and Wideband versions
The first one (
AMR-NB
), is a
narrowband version
which is commonly used in situations where
low bitrates are sufficient
-- such as a basic voice recording facility you may have on your MP3 player. The
frequency range
used for
AMR-NB
is
300-3400 Hz
which is capable of producing sound quality that is comparable to traditional telephone. This narrowband version uses the following bitrates:
The second version of AMR is the
wideband type
which is represented by the acronym,
AMR-WB
. As the name would suggest, this is an enhanced vocoder that
uses a wider bandwith

than AMR-NB
in order to
store voice at a much higher quality
-- the
frequency range
used is for this is
50 -7000 Hz
. The bitrates used for the wideband version of AMR are:
There are essentially two AMR format standards which are
AMR-NB
and
AMR-WB
.
04.75 kbps
05.15 kbps
05.90 kbps
06.70 kbps
07.40 kbps
07.95 kbps
10.20 kbps
12.20 kbps
06.60 kbps
08.85 kbps
12.65 kbps
14.25 kbps
15.85 kbps
18.25 kbps
19.85 kbps
23.05 kbps
23.85 kbps
Due to its higher frequency range and therefore superior speech quality,
AMR-WB
is optimized for use in
GSM (Global System for Mobile Communications)
and
UMTS (Universal Mobile Telecommunications System) technologies
-- otherwise known as
2G
and
3G

mobile networks
respectively.
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