What is an Audio Format

8/2/2019 What is an Audio Format

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What is an audio format ?

An audio file format is a file format for storing audio data

on a computersystem.

The data can then be stored uncompressed,

orcompressed to reduce the file size.
http://en.wikipedia.org/wiki/File_formathttp://en.wikipedia.org/wiki/Soundhttp://en.wikipedia.org/wiki/Computerhttp://en.wikipedia.org/wiki/Audio_compression_(data)http://en.wikipedia.org/wiki/Audio_compression_(data)http://en.wikipedia.org/wiki/Computerhttp://en.wikipedia.org/wiki/Soundhttp://en.wikipedia.org/wiki/File_format


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3 major groups of audio file formats:

Uncompressed audio formats

Lossless data compression

Lossy compression


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Uncompressed audio formats

There is one major uncompressed audioformat, PCM .

Pulse-code modulation is

a digital representation of an

analog signal where the magnitude of the

signal is sampled regularly at uniform intervals
http://en.wikipedia.org/wiki/PCMhttp://en.wikipedia.org/wiki/Digitalhttp://en.wikipedia.org/wiki/Signalling_(telecommunication)http://en.wikipedia.org/wiki/Sampling_(signal_processing)http://en.wikipedia.org/wiki/Sampling_(signal_processing)http://en.wikipedia.org/wiki/Signalling_(telecommunication)http://en.wikipedia.org/wiki/Digitalhttp://en.wikipedia.org/wiki/PCM


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PCM stored as

.WAVOn Windows

.AIFFOn Mac OS

.CDAAudio CD


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Examples

wav standard audio file container formatused mainly in Window PCs.

Aiff the standard audio file format used by

Apple. It is like a wav file for the Mac raw a raw file can contain audio in any codec

but is usually used with PCM audio data.

au the standard audio file format usedby Sun, Unix and Java

Large in sizearound 10 MB per

minute.


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Lossless data compression:

It allows the exact original data to bereconstructed from the compressed data.

For example, it is used in the popular ZIP file

format Lossless compression is used in cases where it

is important that the original and the

decompressed data be identical
http://en.wikipedia.org/wiki/ZIP_(file_format)http://en.wikipedia.org/wiki/ZIP_(file_format)


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Examples

flac- a lossless compression codec. If you compress a

PCM file to flac and then restore it again it will be a

perfect copy of the original.

Apple Lossless Windows Media Audio Lossless (WMA Lossless)


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Lossy compression:

Lossy compression is a datacompression method which discards (loses)

some of the data, in order to achieve its goal,

with the result that decompressing the datayields content that is different from the

original, though similar enough to be useful in

some way.
http://en.wikipedia.org/wiki/Data_compressionhttp://en.wikipedia.org/wiki/Data_compressionhttp://en.wikipedia.org/wiki/Data_compressionhttp://en.wikipedia.org/wiki/Data_compression


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Examples

mp3- By eliminating portions of the audio file that areessentially inaudible, mp3 files are compressed toroughly one-tenth the size of an equivalent PCM filewhile maintaining good audio quality.

wma - the popular Windows Media Audio format owned by

Microsoft.

aac- the Advanced Audio Coding format is based on the

MPEG4 audio standard owned by Dolby.

atrac (.wav) - It always has a .wav file extension.


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Common formats and their description:

The WAV format WAV files tend to be very large, since

they are not compressed at all. WAVs are used where space is not a huge issue, or where

compression is not possible for other reasons standardcompact discs, for example, use an uncompressed digitalaudio file using pulse-code modulation (PCM).

The MP3 format MP3 files are ideal for sharing online, orin any context where space is at a premium, because theycan be compressed down to much smaller sizes than WAV

formats. The quality is reduced most MP3s are encoded at

anywhere between 160 and 320 kb/s, as opposed to the1411.2 kb/s of a WAV file but for many people the lossof sound fidelity is unnoticeable, especially with cheaper

speakers.
http://www.wisegeek.com/what-is-an-mp3.htmhttp://www.wisegeek.com/what-is-an-mp3.htmhttp://www.wisegeek.com/what-is-a-wav-file.htmhttp://www.wisegeek.com/what-is-a-wav-file.htmhttp://www.wisegeek.com/what-is-a-wav-file.htmhttp://www.wisegeek.com/what-is-an-mp3.htmhttp://www.wisegeek.com/what-is-an-mp3.htm


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AAC It is a newer compression system, and isgenerally agreed upon as having a higher-

quality sound at the same compression levelsas MP3.

Windows Media Audio (.wma)Windows Media Audio (.wma) was developed

to compete with the MP3 format for WindowsMedia Player. Microsoft claims that the WMAfiles are compressed three times more thanMP3s yet retain their original sound quality.


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MP3 VS AAC

It's advantage is that AAC files are of smaller

size but of comparatively good.

128kbps mp3 = 96kbps AAC without little

noticeable loss of quality, and the file will be

600kb ~ 750kb smaller in size. If you convert

192kbps mp3 to AAC the target file will be of

96kbps with tiny loss of sound quality, butHALF of the mp3 file size.

Is aac better ?


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Ring tone encoding formats

AAC: Some phones like the SonyEricsson W810i support ring tones in ".m4a" AAC

format. The iPhone supports ring tones in ".m4r"

AAC format.

AMR: Audio compression format specialized in

speech used by Nokia before mp3 became standard.

MID / MIDI: Popular sound format.

eMelody: Older monophonic Ericsson format.


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In telecommunications and computing, bitrateis the number ofbits that are conveyed or

processed per unit of time.

How does bit rate effect file size ?For a 128kbps MP3/AAC file, each second of audiorequires 128kilobits of data. We are talking about kiloBITShere, not kilobytes (there are 8 bits in a byte).
http://en.wikipedia.org/wiki/Telecommunicationshttp://en.wikipedia.org/wiki/Computinghttp://en.wikipedia.org/wiki/Bithttp://en.wikipedia.org/wiki/Bithttp://en.wikipedia.org/wiki/Computinghttp://en.wikipedia.org/wiki/Telecommunications


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Relation b/w size of file and bit rate x = length of song (in seconds)

y = bitrate (in kilobits per second)z = resultant file size (in kilobytes)

z = (x * y) / 8

Example

So if you have a 5 minute song, encoding at 128kbps, you woulddo this as follows:

5 minutes = 300 seconds128kbps * 300 seconds = 38,400 kilobits of data38,400 kilobits / 8 = 4,800 kb

To take this one step further, you can convert this intoMegabytes by dividing by 1,024, so 4800/1024 = 4.6875Mb


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List of audio formats Wav: standard audio file container format used mainly in Windows PCs. Ogg:-- a free, open source container format supporting a variety of codecs Mpc: -- Musepack or MPC (formerly known as MPEGplus

Flac:--Free Lossless Audio Codec Aiff:-- the standard audio file format used by Apple Raw:-- a raw file can contain audio in any codec but is usually used with PCM audio data Au:-- the standard audio file format used by Sun, Unix and Java

mp3- the MPEG Layer-3 format is the most popular format for downloading and storingmusic.

gsm- designed for telephony use in Europe, gsm is a very practical format for telephone

quality voice. dct- A variable codec format designed for dictation. wma- the popular Windows Media Audio format owned by Microsoft aac- the Advanced Audio Coding format is based on the MPEG4 audio standard owned

by Dolby. atrac (.wav)- the older style Sony ATRAC format ra- a Real Audio format designed for streaming audio over the Internet ram- a text file that contains a link to the Internet address where the Real Audio file is

stored dss- Digital Speech Standard files are an Olympus proprietary format. msv- a Sony proprietary format for Memory Stick compressed voice files dvf- a Sony proprietary format for compressed voice files; commonly used by Sony

dictation recorders.


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mp3- the MPEG Layer-3 format is the most popular format for downloading andstoring music.

gsm- designed for telephony use in Europe, gsm is a very practical format fortelephone quality voice.

dct- A variable codec format designed for dictation.

wma- the popular Windows Media Audio format owned by Microsoft

aac- the Advanced Audio Coding format is based on the MPEG4 audio standardowned by Dolby.

atrac (.wav)- the older style Sony ATRAC format

ra- a Real Audio format designed for streaming audio over the Internet

ram- a text file that contains a link to the Internet address where the Real Audio fileis stored

dss- Digital Speech Standard files are an Olympus proprietary format.

msv- a Sony proprietary format for Memory Stick compressed voice files

dvf- a Sony proprietary format for compressed voice files; commonly used by Sonydictation recorders.

KWS: Kyocera's ringer format Morse code: Text files with a .MORSE extension get converted into morse code

songs

MOT: An older ringer format for Motorola phones.

Nokia / SCKL / OTT: Nokia Smart Messaging format


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PDB: Palm database. This is the format used to load ring tones on PDAphones

PMD: Format co-created by Qualcomm and Japanese company Faith

QCP: File format generated by Qualcomm PureVoice software. RTTTL: A popular text format for ring tones

RTX: Similar to RTTTL with some advanced features. Also the octaves aredifferent on RTX.

Samsung1 & Samsung2: Samsung keypress format

Siemens Keypress: Can create and read in a Siemens text file format Siemens SEO: Siemens SEO binary format

SMAF: Yamaha music format that combines MIDI with instrument sound data(aka Module files)

SRT: Sipura ringtone for Sipura Technology VoIP phones


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Video FormatsAVI:- Audio Video Interleaved, is developed

by Microsoft in 1992

Advantages

High image quality

Application in multi-platforms

Disadvantages

Large volume

higher-version Windows Media Player simplycant play AVI videos which are edited with earlier

codes, and vise versa


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MPEG, Moving Picture Expert Group

Is the format of VCD, SVCD, DVD

This format applies lossy compression to reduce redundant info in

active images, and to express it more clearly

MPEG makes use of the fact that the two contiguous images are

almost the same

MOV, developed by Apple

features a high compression ratio and near perfect definition

most outstanding trait is its trans-platform ability, supporting

Windows other than its intimate pal MacOS.


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ASF

Is an extensible file format designed primarily

for storing and playing synchronized digital

media stream.

ASF is the container format for Windows

Media Audio and Windows Media Video-

based content. (WMA,WMV)

WMA

WMV


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Mobile video formats

3GPP (.3gp)

It was developed by the 3rd GenerationPartnership Project, hence the name 3GPP.

Flash Lite Flash Lite is a streamlined version of Flash that

was developed specifically for mobile phonesand portable devices.

The full version of Flash of course is the singlemost common online video file format.

It is designated by an .FLV file extension


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MPEG-4

Is a good sharing format for mobile video

Also commonly used for online video in general but isone of the smaller formats so it works well for mobilevideo too.

MP4

Defines the storage of MPEG-4 audio, scenes andmultimedia.

The entire scene is described by an initial objectdescriptor (IOD). This is stored in a special box withinthe movie atom in MP4 files.


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The latest

H.264 Coding Format

Also known as MPEG-4 Part 10 or AVC (for

Advanced Video Coding).

Provide good video quality at substantially

lower bit rates than previous standards.

Provides quarter-pixel precision for motion

compensation enables very precise description

of the displacements of moving areas.

More attractive for video network delivery and

for delivery of HD, high definition video

Documents

What is an Audio Format