Audio and Video File Formats: An Introduction

FILE FORMATSThere are several audio file formats inmusic sample.WMA: Windows Media Audio A digital
common use. There are fewer video file formats, butsystem invented by Microsoft, and is used in portable
audio video file extensions can be confusing. This isdigital audio players. Using WMA, a file can be
just a brief description of what the more commonlyprogrammed so that it cannot be copied, and can be
used audio and video file formats and systemsused to protect copyright.WMF: Windows Media
are.AAC:Advanced Audio Coding This is the audio fileFormat These are audio-video files comprising WMA
format used by Apple for the iTunes Music Store, andand video codecs. They provide high quality and media
it may appear with the M4A filename extension. It issecurity for streaming and download and play
better than MP3 for sound quality. It was developed asapplications on computers.WMV: Windows Media
part of the MPEG4 group owned by Dolby (seeVideo Used in the Windows media Player, this is used
below).AU: This audio file format is the standard usedto stream and download and play audio and video
by Java, Sun and Unix.MPEG: Moving Pictures Expertcontent.When dealing with audio and video file formats,
Group There are a number of MPEG types now,you will sometimes notice the term 'codec'. A codec is
described below.MPEG-1: This is used in digitalsimply short for encoder-decoder (or compressor -
cameras and camcorders for small video clips. VHSdecompressor). A main function of a codec is to
quality playback can be expected fromcompress audio or video data streams so that
MPEG-1.MPEG-2: Used for digital satellite TV,transmission of digital audio samples and video frames
professional movie recording and recording of homecan be speeded up and storage space reduced.The
DVD recordings. Provides provision for multi-channelobjective of all codecs is to reduce the file size to a
surround sound recordings.MPEG-3: MPEG-3 wasminimum while maintaining audio and video quality. A
propose as an entity, but eventually merged intoquick indication of the codec's place in the path of
MPEG-2.MPEG-4: This is the newest MPEG systemtransmission and reception is:Video device (e.g.
and is used for streaming internet content. It is alsocamcorder) - video capture card - video digitized -
used in portable video recorders and for internetcodec (compresses digital info) - result (MPEG2, AVI,
downloads. Required for DivX. It improves digitalWMV etc) - codec (decompress) - video frames -
broadcasting and interactive graphics anddisplay device.Between the two codecs the
multimedia.MP3: Digital audio files, most commonly usedcompressed result is transferred to the display device
to store and playback music. It compresses the files totransmitted, stored on file, etc). So to condense the
about 10% of a normal audio file, and a normal musicflow even further, we could basically describe it as:raw
track will be about 5 -6 MB in size. MP3 stands fordata - codec - transmit - codec - playThis is simplistic,
MPEG-1 Audio Layer 3, not MPEG-3 as many peoplebut it shows where the codecs are used. Therefore, in
think. A typical MP3 audio file is near CD quality.OGG:order to play a movie, video or piece of music of a
An audio file format supporting a variety of codecs,certain format, you need a codec in your computer to
the most popular of which is the audio codec Vorbis.allow you to decompress the file and play it.Here is
However, MP3 files are much more broadly supportedsome free software which checks what codec a
than Vorbis.RA: Real Audio This format is designed forvideo system uses, and what codec your system
streaming audio over the Internet. It is a self-containedneeds to play it:Codec Tool.The different video file
file format with all the audio information stored withinformats are required to meet the requirements of
the file itself.WAV: The simplest of the audio filevarious video devices. Similarly, audio file formats are
formats, developed by Microsoft and IBM, and built intodesigned to meet the needs of the specific delivery
Windows 95. It is an uncompressed audio file formatmethods and storage and playback devices introduced
with large file sizes (10 x MP3), and does not needby large corporations such as Microsoft, Sony and
further processing to play. The WAV file consists ofApple. Thus, Sony invented the UMD (Universal Media
three blocks of information: The RIFF block whichDisk) for the PSP (Playstation Portable), and Apple
identifies the file as a WAV file, The FORMAT blockintroduced AAC (M4A) for its iPod.Peter Nisbet is the
which identifies parameters such as sample rate andauthor of many articles on audio and video file
the DATA block which contains the actual data, orsystems, their transmission, playback and conversion.