| FILE FORMATSThere are several audio file formats in | | | | music sample.WMA: Windows Media Audio A digital |
| common use. There are fewer video file formats, but | | | | system invented by Microsoft, and is used in portable |
| audio video file extensions can be confusing. This is | | | | digital audio players. Using WMA, a file can be |
| just a brief description of what the more commonly | | | | programmed so that it cannot be copied, and can be |
| used audio and video file formats and systems | | | | used to protect copyright.WMF: Windows Media |
| are.AAC:Advanced Audio Coding This is the audio file | | | | Format These are audio-video files comprising WMA |
| format used by Apple for the iTunes Music Store, and | | | | and video codecs. They provide high quality and media |
| it may appear with the M4A filename extension. It is | | | | security for streaming and download and play |
| better than MP3 for sound quality. It was developed as | | | | applications on computers.WMV: Windows Media |
| part of the MPEG4 group owned by Dolby (see | | | | Video Used in the Windows media Player, this is used |
| below).AU: This audio file format is the standard used | | | | to stream and download and play audio and video |
| by Java, Sun and Unix.MPEG: Moving Pictures Expert | | | | content.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 digital | | | | simply short for encoder-decoder (or compressor - |
| cameras and camcorders for small video clips. VHS | | | | decompressor). A main function of a codec is to |
| quality playback can be expected from | | | | compress 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 home | | | | can be speeded up and storage space reduced.The |
| DVD recordings. Provides provision for multi-channel | | | | objective of all codecs is to reduce the file size to a |
| surround sound recordings.MPEG-3: MPEG-3 was | | | | minimum while maintaining audio and video quality. A |
| propose as an entity, but eventually merged into | | | | quick indication of the codec's place in the path of |
| MPEG-2.MPEG-4: This is the newest MPEG system | | | | transmission and reception is:Video device (e.g. |
| and is used for streaming internet content. It is also | | | | camcorder) - video capture card - video digitized - |
| used in portable video recorders and for internet | | | | codec (compresses digital info) - result (MPEG2, AVI, |
| downloads. Required for DivX. It improves digital | | | | WMV etc) - codec (decompress) - video frames - |
| broadcasting and interactive graphics and | | | | display device.Between the two codecs the |
| multimedia.MP3: Digital audio files, most commonly used | | | | compressed result is transferred to the display device |
| to store and playback music. It compresses the files to | | | | transmitted, stored on file, etc). So to condense the |
| about 10% of a normal audio file, and a normal music | | | | flow even further, we could basically describe it as:raw |
| track will be about 5 -6 MB in size. MP3 stands for | | | | data - codec - transmit - codec - playThis is simplistic, |
| MPEG-1 Audio Layer 3, not MPEG-3 as many people | | | | but 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 supported | | | | some free software which checks what codec a |
| than Vorbis.RA: Real Audio This format is designed for | | | | video system uses, and what codec your system |
| streaming audio over the Internet. It is a self-contained | | | | needs to play it:Codec Tool.The different video file |
| file format with all the audio information stored within | | | | formats are required to meet the requirements of |
| the file itself.WAV: The simplest of the audio file | | | | various video devices. Similarly, audio file formats are |
| formats, developed by Microsoft and IBM, and built into | | | | designed to meet the needs of the specific delivery |
| Windows 95. It is an uncompressed audio file format | | | | methods and storage and playback devices introduced |
| with large file sizes (10 x MP3), and does not need | | | | by large corporations such as Microsoft, Sony and |
| further processing to play. The WAV file consists of | | | | Apple. Thus, Sony invented the UMD (Universal Media |
| three blocks of information: The RIFF block which | | | | Disk) for the PSP (Playstation Portable), and Apple |
| identifies the file as a WAV file, The FORMAT block | | | | introduced AAC (M4A) for its iPod.Peter Nisbet is the |
| which identifies parameters such as sample rate and | | | | author of many articles on audio and video file |
| the DATA block which contains the actual data, or | | | | systems, their transmission, playback and conversion. |