| FILE FORMATS There are several audio file | | | | file format with large file sizes (10 x MP3), |
| formats in common use. There are fewer video | | | | and does not need further processing to play. |
| file formats, but audio video file extensions | | | | The WAV file consists of three blocks of |
| can be confusing. This is just a brief | | | | information: The RIFF block which identifies |
| description of what the more commonly used | | | | the file as a WAV file, The FORMAT block |
| audio and video file formats and systems are. | | | | which identifies parameters such as sample |
| | | | rate and the DATA block which contains the |
| AAC:Advanced Audio Coding This is the audio | | | | actual data, or music sample. |
| file format used by Apple for the iTunes | | | | |
| Music Store, and it may appear with the M4A | | | | WMA: Windows Media Audio A digital system |
| filename extension. It is better than MP3 for | | | | invented by Microsoft, and is used in |
| sound quality. It was developed as part of | | | | portable digital audio players. Using WMA, a |
| the MPEG4 group owned by Dolby (see below). | | | | file can be programmed so that it cannot be |
| | | | copied, and can be used to protect copyright. |
| AU: This audio file format is the standard | | | | |
| used by Java, Sun and Unix. | | | | WMF: Windows Media Format These are |
| | | | audio-video files comprising WMA and video |
| MPEG: Moving Pictures Expert Group There are | | | | codecs. They provide high quality and media |
| a number of MPEG types now, described below. | | | | security for streaming and download and play |
| | | | applications on computers. |
| MPEG-1: This is used in digital cameras and | | | | |
| camcorders for small video clips. VHS quality | | | | WMV: Windows Media Video Used in the Windows |
| playback can be expected from MPEG-1. | | | | media Player, this is used to stream and |
| | | | download and play audio and video content. |
| MPEG-2: Used for digital satellite TV, | | | | |
| professional movie recording and recording of | | | | When dealing with audio and video file |
| home DVD recordings. Provides provision for | | | | formats, you will sometimes notice the term |
| multi-channel surround sound recordings. | | | | 'codec'. A codec is simply short for |
| | | | encoder-decoder (or compressor - |
| MPEG-3: MPEG-3 was propose as an entity, but | | | | decompressor). A main function of a codec is |
| eventually merged into MPEG-2. | | | | to compress audio or video data streams so |
| | | | that transmission of digital audio samples |
| MPEG-4: This is the newest MPEG system and is | | | | and video frames can be speeded up and |
| used for streaming internet content. It is | | | | storage space reduced. |
| also used in portable video recorders and for | | | | |
| internet downloads. Required for DivX. It | | | | The objective of all codecs is to reduce the |
| improves digital broadcasting and interactive | | | | file size to a minimum while maintaining |
| graphics and multimedia. | | | | audio and video quality. A quick indication |
| | | | of the codec's place in the path of |
| MP3: Digital audio files, most commonly used | | | | transmission and reception is: |
| to store and playback music. It compresses | | | | |
| the files to about 10% of a normal audio | | | | Video device (e.g. camcorder) - video capture |
| file, and a normal music track will be about | | | | card - video digitized - codec (compresses |
| 5 -6 MB in size. MP3 stands for MPEG-1 Audio | | | | digital info) - result (MPEG2, AVI, WMV etc) |
| Layer 3, not MPEG-3 as many people think. A | | | | - codec (decompress) - video frames - display |
| typical MP3 audio file is near CD quality. | | | | device. |
| | | | |
| OGG: An audio file format supporting a | | | | Between the two codecs the compressed result |
| variety of codecs, the most popular of which | | | | is transferred to the display device |
| is the audio codec Vorbis. However, MP3 files | | | | transmitted, stored on file, etc). So to |
| are much more broadly supported than Vorbis. | | | | condense the flow even further, we could |
| | | | basically describe it as:raw data - codec - |
| RA: Real Audio This format is designed for | | | | transmit - codec - play |
| streaming audio over the Internet. It is a | | | | |
| self-contained file format with all the audio | | | | This is simplistic, but it shows where the |
| information stored within the file itself. | | | | codecs are used. Therefore, in order to play |
| | | | a movie, video or piece of music of a certain |
| WAV: The simplest of the audio file formats, | | | | format, you need a codec in your computer to |
| developed by Microsoft and IBM, and built | | | | allow you to decompress the file and play it. |
| into Windows 95. It is an uncompressed audio | | | | |