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