About audio and video files on the internet

CODEC - Audio and video (A/V) files can be very large. Consequently, they are generally compressed (encoded) for transmission and storage and decompressed (decoded) for viewing or listening. The term CODEC means Coder/Decoder or Compression/Decompression algorithim. To listen to an audio file, or view a video file, you must have a program that can decompress the particular CODEC used to compress the file.

Two methods of accessing A/V files online:

• Downloading: Some websites set up A/V files to be downloaded to the user’s computer. If this method is used, a copy of the file will remain on your computer, and you may experience a lengthy delay before you can view/listen to the file.
• Streaming: Files that are streamed generally start to play within a few seconds. If this method is used, you may experience some ‘glitches’ when viewing/listening to the file; however, you will not have a large file stored on your computer when you are done.

Audio CODECS – Some of the most common CODECs for audio are MP3, Real Media, and WMA (Windows proprietary CODEC for audio).

Video CODECS – Some of the most common video CODECs are Apple Quicktime, Real Media, and MPEG-4, and WMV (Windows proprietary CODEC for video).

Do you want more detail? Try these websites …

• A list of common file types:  http://www.fileinfo.net/common.php
• A FAQ file on streaming A/V:  http://all-streaming-media.com/streaming-media-faq/faq-streaming-media.htm
• Audio file formats :  http://www.nch.com.au/acm/formats.html
• Audio/Video file formats (PDF file): http://www.it.miami.edu/classes/pdfs/av_formats.pdf