WebM is an open media container compressed with VP8 video codec and Vorbis audio codec. WebM format has high video playback quality and data compression parameters.The format is widely used for adding media to web pages and it is supported by all modern web-browsers like Opera, Mozilla Firefox and Google Chrome. The embedding of WebM videos to a site page realizes without delays and errors. WebM is meant to be an alternative to the h.264 standard. The copyright of the extension is held by Google.

AU is a file extension for a sound file format belonging to Sun, NeXT and DEC and used in UNIX. The AU file format is also known as the Sparc-audio or u-law fomat. AU files contain three parts: the audio data and text for a header (containing 24 bytes) and an annotation block.