ASF is a media container used by Microsoft Windows Media Player. It was designed for streaming audio and video files online. The container determines the structure of the data stream but not how the data should be encoded. Usually the files encoded by Microsoft developers have the .wma or .wmv extensions, other files have .asf extension. Such files generally have MIME type that allows sending files via the internet. The main feature of the ASF is the ability to stream playback, that is the ability to play a video or audio directly at the time of downloading data over the network.

WavPack lossless audio compression. Note that, when converting .wav to this format and back again, the RIFF header is not necessarily preserved losslessly (though the audio is).