Advanced Streaming Format is
Microsoft's new proprietary
audio/
video wrapper[?], especially meant for
streaming[?]. It doesn't specify how the video or audio should be
encoded, but instead just specifies the structure of the video/audio stream. What this means is that ASF files can be encoded with basically any audio/video
codec and still would be in ASF format.
Many cases ASF is confused with Microsoft's own implementation of MPEG-4 video format[?], because most of the ASF streams are encoded using this technology.