The .asf filename extension refers to the Microsoft owned audio and digital video container, advanced systems format. It is a container for windows media audio and windows media video but shares the same internal structure as both WMA and WMV file formats. The format was designed with the goal of increasing efficiency in distribution of audio video files across computer networks. However, it works just as well for local system playback. The asf format forms part of Microsoft's Foundation framework. The major feature of the format is its ability to add digital rights management by providing the framework for encrypting audio and video files.