ASF (Advanced Systems Format) is a digital multimedia format designed to save and open content online. It is the primary container for Windows Media Video and Windows Media Audio content. Today, ASF supports smooth playback on HTTP servers, media servers, and local storage with programs like Windows Media Player.
FLV (Flash Video) is a video container format developed by Adobe Systems and comes with a .flv filename format. FLV is primarily used to stream audio, video, and text data such as subtitles. It supports MPEG-4 Part 10 (H.264) video codec and AAC sound.
RealPlayer, Apple QuicTime Player
VLC Media Player