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.
F4V is a filename extension for Flash Video (FLV) container format. It supports H.264 (MPEG-4 AVC) video codec compression standard, which is known to offer significant compression. FLV videos come in multiple formats apart from F4V, including F4P, F4A, and F4B. Also, it opens on Adobe Flash Player 6 or later and Windows Media Player.
Windows Media Player Adobe Flash Player 6 or later Media Monkey