What are FLV files?
An FLV file is a binary file format that delivers "bitmapped" video, limited to one video and one audio stream per file. It is mainly used over the Internet to one or another versions of the Flash Player. FLV content may also be embedded in SWF files (which are also a type of Flash file which can wrap video streams, audio, or games) submitted by ActionScript external references.
How to open FLV files?
In order to be able to play FLV files, you need a multimedia player which can support Flash Videos. Since FLV is an open format (meaning that it is publicly documented how it encodes and decodes files) any developers who wish to make their own video players which support the FLV file extension. The most popular online video players like YouTube, Google Video, Yahoo! Video, and many news providers make use of FLV players on their websites to provide video content. This is because "Bitmapped" video in FLV files may be compressed in various ways and the video quality in these encodings is expected to range from good to very good.
Flash Video is viewable on most operating systems, via the widely available Adobe Flash Player and web browser plugin, or one of several third-party programs such as MPlayer, VLC media player, Quicktime, or any player which uses DirectShow filters (such as Media Player Classic, Windows Media Player, and Windows Media Center) when the ffdshow filter is installed.
Although the container format itself is open, the codecs used with it are patented.
Macromedia was acquired by Adobe in 2005, so Macromedia Flash Player is now Adobe Flash Player.
Tools to convert from and to FLV file format