FLV is short for Flash Video. It contains material encoded with codecs following the Sorenson Spark or VP 6 video compression formats. The most recent public release of the Flash Player also supports H.264 video and HE-AAC audio. However, all of these codecs are restricted by patens. Flash video content may also be embedded within SWF Files. Audio and video data within FLV and SWF files are encoded with the same way. 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.

F4V is a new type of FLV file. A F4V file is encoded based on the ISO base media file format ( MPEG-4 PART 2) and is supported starting with Flash Player 9 update 3. Compared with the functional limits with the FLV structure when streaming H.264 or AAC which could not be overcome without a redesign of the file format, it owns better quality under the same situation. Many of the mainstream video-sharing webs start to accept the F4V file format. F4V does not support Screen video, Sorenson Spark, VP6 video compression formats and ADPCM, Nellymoser audio compression formats. A large part of the F4V format involves metadata. When Flash Player loads an F4V file, various stream properties are made available to run action script program are made avaiable to run via the Netstream on Metadata property. 

Supported media types in FLV file format:

Video: On2 VP6, Sorenson Spark (Sorenson H.263), Screen video, H.264 

Audio: MP3, ADPCM, Linear PCM, Nellymoser, Speex, AAC, G.711 (reserved for internal use) 

Supported media types in F4V file format:

Video: H.264 

Images (still frame of video data): GIF, PNG, JPEG 

Audio: AAC, HE-AAC, MP3 

Click here to get the detailed comparsion between FLV and SWF.

If you are interest in creating flash video, please refer to video to flash converter, which help you to convert almost any video format to flash video flv and swf and generate an HTML webpage embedded with flash video.

If you are using Mac OS X, Mac Video to Flash Converter can do the same conversion for you.