The FLV file format contains encoded audio and video data for delivery by using Flash Player. For example, if you have a QuickTime or Windows Media video file, you use an encoder (such as Flash Video Encoder, or Sorenson™ Squeeze) to convert that file to an FLV file.

You can create FLV files by importing video into the Flash authoring tool and exporting it as an FLV file. You can use the FLV Export plug-in to export FLV files from supported video-editing applications.

Using external FLV files provides certain capabilities that are not available when you use imported video:

• Longer video clips can be used in your Flash documents without slowing down playback. External FLV files play using cached memory, which means that large files are stored in small pieces and accessed dynamically, requiring less memory than embedded video files.
• An external FLV file can have a different frame rate than the Flash document in which it plays. For example, you can set the Flash document frame rate to 30 frames per second (fps) and the video frame rate to 21 fps. This setting gives you better control of the video than embedded video, to ensure smooth video playback. It also allows you to play FLV files at different frame rates without the need to alter existing Flash content.
• With external FLV files, Flash document playback does not have to be interrupted while the video file is loading. Imported video files can sometimes interrupt document playback to perform certain functions, such as accessing a CD-ROM drive. FLV files can perform functions independently of the Flash document, which does not interrupt playback.
• Captioning video content is easier with external FLV files because you can access the video's metadata using event handlers.
  To load FLV files from a web server, you might need to register the file extension and MIME type with your web server; check your web server documentation. The MIME type for FLV files is video/x-flv. For more information, see About configuring FLV files for hosting on a server.