Flash Video Encoding Options
The video content in the FLV file can be encoded using the new On2 VP6 video codec for use with Flash Player 8 or the Sorenson Spark codec for use with Flash Player 7.
A codec is an algorithm that controls the way video files are compressed and decompressed during import and export.
The On2 VP6 video codec is the preferred video codec because it provides the best combination of video quality while maintaining a small file size. If your Flash content dynamically loads Flash video, you can use On2 VP6 video without having to republish your SWF file for Flash Player 8—as long as users use Flash Player 8 to view your content. Only Flash Player 8 supports both publish and playback of On2 VP6 video.
The Sorenson Spark codec requires less processing power and is compatible with Flash Player 7, but the On2 VP6 is clearly the better codec.