There are two different video file formats known as Flash Video: FLV and F4V. The audio and video data within FLV files are encoded in the same manner as they are within SWF files. The F4V file format is based on the ISO base media file formatand is starting with Flash Player 9 update 3.
This format was originally created as an alternative to mp3. The idea was to achieve a small file size with better sound quality. The first versions weren’t quite successful, but with the development of AAC, it became possible to store sound with less loss of quality, and with the same file sizes as that of mp3.