FLV (Flash Video) is a video container format developed by Adobe Systems and comes with a .flv filename format. FLV is primarily used to stream audio, video, and text data such as subtitles on sites like YouTube, Metacafe, and more. It supports MPEG-4 Part 10 (H.264) video codec and AAC sound.
RealPlayer, Apple QuicTime Player MPLayer VLC Media Player
AA (Audible Audio) is an audio container format with a .aa filename extension and is used to store audiobooks. It can contain audiobook features such as spoken-word audio, bookmarks, chapter markers, and more. This format is supported by portable devices like Apple iPod, Amazon Kindle, ScanDisk Sansa, Creative Zen, and more.
Apple iTunes, TuneCab Nero 2019 Audible AudibleManager Audials Tubebite 2019