MP4 (MPEG-4 Part 14) is a video container format based on QuickTime MOV. But unlike MOV, it adds support for other MPEG features. MP4 supports video (MPEG-4 Part 2 and MPEG-4 Part 10/H.264), audio (MP3, AAC, SLS, TTSI, and ALAC), and subtitles (MPEG-4 timed text). It’s this codec combination that gives MP4 its flexibility.
Windows Media Player VLC Media Player, Apple QuickTime Player 5KPLayer
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