HTML5: mp3, mp4 (AAC/H.264), ogg (Vorbis/Theora), webm (Vorbis/VP8), wav
Flash: mp3, mp4 (AAC/H.264), flv

For cross-browser support, a format must be supplied that works in both HTML5 and Flash.
Optional additional formats may be supplied to increase cross-browser HTML5 support.