Ogg is a free, open container format, developed and maintained by the Xiph.Org Foundation is unrestricted by software patents and is designed to provide efficient flow diffusion and manipulation of high quality digital multimedia. The Ogg container format can multiplex a number of independent streams for audio, video, text (such as subtitles), and metadata. In the Ogg multimedia framework, Theora provides a layer of lossy video. The audio layer is most commonly provided by the music-oriented Vorbis format but other options include compression codecs Opus, FLAC lossless audio OggPCM.
The AAC file type is primarily associated with 'MPEG-2 Advanced Audio Coding File'. Advanced Audio Coding (AAC) is a standardized, lossy compression and encoding scheme for digital audio. AAC is promoted as the successor to the MP3 format by MP3’s creator, Fraunhofer IIS. AAC’s most noted use is as the default audio format of Apple's iPhone, iPod, iTunes, and the format used for all iTunes Store audio (with extensions for proprietary Digital Rights Management (DRM) where used).