The OggContainer format is the general purpose multimedia file format developed at Xiph.org and used by OggVorbis, OggTarkin, OggTheora, and OggSpeex. This page is linked from the FileExtensions page.
OggVorbis is the patent-free audio format written and sponsored by Xiph.org.
It uses the OggContainer multimedia file format (which is also used for other Xiph.org projects such as OggTarkin, OggTheora, and OggSpeex.
OggVorbis is generally described as having sound quality on par with or slightly better than an MP3 of the same bitrate. It has never gained widespread acceptance, however, because it lacks support in portable players.
OggVorbis is of interest to programmers who need to work with audio encoding but wish to avoid the patent fees associated with the MP3 format.
OggSpeex is the secondary audio codec designed for voice encoding.
OggSpeex, which is based on the OggContainer file format like OggVorbis, is highly optimized for encoding the sound of the human voice, and little else. It is capable of carrying understandable and only mildly distorted speech at extremely low-bitrates. It is intended for use in internet telephony systems and devices.
OggTheora is the flagship video codec based off the open-sourced VP3 codec by On2.
OggTheora, like the rest of Xiph.org’s codecs, uses the OggContainer file format.
OggTheora is a respectable if rather dated video format. As mentioned above, it is based on VP3, while On2 has already created VP5. Nonetheless, it can hold its own in current comparisons with other codecs. Many worry, however, that it will not scale with future advancements like the advent of H.264. Those who believe this tend to hope that the OggTarkin codec will pull through in time to replace the aging OggTheora.
OggTarkin is a secondary video codec, developed entirely from scratch by the Xiph.org community.
It has been in development for many years, but progress has generally been very slow, becoming even slower as attention was diverted to OggTheora. Still, OggTarkin is in theory the better of the two OggContainer based video codecs, and as OggTheora is already an aging codec, many hope that OggTarkin will one day replace it.