Open file formats are published specifications for storing digital data, and open formats not encumbered by any copyrights, patents, trademarks or other restrictions are known as free file formats. These can be used in the public domain at no monetary cost. That is to say that, these formats can be implemented by both proprietary and free and open source software with the help of typical licenses used by each.
The different types of formats that comprise free and open file formats include:
- wav - It is the standard audio file container format for storing an audio bitstream in Windows PC. The application is generally used for storing PCM files in chunks. The format is chiefly used on Windows systems for raw and uncompressed audio. These files use a RIFF structure.
- ogg – The container format supports a variety of audio codecs, Vorbis being the most popular one, offers compression similar to MP3. The filename extensions for audio only files is .oga, for video files with or without sound is .ogv, for applications it is .ogx and for Ogg Vorbis audio files, .ogg is used. Ogg’s codecs have been incorporated into a number of different free and proprietary media players.
- mpc – Musepack or MPC is optimized for transparent compression of stereo audio at bitrates of 160-180 kbit/s. It is an open source lossy audio codec. It is rated as one of the best codecs for high-quality lossy audio compression and is mainly used by the audiophiles.
- flac - Free Lossless Audio Codec is an audio codec for lossless audio data compression. It accomplishes data compression, keeping the integrity of the audio source intact. Audio sources encoded to FLAC are reduced to 50-60% of their original size and a digital audio recording converted by the codec can be decompressed into an identical copy of the audio data. It is suitable for everyday playback and archival and is well-supported by many software applications.
- aiff - Audio Interchange File Format was developed by Apple and Amiga and is the native format for audio on Mac OSX.
- raw – It is a computer format that stores uncompressed audio in raw form. It is usually used with PCM audio data and is rarely used except for technical tests.
- au – The audio file format introduced by Sun Microsystems is the standard audio file format used by Sun, Unix and Java. The audio in these files can be PCM or compressed with the a-law, μ-law or G729 codecs.