TheBigBlack's Guide To Digital Audio

Home | Introduction | Basics | History | Advanced | Formats

Formats

What Is Lossless Compression?

Lossless data compression is a class of data compression algorithm that allows the original data to be perfectly reconstructed from the compressed data. By contrast, lossy data compression, permits reconstruction only of an approximation of the original data, though this usually allows for improved compression rates (and therefore smaller sized files).

Lossless data compression is used in many applications, not just for music. For example, it is used in the ZIP file format used by WinZip. It usages is mainly in cases where it is important that the original and the decompressed data be identical, or where deviations from the original data could be deleterious. Typical examples are executable programs, text documents, and source code. Some image file formats, like PNG or GIF, use only lossless compression, while others like TIFF and MNG may use either lossless or lossy methods.

Lossless audio formats are most often used for archiving or production purposes, while smaller lossy audio files are typically used on portable players and in other cases where storage space is limited or exact replication of the audio is unnecessary.

What Is Lossy Compression?

In information technology, "lossy" compression is the class of data encoding methods that uses inexact approximations (or partial data discarding) for representing the content that has been encoded. Such compression techniques are used to reduce the amount of data that would otherwise be needed to store, handle, and/or transmit the represented content. The amount of data reduction possible using lossy compression can often be much more substantial than what is possible with lossless data compression techniques.

Using well-designed lossy compression technology, a substantial amount of data reduction is often possible before the result is sufficiently degraded to be noticed by the user. Even when the degree of degradation becomes noticeable, further data reduction may often be desirable for some applications (e.g., to make real-time communication possible through a limited bit-rate channel, to reduce the time needed to transmit the content, or to reduce the necessary storage capacity).

Lossy compression is most commonly used to compress multimedia data (audio, video, and still images), especially in applications such as streaming media and internet telephony. By contrast, lossless compression is typically required for text and data files, such as bank records and text articles. In many cases it is advantageous to make a master lossless file that can then be used to produce compressed files for different purposes; for example, a multi-megabyte file can be used at full size to produce a full-page advertisement in a glossy magazine, and a 10 kilobyte lossy copy can be made for a small image on a web page.

What Are FLAC Files?

FLAC (Free Lossless Audio Codec) is a codec for lossless compression of digital audio. Digital audio compressed by FLAC's algorithm can be decompressed to an identical copy of the original audio data. FLAC has support for metadata tagging, album cover art, and fast seeking.

FLAC is currently the most widely used lossless audio compression in non-commercial environments.

Development was started in 2000 by Josh Coalson. The bit-stream format was frozen when FLAC entered beta stage with the release of version 0.5 of the reference implementation on 15 January 2001. Version 1.0 was released on 20 July 2001.

On 29 January 2003, the Xiph.Org Foundation and the FLAC project announced the incorporation of FLAC under the Xiph.org banner. Xiph.org is behind other free compression formats such as Vorbis, Theora and Speex.

Version 1.3.0 was released on 26 May 2013. Development was moved to the Xiph.org git repository.

FLAC is an open format with royalty-free licensing and a reference implementation which is free software. The specification of the stream format can be implemented by anyone without prior permission (Xiph.org reserves the right to set the FLAC specification and certify compliance), and neither the FLAC format nor any of the implemented encoding / decoding methods are covered by any patent. The reference implementation is free software. The source code for libFLAC and libFLAC++ is available under the BSD license, and the sources for flac, metaflac, and the plugins are available under the GNU General Public License.

In its stated goals, the FLAC project encourages its developers not to implement copy prevention features (DRM) of any kind.

 

Home | Introduction | Basics | History | Advanced | Formats

Last Updated: 25/09/2016