FLAC
Developer(s) | Xiph.Org Foundation, Josh Coalson, Erik de Castro Lopo |
---|---|
Initial release | 20 July 2001 |
Stable release | 1.4.3[1]
/ 23 June 2023 |
Repository | |
Written in | GNU GPL Libraries: BSD |
Website | xiph |
Filename extension |
.flac |
---|---|
Internet media type |
audio/flac |
Uniform Type Identifier (UTI) | org.xiph.flac |
Magic number | fLaC[2] |
Type of format | Lossless audio |
Standard | xiph |
Open format? | Yes[3] |
Free format? | Yes |
FLAC (/flæk/; Free Lossless Audio Codec) is an audio coding format for lossless compression of digital audio, developed by the Xiph.Org Foundation, and is also the name of the free software project producing the FLAC tools, the reference software package that includes a codec implementation. Digital audio compressed by FLAC's algorithm can typically be reduced to between 50 and 70 percent of its original size[4] and decompresses to an identical copy of the original audio data.
FLAC is an
History
Development was started in 2000 by Josh Coalson. The bitstream format was frozen with the release of version 0.9 of the reference implementation on 31 March 2001. Version 1.0 was released on 20 July 2001.[5]
On 29 January 2003, the
Version 1.3.0 was released on 26 May 2013, at which point development was moved to the Xiph.org git repository.[8]
In 2019, FLAC was proposed as an IETF standard.[9]
Design
FLAC is a lossless encoding of
File structure
A FLAC file consists of the magic number fLaC
, metadata, and encoded audio.[10]
The encoded audio is divided into frames, each of which consists of a header, a data block, and a
Metadata in FLAC precedes the audio. Properties like the
Encoding and decoding
The FLAC encoding algorithm consists of multiple stages. In the first stage, the input audio is split into blocks. If the audio
The decoding process is the reverse of encoding. The compressed residual is first decoded.[11][12] The description of the mathematical approximation is then used to calculate a waveform. The result is formed by adding the residual and the calculated waveform.[13][14] As FLAC compresses losslessly, the decoded waveform is identical to the waveform before encoding.
For two-channel stereo, the encoder may choose to
Even though the reference encoder uses a single block size for the whole stream,[10] FLAC allows the block size in samples to vary per block.
Compression
The amount of compression is determined by various parameters, including the order of the linear prediction model and the block size. Regardless of the amount of compression, the original data can always be reconstructed perfectly.
For user's convenience, the reference implementation defines 9 compression levels, which are presets of the more technical parameters to the encoding algorithm. The levels are labeled from 0 to 8, with higher numbers resulting in a higher compression ratio, at the cost of compression speed. The meaning of each compression level varies by implementation.[16][17]
FLAC is optimized for decoding speed at the expense of encoding speed. A benchmark has shown that, while there is little variation in decoding speed as compression level increases, beyond the default compression level 5, the encoding process takes up considerably more time with little space saved compared to level 5.[18]
Implementation
Alongside the format, the FLAC project also contains a
flac
and metaflac
, are also part of the reference implementation.
The FLAC format, along with libFLAC, are not known to be covered by any patents, and anyone is free to write their own implementations of FLAC.
Comparison to other formats
FLAC is specifically designed for efficient packing of audio data, unlike general-purpose lossless algorithms such as
The technical strengths of FLAC compared to other lossless formats lie in its ability to be streamed and decoded quickly, independent of compression level.
Since FLAC is a lossless scheme, it is suitable as an archive format for owners of CDs and other media who wish to preserve their audio collections. If the original media are lost, damaged, or worn out, a FLAC copy of the audio tracks ensures that an exact duplicate of the original data can be recovered at any time. An exact restoration from a lossy copy (e.g.,
Adoption and implementations
The reference implementation of FLAC is implemented as the libFLAC core encoder & decoder library, with the main distributable program flac
being the reference implementation of the libFLAC API. This
FLAC playback support in portable audio devices and dedicated audio systems is limited compared to formats such as MP3[20] or uncompressed PCM. FLAC support is included by default in Windows 10, Android, BlackBerry 10 and Jolla devices.
In 2014, several aftermarket mobile electronics companies introduced multimedia solutions that include support for FLAC. These include the NEX series from Pioneer Electronics and the VX404 and NX404 from Clarion.
The
Among others the Pono music player and streaming service used the FLAC format.[26][27] Bandcamp insists on a lossless format for uploading, and has FLAC as a download option.[28] The Wikimedia Foundation sponsored a free and open-source online ECMAScript FLAC tool for browsers supporting the required HTML5 features.[29]
Microsoft Windows | macOS | Android | BlackBerry OS | iOS | |
---|---|---|---|---|---|
Codec support | Yes | Yes | Yes | Yes | Yes |
Container support | FLAC (.flac) Matroska (.mka, .mkv) Ogg (.oga)[30] |
FLAC (.flac) Core Audio Format (.caf) |
FLAC (.flac) | FLAC (.flac) | FLAC (.flac) Core Audio Format (.caf) |
Notes | Support introduced in Windows 10. Windows Media Player (2022) also supports FLAC in an Ogg container for live streams (e.g. Icecast internet radio).[31]
|
Support introduced in High Sierra. | Support introduced in Android 3.1. Android natively supports regular FLAC (.flac), but not Ogg FLAC (.oga).[32] However, support for both regular FLAC and Ogg FLAC were later added to the Files (Google) file manager. |
Support introduced in BlackBerry OS 5.0 | Support introduced in iOS 11 (but depends on hardware used). |
Various other containers are supported, independently from used operating system, depending on used playback software.
See also
References
- ^ "FLAC 1.4.3 Released With More Optimizations, Drops PowerPC-Specific Code". 23 June 2023. Retrieved 19 February 2024.
- ^ Coalson, Josh. "FLAC – format". Xiph.Org Foundation. Retrieved 4 April 2013.
"fLaC", the FLAC stream marker in ASCII, meaning byte 0 of the stream is 0x66, followed by 0x4C 0x61 0x43
- ^ "PlayOgg!". Free Software Foundation. 17 March 2010. Retrieved 1 October 2013.
- ^ "Looking at Flac Compression Ratios". Steven Pigeon. 7 February 2012. Retrieved 10 May 2018.
- ^ a b "Features". Xiph.Org Foundation. Retrieved 23 November 2023.
- ^ "FLAC Joins Xiph.org". Xiph.org Foundation. 29 January 2003. Retrieved 31 August 2009.
- ^ Plant, Emmett. "FLAC Joins Xiph!". Xiph.org Foundation. Archived from the original on 29 May 2008. Retrieved 31 August 2009.
- ^ "FLAC – changelog". Xiph.org Foundation. Retrieved 15 October 2013.
- ^ van Beurden, Martijn; Weaver, Andrew. Free Lossless Audio Codec. I-D draft-ietf-cellar-flac. Retrieved 14 May 2023.
- ^ a b c d e f Coalson, Josh. "About the FLAC Format". Retrieved 13 February 2022.
- ^ "stream_decoder.c". libFLAC. Retrieved 19 February 2022.
- ^ libFLAC/stream_decoder.c, line 2734.
- ^ "lpc.c". libFLAC. Retrieved 19 February 2022.
- ^ libFLAC/lpc.c, lines 813–820.
- ^ "FLAC Format Specification". FLAC. Retrieved 19 February 2022.
- ^ "CUETools FLAC encoders comparison". CUETools Wiki. Retrieved 27 May 2013.
- ^ "Encoding Settings". JRiver Media Centre. Retrieved 27 May 2013.
- ^ "Lossless Codec Comparison". Synthetic-soul.co.uk. Archived from the original on 2 February 2009. Retrieved 26 November 2016.
- ^ "FAQ". FLAC. Retrieved 23 September 2014.
- ^ "Links". FLAC. Retrieved 24 March 2009.
- ^ "What is the EBU Musipop system?". EBU. 24 August 2021.
- ^ "Audio snobs rejoice: Windows 10 will have system-wide FLAC support". PC World. Retrieved 10 July 2015.
- ^ "Android Supported Media Formats". Android.com. 4 August 2011. Retrieved 27 February 2012.
- ^ "Issue 1461 – android – FLAC file support enhancement request". Google Code. Retrieved 5 August 2011.
- ^ "iOS 11 brings lossless FLAC audio playback to iPhone and iPad". idownloadblog.com. 9 June 2017. Retrieved 26 September 2017.
- ^ "FAQ". ponomusic.com. 14 March 2014. Retrieved 14 March 2014.
- ^ "Home". Qobuz.com. Retrieved 10 April 2014.
- ^ "How and why should I upload lossless files?". Bandcamp. Retrieved 16 February 2022.
- ^ Rillke (2015). "JavaScript FLAC de- and encoder". Retrieved 9 February 2015.
- ^ "MIME Types and File Extensions - XiphWiki".
- ^ "FLAC vs Ogg FLAC".
- ^ "The Android Platform Doesn't Fully Support OGG Container Formats (OGA) [36906426] - Visible to Public - Issue Tracker".
External links
- Official website
- Lossless audio formats comparison: measuring FLAC against five other lossless audio formats
- Lossless comparison: FLAC against seven other lossless audio formats on Hydrogenaudio
- GSMArena Phone Finder: all phones & tablets with FLAC support