Musepack
Encyclopedia
Musepack or MPC is an open source
lossy audio codec, specifically optimized for transparent
compression of stereo audio at bitrates of 160–180 (manual set allows bitrates up to 320) kbit/s
. It was formerly known as MPEGplus, MPEG+ or MP+.
Development of MPC was initiated in 1997 by Andree Buschmann and later assumed by Frank Klemm, and as of 2011 is maintained by the Musepack Development Team (MDT) with assistance from Buschmann and Klemm. Encoders and decoders are available for Microsoft Windows
, Linux
and Mac OS X
, and plugins for several third-party media players available from the Musepack website, licensed under the GNU Lesser General Public License
(LGPL) or BSD licenses
, and an extensive list of programs supporting the format.
The psychoacoustic
model of MPC is based on MPEG ISO model 2, but is extended by CVD (clear voice detection). The quantization algorithm of the MPC encoder performs spectral shaping of the noise, called adaptive noise shaping (ANS), in order to overcome the low frequency resolution of the polyphase quadrature filter
bands.
In the past, MPC has been under suspicion of violating multiple patents (MP2, PNS, subband). According to the developers of MPC, all patented code has been removed and it is now believed to be free of patent encumbrance. However, one PNS patent application is still active, and it is not trivial to know if MPC's own "noise substitution techniques" avoid its scope or not.
MPC uses the APEv2 tag
metadata
container.
Musepack is mainly optimized for transparent encoding at the "--standard" preset (175-185 kbit/s). Very few optimisations have been made at lower bitrates (like 128 kbit/s). Nevertheless, various listening tests
have been conducted in which Musepack has performed well at both lower and higher bitrates.
ERROR: WAVE file has no linear PCM format!
ERROR: Invalid file header, not a WAVE file .wav'
, AAC
, WMA
, and ATRAC
.
Listening tests of MPC:
can play MPC. This includes devices running Palm OS
, Symbian
OS, Windows
, Windows CE
and Windows Mobile
(Pocket PC
). All devices with software audio decoding that are supported by Rockbox
, including older revisions of iPod
, can also play Musepack files. Playback on Roku
Photobridge HD is supported with a plugin.
Musepack distributes the libmpcdec library for decoding MPC content. Various plugins have been developed, using that library, including for the XMMS
player (on Unix
).
Open source
The term open source describes practices in production and development that promote access to the end product's source materials. Some consider open source a philosophy, others consider it a pragmatic methodology...
lossy audio codec, specifically optimized for transparent
Transparency (data compression)
In data compression or psychoacoustics, transparency is the ideal result of lossy data compression. If a lossy compressed result is perceptually indistinguishable from the uncompressed input, then the compression can be declared to be transparent...
compression of stereo audio at bitrates of 160–180 (manual set allows bitrates up to 320) kbit/s
Bit rate
In telecommunications and computing, bit rate is the number of bits that are conveyed or processed per unit of time....
. It was formerly known as MPEGplus, MPEG+ or MP+.
Development of MPC was initiated in 1997 by Andree Buschmann and later assumed by Frank Klemm, and as of 2011 is maintained by the Musepack Development Team (MDT) with assistance from Buschmann and Klemm. Encoders and decoders are available for Microsoft Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
, Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
and Mac OS X
Mac OS X
Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...
, and plugins for several third-party media players available from the Musepack website, licensed under the GNU Lesser General Public License
GNU Lesser General Public License
The GNU Lesser General Public License or LGPL is a free software license published by the Free Software Foundation . It was designed as a compromise between the strong-copyleft GNU General Public License or GPL and permissive licenses such as the BSD licenses and the MIT License...
(LGPL) or BSD licenses
BSD licenses
BSD licenses are a family of permissive free software licenses. The original license was used for the Berkeley Software Distribution , a Unix-like operating system after which it is named....
, and an extensive list of programs supporting the format.
Technical details
Musepack was developed using the MP2 codec as a starting point, but many features have since been added, including:- subband selectable M/S encoding (as in AACAdvanced Audio CodingAdvanced Audio Coding is a standardized, lossy compression and encoding scheme for digital audio. Designed to be the successor of the MP3 format, AAC generally achieves better sound quality than MP3 at similar bit rates....
) - Huffman codingHuffman codingIn computer science and information theory, Huffman coding is an entropy encoding algorithm used for lossless data compression. The term refers to the use of a variable-length code table for encoding a source symbol where the variable-length code table has been derived in a particular way based on...
(as in MP3MP3MPEG-1 or MPEG-2 Audio Layer III, more commonly referred to as MP3, is a patented digital audio encoding format using a form of lossy data compression...
and AAC, but more efficient). Since SV8 the bitstream is compressed by highly optimized canonical huffman tables that yields 2% smaller files and faster decoding - noise substitution techniques (as in ATSC A-52 and MPEG-4MPEG-4MPEG-4 is a method of defining compression of audio and visual digital data. It was introduced in late 1998 and designated a standard for a group of audio and video coding formats and related technology agreed upon by the ISO/IEC Moving Picture Experts Group under the formal standard ISO/IEC...
AAC V2) - pure variable bitrate between 0 and 1300 kbit/s (when needed)
The psychoacoustic
Psychoacoustics
Psychoacoustics is the scientific study of sound perception. More specifically, it is the branch of science studying the psychological and physiological responses associated with sound...
model of MPC is based on MPEG ISO model 2, but is extended by CVD (clear voice detection). The quantization algorithm of the MPC encoder performs spectral shaping of the noise, called adaptive noise shaping (ANS), in order to overcome the low frequency resolution of the polyphase quadrature filter
Polyphase quadrature filter
A polyphase quadrature filter, or PQF, is a filter bank which splits an input signal into a given number N of equidistant sub-bands. These sub-bands are subsampled by a factor of N, so they are critically sampled....
bands.
In the past, MPC has been under suspicion of violating multiple patents (MP2, PNS, subband). According to the developers of MPC, all patented code has been removed and it is now believed to be free of patent encumbrance. However, one PNS patent application is still active, and it is not trivial to know if MPC's own "noise substitution techniques" avoid its scope or not.
MPC uses the APEv2 tag
APEv2 tag
An APE tag is a tag used to add metadata, such as the title, artist, or track number, to digital audio files.- APEv1 :The APEv1 tag was designed for the Monkey's Audio format....
metadata
Metadata
The term metadata is an ambiguous term which is used for two fundamentally different concepts . Although the expression "data about data" is often used, it does not apply to both in the same way. Structural metadata, the design and specification of data structures, cannot be about data, because at...
container.
Musepack is mainly optimized for transparent encoding at the "--standard" preset (175-185 kbit/s). Very few optimisations have been made at lower bitrates (like 128 kbit/s). Nevertheless, various listening tests
Codec listening test
A codec listening test is a scientific study designed to compare two or more lossy audio codecs, usually with respect to perceived fidelity or compression efficiency....
have been conducted in which Musepack has performed well at both lower and higher bitrates.
Features
- Container-independent format. An SV8 MPC is a container file for a Musepack stream. Raw stream encoding is possible.
- Packetized stream allows muxing into audio and video containers (e.g. MKA/MKVMatroskaThe Matroska Multimedia Container is an open standard free container format, a file format that can hold an unlimited number of video, audio, picture or subtitle tracks in one file. It is intended to serve as a universal format for storing common multimedia content, like movies or TV shows...
, NUT). - Sample-accurate, fast seeking independent of file length.
- Sample-accurate cutting. Application included in download package (mpccut) allows losslessly cutting stream segments based on selected start/end samples.
- Chapters. Chapter editor (mpcchap) included, for embedding chapters into MPC files.
- No internal clipping.
- Streamable.
Lacks
Not clear support of coding is more 2х than channels and-or paths above 48kHz. Attempt to code WAV 5.1 and-or 96kHz leads to the message:ERROR: WAVE file has no linear PCM format!
ERROR: Invalid file header, not a WAVE file .wav'
Test results
Despite being optimized for 100% transparency at moderately high bitrates, MPC has scored highly on many 128 kbit/s tests. In May 2004, a series of double-blind listening tests (as reported on Slashdot) suggested that Musepack and Ogg Vorbis (which was the 1.1 "aoTuV" fork at the time) were the two best available codecs for high-quality audio compression at bitrates around 128kbit/s, beating MP3MP3
MPEG-1 or MPEG-2 Audio Layer III, more commonly referred to as MP3, is a patented digital audio encoding format using a form of lossy data compression...
, AAC
Advanced Audio Coding
Advanced Audio Coding is a standardized, lossy compression and encoding scheme for digital audio. Designed to be the successor of the MP3 format, AAC generally achieves better sound quality than MP3 at similar bit rates....
, WMA
Windows Media Audio
Windows Media Audio is an audio data compression technology developed by Microsoft. The name can be used to refer to its audio file format or its audio codecs. It is a proprietary technology that forms part of the Windows Media framework. WMA consists of four distinct codecs...
, and ATRAC
ATRAC
Adaptive Transform Acoustic Coding is a family of proprietary audio compression algorithms developed by Sony. MiniDisc was the first commercial product to incorporate ATRAC in 1992. ATRAC allowed a relatively small disc like MiniDisc to have the same running time as CD while storing audio...
.
Listening tests of MPC:
- 2004 – rjamorim's second 128 kbit/s group listening test – between 14 and 27 listeners. MPC and Vorbis tied for first.
- 2003 – rjamorim's first 128 kbit/s group listening test – between 14 and 29 listeners. AAC, MPC, Vorbis, and WMA tied for first.
- 2002 – ff123's second 128 kbit/s group listening test
- 2001 – ff123's 128 kbit/s group listening test
Hardware and software support
Devices supporting The Core Pocket Media PlayerThe Core Pocket Media Player
The Core Pocket Media Player is a software media player which operates on portable devices and Windows-based PCs. It is discontinued, but still available from the official mirror site. Supported operating systems include Palm OS, Symbian OS, and Microsoft Windows, CE, and Mobile. It is also...
can play MPC. This includes devices running Palm OS
Palm OS
Palm OS is a mobile operating system initially developed by Palm, Inc., for personal digital assistants in 1996. Palm OS is designed for ease of use with a touchscreen-based graphical user interface. It is provided with a suite of basic applications for personal information management...
, Symbian
Symbian
Symbian is a mobile operating system and computing platform designed for smartphones and currently maintained by Accenture. The Symbian platform is the successor to Symbian OS and Nokia Series 60; unlike Symbian OS, which needed an additional user interface system, Symbian includes a user...
OS, Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
, Windows CE
Windows CE
Microsoft Windows CE is an operating system developed by Microsoft for embedded systems. Windows CE is a distinct operating system and kernel, rather than a trimmed-down version of desktop Windows...
and Windows Mobile
Windows Mobile
Windows Mobile is a mobile operating system developed by Microsoft that was used in smartphones and Pocket PCs, but by 2011 was rarely supplied on new phones. The last version is "Windows Mobile 6.5.5"; it is superseded by Windows Phone, which does not run Windows Mobile software.Windows Mobile is...
(Pocket PC
Pocket PC
A Pocket PC is also known by Microsoft as a 'Windows Mobile Classic device'. It is a hardware specification for a handheld-sized computer, personal digital assistant , that runs the Microsoft 'Windows Mobile Classic' operating system...
). All devices with software audio decoding that are supported by Rockbox
Rockbox
Rockbox is a replacement for the standard firmware in various forms of digital audio players . It offers an alternative to the player's operating system, in many cases without removing the original firmware, which provides a plug-in architecture for adding various enhancements and functions...
, including older revisions of iPod
IPod
iPod is a line of portable media players created and marketed by Apple Inc. The product line-up currently consists of the hard drive-based iPod Classic, the touchscreen iPod Touch, the compact iPod Nano, and the ultra-compact iPod Shuffle...
, can also play Musepack files. Playback on Roku
Roku
Roku , is an American, privately held, consumer electronics company that sells home digital media products. The Company is based in Saratoga, California.- Company profile and products :...
Photobridge HD is supported with a plugin.
Musepack distributes the libmpcdec library for decoding MPC content. Various plugins have been developed, using that library, including for the XMMS
XMMS
The X Multimedia System is a free audio player for Unix-like systems.-History:XMMS was originally written as X11Amp by Peter and Mikael Alm in November 1997. The player was made to resemble Winamp, which was first released in May that year. As such, XMMS has supported Winamp 2 "classic" skins...
player (on Unix
Unix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
).