Audio Lossless Coding
Encyclopedia
MPEG-4 Audio Lossless Coding, also known as MPEG-4 ALS, is an extension to the MPEG-4 Part 3
audio standard to allow lossless
audio compression. The extension was finalized in December 2005 and published as ISO/IEC
14496-3:2005/Amd 2:2006 in 2006. The latest description of MPEG-4 ALS was published as subpart 11 of the MPEG-4
Audio standard (ISO/IEC 14496-3:2009) (4th edition) in August 2009.
MPEG-4 ALS combines together a short-term predictor and a long term predictor. The short-term predictor is similar to FLAC in its operation - it is a quantized LPC
predictor with a losslessly coded residual using Golomb Rice Coding
or Block Gilbert Moore Coding (BGMC). The long term predictor is modeled by 5 long-term weighted residues, each with its own lag (delay). The lag can be hundreds of samples. This predictor improves the compression for sounds with rich harmonics (containing multiples of a single fundamental frequency, locked in phase) present in many musical instruments and human voice.
A reference implementation of MPEG-4 ALS encoder and decoder (mp4als - e.g. mp4alsRM22rev2) can be obtained at the MPEG-4 ALS homepage and it was also published as ISO/IEC 14496-5:2001/Amd 10:2007/Cor 3:2009.
There is a MPEG-4 ALS Decoder plugin for Winamp
player.
On November 11, 2009, the FFmpeg
open source
project gained an MPEG-4 ALS decoder in its development version.
issued a call for proposals of lossless audio coding procedures to be sent in before December. Seven companies submitted their proposals which were examined taking into consideration compression efficiency, complexity and flexibility. By July 2003, Lossless Predictive Audio Compression
(LPAC) was selected as the first draft for the future standard. The reference model was further developed under participation of the Technical University of Berlin
(TUB), RealNetworks
, and Nippon Telegraph and Telephone
(NTT).
MPEG-4 Part 3
MPEG-4 Part 3 or MPEG-4 Audio is the third part of the ISO/IEC MPEG-4 international standard developed by Moving Picture Experts Group. It specifies audio coding methods...
audio standard to allow lossless
Lossless data compression
Lossless data compression is a class of data compression algorithms that allows the exact original data to be reconstructed from the compressed data. The term lossless is in contrast to lossy data compression, which only allows an approximation of the original data to be reconstructed, in exchange...
audio compression. The extension was finalized in December 2005 and published as ISO/IEC
International Electrotechnical Commission
The International Electrotechnical Commission is a non-profit, non-governmental international standards organization that prepares and publishes International Standards for all electrical, electronic and related technologies – collectively known as "electrotechnology"...
14496-3:2005/Amd 2:2006 in 2006. The latest description of MPEG-4 ALS was published as subpart 11 of the MPEG-4
MPEG-4
MPEG-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...
Audio standard (ISO/IEC 14496-3:2009) (4th edition) in August 2009.
MPEG-4 ALS combines together a short-term predictor and a long term predictor. The short-term predictor is similar to FLAC in its operation - it is a quantized LPC
Linear predictive coding
Linear predictive coding is a tool used mostly in audio signal processing and speech processing for representing the spectral envelope of a digital signal of speech in compressed form, using the information of a linear predictive model...
predictor with a losslessly coded residual using Golomb Rice Coding
Golomb coding
Golomb coding is a lossless data compression method using a family of data compression codes invented by Solomon W. Golomb in the 1960s. Alphabets following a geometric distribution will have a Golomb code as an optimal prefix code, making Golomb coding highly suitable for situations in which the...
or Block Gilbert Moore Coding (BGMC). The long term predictor is modeled by 5 long-term weighted residues, each with its own lag (delay). The lag can be hundreds of samples. This predictor improves the compression for sounds with rich harmonics (containing multiples of a single fundamental frequency, locked in phase) present in many musical instruments and human voice.
Features
- Support for PCM resolutions of up to 32-bit
- Arbitrary sampling rates (tested up to 192 kHz, higher frequencies such as 384 kHz can be handled with the current specifications)
- Multi-channel / multi-track support (up to 65536 channels)
- Fast random access to any part of the encoded data.
- Tagging
- StreamingStreaming mediaStreaming media is multimedia that is constantly received by and presented to an end-user while being delivered by a streaming provider.The term "presented" is used in this article in a general sense that includes audio or video playback. The name refers to the delivery method of the medium rather...
- Error correction mechanisms
- Optional storage in MP4 file format
- Can be multiplexed with video data using MP4 file format
- An MPEG-4 Audio profile "ALS Simple Profile".
Software support
, there has not been wide acceptance of this format, possibly due to the lack of encoders and decoders available.A reference implementation of MPEG-4 ALS encoder and decoder (mp4als - e.g. mp4alsRM22rev2) can be obtained at the MPEG-4 ALS homepage and it was also published as ISO/IEC 14496-5:2001/Amd 10:2007/Cor 3:2009.
There is a MPEG-4 ALS Decoder plugin for Winamp
Winamp
Winamp is a media player for Windows-based PCs and Android devices, written by Nullsoft, now a subsidiary of AOL. It is proprietary freeware/shareware, multi-format, extensible with plug-ins and skins, and is noted for its graphical sound visualization, playlist, and media library features.Winamp...
player.
On November 11, 2009, the FFmpeg
FFmpeg
FFmpeg is a free software project that produces libraries and programs for handling multimedia data. The most notable parts of FFmpeg are libavcodec, an audio/video codec library used by several other projects, libavformat, an audio/video container mux and demux library, and the ffmpeg command line...
open source
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...
project gained an MPEG-4 ALS decoder in its development version.
History
In July 2002, the Moving Picture Experts GroupMoving Picture Experts Group
The Moving Picture Experts Group is a working group of experts that was formed by ISO and IEC to set standards for audio and video compression and transmission. It was established in 1988 by the initiative of Hiroshi Yasuda and Leonardo Chiariglione, who has been from the beginning the Chairman...
issued a call for proposals of lossless audio coding procedures to be sent in before December. Seven companies submitted their proposals which were examined taking into consideration compression efficiency, complexity and flexibility. By July 2003, Lossless Predictive Audio Compression
Lossless Predictive Audio Compression
Lossless predictive audio compression is an improved lossless audio compression algorithm developed by Tilman Liebchen, Marcus Purat and Peter Noll at , Technical University Berlin , to compress PCM audio in a lossless manner, unlike conventional audio compression algorithms which are...
(LPAC) was selected as the first draft for the future standard. The reference model was further developed under participation of the Technical University of Berlin
Technical University of Berlin
The Technische Universität Berlin is a research university located in Berlin, Germany. Translating the name into English is discouraged by the university, however paraphrasing as Berlin Institute of Technology is recommended by the university if necessary .The TU Berlin was founded...
(TUB), RealNetworks
RealNetworks
RealNetworks, Inc. is a provider of Internet media delivery software and services based in Downtown Seattle, Washington, United States. The company is the creator of RealAudio, a compressed audio format; RealVideo, a compressed video format; RealPlayer, a media player; RealDownloader, a download...
, and Nippon Telegraph and Telephone
Nippon Telegraph and Telephone
, commonly known as NTT, is a Japanese telecommunications company headquartered in Tokyo, Japan. Ranked the 31st in Fortune Global 500, NTT is the largest telecommunications company in Asia, and the second-largest in the world in terms of revenue....
(NTT).
See also
- Lossless Predictive Audio CompressionLossless Predictive Audio CompressionLossless predictive audio compression is an improved lossless audio compression algorithm developed by Tilman Liebchen, Marcus Purat and Peter Noll at , Technical University Berlin , to compress PCM audio in a lossless manner, unlike conventional audio compression algorithms which are...
(predecessor) - Lossless Transform Audio Compression (pre-predecessor)
- MPEG-4 SLSMPEG-4 SLSMPEG-4 SLS, or MPEG-4 Scalable to Lossless as per ISO/IEC 14496-3:2005/Amd 3:2006 , is an extension to the MPEG-4 Part 3 standard to allow lossless audio compression scalable to lossy MPEG-4 General Audio coding methods...
(MPEG-4 Scalable Lossless Coding) - 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...
External links
- MPEG-4 ALS homepage - Technical University Berlin, old homepage - dead link
- MPEG-4 Audio Lossless Coding (ALS) - MultimediaWiki
- MPEG-4 ALS: Performance, Applications, and Related Standardization Activities - NTT (2007)
- Technical papers describing design of resdual coding and quantization algorithms in MPEG-4 ALS codec
- Announcement on ACN Newswire
- Technical specifications (ISO/IEC 14496-3:2005/Amd 2:2006) (not free)
- Official MPEG web site