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 MPEG-4 is a group of international standards for the compression of digital audio and visual data, multimedia systems, and file storage formats. It was originally introduced in late 1998 as a group of audio and video coding formats and related tec ...

Audio standard (ISO/IEC 14496-3:2019) (5th edition) in December 2019. MPEG-4 ALS combines a short-term predictor and a long term predictor. The short-term predictor is similar to

FLAC FLAC (; 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 p ...

in its operation - it is a quantized

LPC LPC may refer to: Science and technology * Linear predictive coding, a method used in audio signal processing and speech processing * Leaf protein concentrate, a concentrated form of the proteins found in the leaves of plants * Long period comet, ...

predictor with a losslessly coded residual using Golomb Rice Coding or

Block Gilbert Moore Coding Block or blocked may refer to: Arts, entertainment and media Broadcasting * Block programming, the result of a programming strategy in broadcasting * W242BX, a radio station licensed to Greenville, South Carolina, United States known as ''96.3 ...

(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 Pulse-code modulation (PCM) is a method used to digitally represent sampled analog signals. It is the standard form of digital audio in computers, compact discs, digital telephony and other digital audio applications. In a PCM stream, the amp ...

resolutions of up to 32-bit including floating-point * Arbitrary sampling rates * Multi-channel / multi-track support (up to 65536 channels) *

Streaming Streaming media is multimedia that is delivered and consumed in a continuous manner from a source, with little or no intermediate storage in network elements. ''Streaming'' refers to the delivery method of content, rather than the content it ...

* Seekable (fast random access to any part of the encoded data). * Optional storage in MP4 file format; can be multiplexed with video and other media content supported by the MP4 container. * An MPEG-4 Audio profile "ALS Simple Profile", invoked with "-sp1" in the reference encoder.

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. mp4alsRM23) 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 Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use the source code, design documents, or content of the product. The open-source model is a decentralized sof ...

project gained an MPEG-4 ALS decoder in its development version. Only a subset of the format is currently supported.

History

In July 2002, the

Moving Picture Experts Group The Moving Picture Experts Group (MPEG) is an alliance of working groups established jointly by ISO and IEC that sets standards for media coding, including compression coding of audio, video, graphics, and genomic data; and transmission and f ...

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 The Technical University of Berlin (official name both in English and german: link=no, Technische Universität Berlin, also known as TU Berlin and Berlin Institute of Technology) is a public research university located in Berlin, Germany. It was ...

(TUB),

RealNetworks RealNetworks, Inc. is a provider of artificial intelligence and computer vision based products. RealNetworks was a pioneer in Internet streaming software and services. They are based in Seattle, Washington, United States. The company also p ...

, and Nippon Telegraph and Telephone (NTT).

References

External links

MPEG-4 ALS homepage - Technical University of Berlin

MPEG-4 Audio Lossless Coding (ALS) - MultimediaWiki

- NTT (2007) * ttp://www.reznik.org/software.html#ALS Technical papers describing design of residual 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
{{Compression software implementations MPEG-4 Lossless audio codecs

Features

Software support

History

See also

References

External links