Audio Lossless Coding

Audio Lossless Coding
Developed byISO
Initial releaseMarch 2006; 18 years ago (2006-03)
Latest release
RM23
2009; 15 years ago (2009)
Type of formatLossless audio
Contained byMP4
StandardISO/IEC 14496-3
Open format?Yes
Free format?No

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.[1] The latest description of MPEG-4 ALS was published as subpart 11 of the MPEG-4 Audio standard (ISO/IEC 14496-3:2019) (5th edition) in December 2019.[2]

MPEG-4 ALS combines 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).[3][4] 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.

  1. ^ ISO (2006). "Audio Lossless Coding (ALS), new audio profiles and BSAC extensions – ISO/IEC 14496-3:2005/Amd 2:2006". ISO. Retrieved 2009-10-07.
  2. ^ ISO/IEC (2019). "ISO/IEC 14496-3:2019: Information technology — Coding of audio-visual objects — Part 3: Audio" (PDF). ISO. Retrieved 2022-01-01.
  3. ^ Tilman Liebchen & Yuriy Reznik (2004-04-03). "MPEG-4 ALS: an Emerging Standard for Lossless Audio Coding" (PDF). Data Compression Conference. Retrieved 2010-09-03.
  4. ^ Tilman Liebchen; Takehiro Moriya; Noboru Harada; Yutaka Kamamoto; Yuriy A. Reznik (2005-08-03). The MPEG-4 Audio Lossless Coding (ALS) Standard – Technology and Applications (PDF). 119th Audio Engineering Society Convention, 2005 October 7–10 New York. Audio Engineering Society. Retrieved 2009-10-08 – via Technische Universität Berlin.