In today's article we are going to talk about Audio Lossless Coding, a topic that has gained great relevance in recent years. Audio Lossless Coding is a topic that has captured the attention of experts and fans alike, due to its impact on various aspects of society. Since its appearance, Audio Lossless Coding has sparked debates and discussions around its importance and relevance in today's world. In this article, we will explore different perspectives and approaches on Audio Lossless Coding, with the aim of providing a comprehensive and enriching vision on this topic that interests so many people.
Developed by | ISO |
---|---|
Initial release | March 2006 |
Latest release | RM23 2009 |
Type of format | Lossless audio |
Contained by | MP4 |
Standard | ISO/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. 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.
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). 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.
As of 2020, 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 project gained an MPEG-4 ALS decoder in its development version. Only a subset of the format is currently supported.
In July 2002, the Moving Picture Experts Group 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).