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]
| 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 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.
Features
edit- Support for PCM resolutions of up to 32-bit including floating-point
- Arbitrary sampling rates
- Multi-channel / multi-track support (up to 65536 channels)
- Streaming[5]
- 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",[6] invoked with "-sp1" in the reference encoder.[7]
Software support
editAs of 2020[update], there has not been wide acceptance of this format, possibly due to the lack of encoders and decoders available.[8]
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.[7]
There is a MPEG-4 ALS Decoder plugin for Winamp player.[9]
On November 11, 2009, the FFmpeg open source project gained an MPEG-4 ALS decoder in its development version.[10] Only a subset of the format is currently supported.
History
editIn 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 Technische Universität Berlin (TUB), RealNetworks, and Nippon Telegraph and Telephone (NTT).
See also
edit- Lossless predictive audio compression (predecessor)
- Lossless Transform Audio Compression (pre-predecessor)
- MPEG-4 SLS (MPEG-4 Scalable Lossless Coding)
- MPEG-4
References
edit- ^ 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.
- ^ ISO/IEC (2019). "ISO/IEC 14496-3:2019: Information technology — Coding of audio-visual objects — Part 3: Audio" (PDF). ISO. Retrieved 2022-01-01.
- ^ 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.
- ^ 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.
- ^ Noboru Harada; Takehiro Moriya & Yutaka Kamamoto (2009-05-07). "MPEG-4 ALS: Performance, Applications, and Related Standardization Activities". NTT Technical Review. Retrieved 2009-10-08.
- ^ ISO/IEC 14496-3:200X/PDAM 2 – ALS Simple Profile and Transport of SAOC – N10826, 2009-07-03, archived from the original (DOC) on 2014-07-29, retrieved 2009-10-15
- ^ a b Communication Systems Group (2009-10-01). "MPEG-4 Audio Lossless Coding (ALS)". Technische Universität Berlin. Archived from the original on 2019-03-21. Retrieved 2019-03-21.
- ^ Hydrogenaudio Knowledgebase (2006). "Lossless comparison". Hydrogenaudio Knowledgebase. Retrieved 2022-01-01.
- ^ "MPEG-4 ALS Decoder plugin 1.00 for Winamp". Codecs.com. 2007-06-05. Retrieved 2009-10-08.
- ^ FFmpeg (2009-11-11). "FFmpeg-cvslog r20517". FFmpeg. Archived from the original on 2010-02-11. Retrieved 2009-11-20.
External links
edit- MPEG-4 ALS homepage – Technische Universität Berlin Archived 2019-03-21 at the Wayback Machine
- MPEG-4 Audio Lossless Coding (ALS) – MultimediaWiki
- MPEG-4 ALS: Performance, Applications, and Related Standardization Activities – NTT (2007)
- 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