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MP3 is a coding format for digital audio developed largely by the Fraunhofer Society in Germany under the lead of Karlheinz Brandenburg, with support from other digital scientists in other countries. Originally defined as the third audio format of the MPEG-1 standard, it was retained and further extended — defining additional bit-rates and support for more audio channels — as the third audio format of the subsequent MPEG-2 standard. A third version, known as MPEG-2.5 — extended to better support lower bit rates — is commonly implemented, but is not a recognized standard.
Advanced Audio Coding (AAC) is an audio coding standard for lossy digital audio compression. Designed to be the successor of the MP3 format, AAC generally achieves higher sound quality than MP3 encoders at the same bit rate.
Karlheinz Brandenburg is a German electrical engineer and mathematician. Together with Ernst Eberlein, Heinz Gerhäuser, Bernhard Grill, Jürgen Herre and Harald Popp, he developed the widespread MP3 method for audio data compression. He is also known for his elementary work in the field of audio coding, the perception measurement, the wave field synthesis and psychoacoustics. Brandenburg has received numerous national and international research awards, prizes and honors for his work. Since 2000 he has been a professor of electronic media technology at the Technical University Ilmenau. Brandenburg was significantly involved in the founding of the Fraunhofer Institute for Digital Media Technology (IDMT) and currently serves as its director.
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. The first version of ISO/IEC 14496-3 was published in 1999.
mp3PRO is an unmaintained proprietary audio compression codec that combines the MP3 audio format with the spectral band replication (SBR) compression method. At the time it was developed it could reduce the size of a stereo MP3 by as much as 50% while maintaining the same relative quality. This works, fundamentally, by discarding the higher half of the frequency range and algorithmically replicating that information while decoding.
Spectral band replication (SBR) is a technology to enhance audio or speech codecs, especially at low bit rates and is based on harmonic redundancy in the frequency domain.
High-Efficiency Advanced Audio Coding (HE-AAC) is an audio coding format for lossy data compression of digital audio defined as an MPEG-4 Audio profile in ISO/IEC 14496–3. It is an extension of Low Complexity AAC (AAC-LC) optimized for low-bitrate applications such as streaming audio. The usage profile HE-AAC v1 uses spectral band replication (SBR) to enhance the modified discrete cosine transform (MDCT) compression efficiency in the frequency domain. The usage profile HE-AAC v2 couples SBR with Parametric Stereo (PS) to further enhance the compression efficiency of stereo signals.
FAAC or Freeware Advanced Audio Coder is a software project which includes the AAC encoder FAAC and decoder FAAD2. It supports MPEG-2 AAC as well as MPEG-4 AAC. It supports several MPEG-4 Audio object types, file formats, multichannel and gapless encoding/decoding and MP4 metadata tags. The encoder and decoder is compatible with standard-compliant audio applications using one or more of these object types and facilities. It also supports Digital Radio Mondiale.
The following tables compare general and technical information for a variety of audio coding formats.
MPEG Multichannel also known as MPEG-2 Backwards Compatible, or MPEG-2 BC, is an extension to the MPEG-1 Layer II audio compression specification, as defined in the MPEG-2 Audio standard which allows it provide up to 5.1-channels of audio. To maintain backwards compatibility with the older 2-channel (stereo) audio specification, it uses a channel matrixing scheme, where the additional channels are mixed into the two backwards compatible channels. Extra information in the data stream contains signals to process extra channels from the matrix.
MPEG-4 SLS, or MPEG-4 Scalable to Lossless as per ISO/IEC 14496-3:2005/Amd 3:2006 (Scalable Lossless Coding), is an extension to the MPEG-4 Part 3 (MPEG-4 Audio) standard to allow lossless audio compression scalable to lossy MPEG-4 General Audio coding methods (e.g., variations of AAC). It was developed jointly by the Institute for Infocomm Research (I2R) and Fraunhofer, which commercializes its implementation of a limited subset of the standard under the name of HD-AAC. Standardization of the HD-AAC profile for MPEG-4 Audio is under development (as of September 2009).
The MPEG-4 Low Delay Audio Coder is audio compression standard designed to combine the advantages of perceptual audio coding with the low delay necessary for two-way communication. It is closely derived from the MPEG-2 Advanced Audio Coding (AAC) standard. It was published in MPEG-4 Audio Version 2 and in its later revisions.
MPEG Surround, also known as Spatial Audio Coding (SAC) is a lossy compression format for surround sound that provides a method for extending mono or stereo audio services to multi-channel audio in a backwards compatible fashion. The total bit rates used for the core and the MPEG Surround data are typically only slightly higher than the bit rates used for coding of the core. MPEG Surround adds a side-information stream to the core bit stream, containing spatial image data. Legacy stereo playback systems will ignore this side-information while players supporting MPEG Surround decoding will output the reconstructed multi-channel audio.
Unified Speech and Audio Coding (USAC) is an audio compression format and codec for both music and speech or any mix of speech and audio using very low bit rates between 12 and 64 kbit/s. It was developed by Moving Picture Experts Group (MPEG) and was published as an international standard ISO/IEC 23003-3 and also as an MPEG-4 Audio Object Type in ISO/IEC 14496-3:2009/Amd 3 in 2012.
An audio coding format is a content representation format for storage or transmission of digital audio. Examples of audio coding formats include MP3, AAC, Vorbis, FLAC, and Opus. A specific software or hardware implementation capable of audio compression and decompression to/from a specific audio coding format is called an audio codec; an example of an audio codec is LAME, which is one of several different codecs which implements encoding and decoding audio in the MP3 audio coding format in software.
Fraunhofer FDK AAC is an open-source library for encoding and decoding digital audio in the Advanced Audio Coding (AAC) format. Fraunhofer IIS, developed this library for Android 4.1. It supports several Audio Object Types including MPEG-2 and MPEG-4 AAC LC, HE-AAC, HE-AACv2 as well AAC-LD and AAC-ELD for real-time communication. The encoding library supports sample rates up to 96 kHz and up to eight channels.
MPEG-H 3D Audio, specified as ISO/IEC 23008-3, is an audio coding standard developed by the ISO/IEC Moving Picture Experts Group (MPEG) to support coding audio as audio channels, audio objects, or higher order ambisonics (HOA). MPEG-H 3D Audio can support up to 64 loudspeaker channels and 128 codec core channels.
Enhanced Voice Services (EVS) is a superwideband speech audio coding standard that was developed for VoLTE. It offers up to 20 kHz audio bandwidth and has high robustness to delay jitter and packet losses due to its channel aware coding and improved packet loss concealment. It has been developed in 3GPP and is described in 3GPP TS 26.441. The application areas of EVS consist of improved telephony and teleconferencing, audiovisual conferencing services, and streaming audio. Source code of both decoder and encoder in ANSI C is available as 3GPP TS 26.442 and is being updated regularly. Samsung uses the term HD+ when doing a call using EVS.
Lars "Stockis" Liljeryd (1951-2020) was a Swedish audio and medical engineer, inventor, and entrepreneur. He is noted for his pioneering work in the development of the audio compression technology called AAC, which revolutionized audio processing in portable music, video, and streaming media devices. He was one of the founders of the startup company called Coding Technologies.
References
- 1 2 3 "Coding Technologies' Digital Revolution". Fraunhofer Venture. Retrieved 7 July 2015.
- 1 2 "IEEE Masaru Ibuka Consumer Electronics Award". IEEE.org. Retrieved 7 July 2015.
- ↑ "Orban and Coding Technologies bring MPEG-4 aacPlus audio to Windows Media Players". EE Times. April 24, 2006. Retrieved April 5, 2023.
- ↑ Office, European Patent. "Lars Liljeryd (Sweden)". www.epo.org. Retrieved 2023-04-04.
- ↑ "Dolby Laboratories to Acquire Coding Technologies". 8 November 2007. Archived from the original on 12 June 2010. Retrieved 25 May 2015.
- ↑ "XM Drops PAC for CT-aacPlus". Radio. 14 May 2002. Archived from the original on 26 May 2015. Retrieved 25 May 2015.
- ↑ RadioWorld (2004-03-22). "Qualcomm Chooses Coding Technologies' aacPlus". Radio World. Retrieved 2023-04-04.
- ↑ "Interview with Martin Dietz, Kristofer Kjörling, and Lars Liljeryd". YouTube. Retrieved 7 July 2015.