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Audio Coding

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Karlheinz Brandenburg – One of the best experts on this subject based on the ideXlab platform.

  • MPEG-4 natural Audio Coding
    Signal Processing-image Communication, 2002
    Co-Authors: Karlheinz Brandenburg, Oliver Kunz, Akihiko Sugiyama

    Abstract:

    MPEG-4 Audio represents a new kind of Audio Coding standard. Unlike its predecessors, MPEG-1 and MPEG-2 high-quality Audio Coding, and unlike the speech Coding standards which have been completed by the ITU-T, it describes not a single or small set of highly efficient compression schemes but a complete toolbox to do everything from low bit-rate speech Coding to high-quality Audio Coding or music synthesis. The natural Coding part within MPEG-4 Audio describes traditional type speech and high-quality Audio Coding algorithms and their combination to enable new functionalities like scalability (hierarchical Coding) across the boundaries of Coding algorithms. This paper gives an overview of the basic algorithms and how they can be combined.

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  • intmdct a link between perceptual and lossless Audio Coding
    International Conference on Acoustics Speech and Signal Processing, 2002
    Co-Authors: Ralf Geiger, Jürgen Herre, Jürgen Koller, Karlheinz Brandenburg

    Abstract:

    The Modified Discrete Cosine Transform (MDCT) is widely used in modem perceptual Audio Coding schemes. In this paper we present an integer approximation of this lapped transform, called IntMDCT, which is derived from the MDCT using the lifting scheme. This reversible integer transform inherits most of the attractive properties of the MDCT, exhibiting a good spectral representation of the Audio signal, critical sampling and overlapping of blocks. This makes the IntMDCT well suited for both lossless Audio Coding as well as for combined perceptual and lossless Audio Coding. A scalable system is presented providing a lossless enhancement of perceptual Audio Coding schemes, such as MPEG-2 AAC.

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  • ICASSP – IntMDCT – A link between perceptual and lossless Audio Coding
    IEEE International Conference on Acoustics Speech and Signal Processing, 2002
    Co-Authors: Ralf Geiger, Jürgen Herre, Jürgen Koller, Karlheinz Brandenburg

    Abstract:

    The Modified Discrete Cosine Transform (MDCT) is widely used in modem perceptual Audio Coding schemes. In this paper we present an integer approximation of this lapped transform, called IntMDCT, which is derived from the MDCT using the lifting scheme. This reversible integer transform inherits most of the attractive properties of the MDCT, exhibiting a good spectral representation of the Audio signal, critical sampling and overlapping of blocks. This makes the IntMDCT well suited for both lossless Audio Coding as well as for combined perceptual and lossless Audio Coding. A scalable system is presented providing a lossless enhancement of perceptual Audio Coding schemes, such as MPEG-2 AAC.

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Susanto Rahardja – One of the best experts on this subject based on the ideXlab platform.

  • ICASSP – Enhanced scalable to lossless Audio Coding scheme
    2010 IEEE International Conference on Acoustics Speech and Signal Processing, 2010
    Co-Authors: Haiyan Shu, Haibin Huang, Susanto Rahardja

    Abstract:

    Scalable to lossless (SLS) Audio Coding is a state-of-art Audio Coding technique that has been adopted as MPEG scalable Audio Coding tool. To realize bit-plane refinement, this technique employs bit-plane arithmetic Coding for lossless entropy Coding, and Laplacian distribution is used to model the input data to realize high compression efficiency. In this paper, bit-plane probability is analyzed when generalized Gaussian distribution is used to model the input data. Based on the result of bit-plane probability for generalized Gaussian distribution, a low cost bit-plane arithmetic Coding method is presented. This scheme is implemented in the SLS Audio Coding platform. With the same computational complexity, the proposed algorithm presents higher compression efficiency than SLS.

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  • On integer MDCT for perceptual Audio Coding
    IEEE Transactions on Audio, Speech and Language Processing, 2007
    Co-Authors: Te Li, Susanto Rahardja, Rongshan Yu, Soo Ngee Koh

    Abstract:

    In MPEG-4 scalable lossless Coding (SLS) which was recently published as an ISO standard in June 2006, the integer modified discrete cosine transform (IntMDCT) was adopted to enable efficient lossless reconstruction. In addition, there is an MDCT filterbank which is inherent to the advanced Audio Coding (AAC) core that is present in the SLS codec. The presence of two filterbanks have undoubtedly increased the complexity of the implementation, and it is for this reason that the MDCT is disabled and the IntMDCT is then the only type of filterbank that is employed in SLS for both lossy and lossless operations. Because of the rounding operations in the IntMDCT, there is a concern if the use of IntMDCT for perceptual Audio Coding will eventually degrade the fidelity of the Audio codec. This paper addresses this concern by analyzing the performance of the IntMDCT in a lossy Coding scenario. It is found that noise introduced by the IntMDCT does not affect the perceptual quality of the coded Audio under standard playback circumstances. As such, it concludes that the MDCT and IntMDCT filterbanks are interchangeable at lossy bitrate, and the way of using only the IntMDCT filterbank in scalable Audio Coding is also justified.

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  • ISM – Perceptually Prioritized Bit-Plane Coding for High-Definition Advanced Audio Coding
    Eighth IEEE International Symposium on Multimedia (ISM'06), 2006
    Co-Authors: Susanto Rahardja, Soo Ngee Koh

    Abstract:

    Wide bitrate range scalability is now the latest trend in Audio Coding. A lot of efforts has been devoted to the development of algorithms for more efficient scalable Audio coder that scales from very low bitrate. Scalable Audio Coding technique such as MPEG-4 Scalable Lossless Coding (SLS) offers a unified solution for high-compression perceptual Audio and high-quality lossless Audio. SLS provides a fine-grain scalable extension of the well-known MPEG-4 Advanced Audio Coding (AAC) perceptual Audio coder up to fully lossless reconstruction. Recently, the combination of SLS and AAC coder is renamed as “High Definition Advanced Audio Coding” (HD-AAC). It is observed that HD-AAC can be further improved at intermediate enhancement bitrate when the core bitrate is low. In this paper, a Perceptually Prioritized Bit-Plane Coding (PPBPC) is proposed. With this novel Coding scheme, the bit-plane Coding is performed with priorities according to the perceptual information of the signal to be coded. By using this low-complexity structure with trivial extra side information, the bit-plane Coding for scalable Audio can be implemented in a perceptually more efficient manner and the quality of the Audio under aforementioned scenario is greatly improved.

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Ralf Geiger – One of the best experts on this subject based on the ideXlab platform.

  • low delay filterbanks for enhanced low delay Audio Coding
    Workshop on Applications of Signal Processing to Audio and Acoustics, 2007
    Co-Authors: Markus Schnell, Jürgen Herre, Ralf Geiger, Markus Multrus, Markus Schmidt, Michael Mellar, Gerald Schuller

    Abstract:

    Low delay perceptual Audio Coding has recently gained wide acceptance for high quality communication. While common schemes are based on the well-known Modified Discrete Cosine Transform (MDCT) filterbank, this paper describes novel Coding algorithms that, for the first time, make use of dedicated low delay filterbanks, thus achieving improved Coding efficiency while maintaining or even reducing the low codec delay. The MPEG-4 Enhanced Low Delay AAC (AAC-ELD) coder currently under development within ISO/MPEG combines a traditional perceptual Audio Coding scheme with spectral band replication (SBR), both running in a delay-optimized fashion by using low delay filterbanks.

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  • mpeg 4 scalable to lossless Audio Coding
    Journal of The Audio Engineering Society, 2004
    Co-Authors: Ralf Geiger, Juergen Herre, Haibin Huang, Xiao Lin, Susanto Rahardja

    Abstract:

    As the latest extension of MPEG-4 Audio Coding, MPEG-4 Lossless Audio Coding includes a scalable Audio Coding solution (SLS) that integrates the functionalities of lossless Audio Coding, perceptual Audio Coding, and fine granular scalable Audio Coding into a single coder framework while providing backward compatibility to MPEG Advanced Audio Coding (AAC) at the bit-stream level. Despite its abundant functionalities, SLS still achieves a compression performance that is comparable to state-of-the-art non-scalable lossless Audio Coding algorithms. As a result, SLS provides a universal digital Audio format for a variety of application domains including professional Audio, Internet music, consumer electronics, broadcasting and others. This paper presents the structure of SLS and its latest developments during the MPEG standardization process.

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  • fine grain scalable perceptual and lossless Audio Coding based on intmdct
    International Conference on Acoustics Speech and Signal Processing, 2003
    Co-Authors: Ralf Geiger, Gerald Schuller, A Herre, Thomas Sporer

    Abstract:

    This papers presents an embedded fine grain scalable perceptual and lossless Audio Coding scheme. The enabling technology for this combined perceptual and lossless Audio Coding approach is the integer modified discrete cosine transform (IntMDCT), which is an integer approximation of the MDCT based on the lifting scheme. It maintains the perfect reconstruction property and therefore enables efficient lossless Coding in the frequency domain. The close approximation of the MDCT also allows us to build a perceptual Coding scheme based on the IntMDCT. In this paper a bitsliced arithmetic Coding technique is applied to the IntMDCT values. Together with the encoded shape of the masking threshold a perceptually hierarchical bitstream is obtained, containing several stages of perceptual quality and extending to lossless operation when transmitted completely. A concept of enCoding subslices is presented in order to obtain a fine adaptation to the masking threshold especially in the range of perceptually transparent quality.

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