Friday, October 10 2:00 pm – 4:30 pm
Session C Low Bit-Rate Audio Coding

C-1 Scalable Perceptual and Lossless Audio Coding Based on MPEG-4 AAC—Ralf Geiger, Gerald Schuller, Fraunhofer IIS AEMT, Ilmenau, Germany; Jürgen Herre , Ralph Sperschneider, Fraunhofer IIS AEMT, Erlangen, Germany; Thomas Sporer, Fraunhofer IIS AEMT, Ilmenau, Germany
This paper presents a scalable lossless enhancement of MPEG-4 Advanced Audio Coding (AAC). Scalability is achieved in the frequency domain using the Integer Modified Discrete Cosine Transform (IntMDCT), which is an integer approximation of the MDCT providing perfect reconstruction. With this transform, and only minor extension of the bitstream syntax, the MPEG-4 AAC Scalable codec can be extended to a lossless operation. The system provides bit-exact reconstruction of the input signal independent of the implementation accuracy of the AAC core coder. Furthermore, scalability in sampling rate and reconstruction word length is supported.

C-2 Robust MPEG Advanced Audio Coding Over Wireless Channels—T. H. Yeo, National University of Singapore, Singapore; W. C. Wong, National University of Singapore, Singapore, Institute for Infocomm Research, Singapore; Dong-Yan Huang, Institute for Infocomm Research, Singapore
In this paper a concatenated system combining turbo product codes and convolutional codes with soft decision Viterbi decoding algorithm and diversity is proposed to enhance the robustness of the Unequal Error Protection (UEP) scheme for wireless transmission of MPEG-4 Advanced Audio Coding (AAC). The proposed scheme has been tested over the Gaussian and Rician fading channels. Under severe channels with random, burst, and mixed bit error rates (BER) of 6.00x10^-2 and above, the proposed scheme provides a 90 percent improvement in residual BER performance, which is approximately 3 dB, with 19 percent increase in bandwidth over the original UEP scheme. At a high channel BER of 6.00x10^-2, the proposed scheme gives an error-free header frame. Compared with the concatenated convolutional codes, the proposed scheme provides 0.5 dB BER performance improvements with the same bandwidth. With diversity, the performance can be further improved by 3 dB at low SNR for proposed scheme and 2.5 dB for original UEP scheme.

C-3 MP3 in MPEG-4— Bernhard Grill, Harald Gernhardt, Michael Härtl, Johannes Hilpert, Manfred Lutzky, Martin Weishart, Fraunhofer IIS, Erlangen, Germany
MP3 is the most commonly used audio coding scheme worldwide. Today it is present on virtually any computer, CD, DVD-player, many car radios, and of course in the many MP3 audio player devices. This paper describes a new MPEG-4 working draft currently under development by ISO/MPEG, which will allow MP3 to be fully integrated into MPEG-4 audio-visual systems. Among other new features, such as enhanced editability, MP3 is scheduled to get a full multichannel audio capability, which can be implemented with a few additional lines of code on top of a standard stereo MP3 codec.

C-4 A Closer Look into MPEG-4 High Efficiency AAC—Martin Wolters, Coding Technologies, Nürnberg, Germany; Kristofer Kjörling, Coding Technologies, Stockholm, Sweden; Daniel Homm, Coding Technologies, Nürnberg, Germany; Heiko Purnhagen, Coding Technologies, Stockholm, Germany
MPEG Spectral Band Replication (SBR) is the newest compression technology available as part of the MPEG standards. It is combined with MPEG Advanced Audio Coding (AAC) and improves coding efficiency by more than 30 percent. The resulting scheme is called High-Efficiency AAC (HE-AAC). This paper explains MPEG-SBR and its integration into the existing MPEG-4 bitstream format. The SBR technology itself, as well as the implications on systems based on MPEG-4 technology, are described. The signaling through MPEG-4 systems and other transport formats is introduced and typical applications and usage scenarios are listed.

C-5 MPEG-4 Lossless Coding for High-Definition Audio—Tilman Liebchen, Technical University of Berlin, Berlin, Germany
Lossless coding will become the latest extension of the MPEG-4 audio standard. In response to a call for proposals, many companies have submitted lossless audio codecs for evaluation. The codec of the Technical University of Berlin was chosen as reference model for MPEG-4 Audio Lossless Coding, attaining working draft status in July 2003. The encoder is based on linear prediction, which enables high compression even with moderate complexity, while the corresponding decoder is straightforward. The paper describes the basic elements of the codec, points out envisaged applications, and gives an outline of the standardization process.