Electrical audio signal processing systems and devices – Binaural and stereophonic – Quadrasonic
Reexamination Certificate
1998-06-29
2003-03-04
Mei, Xu (Department: 2644)
Electrical audio signal processing systems and devices
Binaural and stereophonic
Quadrasonic
C381S023000, C700S094000
Reexamination Certificate
active
06529604
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to audio encoding and decoding, and more particularly, to a scalable stereo audio encoding/decoding method and apparatus using bit-sliced arithmetic coding.
2. Description of the Related Art
In a conventional scalable audio encoding/decoding apparatus, scalability of a 1-channel mono signal was taken into consideration [K. Brandenbrug, et. al., “First Ideas on Scalable Audio Coding”, 97th AES-Convention, preprint 3924, San Francisco, 1994] and [K. Brandenburg, et al., “A two- or Three-Stage Bit Rate Scalable Audio Coding Sustem”, 99th AES-Convention, preprint 4132, New York, 1995]. However, MPEG audio standards [MPEG Committee ISO/IEC/JTCI/SC29/WG11, Information technology—Coding of moving pictures and associated audio for data storage media to about 1.5 Mbit/s—Part 3: Audio, ISO/IEC IS 11172-3, 1998] or AC-2/AC-3 methods [Dolby, “Dolby AC-3 Multi-Channel Audio Coding—Submission to the Grand Alliance Audio Specialist Group”, Dolby Lab., August, 1993] provide a technology for processing stereo and multi-channel signals as well as mono signals. In practice, most musical signals are composed of stereo signals. Thus, it is necessary to employ scalable audio codec adoptable to signals composed of two or more channel bitstreams as in the Internet or communications network.
Generally, musical signals are stereo signals. The stereo signals are provided through a compact disc (CD), a communications network or a broadcast network, and will be provided under multimedia environments in the future. However, existing scalable audio codecs have mostly treated mono signals and have not yet processed stereo signals. To process stereo signals, signal transmission must be performed such that all signals for one channel are transmitted and signals for another channel are then transmitted. In this case, however, since the quantities of bits generated in two channels are not always the same, the performance of scalable audio codec is considerably lower at a lower bitrate for the stereo signals.
SUMMARY OF THE INVENTION
To solve the above problems, it is an objective of the present invention to provide a scalable stereo digital audio data encoding method and apparatus, and a recording medium for recording the encoding method. Encoding is performed by generating bitstreams comprised of several enhancement layers based on a base layer using a bit-sliced arithmetic coding (BSAC) technique.
To achieve the objective of the present invention, there is provided scalable stereo audio encoding method for coding audio signals into a layered datastream having a base layer and at least two enhancement layers, including the steps of: signal-processing input audio signals and quantizing the same for each predetermined coding band, coding the quantized data corresponding to the base layer among the quantized data, coding the quantized data corresponding to the next enhancement layer of the coded base layer and the remaining quantized data uncoded due to a layer size limit and belonging to the coded layer, and sequentially performing the layer coding steps for all enhancement layers to form bitstreams, wherein the base layer coding step, the enhancement layer coding step and the sequential coding step are performed such that the side information and quantized data corresponding to a layer to be coded are represented by digits of a same predetermined number, and then arithmetic-coded using a predetermined probability model in the order ranging from the Most Significant Bit (MSB) sequences to the Least Significant Bit (LSB) sequences, bit-sliced left-channel data and right-channel data being alternately coded in units of predetermined vectors. The side information includes at least scale factors and information on a probability model to be used in arithmetic coding. The predetermined vectors are four-dimensional vectors produced by coupling the four bit-sliced audio channel data into one vector. The four-dimensional vectors are divided into two subvectors according to prestates indicating whether non-zero bit-sliced frequency components are coded or not, to then be coded.
Also, the step of coding the scale factors includes the steps of obtaining the maximum scale factor, obtaining the difference between the maximum scale factor and the first scale factors and arithmetic-coding the difference, and obtaining differences between the immediately previous arithmetic-coded scale factor and the respective scale factors subsequent to the first scale factor, mapping the differences into a predetermined value and arithmetic-coding the mapped values.
The step of coding the scale factors includes the steps of obtaining the maximum scale factor, and obtaining differences between the maximum scale factor and the respective scale factors and arithmetic-coding the differences.
The header information commonly used for all bands is coded and the side information and the quantized frequencies necessary for the respective layer are formed by bit-sliced information to then be coded to have a layered structure.
The quantization is performed by the steps of converting the input audio signals of a time domain into signals of a frequency domain, coupling the converted signals as signals of predetermined scale factor bands by time/frequency mapping and calculating a masking threshold at each scale factor band, performing temporal-noise shaping for controlling the temporal shape of the quantization noise within each window for conversion, performing intensity stereo processing such that only the quantized information of a scale factor band for one of two channels is coded, and only the scale factor for the other channel is transmitted, predicting frequency coefficients of the present frame, performing Mid/Side (M/S) stereo processing for converting a left-channel signal and a right-channel signal into an additive signal of two signals and a subtractive signal thereof, and quantizing the signals for each predetermined coding band so that quantization noise of each band is smaller than the masking threshold.
When the quantized data is composed of sign data and magnitude data, the steps of coding of the base layer and enhancement layers and forming bitstreams include the steps of: arithmetic-coding the most significant digit sequences composed of most significant digits of the magnitude data, coding sign data corresponding to non-zero data among the coded most significant digit sequences, coding the most significant digit sequences among uncoded magnitude data of the digital data, coding uncoded sign data among the sign data corresponding to non-zero magnitude data among coded digit sequences, and performing the magnitude coding step and the sign coding step on the respective digits of the digital data, the respective steps being alternately performed on the left-channel data and the right-channel data in units of predetermined vectors.
The scalable stereo audio decoding apparatus further includes an M/S stereo processing portion for performing M/S stereo processing for checking whether or not M/S stereo processing has been performed in the bitstream encoding method, and converting a left-channel signal and a right-channel signal into an additive signal of two signals and a subtractive signal thereof if the M/S stereo processing has been performed, a predicting portion for checking whether or not predicting step has been performed in the bitstream encoding method, and predicting frequency coefficients of the current frame if the checking step has been performed, an intensity stereo processing portion for checking whether or not intensity stereo processing has been performed in the bitstream encoding method, and, if the intensity stereo processing has been performed, then since only the quantized information of the scale factor band for one channel (the left channel) two channels is coded, performing the intensity stereo processing for restoring the quantized information of the other channel (the right channel) into a left c
Kim Yeon-bae
Park Sung-hee
Burns Doane , Swecker, Mathis LLP
Mei Xu
Samsung Electronics Co,. Ltd.
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