Dae Hee Youn

Bit Rate Reduction Algorithm For A Digital VCR

The authors describe a bit rate reduction algorithm for use in digital VCRs, based on block scrambling and the two-dimensional adaptive discrete cosine transform. This method satisfies many of the demands unique to digital VCRs. Before the encoding process, the input image is divided into 8*8 pixel blocks and then scrambled on a block-by-block basis to achieve efficient bit distribution in a frame and to simplify buffer control strategy. In addition to block scrambling, a simple yet efficient variable length coding method is proposed. Simulation results are presented. >

On detecting the presence of fetal R-wave using the moving averaged magnitude difference algorithm

An efficient algorithm for detecting the presence of a fetal QRS complex is presented. The proposed fetal QRS detection method computes the averaged magnitude of the difference between the fetal ECG signal and the reference signal to detect the fetal QRS event. The detected signal fetal QRS complexes are exponentially averaged to generate the template signal which can track the slowly varying shape of the fetal ECG signal. As an effort to obtain improved detection performances, two approaches of normalizing the fetal ECG signal and the template are considered.<<ETX>>

Realization of a generalized sidelobe canceller

The use of adaptive multichannel lattice/escalator filters to realize a generalized sidelobe canceller is proposed. This paper studies the performances of the proposed methods and the TDL counterpart via computer simulations for both stationary and nonstationary environments. Experimental results show that the lattice/escalator realizations converge faster and yield smaller mean-square errors than the TDL counterpart. Also, experiments seem to indicate that the beam patterns of the escalator realization are the most consistent, while those of the lattice realization are more consistent than the TDL counterpart.

A fetal ECG signal monitoring system using digital signal processor

The authors describe the implementation of a real-time fetal ECG (electrocardiogram) monitoring system in which an adaptive multichannel noise canceller is realized using the TMS32020 programmable digital signal processor. An ECG signal from the electrode placed on the mothers abdomen and three ECGs from those on the chest are applied as the desired signal and the reference inputs, respectively, of the multichannel filter. The coefficients of the filter are updated using the LMS (least-mean-square) algorithm, such that the output of the multichannel filter copies the maternal ECG embedded in the abdominal ECG. The enhanced fetal ECG is obtained by subtracting the filter output from the abdominal ECG, and the difference signal is recorded.<<ETX>>

Adaptive multichannel digital filter with lattice-escalator hybrid structure

An adaptive multichannel digital filter structure that can be used in multichannel noise-cancelling applications is described. The proposed structure is a hybrid of the lattice and the escalator (Gram-Schmidt) structures, and the coefficients are updated using the least-mean-square algorithm. In the lattice-escalator hybrid structure, complete decorrelation of multiple reference signals is achieved by successively generating forward prediction error vectors via the lattice structure and decorrelating the elements of the error vectors using escalator linear combiners at each lattice stage. Simulation results indicate that the convergence speed of the hybrid structure is as fast as the escalator realization.<<ETX>>

A Robust Frequency-Domain Multi-Reference Narrowband Adaptive Noise Canceller

In this paper, it is shown that the performance of the frequency-domain multi-reference narrowband noise canceller is determined by the narrowband component to the broadband disturbance power ratio in the reference signals. To overcome this problem, a new narrowband ANC is proposed, where the update of the adaptive filter is determined based on SNR of the reference inputs being measured using the magnitude squared coherence (MSC) between the primary and the reference signals. Simulation results show that the proposed ANC has superior performance over the conventional one.

Adaptive implementation of optimum MTI processor

The authors propose an adaptive processor implementing an optimum moving target indicator (MTI) in the sense of maximizing the improvement factor (IF). A multichannel scheme for preventing coefficient fluctuation due to the presence of target echoes or impulse interferences is also discussed. The proposed eigenfilter recursively estimates the minimum eigenvector of the input clutter covariance matrix based on the inverse power method (IPM). In the proposed scheme, the IPM iteration is performed in a numerically efficient way using systolic processing architectures. Simulation results demonstrate that the convergence speed of the eigenfilter is faster than that of the prediction error filters and IF values of the eigenfilter always approach the optimum. The multichannel adaptive eigenfilter is shown to be a robust scheme preventing coefficient fluctuation in the presence of target echoes.<<ETX>>

Quality Improvement of Karaoke Mode in SAOC using Cross Prediction based Vocal Estimation Method

In this paper, we present a vocal suppression algorithm that can enhance the quality of music signal coded using Spatial Audio Object Coding (SAOC) in Karaoke mode. The residual vocal component in the coded music signal is estimated by using a cross prediction method in which the music signal coded in Karaoke mode is used as the primary input and the vocal signal coded in Solo mode is used as a reference. However, the signals are extracted from the same downmix signal and highly correlated, so that the music signal can be severely damaged by the cross prediction. To prevent this, a psycho-acoustic disturbance rule is proposed, in which the level of disturbance to the reference input of the cross prediction filter is adapted according to the auditory masking property. Objective and subjective test were performed and the results confirm that the proposed algorithm offers improved quality.

Improved Synthesis Method of Negative Inter-channel Correlation Parameter Based on Anti-phase Primary Component

Parametric stereo(PS) and MPEG surround(MPS) are major spatial audio coding(SAC) tools. In this paper, the problem of the inter-channel correlation(ICC) synthesis in the conventional SAC is analyzed. Conventional methods assume that ambient components mixed to two output channels are anti-phased, while the primary components are assumed to be in-phased. This assumption can cause excessive ambient mixing for a negative-valued ICC. As a remedy to this problem, we propose a new ICC synthesis method based on an assumption that the primary components are anti-phased each other for a negative ICC. The proposed method is also applied to the approximation which works in practice. The performance of the proposed method was evaluated by computer simulations and the subjective listening tests verified that the proposed method is effective in not only headphones but also loudspeakers playback.

Multichannel lattice filter for an adaptive array processor with linear constraints

It is proposed to implement the linearly constrained adaptive array processor using multichannel lattice filter. Due to the Gram Schmidt orthogonalization properties of the lattice structure, the proposed realization converges faster and yields smaller estimation errors than the TDL counterpart. Computer simulation results comparing the performances of the mulichannel TDL and lattice filters for the linearly constrained adaptive array processing problem are presented.