Hong-Seok Kwon

Modification of Polar Echo Kernel for Performance Improvement of Audio Watermarking

In this paper, we present a new echo kernel, which is a modification of polar echo kernel, to improve the detection performance and robustness against attacks. Polar echo kernel may have the advantage of large detection margin from the polarity of inserted echo signal, but its poor frequency response in low frequency band degrades sound quality. To solve this problem, we applied bipolar echo pulses to the polar echo kernel. Using the proposed echo kernel, the distributions of autocepstrum peaks for data ‘0’ and ‘1’ are located more distant and improvement of detection performance is achieved. It also makes the low frequency band flat so that the timbre difference in the polar echo kernel can be removed to reproduce the imperceptible sound quality. Informal listening tests as well as robustness test against attacks were performed to evaluate the proposed echo kernel. Experimental results demonstrated the superiority of the proposed echo kernel to both conventional unipolar and polar echo kernels.

Real time implementation of MPEG-1 Layer III audio decoder with TMS320C6201 DSP

The goal of this research is the real-time implementation of an MPEG-1 Layer III audio decoder using the TMS320C6201 fixed-point digital signal processor (DSP). The main jobs for this work are twofold: one is to convert the floating-point operation in the decoder into a fixed-point operation while maintaining high resolution, and the other is to optimize the program to make it run in real time with a memory size that is as small as possible. The implemented decoder uses 6.77 kwords of program memory, 3.13 kwords of data ROM and 9.94 kwords of data RAM, respectively. It also uses about 26% of the maximum computation capacity of the TMS320C6201. Comparing the PCM (pulse code modulation) output of the fixed-point computation with that of the floating-point computation for test bit streams, we achieved a signal-to-noise ratio (SNR) of more than 60 dB.

Endpoint Detection of Isolated Korean Utterances for Bimodal Speech Recognition in Acoustic Noisy Environments

This paper proposes a reliable endpoint detection method for a bimodal system in an acoustically noisy environment. Endpoints are detected in the audio and video signals, and then suitable ones are selected depending on the signal-to-noise ratio (SNR) estimated in the input audio signal. Experimental results show that the proposed method can significantly reduce a detection error rate and produce acceptable recognition accuracy in a bimodal system, even with a very low SNR.