Hochong Park

Efficient codebook search method of EVRC speech codec

An efficient enhanced variable rate codec (EVRC) codebook search method based on a two-stage search is proposed. At the first stage, a coarse codevector is selected by a fast sequential search, and at the second stage, the pulse replacement procedure is run to enhance the performance of selected codevector. Simulations with various speech data show that the proposed method yields voice quality equivalent to that by the standard method with only 23% codebook search load.

Improving the Speech Quality of VoIP by Packet Prioritization

This letter proposes a new method of improving the speech quality of VoIP by assigning a priority to each packet at the edge router of a DiffServ-based network. The proposed method determines the importance of a packet in the parameter domain by estimating the quality degradation caused by its loss and assigns a priority to the packet according to its importance, which ensures that important packets are more robust during transmission. The subjective and objective evaluation shows that the proposed method improves the VoIP speech quality in an environment prone to packet loss.

Improving Perceptual Quality of Speech in a Noisy Environment by Enhancing Temporal Envelope and Pitch

This letter proposes a new method of improving perceptual quality of speech in a noisy environment. Based on the perception theory that the temporal envelope plays a major role in assessing intelligibility, the proposed method uses a novel operation that enhances the fluctuation of the band-wise temporal envelope. It also contains pitch enhancement in frequency domain to further improve the perceptual quality. A new subjective evaluation scheme employing binaural listening is proposed in order to measure perceptual quality more reliably. The subjective evaluation shows that the proposed method improves perceptual quality of speech in various noisy environments.

Location Estimation of Predominant Sound Source with Embedded Source Separation in Amplitude-Panned Stereo Signal

This letter proposes a new method of estimating the location of a predominant source in an amplitude-panned stereo signal with two sources. When the conventional method of location estimation is applied to an amplitude-panned multi-source sound, a serious estimation error occurs due to interference between sources. To solve this problem, the proposed method includes an embedded source separation based on non-negative matrix factorization, which first determines the initial estimate of source location, and then computes the basis matrix of the source using the initial location estimate. In this way, the proposed method can perform the source separation without a training stage. The comparative evaluation confirms that the proposed method provides higher performance in location estimation than the conventional method with a training stage.

Measurement of Rhythmic Similarity for Auditory Memory Game

In this paper, a method for measuring rhythmic similarity between two sound signals for auditory memory game is proposed. The proposed method analyzes energy fluctuation, the temporal duration of energy peak, the timbre of two signals, and detects beat positions for each signal. Then, it determines the rhythm vector after compensating a difference in tempo and the number of beats between two signals. Finally, a method for rhythmic similarity measurement is defined as a function of the dissimilarity between two rhythm vectors and a difference in the number of beats. The rhythmic similarity measured by the proposed method and that by the subjective listening test are compared, and the correlation of 0.86 between two results is achieved.

Fast Graphic Visualization of Frequency Response for Audio Equalizer

This paper proposes a new method for fast graphic visualization of accurate frequency response of audio equalizer (EQ). When a logarithmic frequency scale is used, a frequency response in high resolution is required for accurate low-band frequency response. However, the high-resolution frequency response requires a huge amount of computational load, which makes the real-time graphic visualization of frequency response impossible. In order to solve the problem of computational load, the proposed method utilizes a low-resolution virtual frequency response in the mid band. It first computes the virtual frequency response of each filter of EQ in the mid band, and then moves it to the target band so that the result corresponds to the desired filter response. Then, it determines the final frequency response of EQ by combining all filter responses. The experiments confirm that the proposed method provides the frequency response of EQ which has an equivalent shape to that computed in high frequency resolution with huge computational load.

Implementation of Stereophonic Sound System Using Multiple Smartphones

In this paper, we propose a stereophonic sound system using multiple smartphones. In the conventional sound systems using smartphones, all devices play the same signal so that it is difficult to provide true stereophonic effect. In order to solve this problem, we propose a novel sound system which can generate a virtual sound source at any location in such a way that smartphones at different locations play different signals with amplitude panning. By using the proposed system, we can generate more realistic stereophonic effect than the conventional system, and can control the sound effect by users command. We developed the proposed system using commercial smartphones and verified that the developed sound system effectively provides the desired stereophonic effect.

Vocal Enhancement for Improving the Performance of Vocal Pitch Detection

This paper proposes a vocal enhancement technique for improving the performance of vocal pitch detection in polyphonic music signal. The proposed vocal enhancement technique predicts an accompaniment signal from the input signal and generates an accompaniment replica signal according to the vocal power. Then, it removes the accompaniment replica signal from the input signal, resulting in a vocal-enhanced signal. The performance of the proposed method was measured by applying the same vocal pitch extraction method to the original and the vocal-enhanced signal, and the vocal pitch detection accuracy was increased by 7.1 % point in average.

An Efficient Error Compensation Method for Thumbnail Extraction in H.264/AVC Bitstreams

Recently, high definition media services like HDTV and IPTV are growing. A fast reduced-size image extracting method is required to meet what those services require. Conventional DC image extracting methods, however, can`t be applied to H.264/AVC streams since a spatial domain prediction scheme is adopted in H.264/AVC intra mode. To solve this problem, a thumbnail extraction method in H.264/AVC was proposed. However, the method has mismatch problem which was caused by round-off operation in intra prediction and mismatch between integer and floating point calculation. In this paper, we propose an error compensation method for extracting thumbnail directly in H.264/AVC bitstreams. The compensation method introduces the mismatch problem in thumbnail extraction and presents compensation values. Through the implementation and performance evaluation, proposed method compensated round-off error efficiently in D1 and HD sequences while the additional extraction time is negligible.