Jeongil Seo

Maximization of acoustic energy difference between two spaces

There has recently been an increasing interest in the generation of a sound field that is audible in one spatial region and inaudible in an adjacent region. The method proposed here ensures the control of the amplitude and phase of multiple acoustic sources in order to maximize the acoustic energy difference between two adjacent regions while also ensuring that evenly distributed source strengths are used. The performance of the method proposed is evaluated by computer simulations and experiments with real loudspeaker arrays in the shape of a circle and a sphere. The proposed method gives an improvement in the efficiency of radiation into the space in which the sound should be audible, while maintaining the acoustic pressure difference between two acoustic spaces. This is shown to give an improvement of performance compared to the contrast control method previously proposed.

A multi-channel audio compression method with virtual source location information for MPEG-4 SAC

Binaural cue coding (BCC) was introduced as an efficient representation method for MPEG-4 SAC (spatial audio coding). However, in a low bit-rate environment, the spectrum of BCC output signals degrades with respect to the perceptual level. The proposed system in this paper estimates VSLI (virtual source location information) as the side information. The VSLI is the angle representation of spatial images between channels on playback layout. The subjective assessment results show that the proposed method provides better audio quality than the BCC method for encoding multi-channel signals.

Development of Multichannel Sound Scene Visualization Tool with MPEG Surround Multichannel Decoder

In this paper, a multichannel sound scene visualization tool is designed and implemented based on MPEG surround multichannel decoder. The aim of this tool is to effectively display frequency dependent dynamic characteristics of multichannel sound scene. It uses only spatial cue parameters extracted from MPEG Surround bitstream without additional computations such as T/F transform.

Enhancement of principal to ambient energy ratio for PCA-based parametric audio coding

In this paper, we propose a method of restoring principal to ambient energy ratio (PAR) at the decoder in the principal component analysis (PCA)-based parametric audio coding. The conventional approach applies the post-scaling at the decoder using the energy information extracted from the input signal at the encoder. However, this approach has a problem that the relative energy of principal source in the reconstructed signal is smaller than the original signal and also affected by the panning angle of principal source. To restore the PAR at the decoder, the proposed method estimates the post-scaling factors using parametric information extracted from PCA-based formulation. The objective and subjective results verify the performance improvement of proposed method.

Variable Subband Analysis for High Quality Spatial Audio Object Coding

Spatial Audio Object Coding (SAOC) handles a number of audio objects to provide a user with active audio services. It represents all objects as a stereo downmixed signal with some side information, and the bitrate can be significantly reduced compared to that of the conventional audio coders. In spite of the advantage of bitrate reduction, the SAOC has the severe problem such as the degradation of sound quality. To solve the problem while minimizing increase of the bitrate, variable subband analysis and the revised SAOC structure called two-step structure were proposed in this paper. Through a subjective listening test, it was confirmed that the proposed method improves sound quality by a small bitrate increase.

Spatial Audio Object Coding With Two-Step Coding Structure for Interactive Audio Service

An interactive audio service is a new conceptual audio service that provides the users with opportunities for a variety of experiences on the alternative and advanced audio services. In the interactive audio service, users can freely control various audio objects to make their own audio sounds. A spatial audio object coding (SAOC) is a useful technology that can support most parts of the interactive audio service with a relatively low bit-rate, but is very poor to perfect gain control of a certain audio object, i.e., the target audio object. In this paper, the SAOC with a two-step coding structure is proposed to efficiently handle the target audio object as well as the normal audio objects. A transform coded excitation (TCX) based residual coding scheme is presented in the context of the sound quality enhancement. From experimental results, it can be noted that the various audio objects can be successfully handled with respect to the bit-rate and the sound quality by using the proposed two-step coding structure SAOC.

Spatial Cue Based Sound Scene Control for MPEG Surround

Spatial audio coding scheme is advanced technology in the sense of saving bitrate without any scarifications of sound quality. In this paper, the method to utilizing the spatial cues is present. This utilization is for supporting a new useful functionality, i.e., flexible sound scene control. The function of sound scene control may result in providing user preferable audio service by interaction and be utilized in upcoming applications such as multi-view video service and virtual reality applications. It will be shown that even with a little addition of computational operations; this useful functionality will be achievable maintaining the corresponding sound quality.

Audio Transcoding for Audio Streams from a T-DTV Broadcasting Station to a T-DMB Receiver

We propose an efficient audio transcoding algorithm that can convert audio streams from terrestrial digital television broadcasting service stations to those for terrestrial digital multimedia broadcasting hand-held receivers. The proposed algorithm avoids the complicated psychoacoustic analysis by calculating the scalefactors of the bit-sliced arithmetic coding encoder directly from the signal-to- noise ratio parameters of the AC-3 decoder. The bit-allocation process is also simplified by cascading the nested distortion control loop. Through subjective evaluation, it is shown that the proposed algorithm provides comparable audio quality to tandem coding but it requires much smaller complexity.

Residual signal compression based on the blind signal decomposition for video coding

In this paper, a new residual signal compression method is proposed based on the blind signal decomposition for video coding. Blind signal decomposition is derived based on the fact that most of the natural signals in the real world could be decomposed into their basis signals and their weight values used in the composition process. In the proposed video coding system, composite data generated by adding two or more blocks are coded. Then the proposed decoder parses the coded bitstream and reconstructs the composite residual. The reconstructed composite residual is decomposed into the original residual blocks based on the blind signal decomposition. In the proposed system, the blind source separation is selectively used, depending on the performance of source separation. It is found that we can achieve approximately 2 ∼ 3dB gain by embedding our algorithm into an MPEG-4 baseline encoder.

Tiled panoramic video transmission system based on MPEG-DASH

This paper presents a panoramic video transmission system using spatially divided tiles based on the spatial relationships descriptions of MPEG-DASH. The proposed server system provides tiling and encoding functionalities for ROI-based retrieving. Moreover, it guarantees the temporal and spatial synchronization when rendering multiple tiles by a deterministic tile size and intra-coded frames at the starting of all segments. Finally, we conduct a performance evaluation with panoramic videos at the eight HD-quality to show the feasibility of the tile-based transmission.