• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2021.06a
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• pp.57-60
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• 2021

오디오 대역 확장 기술은 저 해상도의 오디오 신호를 고 해상도의 오디오 신호로 복원 또는 생성해 내는 기술이다. 이와 관련하여 오디오 코덱에서는 고 대역 오디오 신호의 저 비트 부호화를 위해 사람이 청각이 둔감하게 인지하는 고 대역의 오디오 신호에 대해 실제 신호에 대한 양자화를 수행하지 않고, 코딩 되어 전송된 저 대역 신호와 고 대역의 파라미터를 이용하여 신호를 합성하는 스펙트럼 대역 복제 기술이 널리 사용된다. 본 연구에서는 선형 예측 기반의 주파수 대역 복제 방법을 통해 추가 정보를 활용한 오디오 대역 확장을 수행하고 신경망 기반의 오디오 신호 개선을 통해 복제된 신호의 개선 가능성을 검토하였다. 실험 평가는 MPEG 에서 코덱 평가용으로 사용되는 테스트 시퀀스를 사용하였으며, 실험 결과 제안하는 방법을 적용하여 기존 오디오 대역 확장 기술 대비 성능이 향상됨을 확인하였다.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.12
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• pp.197-204
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• 2013

In this paper, we propose a new method for artificial bandwidth extension of narrow-band signal in frequency domain. In the proposed method, a narrow-band signal is decomposed into excitation signal and spectral envelope, which are extended independently in frequency domain. The excitation signal is extended such that low-band harmonic structure is maintained in high band, and the spectral envelope is extended based on sub-band energy using NMF. Finally, the spectral phase is determined based on signal correlation between frames in time domain, resulting in the final wide-band signal. The subjective evaluation verified that the wide-band signal generated by the proposed method has a higher quality than the original narrow-band signal.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.4
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• pp.1072-1086
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• 1998

Transform, subband, and wavelet transform decompositions are powerful linear transformation tools in image coding because of their decorrelating effects on image pixels, the concentration of energy in a few coefficients, their multirat/multiresolution framework, and their frequency splitting, which allows for efficient coding matched to the statistics of each frequency band and to the characteristics of the human visulal system. Thus, a growingbody of research has bee performed to extend these tools in various kinds of modified formations. Hence, in this paper, an overall survey to achieve a general view on these transformation tools have been attempted. Starting from basic tools such as orthogonal transforms, lapped transforms, QMF(quadrature mirror filter) subband filter banks, and wavelet transforms, their hierarchical extensions, vector extensions, and linear time-varying extensions are investugated in detail.

• The Journal of the Acoustical Society of Korea
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• v.30 no.4
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• pp.190-196
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• 2011

Bandwidth extension is a technique to improve speech quality and intelligibility, extending from 300-3400 Hz narrowband speech to 50-7000 Hz wideband speech. This paper designs an artificial bandwidth extension (ABE) module embedded in the AMR (adaptive multi-rate) decoder, reducing LPC/LSP analysis and algorithm delay of the ABE module. We also introduce a fast search codebook mapping method for ABE, and design a low power BWE technique based on the AMR decoder. The proposed ABE method reduces the computational complexity and the algorithm delay, respectively, by 28 % and 20 msec, compared to the traditional DTE (decode then extend) method. We also introduce a weighted classified codebook mapping method for constructing the spectral envelope of the wideband speech signal.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2021.06a
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• pp.63-64
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• 2021

본 논문은 wavenet을 이용하여 음성 신호의 대역폭을 확장하는 새로운 모델을 제안한다. 기존의 대역폭 확장은 주로 주파수 영역에서 진행되며, 확장 대역의 주파수 크기는 높은 성능으로 복원하지만 위상 정보를 정확히 복원할 수 없다는 문제점을 가진다. 이를 해결하기 위해 wavenet 모델을 기반으로 시간 영역에서 저대역과 고대역의 상관관계를 이용하여 고대역 성분을 생성하도록 한다. 제안하는 방법은 모든 동작을 시간 영역에서 수행하며, 제안 방법으로 생성한 고대역 성분이 원음의 고대역 성분과 유사한 것을 확인하였다.

• Journal of IKEEE
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• v.24 no.4
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• pp.1122-1128
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• 2020

Bandwidth Extension refers to restoring and expanding a narrow band signal(NB) that is damaged or damaged in the encoding and decoding process due to the lack of channel capacity or the characteristics of the codec installed in the mobile communication device. It means converting to a wideband signal(WB). Bandwidth extension research mainly focuses on voice signals and converts high bands into frequency domains, such as SBR (Spectral Band Replication) and IGF (Intelligent Gap Filling), and restores disappeared or damaged high bands based on complex feature extraction processes. In this paper, we propose a model that outputs an bandwidth extended signal based on an autoencoder among deep learning models, using the residual connection of one-dimensional convolutional neural networks (CNN), the bandwidth is extended by inputting a time domain signal of a certain length without complicated pre-processing. In addition, it was confirmed that the damaged high band can be restored even by training on a dataset containing various types of sound sources including music that is not limited to the speech.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.39 no.5
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• pp.486-493
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• 2002

In this paper, we proposed the effective multispectral image compression method using CIBP(classified interband bidrectional prediction) and extended SPIHT(set partition in hierarchical trees) in wavelet domain. We determine separately feature bands that have the highest correlation with other bands in the visible range and in the infrared range of wavelengths. Feature bands are coded to remove the spatial redundancy with SPIHT in the wavelet domain. Prediction bands that have high correlation with feature bands are wavelet transformed and they are classified into one of three classes considering reflection characteristics of the baseband. For Prediction bands, CIBP is performed to reduce the spectral redundancy. for the difference bands between prediction bands and the predicted bands, They are ordered to upgrade the compression efficiency of extended SPIHT with the largest error magnitude. The arranged bands are coded to compensate the prediction error with extended SPIHT. Experiments are carried out on the multispectral images. The results show that the proposed method reconstructs higher quality images than images reconstructed by the conventional methods at the same bit rate.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.1-5
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• 2017

In this paper, we propose a wideband band-stop filter (BSF) in order to extend the stopband of the band-stop filter using a symmetric dual spurline and the coupled open stub. First, we know that the symmetric dual spurline structure is advantageous in widening the stopband, as compared to the asymmetric dual spurline structure. So we designed a band-stop filter that combines the electrically coupled open stub (ECOS) band-stop filter with a symmetric dual spurline. We can greatly extend the stopband, when it is combined with the dual spurline and electrically coupled open stub on a microstrip transmission line, without any size increment. The stopband of the proposed band-stop filter is extended by approximately 244% (rejection depth: -20 dB) compared with a band-stop filter without a dual spurline.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.245-250
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• 1999

일반적으로 초음파현미경에서 획득한 초음파 영상은 단일 동작주파수를 사용하여 획득하였으며, 분해능은 동작주파수와 초음파변환기에 의해 결정되는 공간주파수 대역에 의하여 제한되어 졌다. 본 연구에서는 초음파현미경에서 동작주파수를 변화시키면서 획득한 영상들을 합성하여 공간주파수의 축 방향 대역을 확장시킨 개선된 고체 내부의 진폭영상을 얻는 방법에 대하여 연구하였다. 실험에서는 동작주파수가 5MHz이고 비대역폭이 $35\%$인 초음파변환기를 사용하여 초음파현미경 시스템을 구성하였고, 이러한 처리를 위해서는 진폭과 위상영상 데이터가 필요하기 때문에 진폭과 위상을 동시에 획득할 수 있도록 검출기로서 쿼드러춰 검출기를 사용하였다. 시편으로는 알루미늄을 선택하였고, 시료의 표면으로부터 깊이를 다르게 하여 내부에 4개의 원형결함을 제작하였다. 실험결과 단일 주파수를 사용한 경우에는 결함의 형태는 나타났으나, 고체 내부 결함의 깊이와 영상 강도의 변화가 비례하여 나타나지 않는 반면에, 개선된 영상에서는 깊이 변화에 대해서 영상 강도의 변화가 비례하여 출력되었다.

• Journal of Digital Contents Society
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• v.18 no.6
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• pp.1207-1211
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• 2017

Long-Reach PON (LR-PON) is a broadband access network using passive optical network (PON) technology which the reach is extended to 100 km or higher. A major challenge in LR-PON is that the propagation delay between OLT and ONUs is increased by a very significant amount. To effectively and fairly distribute the upstream bandwidth dynamically in LR-PON, we propose a new periodic and multi-thread polling based dynamic bandwidth allocation (DBA) algorithm. We compare the proposed algorithm with traditional DBAs and show its advantage on average packet delay. Numerical results are analyzed under varying offered loads.