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AMR 기반 저 전력 대역 확장 기술 개발

Title
AMR 기반 저 전력 대역 확장 기술 개발
Other Titles
Developing a low power BWE technique based on the AMR coder
Author
구본강
Alternative Author(s)
Koo, Bon Kang
Advisor(s)
강상원
Issue Date
2011-02
Publisher
한양대학교
Degree
Master
Abstract
대역폭 확장(bandwidth extension)은 0.3~3.4kHz 대역의 협대역 (narrow band) 음성 신호를 0.05~8kHz의 광대역(wideband) 음성 신호로 확장하여 기존 협대역 음성 신호의 음질(quality)과 명료도(intelligibility)를 높이는 기술이다. 본 논문에서는 협대역 음성 정보만을 이용해서 광대역 음성신호를 생성하는 인공 대역폭 확장(artificial bandwidth extension)을 설계하여, ITU-T 협대역 표준 음성 코덱인 AMR(adaptive multi-rate) 시스템의 복호화기에 내장시킴(embedded)으로써, 기존의 대역폭 확장 모듈에서의 LPC 분석 및 LSF 해석에 관련 계산량을 18% 감소시켰고, 알고리즘 지연을 20ms 감소시켰다. 그리고 코드북 매핑 모듈의 계산량 감소를 위해 SDS(single distance search) 방식과 LSF 계수의 순서 성질을 이용한 고속 탐색 방식을 설계하여 전체 탐색에 비해 계산량을 47% 감소시켰고, 이를 대역폭 확장 시스템의 코드북 탐색에 적용한 저 전력의 대역 확장 AMR 복호화기를 설계하였다. 제안된 대역폭 확장 방법은 AMR 복호화기의 피치정보를 이용한 classified 코드북 매핑방식을 사용한 스펙트럼 포락선 확장과 스펙트럼 시프팅을 이용한 여기(excitation) 신호 확장을 기초로 한다. 또한 과거와 현재 프레임간의 상관도를 이용한 time-smoothing 필터를 설계하고, 코드 벡터 각각에 가중치(weighting)를 계산하여 적용함으로써 출력되는 광대역 음질의 PESQ(perceptual evaluation of speech quality)를 0.015 향상시켰다. | This paper proposes a low power artificial bandwidth extension (ABE) technique that is embedded into the ITU-T AMR narrowband speech coder. For the low power ABE system, we propose a reduced complexity codebook mapping method for LSP parameters. The method uses two criteria to reduce the size of the narrowband LSP codebook that should be searched. In the first criterion, the distortion of a specific element of the input vector is compared with a threshold to reduce the codebook search range. In the second criterion, the LSF ordering property is used to reduce the codebook search range. A weighted classified codebook mapping method is also proposed for constructing the spectral envelope of the wideband speech signal. Classified codebooks are used to reduce spectrum mapping errors caused by characteristic difference voiced and unvoiced sound. The weighted distortion measure is also used to handle the spectral sensibility. The performance of the proposed ABE system is evaluated by a perceptual evaluation of speech quality (PESQ), informal listening tests and weighted million operations per second (WMOPS) calculations. With the use of fast codebook mapping, the WMOPS complexity of the codebook mapping module is reduced by 47%.
This paper proposes a low power artificial bandwidth extension (ABE) technique that is embedded into the ITU-T AMR narrowband speech coder. For the low power ABE system, we propose a reduced complexity codebook mapping method for LSP parameters. The method uses two criteria to reduce the size of the narrowband LSP codebook that should be searched. In the first criterion, the distortion of a specific element of the input vector is compared with a threshold to reduce the codebook search range. In the second criterion, the LSF ordering property is used to reduce the codebook search range. A weighted classified codebook mapping method is also proposed for constructing the spectral envelope of the wideband speech signal. Classified codebooks are used to reduce spectrum mapping errors caused by characteristic difference voiced and unvoiced sound. The weighted distortion measure is also used to handle the spectral sensibility. The performance of the proposed ABE system is evaluated by a perceptual evaluation of speech quality (PESQ), informal listening tests and weighted million operations per second (WMOPS) calculations. With the use of fast codebook mapping, the WMOPS complexity of the codebook mapping module is reduced by 47%.
URI
https://repository.hanyang.ac.kr/handle/20.500.11754/139558http://hanyang.dcollection.net/common/orgView/200000415746
Appears in Collections:
GRADUATE SCHOOL[S](대학원) > ELECTRONIC,ELECTRICAL,CONTROL & INSTRUMENTATION ENGINEERING(전자전기제어계측공학과) > Theses (Master)
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