• Title/Summary/Keyword: IMDCT

Search Result 33, Processing Time 0.023 seconds

Audio /Speech Codec Using Variable Delay MDCT/IMDCT (가변 지연 MDCT/IMDCT를 이용한 오디오/음성 코덱)

  • Sangkil Lee;In-Sung Lee
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
    • /
    • v.16 no.2
    • /
    • pp.69-76
    • /
    • 2023
  • A high-quality audio/voice codec using the MDCT/IMDCT process can perfectly restore the current frame through an overlap-add process with the previous frame. In the overlap-add process, an algorithm delay equal to the frame length occurs. In this paper, we propose a MDCT/IMDCT process that reduces algorithm delay by using a variable phase shift in MDCT/IMDCT process. In this paper, a low-delay audio/speech codec was proposed by applying the low delay MDCT/IMDCT algorithm to the ITU-T standard codec G.729.1 codec. The algorithm delay in the MDCT/IMDCT process can be reduced from 20 ms to 1.25 ms. The performance of the decoded output signal of the audio/speech codec to which low-delay MDCT/IMDCT is applied is evaluated through the PESQ test, which is an objective quality test method. Despite of the reduction in transmission delay, it was confirmed that there is no difference in sound quality from the conventional method.

An Efficient Algorithm for Improving Calculation Complexity of the MDCT/IMDCT (MDCT/IMDCT의 계산 복잡도를 개선하기 위한 효율적인 알고리즘)

  • 조양기;이원표;김희석
    • Journal of the Institute of Electronics Engineers of Korea SP
    • /
    • v.40 no.6
    • /
    • pp.106-113
    • /
    • 2003
  • The modified discrete cosine transform (MDCT) and inverse MDCT (IMDCT) are employed in subband/transform coding schemes as the analysis/synthesis filter bank based on time domain aliasing cancellation (TDAC). And the MDCT and IMDCT are the most computational intensive operations in layer III of the MPEG audio coding standard. In this paper, we propose a new efficient algorithm for the MDCT/IMDCT computation in various audio coding systems. It is based on the MDCT/IMDCT computation algorithm using the discrete cosine transforms (DCTs), and It employs two discrete cosine transform of type II (DCT-II) to compute the MDCT/IMDCT In addition, it takes advantage of ability in calculating the MDCT/IMDCT computation, where the length of a data block Is divisible by 4. The Proposed algorithm in this paper requires less calculation complexity than the existing method does. Also, it can be implemented by the parallel structure, therefore its structure is particularly suitable for VLSI realization

A Fast IFFT Algorithm for IMDCT of AAC Decoder (AAC 디코더의 IMDCT를 위한 고속 IFFT 알고리즘)

  • Chi, Hua-Jun;Kim, Tae-Hoon;Park, Ju-Sung
    • The Journal of the Acoustical Society of Korea
    • /
    • v.26 no.5
    • /
    • pp.214-219
    • /
    • 2007
  • This paper proposes a new IFFT(Inverse Fast Fourier Transform) algorithm, which is proper for IMDCT(Inverse Modified Discrete Cosine Transform) of MPEG-2 AAC(Advanced Audio Coding) decoder. The $2^n$(N-point) type IMDCT is the most powerful among many IMDCT algorithms, however it includes IFFT that requires many calculation cycles. The IFFT used in $2^n$(N-point) type IMDCT employ the bit-reverse data arrangement of inputs and N/4-point complex IFFT to reduce the calculation cycles. We devised a new data arrangement method of IFFT input and $N/4^{n+1}$-type IFFT and thus we can reduce multiplication cycles, addition cycles, and ROM size.

A New Algorithm for An Efficient Implementation of the MDCT/IMDCT (MDCT/IMDCT의 효율적인 구현을 위한 새로운 알고리즘)

  • 조양기;이원표;인치호;김희석
    • Proceedings of the IEEK Conference
    • /
    • 2003.07e
    • /
    • pp.2471-2474
    • /
    • 2003
  • The modified discrete cosine transform (MDCT) and its inverse transform (IMDCT) are employed in subband/transform coding schemes as the analysis/synthesis filter bank based on time domain aliasing cancellation (TDAC). And they are the most computational intensive operations in layer III of the MPEG audio coding standard. In this paper, we propose a new efficient algorithm for the MDCT/IMDCT computation. It is based on the MDCT/IMDCT computation algorithm using the discrete cosine transforms (DCTs), and it employs two discrete cosine transform of type II(DCT-II) to compute the MDCT/IMDCT. In addition to, it takes advantage of ability in calculating the MDCT/IMDCT computation, where the length of a data block is divisible by 4. The proposed algorithm in this paper requires less calculation complexity than the existing methods. Also, it can be implemented by the parallel structure,, and its structure is particularly suitable for VLSI realization.

  • PDF

A Low-Delay MDCT/IMDCT

  • Lee, Sangkil;Lee, Insung
    • ETRI Journal
    • /
    • v.35 no.5
    • /
    • pp.935-938
    • /
    • 2013
  • This letter presents an algorithm for selecting a low delay for the modified discrete cosine transform (MDCT) and inverse MDCT (IMDCT). The implementation of conventional MDCT and IMDCT requires a 50% overlap-add (OLA) for a perfect reconstruction. In the OLA process, an algorithmic delay in the frame length is employed. A reduced overlap window and MDCT/IMDCT phase shifting is used to reduce the algorithmic delay. The performance of the proposed algorithm is evaluated by applying the low-delay MDCT to the G.729.1 speech codec.

A low-power systolic structure for MP3 IMDCT Using addition and shift operation (덧셈과 쉬프트 연산을 사용한 MP3 IMDCT의 저전력 Systolic 구조)

  • Jang Young Beom;Lee Won Sang
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.29 no.10C
    • /
    • pp.1451-1459
    • /
    • 2004
  • In this paper, a low-power 32-point IMDCT structure is proposed for MP3. Through re-odering of IMDCT matrices, we propose the systolic structure operating with 16, 8, 4, 2, and 1 cycle, respectively. To reduce power consumption, multiplication of each sub blocks are implemented by add and shift operation with CSD(Canrmic sigled digit) form coefficients. To reduce, furthermore, the number of adders, we utilize the common sub-expression sharing techniques. With these techniques, the relative power consumption of the proposed structure is reduced by 58.4% comparison to the conventional structure using only 2's complement form coefficient. Validity of the proposed structure is proved through Verilog-HDL coding.

Executable Specification based Design Methodology - MPEG Audio IMDCT Design and Functional Verification (Executable Specification 기법을 이용한 MPEG Audio용 IMDCT 설계 및 기능검증)

  • 박원태;조원경
    • Proceedings of the IEEK Conference
    • /
    • 2000.06b
    • /
    • pp.173-176
    • /
    • 2000
  • Silicon semiconductor technology agree that the number of transistors on a chip will keep growing exponentially, and it is pushing technology toward the System-On-Chip. In SoC Design, Specification at system level is key of success. Executable Specification reduce verification time. This Paper describe the design of IMDCT for MPEG Audio Decoder employing system-level design methodology and Executable Specification Methodology in the VHDL simulator with FLI environment.

  • PDF

A Development on the Optimization Algorithm for MDCT/IMDCT of MPEG-2 AAC (MPEG-2 AAC의 MDCT/IMDCT를 위한 최적 알고리즘 개발)

  • 김병규;이강현
    • Proceedings of the IEEK Conference
    • /
    • 1999.06a
    • /
    • pp.538-541
    • /
    • 1999
  • MPEG-2 AAC(Advanced Audio Coding) is the most advanced coding scheme available for high quality audio coding. This MPEG-2 AAC audio Standard allows for ITU-R ‘indistinguishable’ quality according to at data rates of 320 kb/s for five full-bandwidth channel audio signals. The compression ratio is around a factor of 1.4 better compared to MPEG Layer 3, you get the same quality at 70% of the bitrate. This paper suggest optimization method for MDCT/IMDCT (Modified Discrete Cosine Transform/Inverse Modified Discrete Cosine Transform) in Encoder and Decoder for AAC.

  • PDF

The Design of Vector Processor for MDCT/IMDCT of MPEG-II AAC (MPEG-II AAC의 MDCT/IMDCT를 위한 벡터 프로세서 설계)

  • 이강현
    • Proceedings of the IEEK Conference
    • /
    • 1999.06a
    • /
    • pp.329-332
    • /
    • 1999
  • Currently, the most important technology is compression methods in the multimedia society. In audio compression, the method using human auditory nervous property is used. This method using psychoacoustical model is applied to perceptual audio coding, because human's audibility is limited. MPEG-II AAC(Advanced Audio Coding) is the most advanced coding scheme that is of benefit to high quality audio coding. The compression ratio is 1.4 times compared with MPEG-I layer-III. In this paper, the vector processor for MDCT/IMDCT(Modified Discrete Cosine Transform /Inverse Modified Discrete Cosine Transform) of MPEG-II AAC is designed.

  • PDF

MDCT/IMDCT (MPEG 오디오 신호처리를 위한 MDCT/IMDCT의 FPGA 구현)

  • 노진수;이강현
    • Proceedings of the Korea Multimedia Society Conference
    • /
    • 2003.05b
    • /
    • pp.69-73
    • /
    • 2003
  • 음향압축에 있어서 인간의 청각신경의 특성을 이용하는 방식이 사용되고 있다. 이러한 방법은 심리음향모델(psychoacustical model)에서 도입되었다. 음향압축에서는 이러한 심리음향모델을 사용하여 인간이 지각할 수 없는 한도 내에서 부호화하지 않는 지각음향부호화(perceptual audio coding)사용한다. 지각음향부호화는 분석필터와 합성필터로 각각 부호화 복호화하는데 이것은 필터뱅크(filter bank)로 구현된 서브밴드코더(subband coder) 이다. 본 논문에서는 분석필터와 합성필터에 사용되는 MDCT(Modified Discrete Cosine Transform)와 IMDCT(Inverse Modified Discrete Cosine Transform)를 FPGA에 구현하였다.

  • PDF