Adaptive block length, constant converting audio frequency decoding method

An audio and inverse transformation technology, applied in the direction of code conversion, speech analysis, electrical components, etc., can solve problems that have not been raised

Inactive Publication Date: 2006-11-15
NERO AG
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  • Adaptive block length, constant converting audio frequency decoding method
  • Adaptive block length, constant converting audio frequency decoding method
  • Adaptive block length, constant converting audio frequency decoding method

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[0034] A problem with prior art audio transform decoders using adaptively varying block lengths is that they are not suitable for fixed transform length processing. The present invention solves this problem by refactoring the decoder to support the use of fixed-length inverse transforms.

[0035] The invention is limited to transform lengths that are powers of 2, practically no limit, since this describes the lengths used in all known audio codecs. Throughout the specification, we will use N to describe the number of MDCT coefficients, which is derived from the encoding block's length 2N samples. The length M describes the length of the fixed-length inverse transform in the number of spectral coefficients. The length N may vary between blocks of received MDCT coefficients, but the transform length M will remain constant. I will assume in a preferred embodiment of the invention that there are only two different block lengths, and that short blocks come in pairs. To simplify ...

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Abstract

The invention discloses the method used to supply the audio signal from the compressing audio code stream, it includes the below steps: the code stream can be conducted the unbinding format to distill the changing modulus and the number of the changing modulus of the every blocks; the gained changing modulus are separated into these blocks: the length of the block is equal to the power of the two, and the length of the block is more length than the times of then the number of the changing modulus of every blocks through the unbinding format; the constant length of the reverse scatter changing is used to process the reverse transform of the changing modulus after the blocking, so the transformed reversely sampling buffer is gained; the time field sampling is distilled from the gained reverse changing sampling buffer; the block through the window changing are folded by the composing window conducting the window changing to the distilled time domain sampling block. Thereinto, the numbers of the received changing modulus can be different each other.

Description

technical field [0001] The present invention relates to the decoding of compressed audio signals, where the compression scheme employs a method based on the Modified Discrete Cosine Transform (MDCT), also known as time-domain aliasing cancellation. More specifically, the present invention relates to the decoding of compressed audio streams by varying the block length, wherein the block length is given as side information in the compressed audio stream. The present invention provides a method for constant length inverse transform of audio blocks using adaptively changing block length. Such approaches are sometimes necessary in the use of Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) or Programmable Logic Devices (PLDs). Background technique [0002] In audio coding, compressing the space used to store audio data is a focus. Current state-of-the-art methods for high-quality audio employ perceptual coding for compression. Typically,...

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Application Information

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IPC IPC(8): H03M7/30G10L19/02H03M7/40
Inventor 亚当·伦德奎斯特斯蒂安·阿格达尔
Owner NERO AG
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