An audio encoder implements multi-channel coding decision, band truncation, multi-channel rematrixing, and header reduction techniques to improve quality and coding efficiency. In the multi-channel coding decision technique, the audio encoder dynamically selects between joint and independent coding of a multi-channel audio signal via an open-loop decision based upon (a) energy separation between the coding channels, and (b) the disparity between excitation patterns of the separate input channels. In the band truncation technique, the audio encoder performs open-loop band truncation at a cut-off frequency based on a target perceptual quality measure. In multi-channel rematrixing technique, the audio encoder suppresses certain coefficients of a difference channel by scaling according to a scale factor, which is based on current average levels of perceptual quality, current rate control buffer fullness, coding mode, and the amount of channel separation in the source. In the header reduction technique, the audio encoder selectively modifies the quantization step size of zeroed quantization bands so as to encode in fewer frame header bits.

Quality improvement techniques in an audio encoder

An audio decoder provides a combination of decoding components including components implementing base band decoding, spectral peak decoding, frequency extension decoding and channel extension decoding techniques. The audio decoder decodes a compressed bitstream structured by a bitstream syntax scheme to permit the various decoding components to extract the appropriate parameters for their respective decoding technique.

Bitstream syntax for multi-process audio decoding

Traditional audio encoders may conserve coding bit-rate by encoding fewer than all spectral coefficients, which can produce a blurry low-pass sound in the reconstruction An audio encoder using wide-sense perceptual similarity improves the quality by encoding a perceptually similar version of the omitted spectral coefficients, represented as a scaled version of already coded spectrum The omitted spectral coefficients are divided into a number of sub-bands The sub-bands are encoded as two parameters: a scale factor, which may represent the energy in the band; and a shape parameter, which may represent a shape of the band The shape parameter may be in the form of a motion vector pointing to a portion of the already coded spectrum, an index to a spectral shape in a fixed code-book, or a random noise vector The encoding thus efficiently represents a scaled version of a similarly shaped portion of spectrum to be copied at decoding

Efficient coding of digital media spectral data using wide-sense perceptual similarity

A spectrum coding apparatus capable of performing coding at a low bit rate and with high quality is disclosed This apparatus is provided with a section that performs the frequency transformation of a first signal and calculates a first spectrum, a section that converts the frequency of a second signal and calculates a second spectrum, a section that estimates the shape of the second spectrum in a band of FL≦k<FH using a filter having the first spectrum in a band of 0≦k<FL as an internal state and a section that codes an outline of the second spectrum determined based on a coefficient indicating the characteristic of the filter at this time

Spectrum coding apparatus, spectrum decoding apparatus, acoustic signal transmission apparatus, acoustic signal reception apparatus and methods thereof

A multi-channel audio decoder provides a reduced complexity processing to reconstruct multi-channel audio from an encoded bitstream in which the multi-channel audio is represented as a coded subset of the channels along with a complex channel correlation matrix parameterization. The decoder translates the complex channel correlation matrix parameterization to a real transform that satisfies the magnitude of the complex channel correlation matrix. The multi-channel audio is derived from the coded subset of channels via channel extension processing using a real value effect signal and real number scaling.

Low complexity decoder for complex transform coding of multi-channel sound

PROBLEM TO BE SOLVED: To provide a frequency interpolation device, etc., which restores a modulated wave obtained by using a band-limited signal of a source signal to a signal close to the source signal or restores an audio signal with high sound quality. SOLUTION: An analyzer 1 converts a PCM signal into the spectrum of the PCM signal. A frequency interpolation processing part 2 specifies the combination having the highest correlation of a spectrum distribution among combinations of a reference band including the band of the highest frequency among bands obtained by equally dividing the spectrum into several and other bands when one is standardized. An interpolation band addition part 3 estimates the envelope of the PCM signal, scales the spectrum of the same distribution as the spectrum distribution in the reference band included in the combination specified by the frequency interpolation processing part 2 along the function of the envelope, and adds the result to a frequency side higher than the reference band. A synthesizer 4 generates a signal giving the spectrum after the interpolation band addition part 3 performs the addition. COPYRIGHT: (C)2001,JPO

寧佐藤

Papers

Device and method for frequency interpolation and recording medium

寧 佐藤

Papers

Device and method for frequency interpolation and recording medium

寧佐藤