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Transform encoding/decoding of harmonic audio signals

A technology of audio signal and frequency transformation, applied in the field of transformation coding/decoding, which can solve problems such as inappropriateness and achieve good sensory quality effects

Active Publication Date: 2014-12-31
TELEFON AB LM ERICSSON (PUBL)
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  • Description
  • Claims
  • Application Information

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Problems solved by technology

This mismatch between signal and coding model can only be resolved at very high bit rates, but in most cases this scheme is not suitable

Method used

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  • Transform encoding/decoding of harmonic audio signals
  • Transform encoding/decoding of harmonic audio signals
  • Transform encoding/decoding of harmonic audio signals

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Embodiment Construction

[0058] figure 2 shows a typical spectrum of a harmonic audio signal, image 3A typical spectrum of a non-harmonic audio signal is shown. The spectrum of a harmonic signal is formed by strong spectral peaks separated by very weak frequency bands, whereas the spectrum of a non-harmonic signal is smoother.

[0059] The proposed technique provides an alternative audio coding model that better handles harmonic audio signals. The main concept is that frequency transform vectors (eg MDCT vectors) are not split into envelope and residual parts, but spectral peaks and adjacent MDCT bins (bins) are directly extracted and quantized together. At high frequencies, low-energy coefficients outside adjacent peaks are not coded, but noise-filled at the decoder. Here, the signal model used in conventional encoding, {spectral envelope + residual} is replaced by a new model {spectral peak + noise floor}. At low frequencies, coefficients outside adjacent peaks are still coded because they hav...

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Abstract

An encoder (20) for encoding frequency transform coefficients (Y(k)) of a harmonic audio signal include the following elements: A peak locator (22) configured to locate spectral peaks having magnitudes exceeding a predetermined frequency dependent threshold. A peak region encoder (24) configured to encode peak regions including and surrounding the located peaks. A low-frequency set encoder (26) configured to encode at least one low-frequency set of coefficients outside the peak regions and below a crossover frequency that depends on the number of bits used to encode the peak regions. A noise-floor gain encoder (28) configured to encode a noise- floor gain of at least one high-frequency set of not yet encoded coefficients outside the peak regions.

Description

technical field [0001] The technique proposed by the present invention relates to transform coding / decoding of audio signals, especially harmonic audio signals. Background technique [0002] Transform coding is the main technique used to compress and transmit audio signals. The concept of transform coding is to first transform the signal into the frequency domain, then quantize and send the transform coefficients. The decoder uses the received transform coefficients to reconstruct the signal waveform by applying an inverse frequency transform, see figure 1 . exist figure 1 , the audio signal X(n) is forwarded to the frequency converter 10 . The resulting frequency transform Y(k) is forwarded to a transform encoder 12 and the encoded transform is sent to a decoder, which decodes the encoded transform. Transform the decoded Forwarded to inverse frequency transformer 16, inverse frequency transformer 16 transforms it into decoded audio signal The motivation behind this...

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G10L19/028G10L19/038
CPCG10L19/028G10L19/038G10L19/002G10L19/02G10L19/0212
Inventor 沃洛佳·格兰恰诺夫托马斯·托夫特戈德塞巴斯蒂安·内斯隆德哈拉尔德·波布洛斯
Owner TELEFON AB LM ERICSSON (PUBL)