Audio encoder and decoder
First Claim
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1. Audio coding system comprising:
- a linear prediction unit for filtering an input signal based on an adaptive filter;
a transformation unit for transforming a frame of the filtered input signal into a transform domain;
a quantization unit for quantizing the transform domain signal;
a scalefactor determination unit for generating scalefactors, based on a masking threshold curve, for usage in the quantization unit when quantizing the transform domain signal;
a linear prediction scalefactor estimation unit for estimating linear prediction based scalefactors based on parameters of the adaptive filter; and
a scalefactor encoder for encoding the difference between the masking threshold curve based scalefactors and the linear prediction based scalefactors.
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Abstract
The present invention teaches a new audio coding system that can code both general audio and speech signals well at low bit rates. A proposed audio coding system comprises linear prediction unit for filtering an input signal based on an adaptive filter; a transformation unit for transforming a frame of the filtered input signal into a transform domain; and a quantization unit for quantizing the transform domain signal. The quantization unit decides, based on input signal characteristics, to encode the transform domain signal with a model-based quantizer or a non-model-based quantizer. Preferably, the decision is based on the frame size applied by the transformation unit.
39 Citations
9 Claims
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1. Audio coding system comprising:
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a linear prediction unit for filtering an input signal based on an adaptive filter; a transformation unit for transforming a frame of the filtered input signal into a transform domain; a quantization unit for quantizing the transform domain signal; a scalefactor determination unit for generating scalefactors, based on a masking threshold curve, for usage in the quantization unit when quantizing the transform domain signal; a linear prediction scalefactor estimation unit for estimating linear prediction based scalefactors based on parameters of the adaptive filter; and a scalefactor encoder for encoding the difference between the masking threshold curve based scalefactors and the linear prediction based scalefactors. - View Dependent Claims (2, 3, 4, 5, 6)
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7. Audio decoder comprising:
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a de-quantization unit for de-quantizing a frame of an input bitstream based on scalefactors; an inverse transformation unit for inversely transforming a transform domain signal; a linear prediction unit for filtering the inversely transformed transform domain signal; and a scalefactor decoding unit for generating the scalefactors used in de-quantization based on received scalefactor delta information that encodes the difference between the scalefactors applied in the encoder and scalefactors that are generated based on parameters of an adaptive filter. - View Dependent Claims (8)
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9. A method for decoding an audio signal comprising the steps:
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de-quantizing a frame of an input bitstream based on scalefactors; inversely transforming a transform domain signal; linear prediction filtering the inversely transformed transform domain signal; estimating second scalefactors based on parameters of an adaptive filter; generating the scalefactors used in de-quantization based on received scalefactor difference information and the estimated second scalefactors; and outputting the audio signal.
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Specification