Scalable Audio Encoding Using Residual Filter Parameters
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Solution Overview
Problem
Conventional scalable coding methods require a large bit rate to achieve high-quality decoded signals, especially when encoding residual signals with characteristics close to noise sequences, leading to inefficient use of bit resources.
Innovation Solution
The proposed solution involves generating low-frequency and high-frequency band encoding information from an original signal using spectrum calculations and parameter encoding, where the degree of similarity and fluctuation components between the bands are calculated and encoded, allowing for improved quality decoding at lower bit rates by optimizing the encoding of residual components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If transform coding is used at the second layer to encode residual signals with noise-like characteristics, then decoding quality can be improved, but the bit rate becomes large
Solution Approach 1:
The patent changes the encoding parameters by using filter information (transfer function coefficients) instead of directly encoding the residual signal spectrum. This parameter transformation allows the decoder to reconstruct the high-frequency band more accurately from the low-frequency band information, improving decoding quality while reducing the number of bits required to represent the residual components
2Measurement precision
If a large number of bits are allocated to encode residual signals at the second layer, then high-quality decoded signals can be obtained, but bit rate efficiency deteriorates
Solution Approach 1:
The patent extracts the essential characteristics of the residual signal by identifying and encoding only the filter information that governs the relationship between low-frequency and high-frequency bands. Instead of encoding all residual signal components, it extracts and transmits only the necessary filter parameters, thereby achieving high reconstruction quality with reduced bit allocation
Solution Approach 2:
The patent inverts the conventional approach by not directly encoding the residual signal itself, but rather encoding the filter that generates the residual signal from the low-frequency band. This inversion allows the decoder to synthesize the residual components on-demand, improving bit rate efficiency while maintaining signal quality
Data Source
AI summary
An encoder, decoder, encoding method, and decoding method enabling acquisition of high-quality decoded signal in scalable encoding of an original signal in first and second layers even if the second or upper layer section performs low bit-rate encoding. In the encoder, a spectrum residue shape codebook (305) stores candidates of spectrum residue shape vectors, a spectrum residue gain codebook (307) stores candidates of spectrum residue gains, and a spectrum residue shape vector and a spectrum residue gain are sequentially outputted from the candidates according to the instruction from a search section (306). A multiplier (308) multiplies a candidate of the spectrum residue shape vector by a candidate of the spectrum residue gain and outputs the result to a filtering section (303). The filtering section (303) performs filtering by using a pitch filter internal state set by a filter state setting section (302), a lag T outputted by a lag setting section (304), and a spectrum residue shape vector which has undergone gain adjustment.