High-Frequency Audio Coding with Low-Band Linear Prediction
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Solution Overview
Problem
Existing audio signal encoding and decoding methods are inefficient in handling high frequency signals, as they require significant bits for accurate representation, which is not crucial for human perception due to hearing characteristics.
Innovation Solution
The method involves linear prediction of high frequency signals to extract coefficients, generating signals using low frequency signals, and calculating energy ratios to encode and decode high frequency signals efficiently, reducing the bit requirement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional encoding methods are used for high frequency signals, then accurate representation is achieved, but significant bits are required which is inefficient
Solution Approach 1:
The patent extracts only the essential characteristics of high frequency signals (energy values and spectral shape parameters) rather than encoding the entire signal. This extraction approach maintains adequate representation accuracy while dramatically reducing the bit requirement, as only key parameters need to be transmitted.
Solution Approach 2:
The patent applies partial action by encoding only part of the high frequency signal information - specifically the energy values and spectral shape - rather than the complete signal. This partial encoding is sufficient for perceptual audio quality and significantly reduces computational complexity and bit rate requirements.
2Quantity of substance
If spectral band replication is used to encode high frequency signals, then bit rate is reduced, but the method requires complex processing to generate and decode signals
Solution Approach 1:
The patent segments the audio signal into low frequency and high frequency components, applying different encoding strategies to each. The low frequency signal is fully encoded while the high frequency signal is represented by extracted parameters (energy values and spectral shape), simplifying the overall processing complexity while maintaining efficiency.
Solution Approach 2:
The patent changes the representation parameters of high frequency signals from time-domain waveforms to frequency-domain parameters (energy values and spectral shape parameters). This parameter transformation simplifies the encoding and decoding processes while achieving effective compression.
3Loss of information
If high frequency signals are fully encoded, then complete audio information is preserved, but compression efficiency is reduced due to the non-critical nature of high frequency components in human perception
Solution Approach 1:
The patent applies local quality by differentiating the encoding quality between frequency bands. High frequency components are encoded with lower precision (using extracted parameters) compared to low frequency components (fully encoded), matching the perceptual importance of each band and optimizing compression efficiency while preserving essential audio information.
Solution Approach 2:
The patent converts the limitation of reduced high frequency encoding precision into a benefit by leveraging human auditory characteristics. The reduced representation of high frequency signals, which are less critical for perception, actually improves overall compression efficiency while maintaining perceptual audio quality.
Data Source
AI summary
Provided are a method and apparatus for encoding and decoding a high frequency signal by using a low frequency signal. The high frequency signal can be encoded by extracting a coefficient by linear predicting a high frequency signal, and encoding the coefficient, generating a signal by using the extracted coefficient and a low frequency signal, and encoding the high frequency signal by calculating a ratio between the high frequency signal and an energy value of the generated signal. Also, the high frequency signal can be decoded by decoding a coefficient, which is extracted by linear predicting a high frequency signal, and a low frequency signal, and generating a signal by using the decoded coefficient and the decoded low frequency signal, and adjusting the generated signal by decoding a ratio between the generated signal and an energy value of the high frequency signal.