Adaptive High Frequency Audio Encoding Using Low Band Signals
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Solution Overview
Problem
Existing audio encoding methods prioritize low frequency signals over high frequency signals, resulting in suboptimal quality of high frequency sounds when bit allocation is limited, as high frequency signals are often encoded with fewer bits, leading to reduced recognition and quality of sound by humans.
Innovation Solution
The method involves adaptive encoding and decoding of high frequency signals above a preset frequency band by utilizing signals or spectra from a low frequency band, converting between time and frequency domains, and selecting appropriate encoding domains to maximize sound quality using excitation signals and spectra from the low frequency band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high frequency signals are coded by allocating a small number of bits to improve coding efficiency, then coding efficiency is improved, but the quality of high frequency sound is deteriorated
Solution Approach 1:
The patent uses low frequency band signals as an intermediary to generate high frequency band excitation signals. By deriving high frequency excitation from low frequency excitation signals through spectral transformation and filtering, the system can encode high frequency bands with fewer bits while maintaining sound quality, as the low frequency band contains sufficient information to reconstruct high frequency characteristics.
2Manufacturing precision
If low frequency signals are coded by allocating a great number of bits to improve sound quality, then low frequency sound quality is improved, but coding efficiency is reduced
Solution Approach 1:
The low frequency band excitation signal serves multiple functions: it is used directly for low frequency band synthesis and also as the basis for generating high frequency band excitation signals. This multi-functional use of the low frequency excitation signal allows the system to maintain both low and high frequency sound quality without requiring separate full-resolution encoding for each band, thereby improving overall coding efficiency.
3Productivity
If high frequency signals are encoded with fewer bits to improve coding efficiency, then coding efficiency is improved, but the recognition and quality of sound by humans is reduced
Solution Approach 1:
The patent transforms the excitation signal from the time domain to the frequency domain using spectral transformation techniques. By operating in the frequency domain and applying spectral filtering, the system can efficiently allocate bits to the most perceptually important frequency components while maintaining overall sound recognition quality, even with reduced bit allocation for high frequency bands.
Data Source
AI summary
Provided are a method and apparatus for encoding and decoding an audio signal. According to the present application, a signal of a high frequency band above a preset frequency band is adaptively encoded or decoded in the time domain or in the frequency domain by using a signal of a low frequency band below the preset frequency band. As such, the sound quality of a high frequency signal is not deteriorate even when an audio signal is encoded or decoded by using a small number of bits and thus coding efficiency may be maximized.