Audio Bandwidth Extension Encoding Using Spectral Copy and Folding
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Solution Overview
Problem
Current audio signal encoding methods face limitations in efficiently encoding high-frequency domains due to bit restrictions, necessitating improved methods to enhance encoding efficiency and bandwidth extension.
Innovation Solution
The proposed solution involves an encoding apparatus and method that includes a down-sampling unit, core-encoding unit, frequency transforming unit, and extension encoding unit, which generates a basic signal for the high-frequency domain by copying and folding the low-frequency section, estimating an envelope, and controlling energy using an energy control factor to perform bandwidth extension encoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large number of bits are allocated to low-frequency domain signals, then encoding precision of low-frequency signals is improved, but encoding efficiency for high-frequency signals deteriorates due to bit restrictions
Solution Approach 1:
The patent segments the audio signal into low-frequency and high-frequency domains, applying different encoding strategies to each. The low-frequency domain receives detailed encoding with more bits, while the high-frequency domain uses bandwidth extension techniques that require fewer bits, thus resolving the contradiction between encoding precision and encoding efficiency
Solution Approach 2:
The patent changes the encoding parameters for different frequency domains. For high-frequency signals, it uses spectral band replication parameters and bandwidth extension parameters instead of full-spectrum encoding parameters, reducing the bit allocation required for high-frequency encoding while maintaining perceptual quality
2Productivity
If a smaller number of bits are allocated to high-frequency domain signals, then encoding efficiency is improved, but encoding precision of high-frequency signals deteriorates
Solution Approach 1:
The patent uses spectral band replication to copy the spectral envelope from the low-frequency domain to the high-frequency domain. By copying and folding the low-frequency spectrum to generate the high-frequency spectrum, the system achieves acceptable encoding precision for high-frequency signals with minimal bit allocation, thus improving encoding efficiency
Solution Approach 2:
The patent introduces spectral envelopes and bandwidth extension parameters as intermediaries between the low-frequency encoded signal and the reconstructed high-frequency signal. These intermediaries carry essential spectral information that enables accurate high-frequency reconstruction without requiring direct encoding of all high-frequency components
3Productivity
If Spectral Band Replication technology is used to represent high-band component signals as an envelope, then encoding efficiency is improved, but bandwidth extension capability deteriorates
Solution Approach 1:
The patent dynamically adjusts the bandwidth extension parameters and spectral replication factors based on the characteristics of the input signal. By making the encoding adaptive to different signal types and frequency content, the system maintains both encoding efficiency and enhanced bandwidth extension capability across various audio scenarios
Data Source
AI summary
An apparatus and method for encoding and decoding a signal for high frequency bandwidth extension are provided. An encoding apparatus may down-sample a time domain input signal, may core-encode the down-sampled time domain input signal, may transform the core-encoded time domain input signal to a frequency domain input signal, and may perform bandwidth extension encoding using a basic signal of the frequency domain input signal.