Audio Coding Envelope Correction for Beat Suppression
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Solution Overview
Problem
The Spectral Band Replication (SBR) technique in audio coding often results in a beat phenomenon due to adjacent peaks in the decoded signal when the frequency of the peak on the envelope and the tone signal have a small frequency difference, leading to a deterioration in audio quality.
Innovation Solution
An audio coding device that includes a filter to extract a low-band signal, a processor to extract envelope and tone information, and a correction unit to adjust the envelope information based on the difference between the tone signal and envelope peak frequencies, preventing adjacent peaks in the decoded signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the SBR technique extracts envelope information and tone information from the high-band component for information amount compression, then coding efficiency is improved, but adjacent peaks in the decoded signal cause beat phenomenon and audio quality deterioration
Solution Approach 1:
The patent applies preliminary action by detecting tone information and envelope peak frequencies before decoding, and pre-correcting the envelope information by suppressing peaks that would cause beats. This preventive correction is performed in advance during the coding stage, ensuring that adjacent peaks are eliminated before the signal is decoded and reconstructed, thereby preventing the beat phenomenon from occurring in the final audio output
Solution Approach 2:
The patent implements feedback by using the detected tone information to guide the correction of envelope information. The system continuously monitors the relationship between tone signal frequencies and envelope peak frequencies, and automatically adjusts the envelope information accordingly. This feedback mechanism ensures that envelope peaks that would create beats with tone signals are suppressed, while maintaining the integrity of the original audio signal's envelope characteristics
2Manufacturing precision
If envelope information is used to correct the magnitude of energy of the high-band component, then sound quality is improved, but adjacent peaks cause beat phenomenon
Solution Approach 1:
The patent applies local quality by selectively correcting only the problematic portions of the envelope information. Instead of uniformly processing all envelope peaks, the system identifies specific frequency regions where envelope peaks are adjacent to tone signals and suppresses only those localized peaks. This selective correction maintains the overall envelope structure and sound quality while eliminating the specific beats caused by adjacent peaks
Solution Approach 2:
The patent changes the parameters of the envelope information by adjusting the magnitude of energy correction in specific frequency regions. When an envelope peak is detected to be adjacent to a tone signal, the system modifies the envelope parameter (energy magnitude) in that local region to suppress the peak. This parameter change is applied selectively based on the detected frequency relationship between envelope peaks and tone signals, thereby preventing beats while preserving the general energy distribution of the original signal
Data Source
AI summary
An audio coding device includes a filter configured to extract a low-band signal having a first frequency component from an input signal, a memory, and a processor coupled to the memory and configured to extract envelope information relating to an envelope of a high-band signal having a second frequency component which is higher than the first frequency component in the input signal, detect tone information that is information on a tone signal included in a high-band signal spectrum from the input signal, correct the envelope information based on a difference between frequency of the tone signal and frequency of a peak of the envelope, and code the low-band signal, the tone information, and the envelope information that is corrected.