Audio Encoding Tone Suppression at Band Boundaries
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Solution Overview
Problem
The existing spectral band replication (SBR) technology in audio encoding and decoding leads to deterioration in sound quality due to coarse high-frequency resolution at tone boundaries, resulting in frequency shifts and vibrations during decoding.
Innovation Solution
An audio encoding apparatus that detects tones at the boundary between low-frequency and high-frequency bands and suppresses one of the tones, using a determination unit, low-frequency correction unit, and high-frequency correction unit to adjust the encoding and decoding processes, thereby improving sound quality by reducing vibration components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If spectral band replication (SBR) technology is used for audio encoding, then compression efficiency is improved, but sound quality deteriorates due to coarse high-frequency resolution at tone boundaries
Solution Approach 1:
The patent applies local quality by making different parts of the frequency spectrum have different resolution characteristics. Specifically, the low-frequency band is encoded with high resolution while the high-frequency band is encoded with lower resolution, and tone components are selectively suppressed at boundary frequencies where aliasing occurs. This localized differentiation resolves the contradiction by preserving sound quality in critical regions while maintaining compression efficiency in less critical regions.
Solution Approach 2:
The patent applies preliminary anti-action by proactively suppressing tone components at boundary frequencies before they can cause aliasing and sound quality deterioration during decoding. The encoding apparatus detects tone components in the low-frequency band and preemptively suppresses them at frequencies that would map to the high-frequency band, preventing the harmful aliasing effect from occurring in the first place.
2Device complexity
If high-frequency signal is generated by replicating low-frequency waveform, then decoding complexity is reduced, but frequency shifts and vibrations occur due to coarse resolution
Solution Approach 1:
The patent applies preliminary anti-action by detecting tone components in the low-frequency band and preemptively suppressing them at boundary frequencies before replication. This prevents the tone components from being copied to the high-frequency band where they would cause aliasing and vibrations, thereby maintaining frequency accuracy while keeping the simple replication-based decoding approach.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the suppression threshold and suppression amount based on the detected tone component characteristics (frequency, amplitude). This allows the system to maintain high frequency accuracy for important tone components while still using the computationally efficient replication method for generating high-frequency signals.
3Manufacturing precision
If tone components are suppressed at boundary frequencies, then vibrations are reduced, but encoding complexity increases due to additional processing
Solution Approach 1:
The patent applies local quality by focusing tone suppression processing only at boundary frequencies where aliasing problems occur, rather than applying uniform processing across the entire frequency spectrum. The encoding apparatus identifies specific boundary frequency regions and applies suppression selectively to tone components in these regions, thereby improving sound quality without excessively increasing encoding complexity.
Solution Approach 2:
The patent applies partial action by implementing tone suppression only for significant tone components that exceed a certain threshold, rather than suppressing all frequency components at boundaries. This selective approach ensures that important tone components are preserved while only suppressing those that would cause noticeable vibrations, thus achieving sound quality improvement with minimal additional encoding complexity.
Data Source
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AI summary
There is provided an audio encoding apparatus including a determination unit configured to determine whether a tone is included in a boundary between a low-frequency that is a frequency bandwidth below a predetermined frequency of an input signal and a high-frequency that is a frequency bandwidth above the predetermined frequency of the input signal, an encoding unit configured to suppress a tone in one of the low-frequency and the high-frequency, encode the input signal having the low-frequency to generate a low-frequency code, and encode the input signal having the high-frequency to generate a high-frequency code, and a multiplexing unit configured to generate an encoded stream by multiplexing the low-frequency code and the high-frequency code.