Audio Decoder Frequency Regeneration for Low-Bitrate Wideband Signals
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Solution Overview
Problem
Current audio codecs face limitations in coding wide-band signals at low bitrates, leading to perceptual annoyance and loss of high-frequency detail due to the inability to accurately align tonal harmonics and the need for domain transformation, which increases computational complexity and memory requirements.
Innovation Solution
The proposed solution involves a decoder-side signal analysis for signal-dependent frequency regeneration, where local minima in the core signal are used to adjust frequency borders, and adaptive techniques such as interpolation or noise generation are applied to minimize artifacts, allowing for accurate reconstruction of spectral portions without fixed patching or transformation into new domains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If bandwidth extension methods are used to code wide-band signals at low bitrates, then compression efficiency is improved, but perceptual annoyance increases due to inability to accurately align tonal harmonics
Solution Approach 1:
The patent implements signal-dependent frequency regeneration where the frequency borders are dynamically adjusted based on local minima detection in the decoded core signal. This allows the system to adapt to the actual signal characteristics rather than using fixed patching boundaries, thereby accurately aligning tonal harmonics and reducing perceptual annoyance while maintaining compression efficiency.
Solution Approach 2:
The patent employs a feedback mechanism where the decoded core signal is analyzed to detect local minima, and this analysis feedback is used to adjust the frequency borders for spectral portion regeneration. This closed-loop approach ensures that the frequency regeneration process adapts to the actual signal content, preventing misalignment of tonal harmonics and reducing beating artifacts.
2Device complexity
If fixed patching or domain transformation is used for frequency regeneration, then device complexity is reduced, but audio quality deteriorates due to artifacts like beating and dissonance
Solution Approach 1:
The patent replaces fixed patching with dynamic frequency border adjustment based on local minima detection in the decoded signal. This dynamic approach allows the system to identify appropriate transition points that avoid splitting tonal components, thereby eliminating beating and dissonance artifacts while maintaining reasonable device complexity through efficient signal analysis algorithms.
Solution Approach 2:
The patent applies local quality analysis by detecting local minima at specific frequency locations in the decoded core signal. This localized analysis enables precise determination of frequency borders for spectral regeneration, ensuring that tonal harmonics are not split across patches and that the regenerated spectral portions seamlessly integrate with the original signal, thus preventing audio quality degradation.
3Speed
If signal-independent frequency regeneration is used, then processing speed is improved, but manufacturing precision deteriorates due to inaccurate spectral reconstruction
Solution Approach 1:
The patent implements signal-dependent frequency regeneration where the frequency borders are dynamically determined based on local minima detection in the decoded core signal. This approach maintains processing speed by using efficient signal analysis techniques while significantly improving spectral reconstruction accuracy by adapting to the actual signal characteristics rather than using fixed or predetermined frequency borders.
Solution Approach 2:
The patent performs preliminary analysis of the decoded core signal to detect local minima before proceeding with frequency regeneration. This preliminary action enables the system to identify appropriate frequency borders in advance, ensuring accurate spectral reconstruction while maintaining processing efficiency by avoiding iterative adjustments during the regeneration process.
Data Source
Figure 1A~1B
Figure 2A
Figure 2B
AI summary
Apparatus for decoding an encoded audio signal comprising an encoded core signal and parametric data, comprising: a core decoder (600) for decoding the encoded core signal to obtain a decoded core signal; an analyzer (602) for analyzing the decoded core signal before or after performing a frequency regeneration operation to provide an analysis result (603); and a frequency regenerator (604) for regenerating spectral portions not included in the decoded core signal using a spectral portion of the decoded core signal, the parametric data (605), and the analysis result (603).