Weighted Noise Injection for Audio Frame Loss Correction
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Solution Overview
Problem
Current frame loss correction techniques in digital signal processing, particularly in audio signal decoding, often result in audible phase discontinuities and unpleasant hearing imperfections due to inadequate handling of signal energy and periodicity, leading to artifacts like metallic sounds and energy inconsistencies.
Innovation Solution
A method that generates a replacement signal structure using spectral components from valid samples, injecting blocks with variable parameters to ensure energy homogenization and reduce periodicity effects, thereby smoothing transitions and maintaining consistent signal energy levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If frame loss correction is performed by repeating the decoded spectrum in the last received frame, then the technique is inexpensive in terms of resources and does not require additional delay, but it produces audible phase discontinuities and significant audio artifacts
Solution Approach 1:
The patent applies dynamics by making the frame loss correction adaptive rather than static. The system dynamically adjusts the correction parameters (pitch period, spectral components, energy levels) based on the actual signal characteristics in the lost frame region, allowing the correction to evolve with the signal rather than applying a fixed repetition pattern
Solution Approach 2:
The patent changes key parameters including pitch period estimation, spectral components, and energy levels to match the surrounding valid frames. By adjusting these parameters dynamically based on signal analysis, the system maintains spectral and temporal consistency while avoiding the artifacts produced by simple frame repetition
2Loss of time
If the overlap time between frames is reduced to achieve low delay, then the delay is minimized, but the phase discontinuities become more audible and artifacts increase
Solution Approach 1:
The patent performs preliminary analysis of the signal characteristics (pitch period, spectral components, energy) from valid frames before attempting correction. This preliminary characterization allows the system to pre-calculate appropriate correction parameters that will maintain consistency even with reduced overlap, preventing phase discontinuities before they occur
Solution Approach 2:
The system dynamically adjusts the correction strength and parameters based on the actual overlap duration. When overlap is reduced, the correction algorithm adapts by using more aggressive parameter matching and energy adjustment to compensate for the shorter transition zone, maintaining quality despite lower delay
3Reliability
If synthesized signal is generated from pitch period structure to replace lost frames, then frame loss correction is achieved, but the physical properties do not correspond to the original signal causing unpleasant hearing imperfections
Solution Approach 1:
The patent carefully adjusts parameters including pitch period, spectral envelope, and energy levels to match the characteristics of the original signal. By deriving these parameters from actual signal analysis rather than using fixed synthesized patterns, the correction maintains physical properties consistent with the original audio
Solution Approach 2:
The system copies spectral and temporal characteristics from valid frames to reconstruct the lost frame content. Rather than generating entirely synthetic signals, it copies the essential signal properties (spectral components, pitch structure, energy distribution) from surrounding valid frames, ensuring fidelity to the original signal's physical properties
4Reliability
If energy levels of correctly received signal and reconstructed signal are significantly different, then frame loss correction is achieved, but it causes auditory sensation of jumping with noise level changes
Solution Approach 1:
The patent dynamically adjusts energy parameters including overall signal level, spectral energy distribution, and transient energy to match between valid and reconstructed frames. This energy normalization prevents audible jumps by ensuring smooth transitions in noise levels and signal intensity
Solution Approach 2:
The system uses feedback from energy analysis of valid frames to adjust the reconstruction parameters. By measuring the energy characteristics of surrounding valid frames and using this information to guide the reconstruction energy levels, the system maintains energy consistency and eliminates auditory jumping sensations
Data Source
Figure 1A~1B
Figure 1C
Figure 2
AI summary
The invention relates to a method for processing a digital signal, implemented during decoding of the signal, in order to replace a succession of samples lost during decoding, the method comprising steps of: generating a structure of a signal for replacing the lost succession, this structure comprising spectral components determined from valid samples received during decoding before the succession of lost samples; generating a residue between a digital signal available to the decoder, comprising received valid samples, and a signal generated from the spectral components; and extracting blocks from the residue, method in which window weighted blocks are injected into the structure using an overlap-add approach, the injected blocks partially overlapping in time.