Adaptive Comfort Noise Spectral Shaping for Corrupted Audio Frames
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Solution Overview
Problem
Current audio coding systems face challenges in effectively managing signal fade-out during error concealment in switched audio coding systems, particularly in matching the spectral shape of comfort noise to the background noise, leading to unpleasant noise characteristics and computational complexity due to separate noise level tracing for different coding modes.
Innovation Solution
An apparatus and method for decoding audio signals that utilize a common comfort noise level tracing in the excitation domain, ensuring the comfort noise level is up-to-date and consistent across core codecs, and fading the signal to a comfort noise-like signal during burst packet losses, while avoiding aliasing and computational overhead by using a correction factor for LPC synthesis gain and tracing the spectral shape of background noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate noise level tracing is performed for different coding modes (ACELP and TCX), then the comfort noise level can be mode-specific, but the computational complexity increases and consistency across modes is difficult to maintain
Solution Approach 1:
The patent merges the separate noise level tracing operations for ACELP and TCX modes into a single common noise level tracing mechanism. By tracing the spectral shape of background noise once and reusing it across different coding modes, the system maintains consistent comfort noise levels while avoiding the computational overhead and complexity of maintaining separate tracing operations for each mode.
Solution Approach 2:
The patent creates a universal noise level tracing mechanism that serves multiple coding modes (ACELP, TCX, and hybrid modes) simultaneously. The common noise level tracer generates a single spectral shape representation that is universally applicable across all modes, eliminating the need for mode-specific tracing operations and ensuring consistency throughout the switched audio coding system.
2Object-affected harmful factors
If the spectral shape of comfort noise is matched to the background noise, then the noise characteristic becomes pleasant and matches the signal before packet loss, but computational complexity increases due to separate tracing for each mode
Solution Approach 1:
The patent combines the spectral shape tracing operations into a single common process that traces the background noise spectral shape once. This traced spectral shape is then applied to comfort noise generation across all coding modes, ensuring pleasant noise characteristics that match the original signal while avoiding the redundant computational complexity of performing separate tracing operations for each mode.
3Device complexity
If a common comfort noise level tracing is used for all core codecs, then computational complexity is reduced and consistency is improved, but the comfort noise level may not be optimized for specific coding modes
Solution Approach 1:
The patent creates a common noise level trace that is copied and reused across different coding modes. Instead of performing separate tracing operations, the system generates a single spectral shape representation of the background noise and copies this representation for use in ACELP, TCX, and hybrid modes, significantly reducing computational complexity while maintaining adequate performance across all modes.
Data Source
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AI summary
An apparatus for decoding an encoded audio signal to obtain a reconstructed audio signal is provided. The apparatus comprises a receiving interface (1110) for receiving one or more frames, a coefficient generator (1120), and a signal reconstructor (1130). The coefficient generator (1120) is configured to determine, if a current frame of the one or more frames is received by the receiving interface (1110) and if the current frame being received by the receiving interface (1110) is not corrupted, one or more first audio signal coefficients, being comprised by the current frame, wherein said one or more first audio signal coefficients indicate a characteristic of the encoded audio signal, and one or more noise coefficients indicating a background noise of the encoded audio signal. Moreover, the coefficient generator (1120) is configured to generate one or more second audio signal coefficients, depending on the one or more first audio signal coefficients and depending on the one or more noise coefficients, if the current frame is not received by the receiving interface (1110) or if the current frame being received by the receiving interface (1110) is corrupted. The audio signal reconstructor (1130) is configured to reconstruct a first portion of the reconstructed audio signal depending on the one or more first audio signal coefficients, if the current frame is received by the receiving interface (1110) and if the current frame being received by the receiving interface (1110) is not corrupted. Moreover, the audio signal reconstructor (1130) is configured to reconstruct a second portion of the reconstructed audio signal depending on the one or more second audio signal coefficients, if the current frame is not received by the receiving interface (1110) or if the current frame being received by the receiving interface (1110) is corrupted.