Switched Audio Decoder Fade-Out With Shared Noise Level Tracing
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Solution Overview
Problem
Current audio signal encoding and decoding technologies face challenges in effectively managing signal fade-out during packet loss in switched audio coding systems, particularly in maintaining a pleasant background noise level during error concealment.
Innovation Solution
An apparatus and method for improved signal fade-out in switched audio coding systems, which involves a noise level tracing unit to determine noise information and a reconstruction unit to reconstruct audio signals based on this information, ensuring a comfortable noise level during burst packet losses, regardless of the core coder used, and fading the signal to a comfort noise-like signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate noise level tracing modules are used for different core coders (ACELP/TCX), then each coder can maintain its own comfort noise level, but the overall system complexity increases and computational overhead increases
Solution Approach 1:
The patent implements a single universal noise level tracing module that serves both ACELP and TCX core coders. This module traces the comfort noise level in the excitation domain and provides a common reference for fade-out operations across different coding modes, eliminating the need for separate tracing modules while maintaining consistent comfort noise levels.
Solution Approach 2:
The patent merges the noise level tracing functionality into a shared resource that is common to both ACELP and TCX coders. By combining the tracing operations and sharing the traced comfort noise level information, the system reduces complexity while ensuring that both coders benefit from accurate and up-to-date comfort noise level estimation.
2Reliability
If separate noise level tracing modules are used for different core coders, then each coder can independently trace comfort noise, but computational overhead increases due to redundant operations
Solution Approach 1:
The single universal noise level tracing module performs trace operations once and makes the traced comfort noise level available to both ACELP and TCX coders. This eliminates redundant computational operations while maintaining tracing accuracy, as the same rigorous tracing process is applied but shared across multiple coders.
Solution Approach 2:
The universal noise level tracing module serves multiple coders simultaneously, providing them with the traced comfort noise level information they need. Each coder uses this shared information for its fade-out operations, eliminating the need for each coder to independently perform the computationally intensive tracing operations.
3Shape
If fading is performed in the frequency domain for TCX, then spectral shape is preserved, but aliasing may occur in the overlap-add region
Solution Approach 1:
The patent introduces a time domain conversion as an intermediary step between frequency domain fading and overlap-add synthesis. By converting the faded frequency domain signal back to the time domain before overlap-add, the system preserves the spectral shaping benefits while avoiding the aliasing problems that would otherwise occur in the overlap-add region.
4Adaptability or versatility
If different fade-out methods are used for ACELP and TCX coders, then each coder can optimize its concealment, but consistency in comfort noise level across coding modes is lost
Solution Approach 1:
The patent implements a universal noise level tracing module that provides a common comfort noise level reference for both ACELP and TCX coders. This ensures consistency across coding modes while allowing each coder to apply its own fade-out method, thus maintaining both adaptability and stability.
Solution Approach 2:
The patent allows different fade-out parameters and methods to be applied by each coder (ACELP/TCX) while maintaining a consistent target comfort noise level. The trace domain excitation level serves as a stable reference parameter that both coders use, ensuring that despite different fade-out approaches, the resulting comfort noise levels remain consistent across coding mode transitions.
Data Source
AI summary
An apparatus for decoding an audio signal includes a receiving interface, wherein the receiving interface is configured to receive a first frame and a second frame. Moreover, the apparatus includes a noise level tracing unit for determining noise level information being represented in a tracing domain. Furthermore, the apparatus includes a first reconstruction unit for reconstructing a third audio signal portion of the audio signal depending on the noise level information and a second reconstruction unit for reconstructing a fourth audio signal portion depending on noise level information being represented in the second reconstruction domain.