LC3 Decoder Concealment for Tonal Frame Loss Recovery
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current audio codecs face challenges in effectively concealing frame losses in the frequency domain, particularly when spectral lines are missing, leading to artefacts in audio signals, and existing methods often rely on fade-out processes or attenuation factors that do not adequately preserve tonality or spectral shape.
Innovation Solution
A decoder and decoding method that conduct error concealment based on whether the previous frame's signal component is tonal or harmonic, using techniques such as sign flipping and non-linear attenuation to reconstruct audio signals, depending on the availability of spectral lines and the nature of the previous frame's encoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If error concealment is conducted using conventional fade-out processes or uniform attenuation factors, then the implementation is simple, but the tonality and spectral shape are not adequately preserved
Solution Approach 1:
The patent applies different attenuation factors to different frequency bands based on their energy characteristics. High-energy bands (likely to contain tonal components) receive smaller attenuation factors to preserve tonality, while low-energy bands receive larger attenuation factors. This local differentiation resolves the contradiction by maintaining implementation simplicity through automated band-based processing while significantly improving tonality preservation accuracy.
2Productivity
If error concealment is conducted without considering signal tonality, then the processing is computationally efficient, but audio quality and spectral shape are degraded
Solution Approach 1:
The patent dynamically changes the attenuation parameter based on the energy characteristics of different frequency bands and the detected tonality of the signal. By adapting the attenuation factor to match the local signal properties (high energy = likely tonal = smaller attenuation), the system maintains processing efficiency through automated parameter selection while achieving high spectral shape accuracy.
3Reliability
If strong attenuation is applied to all frequency bands during frame loss concealment, then the fade-out effect is achieved, but tonal components are lost and audio quality deteriorates
Solution Approach 1:
The patent applies the local quality principle by differentiating attenuation strength across frequency bands based on their energy characteristics. Bands with high energy (likely containing tonal components) receive milder attenuation to preserve tonality, while bands with low energy receive stronger attenuation to achieve the fade-out effect. This resolves the contradiction by applying strong attenuation selectively only where it won't harm tonal components.
4Ease of operation
If error concealment techniques are applied uniformly across the entire frame, then the implementation is straightforward, but partial frame loss with available spectral lines cannot be optimally handled
Solution Approach 1:
The patent enables selective error concealment by applying attenuation only to frequency bands where spectral lines are missing or corrupted, while leaving intact bands unchanged. This local approach maintains operational simplicity through automated band-based processing while achieving high adaptability to partial frame loss scenarios, as the system can selectively process only the affected portions of the spectrum.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Fig. 1 illustrates a decoder (100) for decoding a current frame to reconstruct an audio signal according to an embodiment. The audio signal is encoded within the current frame. The current frame comprises a current bitstream payload. The current bitstream payload comprises a plurality of payload bits. The plurality of payload bits encodes a plurality of spectral lines of a spectrum of the audio signal. Each of the payload bits exhibits a position within the current bitstream payload. The decoder (100) comprises a decoding module (110) and an output interface (120). The decoding module (110) is configured to reconstruct the audio signal. The output interface (120) is configured to output the audio signal. If error concealment is conducted by the decoding module (110), the decoding module (110) is configured to conduct error concealment in a way that depends on whether or not a previous bitstream payload of a previous frame preceding the current frame encodes a signal component of the audio signal which is tonal or harmonic.