Sub-Band Audio Error Concealment Without Frame Discard
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Solution Overview
Problem
Digital Audio Broadcasting (DAB) receivers experience residual bit errors due to poor transmission conditions, leading to audio quality impairment, and existing error concealment techniques result in unnecessary data discard and memory requirements for storing adjacent frames or stereo channel substitution.
Innovation Solution
A decoder for sub-band coded digital audio signals that analyzes individual coefficients for errors, generates a modified sequence to attenuate errors, and combines coefficients using a weighted summation to minimize subjective audio quality impairment without discarding valid data, employing error detection, masking, and reconstruction units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frame-level concealment techniques (muting, repetition, substitution) are used to mask bit errors, then audio quality impairment is reduced, but data memory requirements increase and valid data is discarded
Solution Approach 1:
The patent segments the audio frame into individual sub-band coefficients and processes each coefficient independently for error detection and correction. This allows selective correction of only the erroneous coefficients rather than discarding the entire frame, thus preserving valid data while maintaining audio quality.
Solution Approach 2:
The patent applies different processing to different coefficients based on their individual error status. Error-free coefficients are used directly, erroneous coefficients are corrected using local context information, and this local quality approach avoids the need to discard or replace entire frames.
2Reliability
If frame-level concealment techniques (repetition, substitution) are used to mask bit errors, then audio quality impairment is reduced, but additional data memory is required
Solution Approach 1:
By segmenting the processing to the coefficient level rather than frame level, the patent eliminates the need to store multiple complete frames in memory. Only minimal local context information is needed for correction, dramatically reducing memory requirements compared to frame-level concealment methods.
Solution Approach 2:
The error correction mechanism uses local context within the coefficient sequence itself to correct errors, making the system self-sufficient without requiring external stored frames or additional memory resources for concealment operations.
3Loss of substance
If individual sub-band coefficients are analyzed locally for errors, then valid data waste is reduced, but computational complexity increases
Solution Approach 1:
The patent changes the detection parameter from frame-level error flags to coefficient-level statistical properties (mean, variance, outliers). This allows simple comparative operations on individual coefficients against their local context, achieving accurate error detection with minimal computational overhead.
Solution Approach 2:
The patent replaces complex memory-based concealment mechanisms with simple arithmetic operations on coefficient values. Instead of requiring memory access and frame comparison operations, the system uses local statistical analysis and basic mathematical computations to detect and correct errors.
Data Source
AI summary
A decoder and method of decoding a sub-band coded digital audio signal. The decoder comprises: an input, for receiving sub-band coefficients for a plurality of sub-bands of the audio signal; an error detection unit, adapted to analyze the content of a sequence of coefficients in one of the sub-bands, to derive for each coefficient an indication of whether the coefficient has been corrupted by an error of a predefined type; an error masking unit, adapted to generate from the sequence a modified sequence of coefficients for the sub-band, wherein errors of the predefined type are attenuated; a coefficient combination unit, adapted to combine the received coefficients and the modified coefficients, in dependence upon the indication of error; and a signal reconstruction unit, adapted to reconstruct the audio signal using the combined coefficients.