Bit Error Concealment for Bluetooth Audio
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Solution Overview
Problem
Conventional audio communications systems, particularly those using Bluetooth, face challenges in detecting and concealing bit errors that result in audible artifacts like clicks due to their sensitivity to bursty bit errors, especially in low signal-to-noise ratio conditions, where prior art techniques are ineffective for memory-based codecs like CVSD.
Innovation Solution
A low-complexity bit error concealment system and method that analyzes decoded audio frames for distortions caused by bit errors, using a combination of modules like BER-based threshold biasing, bit error detection, and packet loss concealment to detect and conceal audible artifacts without adding delay, suitable for low-cost and low-power devices like Bluetooth headsets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional audio codecs (PCM, CELP) are used, then audio quality is maintained under normal conditions, but audible clicks are produced when bit errors occur
Solution Approach 1:
The patent converts the harmful effect of bit errors (which cause audible clicks) into a detectable signal characteristic. By analyzing the decoded audio signal for anomalies indicative of bit errors, the system identifies when corruption has occurred and applies concealment techniques to replace the corrupted portions with synthesized audio, thereby transforming the harmful click artifacts into acceptable audio output.
Solution Approach 2:
The patent introduces an intermediary bit error detection and concealment module between the decoder and audio output. This intermediary analyzes the decoded audio signal for signs of bit error corruption and selectively applies concealment processing only to corrupted frames, leaving clean frames unchanged. This mediator approach resolves the contradiction by filtering out harmful clicks while preserving normal audio quality.
2Reliability
If CVSD codec is used, then robustness to random bit errors is improved, but bursty bit errors cause audible clicks
Solution Approach 1:
The patent applies local quality by treating different portions of the audio stream differently based on their integrity. Clean audio frames are passed through unchanged to preserve CVSD's natural robustness and quality, while corrupted frames containing bursty bit errors are identified and subjected to concealment processing. This localized approach maintains CVSD's advantages while compensating for its vulnerability to burst errors.
Solution Approach 2:
The patent changes the processing parameters applied to audio frames based on their error status. For clean frames, standard CVSD decoding parameters are used. For corrupted frames detected through signal analysis, different parameters and concealment techniques are applied to synthesize replacement audio, thereby adapting the processing to the local conditions and resolving the click problem caused by bursty errors.
3Reliability
If packet loss concealment logic is invoked, then quality degradation from lost packets is reduced, but bit errors that go undetected still produce clicks
Solution Approach 1:
The patent implements feedback by continuously monitoring the decoded audio signal for characteristics indicative of bit error corruption. This feedback loop analyzes each decoded frame, compares it against expected signal properties, and identifies when corruption has occurred. The detection results feed back into the processing chain to trigger appropriate concealment actions, thereby solving the problem of undetected bit errors that conventional PLC cannot address.
Solution Approach 2:
The patent applies partial action by selectively processing only those frames that show signs of corruption, rather than applying concealment to all frames. The system performs excessive detection analysis on each frame to identify subtle signs of bit errors, and then applies concealment only where necessary. This partial/excessive approach resolves the contradiction by detecting previously undetectable errors while avoiding unnecessary processing of clean frames.
Data Source
AI summary
A bit error concealment (BEC) system and method is described herein that detects and conceals the presence of click-like artifacts in an audio signal caused by bit errors introduced during transmission of the audio signal within an audio communications system. A particular embodiment of the present invention utilizes a low-complexity design that introduces no added delay and that is particularly well-suited for applications such as Bluetooth® wireless audio devices which have low cost and low power dissipation requirements.