CVSD Decoder Step-Size Compensation for State Divergence
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Solution Overview
Problem
CVSD audio codecs are not robust to bursty bit errors, leading to audible artifacts and diverged state information between encoders and decoders, which results in lingering artifacts in the decoded audio signal.
Innovation Solution
A system and method that calculates and modifies the step size estimates to compensate for diverged states in CVSD decoders, using first and second step size estimators to adjust the decoded audio signal, thereby minimizing the adverse effects of bursty bit errors without requiring re-encoding or direct access to decoder state information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If CVSD decoder processes bursty bit errors, then bit error resiliency is maintained, but decoder state information diverges from encoder state information causing lingering artifacts
Solution Approach 1:
The patent applies preliminary action by calculating and storing step size estimates before the decoder state divergence becomes problematic. The system pre-calculates what the step size should be based on the encoded signal characteristics, so when bursty bit errors occur and cause state divergence, the pre-calculated step size estimates are already available to correct the divergence without waiting for the error to manifest.
Solution Approach 2:
The patent implements feedback by continuously monitoring the decoded signal and comparing the actual step size evolution against the pre-calculated step size estimates. When bursty bit errors cause the decoder state to diverge, the system uses feedback from the signal analysis to detect the divergence and apply corrections based on the stored estimates, creating a closed-loop system that maintains synchronization between encoder and decoder states.
2Object-generated harmful factors
If re-encoding is used to correct decoder state divergence, then artifact removal is effective, but system complexity increases significantly
Solution Approach 1:
The patent extracts only the essential correction information (step size estimates) from the encoding process and stores it separately at the decoder. Instead of re-encoding the entire signal which would require full encoder complexity, the system extracts and utilizes only the step size parameter that is critical for maintaining state synchronization, significantly reducing the complexity required at the decoder while still achieving effective artifact removal.
Solution Approach 2:
The patent creates a simplified copy of the encoder's step size calculation logic and stores these estimates for later use. Rather than implementing a full encoder copy for re-encoding, the system creates lightweight step size estimate copies that can be stored and applied when needed, reducing the computational burden while maintaining the corrective functionality.
3Measurement precision
If step size is adjusted frequently to minimize slope overload, then signal tracking improves, but granular noise increases when signal is constant
Solution Approach 1:
The patent applies dynamics by making the step size adaptive rather than fixed. The step size automatically adjusts its behavior based on the signal characteristics: it increases when the signal changes rapidly (preventing slope overload) and decreases when the signal is constant (reducing granular noise). This dynamic adaptation allows the system to optimize for signal tracking accuracy while minimizing harmful artifacts based on real-time signal conditions.
Solution Approach 2:
The patent changes the step size parameter dynamically based on signal analysis. By monitoring signal characteristics and adjusting the step size parameter accordingly, the system transitions between different operational modes: larger step sizes for rapidly changing signals to prevent slope overload, and smaller step sizes for constant signals to minimize granular noise, thereby optimizing overall performance.
Data Source
AI summary
A system and method is described for compensating for the effects of a corrupted Continuously Variable Delta Slope Modulation (CVSD) decoder memory state on a decoded audio signal. In accordance with the system and method, a first estimated step size associated with a first frame of the decoded audio signal is calculated and a second estimated step size associated with a replacement frame generated to conceal bit errors in the first frame of the decoded audio signal is calculated. At least a second frame of the decoded audio signal is then modified based on the first estimated step size and the second estimated step size.