Dynamic Range Error Correction for Click-Free Audio Gain Changes
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Solution Overview
Problem
Dynamic range enhancement (DRE) systems introduce errors due to gain changes, leading to undesirable audible clicks in audio applications, particularly due to the non-linear behavior of the DRE circuit and the impulse response of digital-to-analog converters.
Innovation Solution
An apparatus with an error correction circuit that applies an error correction factor to the input signal, derived from the error generated by the DRE circuit, to reduce errors associated with gain changes, using a sigma delta modulator and loop filter to adjust the signal before processing, thereby compensating for the errors and improving signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dynamic range enhancement is applied to suppress errors in the signal path, then signal quality is improved, but audible clicks are introduced due to non-linear behavior during gain changes
Solution Approach 1:
The error correction factor is calculated in advance based on the expected error from gain changes, and this correction is applied to the input signal before the DRE processing. By anticipating and counteracting the error before it occurs, the non-linear behavior that causes audible clicks is prevented rather than corrected after the fact.
Solution Approach 2:
The system performs preliminary calculation of the error correction factor using the known impulse response of the DAC and the planned gain changes. This pre-computed correction is then applied to the input signal, allowing the main DRE circuit to process a pre-corrected signal that will not generate the harmful non-linear artifacts during processing.
2Measurement precision
If traditional feedback loops are used to correct errors, then signal accuracy is improved, but power consumption increases
Solution Approach 1:
The invention extracts the error correction function from the traditional feedback loop structure and implements it as a separate feedforward calculation. By calculating the error correction factor independently based on the known system characteristics (DAC impulse response) and planned gain changes, the system achieves error correction without requiring the continuous high-power operation of feedback loops.
Solution Approach 2:
The error correction factor acts as an intermediary element that bridges the input signal and the DRE processing circuit. This intermediary carries pre-calculated correction information that allows the main processing circuit to operate more efficiently without the need for high-power feedback mechanisms, thus reducing overall power consumption while maintaining signal accuracy.
Data Source
AI summary
An apparatus for dynamic range enhancement (DRE) which receives an input signal and provides a DRE output signal is presented. The apparatus has an error correction circuit to apply an error correction factor to the input signal such that the DRE output signal provided by the apparatus is dependent on the input signal and the error correction factor. The error correction factor is representative of an error generated by the apparatus.