Frame-Based IIR Signal Filtering for Smooth Parameter Transitions
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Solution Overview
Problem
Existing audio and speech signal filtering technologies face challenges in avoiding discontinuities and maintaining low complexity, particularly when Infinite Impulse Response (IIR) filter parameters change between frames, leading to instability and increased computational complexity.
Innovation Solution
A system and method that employs two filter units to gradually transition IIR filter parameters from a higher to a lower filtering status and vice versa within an initial subinterval of an update interval, allowing for reduced discontinuities and complexity by eliminating the need for cross-fading and separate filter operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If IIR filter parameters are updated once per frame to adapt to time-varying signals, then filtering adaptability is improved, but discontinuities and instabilities are introduced
Solution Approach 1:
The patent applies preliminary action by performing a first filtering operation at the beginning of each frame using parameters from the previous frame before applying the current frame's parameters. This preparatory step ensures a smooth transition between frames, preventing discontinuities while maintaining adaptability to time-varying signals.
2Stability of the object's composition
If cross-fade approach is used to smooth parameter transitions, then discontinuities are reduced, but computational complexity increases
Solution Approach 1:
The patent merges the transition smoothing function into the filtering operation itself by performing two filtering operations (first with previous frame parameters, then with current frame parameters) rather than separating the smoothing and filtering steps. This consolidation achieves discontinuity reduction without requiring additional cross-fade computational overhead.
3Measurement precision
If filter parameters are changed frequently to track signal variations, then filtering precision is improved, but computational complexity increases
Solution Approach 1:
The patent applies partial action by performing filtering operations only on specific portions of the frame (initial part with previous parameters, remaining part with current parameters) rather than uniformly across the entire frame. This selective approach maintains high filtering precision where needed while reducing unnecessary computational complexity in other regions.
Data Source
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AI summary
There are discussed methods and systems for filtering an information input signal (11, 11a, x), divided into different update intervals, according to parameters varying with the update intervals, to obtain a filtered output signal (y, 15). A system (10) may comprise: - a first filter unit (12) to filter a first filter input signal (11, x) at least at an initial subinterval (T i ) in a current update interval (T) to obtain a first filter output signal (y', 13), according to parameters associated to the preceding update interval, the first filter unit (12) being configured to change the parameters along at least the initial subinterval (T i ) from a higher-filtering status to a lower-filtering status; and - a second filter unit (14) to filter a second filter input signal (13), at the initial interval (T i ), according to parameters associated to the current update interval (T) to obtain a second filter output signal (15), the second filter unit (14) being configured to change the parameters along at least the initial subinterval (T i ) from a lower-filtering status to a higher-filtering status. The first filter input signal (11) is based on the information input signal (x), the first filter output signal (13) is an intermediate signal (y'), the second filter input signal is based on the intermediate signal (y'), and the filtered output signal (y) is based on the second filter output signal (15).